Kill the background saving process before performing SHUTDOWN to avoid races

[redis.git] / redis.c

/*
 * Copyright (c) 2006-2009, Salvatore Sanfilippo <antirez at gmail dot com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#define REDIS_VERSION "0.101"

#include "fmacros.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>
#include <errno.h>
#include <assert.h>
#include <ctype.h>
#include <stdarg.h>
#include <inttypes.h>
#include <arpa/inet.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <limits.h>
#include <execinfo.h>

#include "ae.h"     /* Event driven programming library */
#include "sds.h"    /* Dynamic safe strings */
#include "anet.h"   /* Networking the easy way */
#include "dict.h"   /* Hash tables */
#include "adlist.h" /* Linked lists */
#include "zmalloc.h" /* total memory usage aware version of malloc/free */
#include "lzf.h"    /* LZF compression library */
#include "pqsort.h" /* Partial qsort for SORT+LIMIT */

#include "config.h"

/* Error codes */
#define REDIS_OK                0
#define REDIS_ERR               -1

/* Static server configuration */
#define REDIS_SERVERPORT        6379    /* TCP port */
#define REDIS_MAXIDLETIME       (60*5)  /* default client timeout */
#define REDIS_IOBUF_LEN         1024
#define REDIS_LOADBUF_LEN       1024
#define REDIS_STATIC_ARGS       4
#define REDIS_DEFAULT_DBNUM     16
#define REDIS_CONFIGLINE_MAX    1024
#define REDIS_OBJFREELIST_MAX   1000000 /* Max number of objects to cache */
#define REDIS_MAX_SYNC_TIME     60      /* Slave can't take more to sync */
#define REDIS_EXPIRELOOKUPS_PER_CRON    100 /* try to expire 100 keys/second */

/* Hash table parameters */
#define REDIS_HT_MINFILL        10      /* Minimal hash table fill 10% */
#define REDIS_HT_MINSLOTS       16384   /* Never resize the HT under this */

/* Command flags */
#define REDIS_CMD_BULK          1       /* Bulk write command */
#define REDIS_CMD_INLINE        2       /* Inline command */
/* REDIS_CMD_DENYOOM reserves a longer comment: all the commands marked with
   this flags will return an error when the 'maxmemory' option is set in the
   config file and the server is using more than maxmemory bytes of memory.
   In short this commands are denied on low memory conditions. */
#define REDIS_CMD_DENYOOM       4

/* Object types */
#define REDIS_STRING 0
#define REDIS_LIST 1
#define REDIS_SET 2
#define REDIS_HASH 3

/* Object types only used for dumping to disk */
#define REDIS_EXPIRETIME 253
#define REDIS_SELECTDB 254
#define REDIS_EOF 255

/* Defines related to the dump file format. To store 32 bits lengths for short
 * keys requires a lot of space, so we check the most significant 2 bits of
 * the first byte to interpreter the length:
 *
 * 00|000000 => if the two MSB are 00 the len is the 6 bits of this byte
 * 01|000000 00000000 =>  01, the len is 14 byes, 6 bits + 8 bits of next byte
 * 10|000000 [32 bit integer] => if it's 01, a full 32 bit len will follow
 * 11|000000 this means: specially encoded object will follow. The six bits
 *           number specify the kind of object that follows.
 *           See the REDIS_RDB_ENC_* defines.
 *
 * Lenghts up to 63 are stored using a single byte, most DB keys, and may
 * values, will fit inside. */
#define REDIS_RDB_6BITLEN 0
#define REDIS_RDB_14BITLEN 1
#define REDIS_RDB_32BITLEN 2
#define REDIS_RDB_ENCVAL 3
#define REDIS_RDB_LENERR UINT_MAX

/* When a length of a string object stored on disk has the first two bits
 * set, the remaining two bits specify a special encoding for the object
 * accordingly to the following defines: */
#define REDIS_RDB_ENC_INT8 0        /* 8 bit signed integer */
#define REDIS_RDB_ENC_INT16 1       /* 16 bit signed integer */
#define REDIS_RDB_ENC_INT32 2       /* 32 bit signed integer */
#define REDIS_RDB_ENC_LZF 3         /* string compressed with FASTLZ */

/* Client flags */
#define REDIS_CLOSE 1       /* This client connection should be closed ASAP */
#define REDIS_SLAVE 2       /* This client is a slave server */
#define REDIS_MASTER 4      /* This client is a master server */
#define REDIS_MONITOR 8      /* This client is a slave monitor, see MONITOR */

/* Slave replication state - slave side */
#define REDIS_REPL_NONE 0   /* No active replication */
#define REDIS_REPL_CONNECT 1    /* Must connect to master */
#define REDIS_REPL_CONNECTED 2  /* Connected to master */

/* Slave replication state - from the point of view of master
 * Note that in SEND_BULK and ONLINE state the slave receives new updates
 * in its output queue. In the WAIT_BGSAVE state instead the server is waiting
 * to start the next background saving in order to send updates to it. */
#define REDIS_REPL_WAIT_BGSAVE_START 3 /* master waits bgsave to start feeding it */
#define REDIS_REPL_WAIT_BGSAVE_END 4 /* master waits bgsave to start bulk DB transmission */
#define REDIS_REPL_SEND_BULK 5 /* master is sending the bulk DB */
#define REDIS_REPL_ONLINE 6 /* bulk DB already transmitted, receive updates */

/* List related stuff */
#define REDIS_HEAD 0
#define REDIS_TAIL 1

/* Sort operations */
#define REDIS_SORT_GET 0
#define REDIS_SORT_DEL 1
#define REDIS_SORT_INCR 2
#define REDIS_SORT_DECR 3
#define REDIS_SORT_ASC 4
#define REDIS_SORT_DESC 5
#define REDIS_SORTKEY_MAX 1024

/* Log levels */
#define REDIS_DEBUG 0
#define REDIS_NOTICE 1
#define REDIS_WARNING 2

/* Anti-warning macro... */
#define REDIS_NOTUSED(V) ((void) V)

/*================================= Data types ============================== */

/* A redis object, that is a type able to hold a string / list / set */
typedef struct redisObject {
    void *ptr;
    int type;
    int refcount;
} robj;

typedef struct redisDb {
    dict *dict;
    dict *expires;
    int id;
} redisDb;

/* With multiplexing we need to take per-clinet state.
 * Clients are taken in a liked list. */
typedef struct redisClient {
    int fd;
    redisDb *db;
    int dictid;
    sds querybuf;
    robj **argv;
    int argc;
    int bulklen;            /* bulk read len. -1 if not in bulk read mode */
    list *reply;
    int sentlen;
    time_t lastinteraction; /* time of the last interaction, used for timeout */
    int flags;              /* REDIS_CLOSE | REDIS_SLAVE | REDIS_MONITOR */
    int slaveseldb;         /* slave selected db, if this client is a slave */
    int authenticated;      /* when requirepass is non-NULL */
    int replstate;          /* replication state if this is a slave */
    int repldbfd;           /* replication DB file descriptor */
    long repldboff;          /* replication DB file offset */
    off_t repldbsize;       /* replication DB file size */
} redisClient;

struct saveparam {
    time_t seconds;
    int changes;
};

/* Global server state structure */
struct redisServer {
    int port;
    int fd;
    redisDb *db;
    dict *sharingpool;
    unsigned int sharingpoolsize;
    long long dirty;            /* changes to DB from the last save */
    list *clients;
    list *slaves, *monitors;
    char neterr[ANET_ERR_LEN];
    aeEventLoop *el;
    int cronloops;              /* number of times the cron function run */
    list *objfreelist;          /* A list of freed objects to avoid malloc() */
    time_t lastsave;            /* Unix time of last save succeeede */
    size_t usedmemory;             /* Used memory in megabytes */
    /* Fields used only for stats */
    time_t stat_starttime;         /* server start time */
    long long stat_numcommands;    /* number of processed commands */
    long long stat_numconnections; /* number of connections received */
    /* Configuration */
    int verbosity;
    int glueoutputbuf;
    int maxidletime;
    int dbnum;
    int daemonize;
    char *pidfile;
    int bgsaveinprogress;
    pid_t bgsavechildpid;
    struct saveparam *saveparams;
    int saveparamslen;
    char *logfile;
    char *bindaddr;
    char *dbfilename;
    char *requirepass;
    int shareobjects;
    /* Replication related */
    int isslave;
    char *masterhost;
    int masterport;
    redisClient *master;    /* client that is master for this slave */
    int replstate;
    unsigned int maxclients;
    unsigned int maxmemory;
    /* Sort parameters - qsort_r() is only available under BSD so we
     * have to take this state global, in order to pass it to sortCompare() */
    int sort_desc;
    int sort_alpha;
    int sort_bypattern;
};

typedef void redisCommandProc(redisClient *c);
struct redisCommand {
    char *name;
    redisCommandProc *proc;
    int arity;
    int flags;
};

typedef struct _redisSortObject {
    robj *obj;
    union {
        double score;
        robj *cmpobj;
    } u;
} redisSortObject;

typedef struct _redisSortOperation {
    int type;
    robj *pattern;
} redisSortOperation;

struct sharedObjectsStruct {
    robj *crlf, *ok, *err, *emptybulk, *czero, *cone, *pong, *space,
    *colon, *nullbulk, *nullmultibulk,
    *emptymultibulk, *wrongtypeerr, *nokeyerr, *syntaxerr, *sameobjecterr,
    *outofrangeerr, *plus,
    *select0, *select1, *select2, *select3, *select4,
    *select5, *select6, *select7, *select8, *select9;
} shared;

/*================================ Prototypes =============================== */

static void freeStringObject(robj *o);
static void freeListObject(robj *o);
static void freeSetObject(robj *o);
static void decrRefCount(void *o);
static robj *createObject(int type, void *ptr);
static void freeClient(redisClient *c);
static int rdbLoad(char *filename);
static void addReply(redisClient *c, robj *obj);
static void addReplySds(redisClient *c, sds s);
static void incrRefCount(robj *o);
static int rdbSaveBackground(char *filename);
static robj *createStringObject(char *ptr, size_t len);
static void replicationFeedSlaves(list *slaves, struct redisCommand *cmd, int dictid, robj **argv, int argc);
static int syncWithMaster(void);
static robj *tryObjectSharing(robj *o);
static int removeExpire(redisDb *db, robj *key);
static int expireIfNeeded(redisDb *db, robj *key);
static int deleteIfVolatile(redisDb *db, robj *key);
static int deleteKey(redisDb *db, robj *key);
static time_t getExpire(redisDb *db, robj *key);
static int setExpire(redisDb *db, robj *key, time_t when);
static void updateSalvesWaitingBgsave(int bgsaveerr);
static void freeMemoryIfNeeded(void);

static void authCommand(redisClient *c);
static void pingCommand(redisClient *c);
static void echoCommand(redisClient *c);
static void setCommand(redisClient *c);
static void setnxCommand(redisClient *c);
static void getCommand(redisClient *c);
static void delCommand(redisClient *c);
static void existsCommand(redisClient *c);
static void incrCommand(redisClient *c);
static void decrCommand(redisClient *c);
static void incrbyCommand(redisClient *c);
static void decrbyCommand(redisClient *c);
static void selectCommand(redisClient *c);
static void randomkeyCommand(redisClient *c);
static void keysCommand(redisClient *c);
static void dbsizeCommand(redisClient *c);
static void lastsaveCommand(redisClient *c);
static void saveCommand(redisClient *c);
static void bgsaveCommand(redisClient *c);
static void shutdownCommand(redisClient *c);
static void moveCommand(redisClient *c);
static void renameCommand(redisClient *c);
static void renamenxCommand(redisClient *c);
static void lpushCommand(redisClient *c);
static void rpushCommand(redisClient *c);
static void lpopCommand(redisClient *c);
static void rpopCommand(redisClient *c);
static void llenCommand(redisClient *c);
static void lindexCommand(redisClient *c);
static void lrangeCommand(redisClient *c);
static void ltrimCommand(redisClient *c);
static void typeCommand(redisClient *c);
static void lsetCommand(redisClient *c);
static void saddCommand(redisClient *c);
static void sremCommand(redisClient *c);
static void smoveCommand(redisClient *c);
static void sismemberCommand(redisClient *c);
static void scardCommand(redisClient *c);
static void sinterCommand(redisClient *c);
static void sinterstoreCommand(redisClient *c);
static void sunionCommand(redisClient *c);
static void sunionstoreCommand(redisClient *c);
static void sdiffCommand(redisClient *c);
static void sdiffstoreCommand(redisClient *c);
static void syncCommand(redisClient *c);
static void flushdbCommand(redisClient *c);
static void flushallCommand(redisClient *c);
static void sortCommand(redisClient *c);
static void lremCommand(redisClient *c);
static void infoCommand(redisClient *c);
static void mgetCommand(redisClient *c);
static void monitorCommand(redisClient *c);
static void expireCommand(redisClient *c);
static void getSetCommand(redisClient *c);
static void ttlCommand(redisClient *c);
static void slaveofCommand(redisClient *c);
static void debugCommand(redisClient *c);

/*================================= Globals ================================= */

/* Global vars */
static struct redisServer server; /* server global state */
static struct redisCommand cmdTable[] = {
    {"get",getCommand,2,REDIS_CMD_INLINE},
    {"set",setCommand,3,REDIS_CMD_BULK|REDIS_CMD_DENYOOM},
    {"setnx",setnxCommand,3,REDIS_CMD_BULK|REDIS_CMD_DENYOOM},
    {"del",delCommand,-2,REDIS_CMD_INLINE},
    {"exists",existsCommand,2,REDIS_CMD_INLINE},
    {"incr",incrCommand,2,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"decr",decrCommand,2,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"mget",mgetCommand,-2,REDIS_CMD_INLINE},
    {"rpush",rpushCommand,3,REDIS_CMD_BULK|REDIS_CMD_DENYOOM},
    {"lpush",lpushCommand,3,REDIS_CMD_BULK|REDIS_CMD_DENYOOM},
    {"rpop",rpopCommand,2,REDIS_CMD_INLINE},
    {"lpop",lpopCommand,2,REDIS_CMD_INLINE},
    {"llen",llenCommand,2,REDIS_CMD_INLINE},
    {"lindex",lindexCommand,3,REDIS_CMD_INLINE},
    {"lset",lsetCommand,4,REDIS_CMD_BULK|REDIS_CMD_DENYOOM},
    {"lrange",lrangeCommand,4,REDIS_CMD_INLINE},
    {"ltrim",ltrimCommand,4,REDIS_CMD_INLINE},
    {"lrem",lremCommand,4,REDIS_CMD_BULK},
    {"sadd",saddCommand,3,REDIS_CMD_BULK|REDIS_CMD_DENYOOM},
    {"srem",sremCommand,3,REDIS_CMD_BULK},
    {"smove",smoveCommand,4,REDIS_CMD_BULK},
    {"sismember",sismemberCommand,3,REDIS_CMD_BULK},
    {"scard",scardCommand,2,REDIS_CMD_INLINE},
    {"sinter",sinterCommand,-2,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"sinterstore",sinterstoreCommand,-3,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"sunion",sunionCommand,-2,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"sunionstore",sunionstoreCommand,-3,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"sdiff",sdiffCommand,-2,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"sdiffstore",sdiffstoreCommand,-3,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"smembers",sinterCommand,2,REDIS_CMD_INLINE},
    {"incrby",incrbyCommand,3,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"decrby",decrbyCommand,3,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"getset",getSetCommand,3,REDIS_CMD_BULK|REDIS_CMD_DENYOOM},
    {"randomkey",randomkeyCommand,1,REDIS_CMD_INLINE},
    {"select",selectCommand,2,REDIS_CMD_INLINE},
    {"move",moveCommand,3,REDIS_CMD_INLINE},
    {"rename",renameCommand,3,REDIS_CMD_INLINE},
    {"renamenx",renamenxCommand,3,REDIS_CMD_INLINE},
    {"expire",expireCommand,3,REDIS_CMD_INLINE},
    {"keys",keysCommand,2,REDIS_CMD_INLINE},
    {"dbsize",dbsizeCommand,1,REDIS_CMD_INLINE},
    {"auth",authCommand,2,REDIS_CMD_INLINE},
    {"ping",pingCommand,1,REDIS_CMD_INLINE},
    {"echo",echoCommand,2,REDIS_CMD_BULK},
    {"save",saveCommand,1,REDIS_CMD_INLINE},
    {"bgsave",bgsaveCommand,1,REDIS_CMD_INLINE},
    {"shutdown",shutdownCommand,1,REDIS_CMD_INLINE},
    {"lastsave",lastsaveCommand,1,REDIS_CMD_INLINE},
    {"type",typeCommand,2,REDIS_CMD_INLINE},
    {"sync",syncCommand,1,REDIS_CMD_INLINE},
    {"flushdb",flushdbCommand,1,REDIS_CMD_INLINE},
    {"flushall",flushallCommand,1,REDIS_CMD_INLINE},
    {"sort",sortCommand,-2,REDIS_CMD_INLINE|REDIS_CMD_DENYOOM},
    {"info",infoCommand,1,REDIS_CMD_INLINE},
    {"monitor",monitorCommand,1,REDIS_CMD_INLINE},
    {"ttl",ttlCommand,2,REDIS_CMD_INLINE},
    {"slaveof",slaveofCommand,3,REDIS_CMD_INLINE},
    {"debug",debugCommand,-2,REDIS_CMD_INLINE},
    {NULL,NULL,0,0}
};

/*============================ Utility functions ============================ */

/* Glob-style pattern matching. */
int stringmatchlen(const char *pattern, int patternLen,
        const char *string, int stringLen, int nocase)
{
    while(patternLen) {
        switch(pattern[0]) {
        case '*':
            while (pattern[1] == '*') {
                pattern++;
                patternLen--;
            }
            if (patternLen == 1)
                return 1; /* match */
            while(stringLen) {
                if (stringmatchlen(pattern+1, patternLen-1,
                            string, stringLen, nocase))
                    return 1; /* match */
                string++;
                stringLen--;
            }
            return 0; /* no match */
            break;
        case '?':
            if (stringLen == 0)
                return 0; /* no match */
            string++;
            stringLen--;
            break;
        case '[':
        {
            int not, match;

            pattern++;
            patternLen--;
            not = pattern[0] == '^';
            if (not) {
                pattern++;
                patternLen--;
            }
            match = 0;
            while(1) {
                if (pattern[0] == '\\') {
                    pattern++;
                    patternLen--;
                    if (pattern[0] == string[0])
                        match = 1;
                } else if (pattern[0] == ']') {
                    break;
                } else if (patternLen == 0) {
                    pattern--;
                    patternLen++;
                    break;
                } else if (pattern[1] == '-' && patternLen >= 3) {
                    int start = pattern[0];
                    int end = pattern[2];
                    int c = string[0];
                    if (start > end) {
                        int t = start;
                        start = end;
                        end = t;
                    }
                    if (nocase) {
                        start = tolower(start);
                        end = tolower(end);
                        c = tolower(c);
                    }
                    pattern += 2;
                    patternLen -= 2;
                    if (c >= start && c <= end)
                        match = 1;
                } else {
                    if (!nocase) {
                        if (pattern[0] == string[0])
                            match = 1;
                    } else {
                        if (tolower((int)pattern[0]) == tolower((int)string[0]))
                            match = 1;
                    }
                }
                pattern++;
                patternLen--;
            }
            if (not)
                match = !match;
            if (!match)
                return 0; /* no match */
            string++;
            stringLen--;
            break;
        }
        case '\\':
            if (patternLen >= 2) {
                pattern++;
                patternLen--;
            }
            /* fall through */
        default:
            if (!nocase) {
                if (pattern[0] != string[0])
                    return 0; /* no match */
            } else {
                if (tolower((int)pattern[0]) != tolower((int)string[0]))
                    return 0; /* no match */
            }
            string++;
            stringLen--;
            break;
        }
        pattern++;
        patternLen--;
        if (stringLen == 0) {
            while(*pattern == '*') {
                pattern++;
                patternLen--;
            }
            break;
        }
    }
    if (patternLen == 0 && stringLen == 0)
        return 1;
    return 0;
}

void redisLog(int level, const char *fmt, ...)
{
    va_list ap;
    FILE *fp;

    fp = (server.logfile == NULL) ? stdout : fopen(server.logfile,"a");
    if (!fp) return;

    va_start(ap, fmt);
    if (level >= server.verbosity) {
        char *c = ".-*";
        char buf[64];
        time_t now;

        now = time(NULL);
        strftime(buf,64,"%d %b %H:%M:%S",gmtime(&now));
        fprintf(fp,"%s %c ",buf,c[level]);
        vfprintf(fp, fmt, ap);
        fprintf(fp,"\n");
        fflush(fp);
    }
    va_end(ap);

    if (server.logfile) fclose(fp);
}

/*====================== Hash table type implementation  ==================== */

/* This is an hash table type that uses the SDS dynamic strings libary as
 * keys and radis objects as values (objects can hold SDS strings,
 * lists, sets). */

static int sdsDictKeyCompare(void *privdata, const void *key1,
        const void *key2)
{
    int l1,l2;
    DICT_NOTUSED(privdata);

    l1 = sdslen((sds)key1);
    l2 = sdslen((sds)key2);
    if (l1 != l2) return 0;
    return memcmp(key1, key2, l1) == 0;
}

static void dictRedisObjectDestructor(void *privdata, void *val)
{
    DICT_NOTUSED(privdata);

    decrRefCount(val);
}

static int dictSdsKeyCompare(void *privdata, const void *key1,
        const void *key2)
{
    const robj *o1 = key1, *o2 = key2;
    return sdsDictKeyCompare(privdata,o1->ptr,o2->ptr);
}

static unsigned int dictSdsHash(const void *key) {
    const robj *o = key;
    return dictGenHashFunction(o->ptr, sdslen((sds)o->ptr));
}

static dictType setDictType = {
    dictSdsHash,               /* hash function */
    NULL,                      /* key dup */
    NULL,                      /* val dup */
    dictSdsKeyCompare,         /* key compare */
    dictRedisObjectDestructor, /* key destructor */
    NULL                       /* val destructor */
};

static dictType hashDictType = {
    dictSdsHash,                /* hash function */
    NULL,                       /* key dup */
    NULL,                       /* val dup */
    dictSdsKeyCompare,          /* key compare */
    dictRedisObjectDestructor,  /* key destructor */
    dictRedisObjectDestructor   /* val destructor */
};

/* ========================= Random utility functions ======================= */

/* Redis generally does not try to recover from out of memory conditions
 * when allocating objects or strings, it is not clear if it will be possible
 * to report this condition to the client since the networking layer itself
 * is based on heap allocation for send buffers, so we simply abort.
 * At least the code will be simpler to read... */
static void oom(const char *msg) {
    fprintf(stderr, "%s: Out of memory\n",msg);
    fflush(stderr);
    sleep(1);
    abort();
}

/* ====================== Redis server networking stuff ===================== */
void closeTimedoutClients(void) {
    redisClient *c;
    listNode *ln;
    time_t now = time(NULL);

    listRewind(server.clients);
    while ((ln = listYield(server.clients)) != NULL) {
        c = listNodeValue(ln);
        if (!(c->flags & REDIS_SLAVE) &&    /* no timeout for slaves */
            !(c->flags & REDIS_MASTER) &&   /* no timeout for masters */
             (now - c->lastinteraction > server.maxidletime)) {
            redisLog(REDIS_DEBUG,"Closing idle client");
            freeClient(c);
        }
    }
}

/* If the percentage of used slots in the HT reaches REDIS_HT_MINFILL
 * we resize the hash table to save memory */
void tryResizeHashTables(void) {
    int j;

    for (j = 0; j < server.dbnum; j++) {
        long long size, used;

        size = dictSlots(server.db[j].dict);
        used = dictSize(server.db[j].dict);
        if (size && used && size > REDIS_HT_MINSLOTS &&
            (used*100/size < REDIS_HT_MINFILL)) {
            redisLog(REDIS_NOTICE,"The hash table %d is too sparse, resize it...",j);
            dictResize(server.db[j].dict);
            redisLog(REDIS_NOTICE,"Hash table %d resized.",j);
        }
    }
}

int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
    int j, loops = server.cronloops++;
    REDIS_NOTUSED(eventLoop);
    REDIS_NOTUSED(id);
    REDIS_NOTUSED(clientData);

    /* Update the global state with the amount of used memory */
    server.usedmemory = zmalloc_used_memory();

    /* Show some info about non-empty databases */
    for (j = 0; j < server.dbnum; j++) {
        long long size, used, vkeys;

        size = dictSlots(server.db[j].dict);
        used = dictSize(server.db[j].dict);
        vkeys = dictSize(server.db[j].expires);
        if (!(loops % 5) && used > 0) {
            redisLog(REDIS_DEBUG,"DB %d: %d keys (%d volatile) in %d slots HT.",j,used,vkeys,size);
            /* dictPrintStats(server.dict); */
        }
    }

    /* We don't want to resize the hash tables while a bacground saving
     * is in progress: the saving child is created using fork() that is
     * implemented with a copy-on-write semantic in most modern systems, so
     * if we resize the HT while there is the saving child at work actually
     * a lot of memory movements in the parent will cause a lot of pages
     * copied. */
    if (!server.bgsaveinprogress) tryResizeHashTables();

    /* Show information about connected clients */
    if (!(loops % 5)) {
        redisLog(REDIS_DEBUG,"%d clients connected (%d slaves), %zu bytes in use",
            listLength(server.clients)-listLength(server.slaves),
            listLength(server.slaves),
            server.usedmemory,
            dictSize(server.sharingpool));
    }

    /* Close connections of timedout clients */
    if (server.maxidletime && !(loops % 10))
        closeTimedoutClients();

    /* Check if a background saving in progress terminated */
    if (server.bgsaveinprogress) {
        int statloc;
        /* XXX: TODO handle the case of the saving child killed */
        if (wait4(-1,&statloc,WNOHANG,NULL)) {
            int exitcode = WEXITSTATUS(statloc);
            int bysignal = WIFSIGNALED(statloc);

            if (!bysignal && exitcode == 0) {
                redisLog(REDIS_NOTICE,
                    "Background saving terminated with success");
                server.dirty = 0;
                server.lastsave = time(NULL);
            } else if (!bysignal && exitcode != 0) {
                redisLog(REDIS_WARNING, "Background saving error");
            } else {
                redisLog(REDIS_WARNING,
                    "Background saving terminated by signal");
            }
            server.bgsaveinprogress = 0;
            server.bgsavechildpid = -1;
            updateSalvesWaitingBgsave(exitcode == 0 ? REDIS_OK : REDIS_ERR);
        }
    } else {
        /* If there is not a background saving in progress check if
         * we have to save now */
         time_t now = time(NULL);
         for (j = 0; j < server.saveparamslen; j++) {
            struct saveparam *sp = server.saveparams+j;

            if (server.dirty >= sp->changes &&
                now-server.lastsave > sp->seconds) {
                redisLog(REDIS_NOTICE,"%d changes in %d seconds. Saving...",
                    sp->changes, sp->seconds);
                rdbSaveBackground(server.dbfilename);
                break;
            }
         }
    }

    /* Try to expire a few timed out keys */
    for (j = 0; j < server.dbnum; j++) {
        redisDb *db = server.db+j;
        int num = dictSize(db->expires);

        if (num) {
            time_t now = time(NULL);

            if (num > REDIS_EXPIRELOOKUPS_PER_CRON)
                num = REDIS_EXPIRELOOKUPS_PER_CRON;
            while (num--) {
                dictEntry *de;
                time_t t;

                if ((de = dictGetRandomKey(db->expires)) == NULL) break;
                t = (time_t) dictGetEntryVal(de);
                if (now > t) {
                    deleteKey(db,dictGetEntryKey(de));
                }
            }
        }
    }

    /* Check if we should connect to a MASTER */
    if (server.replstate == REDIS_REPL_CONNECT) {
        redisLog(REDIS_NOTICE,"Connecting to MASTER...");
        if (syncWithMaster() == REDIS_OK) {
            redisLog(REDIS_NOTICE,"MASTER <-> SLAVE sync succeeded");
        }
    }
    return 1000;
}

static void createSharedObjects(void) {
    shared.crlf = createObject(REDIS_STRING,sdsnew("\r\n"));
    shared.ok = createObject(REDIS_STRING,sdsnew("+OK\r\n"));
    shared.err = createObject(REDIS_STRING,sdsnew("-ERR\r\n"));
    shared.emptybulk = createObject(REDIS_STRING,sdsnew("$0\r\n\r\n"));
    shared.czero = createObject(REDIS_STRING,sdsnew(":0\r\n"));
    shared.cone = createObject(REDIS_STRING,sdsnew(":1\r\n"));
    shared.nullbulk = createObject(REDIS_STRING,sdsnew("$-1\r\n"));
    shared.nullmultibulk = createObject(REDIS_STRING,sdsnew("*-1\r\n"));
    shared.emptymultibulk = createObject(REDIS_STRING,sdsnew("*0\r\n"));
    /* no such key */
    shared.pong = createObject(REDIS_STRING,sdsnew("+PONG\r\n"));
    shared.wrongtypeerr = createObject(REDIS_STRING,sdsnew(
        "-ERR Operation against a key holding the wrong kind of value\r\n"));
    shared.nokeyerr = createObject(REDIS_STRING,sdsnew(
        "-ERR no such key\r\n"));
    shared.syntaxerr = createObject(REDIS_STRING,sdsnew(
        "-ERR syntax error\r\n"));
    shared.sameobjecterr = createObject(REDIS_STRING,sdsnew(
        "-ERR source and destination objects are the same\r\n"));
    shared.outofrangeerr = createObject(REDIS_STRING,sdsnew(
        "-ERR index out of range\r\n"));
    shared.space = createObject(REDIS_STRING,sdsnew(" "));
    shared.colon = createObject(REDIS_STRING,sdsnew(":"));
    shared.plus = createObject(REDIS_STRING,sdsnew("+"));
    shared.select0 = createStringObject("select 0\r\n",10);
    shared.select1 = createStringObject("select 1\r\n",10);
    shared.select2 = createStringObject("select 2\r\n",10);
    shared.select3 = createStringObject("select 3\r\n",10);
    shared.select4 = createStringObject("select 4\r\n",10);
    shared.select5 = createStringObject("select 5\r\n",10);
    shared.select6 = createStringObject("select 6\r\n",10);
    shared.select7 = createStringObject("select 7\r\n",10);
    shared.select8 = createStringObject("select 8\r\n",10);
    shared.select9 = createStringObject("select 9\r\n",10);
}

static void appendServerSaveParams(time_t seconds, int changes) {
    server.saveparams = zrealloc(server.saveparams,sizeof(struct saveparam)*(server.saveparamslen+1));
    if (server.saveparams == NULL) oom("appendServerSaveParams");
    server.saveparams[server.saveparamslen].seconds = seconds;
    server.saveparams[server.saveparamslen].changes = changes;
    server.saveparamslen++;
}

static void ResetServerSaveParams() {
    zfree(server.saveparams);
    server.saveparams = NULL;
    server.saveparamslen = 0;
}

static void initServerConfig() {
    server.dbnum = REDIS_DEFAULT_DBNUM;
    server.port = REDIS_SERVERPORT;
    server.verbosity = REDIS_DEBUG;
    server.maxidletime = REDIS_MAXIDLETIME;
    server.saveparams = NULL;
    server.logfile = NULL; /* NULL = log on standard output */
    server.bindaddr = NULL;
    server.glueoutputbuf = 1;
    server.daemonize = 0;
    server.pidfile = "/var/run/redis.pid";
    server.dbfilename = "dump.rdb";
    server.requirepass = NULL;
    server.shareobjects = 0;
    server.maxclients = 0;
    server.maxmemory = 0;
    ResetServerSaveParams();

    appendServerSaveParams(60*60,1);  /* save after 1 hour and 1 change */
    appendServerSaveParams(300,100);  /* save after 5 minutes and 100 changes */
    appendServerSaveParams(60,10000); /* save after 1 minute and 10000 changes */
    /* Replication related */
    server.isslave = 0;
    server.masterhost = NULL;
    server.masterport = 6379;
    server.master = NULL;
    server.replstate = REDIS_REPL_NONE;
}

static void initServer() {
    int j;

    signal(SIGHUP, SIG_IGN);
    signal(SIGPIPE, SIG_IGN);

    server.clients = listCreate();
    server.slaves = listCreate();
    server.monitors = listCreate();
    server.objfreelist = listCreate();
    createSharedObjects();
    server.el = aeCreateEventLoop();
    server.db = zmalloc(sizeof(redisDb)*server.dbnum);
    server.sharingpool = dictCreate(&setDictType,NULL);
    server.sharingpoolsize = 1024;
    if (!server.db || !server.clients || !server.slaves || !server.monitors || !server.el || !server.objfreelist)
        oom("server initialization"); /* Fatal OOM */
    server.fd = anetTcpServer(server.neterr, server.port, server.bindaddr);
    if (server.fd == -1) {
        redisLog(REDIS_WARNING, "Opening TCP port: %s", server.neterr);
        exit(1);
    }
    for (j = 0; j < server.dbnum; j++) {
        server.db[j].dict = dictCreate(&hashDictType,NULL);
        server.db[j].expires = dictCreate(&setDictType,NULL);
        server.db[j].id = j;
    }
    server.cronloops = 0;
    server.bgsaveinprogress = 0;
    server.bgsavechildpid = -1;
    server.lastsave = time(NULL);
    server.dirty = 0;
    server.usedmemory = 0;
    server.stat_numcommands = 0;
    server.stat_numconnections = 0;
    server.stat_starttime = time(NULL);
    aeCreateTimeEvent(server.el, 1000, serverCron, NULL, NULL);
}

/* Empty the whole database */
static long long emptyDb() {
    int j;
    long long removed = 0;

    for (j = 0; j < server.dbnum; j++) {
        removed += dictSize(server.db[j].dict);
        dictEmpty(server.db[j].dict);
        dictEmpty(server.db[j].expires);
    }
    return removed;
}

static int yesnotoi(char *s) {
    if (!strcasecmp(s,"yes")) return 1;
    else if (!strcasecmp(s,"no")) return 0;
    else return -1;
}

/* I agree, this is a very rudimental way to load a configuration...
   will improve later if the config gets more complex */
static void loadServerConfig(char *filename) {
    FILE *fp = fopen(filename,"r");
    char buf[REDIS_CONFIGLINE_MAX+1], *err = NULL;
    int linenum = 0;
    sds line = NULL;
    
    if (!fp) {
        redisLog(REDIS_WARNING,"Fatal error, can't open config file");
        exit(1);
    }
    while(fgets(buf,REDIS_CONFIGLINE_MAX+1,fp) != NULL) {
        sds *argv;
        int argc, j;

        linenum++;
        line = sdsnew(buf);
        line = sdstrim(line," \t\r\n");

        /* Skip comments and blank lines*/
        if (line[0] == '#' || line[0] == '\0') {
            sdsfree(line);
            continue;
        }

        /* Split into arguments */
        argv = sdssplitlen(line,sdslen(line)," ",1,&argc);
        sdstolower(argv[0]);

        /* Execute config directives */
        if (!strcasecmp(argv[0],"timeout") && argc == 2) {
            server.maxidletime = atoi(argv[1]);
            if (server.maxidletime < 0) {
                err = "Invalid timeout value"; goto loaderr;
            }
        } else if (!strcasecmp(argv[0],"port") && argc == 2) {
            server.port = atoi(argv[1]);
            if (server.port < 1 || server.port > 65535) {
                err = "Invalid port"; goto loaderr;
            }
        } else if (!strcasecmp(argv[0],"bind") && argc == 2) {
            server.bindaddr = zstrdup(argv[1]);
        } else if (!strcasecmp(argv[0],"save") && argc == 3) {
            int seconds = atoi(argv[1]);
            int changes = atoi(argv[2]);
            if (seconds < 1 || changes < 0) {
                err = "Invalid save parameters"; goto loaderr;
            }
            appendServerSaveParams(seconds,changes);
        } else if (!strcasecmp(argv[0],"dir") && argc == 2) {
            if (chdir(argv[1]) == -1) {
                redisLog(REDIS_WARNING,"Can't chdir to '%s': %s",
                    argv[1], strerror(errno));
                exit(1);
            }
        } else if (!strcasecmp(argv[0],"loglevel") && argc == 2) {
            if (!strcasecmp(argv[1],"debug")) server.verbosity = REDIS_DEBUG;
            else if (!strcasecmp(argv[1],"notice")) server.verbosity = REDIS_NOTICE;
            else if (!strcasecmp(argv[1],"warning")) server.verbosity = REDIS_WARNING;
            else {
                err = "Invalid log level. Must be one of debug, notice, warning";
                goto loaderr;
            }
        } else if (!strcasecmp(argv[0],"logfile") && argc == 2) {
            FILE *fp;

            server.logfile = zstrdup(argv[1]);
            if (!strcasecmp(server.logfile,"stdout")) {
                zfree(server.logfile);
                server.logfile = NULL;
            }
            if (server.logfile) {
                /* Test if we are able to open the file. The server will not
                 * be able to abort just for this problem later... */
                fp = fopen(server.logfile,"a");
                if (fp == NULL) {
                    err = sdscatprintf(sdsempty(),
                        "Can't open the log file: %s", strerror(errno));
                    goto loaderr;
                }
                fclose(fp);
            }
        } else if (!strcasecmp(argv[0],"databases") && argc == 2) {
            server.dbnum = atoi(argv[1]);
            if (server.dbnum < 1) {
                err = "Invalid number of databases"; goto loaderr;
            }
        } else if (!strcasecmp(argv[0],"maxclients") && argc == 2) {
            server.maxclients = atoi(argv[1]);
        } else if (!strcasecmp(argv[0],"maxmemory") && argc == 2) {
            server.maxmemory = atoi(argv[1]);
        } else if (!strcasecmp(argv[0],"slaveof") && argc == 3) {
            server.masterhost = sdsnew(argv[1]);
            server.masterport = atoi(argv[2]);
            server.replstate = REDIS_REPL_CONNECT;
        } else if (!strcasecmp(argv[0],"glueoutputbuf") && argc == 2) {
            if ((server.glueoutputbuf = yesnotoi(argv[1])) == -1) {
                err = "argument must be 'yes' or 'no'"; goto loaderr;
            }
        } else if (!strcasecmp(argv[0],"shareobjects") && argc == 2) {
            if ((server.shareobjects = yesnotoi(argv[1])) == -1) {
                err = "argument must be 'yes' or 'no'"; goto loaderr;
            }
        } else if (!strcasecmp(argv[0],"shareobjectspoolsize") && argc == 2) {
            server.sharingpoolsize = atoi(argv[1]);
            if (server.sharingpoolsize < 1) {
                err = "invalid object sharing pool size"; goto loaderr;
            }
        } else if (!strcasecmp(argv[0],"daemonize") && argc == 2) {
            if ((server.daemonize = yesnotoi(argv[1])) == -1) {
                err = "argument must be 'yes' or 'no'"; goto loaderr;
            }
        } else if (!strcasecmp(argv[0],"requirepass") && argc == 2) {
          server.requirepass = zstrdup(argv[1]);
        } else if (!strcasecmp(argv[0],"pidfile") && argc == 2) {
          server.pidfile = zstrdup(argv[1]);
        } else if (!strcasecmp(argv[0],"dbfilename") && argc == 2) {
          server.dbfilename = zstrdup(argv[1]);
        } else {
            err = "Bad directive or wrong number of arguments"; goto loaderr;
        }
        for (j = 0; j < argc; j++)
            sdsfree(argv[j]);
        zfree(argv);
        sdsfree(line);
    }
    fclose(fp);
    return;

loaderr:
    fprintf(stderr, "\n*** FATAL CONFIG FILE ERROR ***\n");
    fprintf(stderr, "Reading the configuration file, at line %d\n", linenum);
    fprintf(stderr, ">>> '%s'\n", line);
    fprintf(stderr, "%s\n", err);
    exit(1);
}

static void freeClientArgv(redisClient *c) {
    int j;

    for (j = 0; j < c->argc; j++)
        decrRefCount(c->argv[j]);
    c->argc = 0;
}

static void freeClient(redisClient *c) {
    listNode *ln;

    aeDeleteFileEvent(server.el,c->fd,AE_READABLE);
    aeDeleteFileEvent(server.el,c->fd,AE_WRITABLE);
    sdsfree(c->querybuf);
    listRelease(c->reply);
    freeClientArgv(c);
    close(c->fd);
    ln = listSearchKey(server.clients,c);
    assert(ln != NULL);
    listDelNode(server.clients,ln);
    if (c->flags & REDIS_SLAVE) {
        if (c->replstate == REDIS_REPL_SEND_BULK && c->repldbfd != -1)
            close(c->repldbfd);
        list *l = (c->flags & REDIS_MONITOR) ? server.monitors : server.slaves;
        ln = listSearchKey(l,c);
        assert(ln != NULL);
        listDelNode(l,ln);
    }
    if (c->flags & REDIS_MASTER) {
        server.master = NULL;
        server.replstate = REDIS_REPL_CONNECT;
    }
    zfree(c->argv);
    zfree(c);
}

static void glueReplyBuffersIfNeeded(redisClient *c) {
    int totlen = 0;
    listNode *ln;
    robj *o;

    listRewind(c->reply);
    while((ln = listYield(c->reply))) {
        o = ln->value;
        totlen += sdslen(o->ptr);
        /* This optimization makes more sense if we don't have to copy
         * too much data */
        if (totlen > 1024) return;
    }
    if (totlen > 0) {
        char buf[1024];
        int copylen = 0;

        listRewind(c->reply);
        while((ln = listYield(c->reply))) {
            o = ln->value;
            memcpy(buf+copylen,o->ptr,sdslen(o->ptr));
            copylen += sdslen(o->ptr);
            listDelNode(c->reply,ln);
        }
        /* Now the output buffer is empty, add the new single element */
        o = createObject(REDIS_STRING,sdsnewlen(buf,totlen));
        if (!listAddNodeTail(c->reply,o)) oom("listAddNodeTail");
    }
}

static void sendReplyToClient(aeEventLoop *el, int fd, void *privdata, int mask) {
    redisClient *c = privdata;
    int nwritten = 0, totwritten = 0, objlen;
    robj *o;
    REDIS_NOTUSED(el);
    REDIS_NOTUSED(mask);

    if (server.glueoutputbuf && listLength(c->reply) > 1)
        glueReplyBuffersIfNeeded(c);
    while(listLength(c->reply)) {
        o = listNodeValue(listFirst(c->reply));
        objlen = sdslen(o->ptr);

        if (objlen == 0) {
            listDelNode(c->reply,listFirst(c->reply));
            continue;
        }

        if (c->flags & REDIS_MASTER) {
            nwritten = objlen - c->sentlen;
        } else {
            nwritten = write(fd, ((char*)o->ptr)+c->sentlen, objlen - c->sentlen);
            if (nwritten <= 0) break;
        }
        c->sentlen += nwritten;
        totwritten += nwritten;
        /* If we fully sent the object on head go to the next one */
        if (c->sentlen == objlen) {
            listDelNode(c->reply,listFirst(c->reply));
            c->sentlen = 0;
        }
    }
    if (nwritten == -1) {
        if (errno == EAGAIN) {
            nwritten = 0;
        } else {
            redisLog(REDIS_DEBUG,
                "Error writing to client: %s", strerror(errno));
            freeClient(c);
            return;
        }
    }
    if (totwritten > 0) c->lastinteraction = time(NULL);
    if (listLength(c->reply) == 0) {
        c->sentlen = 0;
        aeDeleteFileEvent(server.el,c->fd,AE_WRITABLE);
    }
}

static struct redisCommand *lookupCommand(char *name) {
    int j = 0;
    while(cmdTable[j].name != NULL) {
        if (!strcasecmp(name,cmdTable[j].name)) return &cmdTable[j];
        j++;
    }
    return NULL;
}

/* resetClient prepare the client to process the next command */
static void resetClient(redisClient *c) {
    freeClientArgv(c);
    c->bulklen = -1;
}

/* If this function gets called we already read a whole
 * command, argments are in the client argv/argc fields.
 * processCommand() execute the command or prepare the
 * server for a bulk read from the client.
 *
 * If 1 is returned the client is still alive and valid and
 * and other operations can be performed by the caller. Otherwise
 * if 0 is returned the client was destroied (i.e. after QUIT). */
static int processCommand(redisClient *c) {
    struct redisCommand *cmd;
    long long dirty;

    /* Free some memory if needed (maxmemory setting) */
    if (server.maxmemory) freeMemoryIfNeeded();

    /* The QUIT command is handled as a special case. Normal command
     * procs are unable to close the client connection safely */
    if (!strcasecmp(c->argv[0]->ptr,"quit")) {
        freeClient(c);
        return 0;
    }
    cmd = lookupCommand(c->argv[0]->ptr);
    if (!cmd) {
        addReplySds(c,sdsnew("-ERR unknown command\r\n"));
        resetClient(c);
        return 1;
    } else if ((cmd->arity > 0 && cmd->arity != c->argc) ||
               (c->argc < -cmd->arity)) {
        addReplySds(c,sdsnew("-ERR wrong number of arguments\r\n"));
        resetClient(c);
        return 1;
    } else if (server.maxmemory && cmd->flags & REDIS_CMD_DENYOOM && zmalloc_used_memory() > server.maxmemory) {
        addReplySds(c,sdsnew("-ERR command not allowed when used memory > 'maxmemory'\r\n"));
        resetClient(c);
        return 1;
    } else if (cmd->flags & REDIS_CMD_BULK && c->bulklen == -1) {
        int bulklen = atoi(c->argv[c->argc-1]->ptr);

        decrRefCount(c->argv[c->argc-1]);
        if (bulklen < 0 || bulklen > 1024*1024*1024) {
            c->argc--;
            addReplySds(c,sdsnew("-ERR invalid bulk write count\r\n"));
            resetClient(c);
            return 1;
        }
        c->argc--;
        c->bulklen = bulklen+2; /* add two bytes for CR+LF */
        /* It is possible that the bulk read is already in the
         * buffer. Check this condition and handle it accordingly */
        if ((signed)sdslen(c->querybuf) >= c->bulklen) {
            c->argv[c->argc] = createStringObject(c->querybuf,c->bulklen-2);
            c->argc++;
            c->querybuf = sdsrange(c->querybuf,c->bulklen,-1);
        } else {
            return 1;
        }
    }
    /* Let's try to share objects on the command arguments vector */
    if (server.shareobjects) {
        int j;
        for(j = 1; j < c->argc; j++)
            c->argv[j] = tryObjectSharing(c->argv[j]);
    }
    /* Check if the user is authenticated */
    if (server.requirepass && !c->authenticated && cmd->proc != authCommand) {
        addReplySds(c,sdsnew("-ERR operation not permitted\r\n"));
        resetClient(c);
        return 1;
    }

    /* Exec the command */
    dirty = server.dirty;
    cmd->proc(c);
    if (server.dirty-dirty != 0 && listLength(server.slaves))
        replicationFeedSlaves(server.slaves,cmd,c->db->id,c->argv,c->argc);
    if (listLength(server.monitors))
        replicationFeedSlaves(server.monitors,cmd,c->db->id,c->argv,c->argc);
    server.stat_numcommands++;

    /* Prepare the client for the next command */
    if (c->flags & REDIS_CLOSE) {
        freeClient(c);
        return 0;
    }
    resetClient(c);
    return 1;
}

static void replicationFeedSlaves(list *slaves, struct redisCommand *cmd, int dictid, robj **argv, int argc) {
    listNode *ln;
    int outc = 0, j;
    robj **outv;
    /* (args*2)+1 is enough room for args, spaces, newlines */
    robj *static_outv[REDIS_STATIC_ARGS*2+1];

    if (argc <= REDIS_STATIC_ARGS) {
        outv = static_outv;
    } else {
        outv = zmalloc(sizeof(robj*)*(argc*2+1));
        if (!outv) oom("replicationFeedSlaves");
    }
    
    for (j = 0; j < argc; j++) {
        if (j != 0) outv[outc++] = shared.space;
        if ((cmd->flags & REDIS_CMD_BULK) && j == argc-1) {
            robj *lenobj;

            lenobj = createObject(REDIS_STRING,
                sdscatprintf(sdsempty(),"%d\r\n",sdslen(argv[j]->ptr)));
            lenobj->refcount = 0;
            outv[outc++] = lenobj;
        }
        outv[outc++] = argv[j];
    }
    outv[outc++] = shared.crlf;

    /* Increment all the refcounts at start and decrement at end in order to
     * be sure to free objects if there is no slave in a replication state
     * able to be feed with commands */
    for (j = 0; j < outc; j++) incrRefCount(outv[j]);
    listRewind(slaves);
    while((ln = listYield(slaves))) {
        redisClient *slave = ln->value;

        /* Don't feed slaves that are still waiting for BGSAVE to start */
        if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) continue;

        /* Feed all the other slaves, MONITORs and so on */
        if (slave->slaveseldb != dictid) {
            robj *selectcmd;

            switch(dictid) {
            case 0: selectcmd = shared.select0; break;
            case 1: selectcmd = shared.select1; break;
            case 2: selectcmd = shared.select2; break;
            case 3: selectcmd = shared.select3; break;
            case 4: selectcmd = shared.select4; break;
            case 5: selectcmd = shared.select5; break;
            case 6: selectcmd = shared.select6; break;
            case 7: selectcmd = shared.select7; break;
            case 8: selectcmd = shared.select8; break;
            case 9: selectcmd = shared.select9; break;
            default:
                selectcmd = createObject(REDIS_STRING,
                    sdscatprintf(sdsempty(),"select %d\r\n",dictid));
                selectcmd->refcount = 0;
                break;
            }
            addReply(slave,selectcmd);
            slave->slaveseldb = dictid;
        }
        for (j = 0; j < outc; j++) addReply(slave,outv[j]);
    }
    for (j = 0; j < outc; j++) decrRefCount(outv[j]);
    if (outv != static_outv) zfree(outv);
}

static void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
    redisClient *c = (redisClient*) privdata;
    char buf[REDIS_IOBUF_LEN];
    int nread;
    REDIS_NOTUSED(el);
    REDIS_NOTUSED(mask);

    nread = read(fd, buf, REDIS_IOBUF_LEN);
    if (nread == -1) {
        if (errno == EAGAIN) {
            nread = 0;
        } else {
            redisLog(REDIS_DEBUG, "Reading from client: %s",strerror(errno));
            freeClient(c);
            return;
        }
    } else if (nread == 0) {
        redisLog(REDIS_DEBUG, "Client closed connection");
        freeClient(c);
        return;
    }
    if (nread) {
        c->querybuf = sdscatlen(c->querybuf, buf, nread);
        c->lastinteraction = time(NULL);
    } else {
        return;
    }

again:
    if (c->bulklen == -1) {
        /* Read the first line of the query */
        char *p = strchr(c->querybuf,'\n');
        size_t querylen;
        if (p) {
            sds query, *argv;
            int argc, j;
            
            query = c->querybuf;
            c->querybuf = sdsempty();
            querylen = 1+(p-(query));
            if (sdslen(query) > querylen) {
                /* leave data after the first line of the query in the buffer */
                c->querybuf = sdscatlen(c->querybuf,query+querylen,sdslen(query)-querylen);
            }
            *p = '\0'; /* remove "\n" */
            if (*(p-1) == '\r') *(p-1) = '\0'; /* and "\r" if any */
            sdsupdatelen(query);

            /* Now we can split the query in arguments */
            if (sdslen(query) == 0) {
                /* Ignore empty query */
                sdsfree(query);
                return;
            }
            argv = sdssplitlen(query,sdslen(query)," ",1,&argc);
            if (argv == NULL) oom("sdssplitlen");
            sdsfree(query);

            if (c->argv) zfree(c->argv);
            c->argv = zmalloc(sizeof(robj*)*argc);
            if (c->argv == NULL) oom("allocating arguments list for client");

            for (j = 0; j < argc; j++) {
                if (sdslen(argv[j])) {
                    c->argv[c->argc] = createObject(REDIS_STRING,argv[j]);
                    c->argc++;
                } else {
                    sdsfree(argv[j]);
                }
            }
            zfree(argv);
            /* Execute the command. If the client is still valid
             * after processCommand() return and there is something
             * on the query buffer try to process the next command. */
            if (processCommand(c) && sdslen(c->querybuf)) goto again;
            return;
        } else if (sdslen(c->querybuf) >= 1024*32) {
            redisLog(REDIS_DEBUG, "Client protocol error");
            freeClient(c);
            return;
        }
    } else {
        /* Bulk read handling. Note that if we are at this point
           the client already sent a command terminated with a newline,
           we are reading the bulk data that is actually the last
           argument of the command. */
        int qbl = sdslen(c->querybuf);

        if (c->bulklen <= qbl) {
            /* Copy everything but the final CRLF as final argument */
            c->argv[c->argc] = createStringObject(c->querybuf,c->bulklen-2);
            c->argc++;
            c->querybuf = sdsrange(c->querybuf,c->bulklen,-1);
            processCommand(c);
            return;
        }
    }
}

static int selectDb(redisClient *c, int id) {
    if (id < 0 || id >= server.dbnum)
        return REDIS_ERR;
    c->db = &server.db[id];
    return REDIS_OK;
}

static void *dupClientReplyValue(void *o) {
    incrRefCount((robj*)o);
    return 0;
}

static redisClient *createClient(int fd) {
    redisClient *c = zmalloc(sizeof(*c));

    anetNonBlock(NULL,fd);
    anetTcpNoDelay(NULL,fd);
    if (!c) return NULL;
    selectDb(c,0);
    c->fd = fd;
    c->querybuf = sdsempty();
    c->argc = 0;
    c->argv = NULL;
    c->bulklen = -1;
    c->sentlen = 0;
    c->flags = 0;
    c->lastinteraction = time(NULL);
    c->authenticated = 0;
    c->replstate = REDIS_REPL_NONE;
    if ((c->reply = listCreate()) == NULL) oom("listCreate");
    listSetFreeMethod(c->reply,decrRefCount);
    listSetDupMethod(c->reply,dupClientReplyValue);
    if (aeCreateFileEvent(server.el, c->fd, AE_READABLE,
        readQueryFromClient, c, NULL) == AE_ERR) {
        freeClient(c);
        return NULL;
    }
    if (!listAddNodeTail(server.clients,c)) oom("listAddNodeTail");
    return c;
}

static void addReply(redisClient *c, robj *obj) {
    if (listLength(c->reply) == 0 &&
        (c->replstate == REDIS_REPL_NONE ||
         c->replstate == REDIS_REPL_ONLINE) &&
        aeCreateFileEvent(server.el, c->fd, AE_WRITABLE,
        sendReplyToClient, c, NULL) == AE_ERR) return;
    if (!listAddNodeTail(c->reply,obj)) oom("listAddNodeTail");
    incrRefCount(obj);
}

static void addReplySds(redisClient *c, sds s) {
    robj *o = createObject(REDIS_STRING,s);
    addReply(c,o);
    decrRefCount(o);
}

static void acceptHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
    int cport, cfd;
    char cip[128];
    redisClient *c;
    REDIS_NOTUSED(el);
    REDIS_NOTUSED(mask);
    REDIS_NOTUSED(privdata);

    cfd = anetAccept(server.neterr, fd, cip, &cport);
    if (cfd == AE_ERR) {
        redisLog(REDIS_DEBUG,"Accepting client connection: %s", server.neterr);
        return;
    }
    redisLog(REDIS_DEBUG,"Accepted %s:%d", cip, cport);
    if ((c = createClient(cfd)) == NULL) {
        redisLog(REDIS_WARNING,"Error allocating resoures for the client");
        close(cfd); /* May be already closed, just ingore errors */
        return;
    }
    /* If maxclient directive is set and this is one client more... close the
     * connection. Note that we create the client instead to check before
     * for this condition, since now the socket is already set in nonblocking
     * mode and we can send an error for free using the Kernel I/O */
    if (server.maxclients && listLength(server.clients) > server.maxclients) {
        char *err = "-ERR max number of clients reached\r\n";

        /* That's a best effort error message, don't check write errors */
        (void) write(c->fd,err,strlen(err));
        freeClient(c);
        return;
    }
    server.stat_numconnections++;
}

/* ======================= Redis objects implementation ===================== */

static robj *createObject(int type, void *ptr) {
    robj *o;

    if (listLength(server.objfreelist)) {
        listNode *head = listFirst(server.objfreelist);
        o = listNodeValue(head);
        listDelNode(server.objfreelist,head);
    } else {
        o = zmalloc(sizeof(*o));
    }
    if (!o) oom("createObject");
    o->type = type;
    o->ptr = ptr;
    o->refcount = 1;
    return o;
}

static robj *createStringObject(char *ptr, size_t len) {
    return createObject(REDIS_STRING,sdsnewlen(ptr,len));
}

static robj *createListObject(void) {
    list *l = listCreate();

    if (!l) oom("listCreate");
    listSetFreeMethod(l,decrRefCount);
    return createObject(REDIS_LIST,l);
}

static robj *createSetObject(void) {
    dict *d = dictCreate(&setDictType,NULL);
    if (!d) oom("dictCreate");
    return createObject(REDIS_SET,d);
}

static void freeStringObject(robj *o) {
    sdsfree(o->ptr);
}

static void freeListObject(robj *o) {
    listRelease((list*) o->ptr);
}

static void freeSetObject(robj *o) {
    dictRelease((dict*) o->ptr);
}

static void freeHashObject(robj *o) {
    dictRelease((dict*) o->ptr);
}

static void incrRefCount(robj *o) {
    o->refcount++;
#ifdef DEBUG_REFCOUNT
    if (o->type == REDIS_STRING)
        printf("Increment '%s'(%p), now is: %d\n",o->ptr,o,o->refcount);
#endif
}

static void decrRefCount(void *obj) {
    robj *o = obj;

#ifdef DEBUG_REFCOUNT
    if (o->type == REDIS_STRING)
        printf("Decrement '%s'(%p), now is: %d\n",o->ptr,o,o->refcount-1);
#endif
    if (--(o->refcount) == 0) {
        switch(o->type) {
        case REDIS_STRING: freeStringObject(o); break;
        case REDIS_LIST: freeListObject(o); break;
        case REDIS_SET: freeSetObject(o); break;
        case REDIS_HASH: freeHashObject(o); break;
        default: assert(0 != 0); break;
        }
        if (listLength(server.objfreelist) > REDIS_OBJFREELIST_MAX ||
            !listAddNodeHead(server.objfreelist,o))
            zfree(o);
    }
}

/* Try to share an object against the shared objects pool */
static robj *tryObjectSharing(robj *o) {
    struct dictEntry *de;
    unsigned long c;

    if (o == NULL || server.shareobjects == 0) return o;

    assert(o->type == REDIS_STRING);
    de = dictFind(server.sharingpool,o);
    if (de) {
        robj *shared = dictGetEntryKey(de);

        c = ((unsigned long) dictGetEntryVal(de))+1;
        dictGetEntryVal(de) = (void*) c;
        incrRefCount(shared);
        decrRefCount(o);
        return shared;
    } else {
        /* Here we are using a stream algorihtm: Every time an object is
         * shared we increment its count, everytime there is a miss we
         * recrement the counter of a random object. If this object reaches
         * zero we remove the object and put the current object instead. */
        if (dictSize(server.sharingpool) >=
                server.sharingpoolsize) {
            de = dictGetRandomKey(server.sharingpool);
            assert(de != NULL);
            c = ((unsigned long) dictGetEntryVal(de))-1;
            dictGetEntryVal(de) = (void*) c;
            if (c == 0) {
                dictDelete(server.sharingpool,de->key);
            }
        } else {
            c = 0; /* If the pool is empty we want to add this object */
        }
        if (c == 0) {
            int retval;

            retval = dictAdd(server.sharingpool,o,(void*)1);
            assert(retval == DICT_OK);
            incrRefCount(o);
        }
        return o;
    }
}

static robj *lookupKey(redisDb *db, robj *key) {
    dictEntry *de = dictFind(db->dict,key);
    return de ? dictGetEntryVal(de) : NULL;
}

static robj *lookupKeyRead(redisDb *db, robj *key) {
    expireIfNeeded(db,key);
    return lookupKey(db,key);
}

static robj *lookupKeyWrite(redisDb *db, robj *key) {
    deleteIfVolatile(db,key);
    return lookupKey(db,key);
}

static int deleteKey(redisDb *db, robj *key) {
    int retval;

    /* We need to protect key from destruction: after the first dictDelete()
     * it may happen that 'key' is no longer valid if we don't increment
     * it's count. This may happen when we get the object reference directly
     * from the hash table with dictRandomKey() or dict iterators */
    incrRefCount(key);
    if (dictSize(db->expires)) dictDelete(db->expires,key);
    retval = dictDelete(db->dict,key);
    decrRefCount(key);

    return retval == DICT_OK;
}

/*============================ DB saving/loading ============================ */

static int rdbSaveType(FILE *fp, unsigned char type) {
    if (fwrite(&type,1,1,fp) == 0) return -1;
    return 0;
}

static int rdbSaveTime(FILE *fp, time_t t) {
    int32_t t32 = (int32_t) t;
    if (fwrite(&t32,4,1,fp) == 0) return -1;
    return 0;
}

/* check rdbLoadLen() comments for more info */
static int rdbSaveLen(FILE *fp, uint32_t len) {
    unsigned char buf[2];

    if (len < (1<<6)) {
        /* Save a 6 bit len */
        buf[0] = (len&0xFF)|(REDIS_RDB_6BITLEN<<6);
        if (fwrite(buf,1,1,fp) == 0) return -1;
    } else if (len < (1<<14)) {
        /* Save a 14 bit len */
        buf[0] = ((len>>8)&0xFF)|(REDIS_RDB_14BITLEN<<6);
        buf[1] = len&0xFF;
        if (fwrite(buf,2,1,fp) == 0) return -1;
    } else {
        /* Save a 32 bit len */
        buf[0] = (REDIS_RDB_32BITLEN<<6);
        if (fwrite(buf,1,1,fp) == 0) return -1;
        len = htonl(len);
        if (fwrite(&len,4,1,fp) == 0) return -1;
    }
    return 0;
}

/* String objects in the form "2391" "-100" without any space and with a
 * range of values that can fit in an 8, 16 or 32 bit signed value can be
 * encoded as integers to save space */
int rdbTryIntegerEncoding(sds s, unsigned char *enc) {
    long long value;
    char *endptr, buf[32];

    /* Check if it's possible to encode this value as a number */
    value = strtoll(s, &endptr, 10);
    if (endptr[0] != '\0') return 0;
    snprintf(buf,32,"%lld",value);

    /* If the number converted back into a string is not identical
     * then it's not possible to encode the string as integer */
    if (strlen(buf) != sdslen(s) || memcmp(buf,s,sdslen(s))) return 0;

    /* Finally check if it fits in our ranges */
    if (value >= -(1<<7) && value <= (1<<7)-1) {
        enc[0] = (REDIS_RDB_ENCVAL<<6)|REDIS_RDB_ENC_INT8;
        enc[1] = value&0xFF;
        return 2;
    } else if (value >= -(1<<15) && value <= (1<<15)-1) {
        enc[0] = (REDIS_RDB_ENCVAL<<6)|REDIS_RDB_ENC_INT16;
        enc[1] = value&0xFF;
        enc[2] = (value>>8)&0xFF;
        return 3;
    } else if (value >= -((long long)1<<31) && value <= ((long long)1<<31)-1) {
        enc[0] = (REDIS_RDB_ENCVAL<<6)|REDIS_RDB_ENC_INT32;
        enc[1] = value&0xFF;
        enc[2] = (value>>8)&0xFF;
        enc[3] = (value>>16)&0xFF;
        enc[4] = (value>>24)&0xFF;
        return 5;
    } else {
        return 0;
    }
}

static int rdbSaveLzfStringObject(FILE *fp, robj *obj) {
    unsigned int comprlen, outlen;
    unsigned char byte;
    void *out;

    /* We require at least four bytes compression for this to be worth it */
    outlen = sdslen(obj->ptr)-4;
    if (outlen <= 0) return 0;
    if ((out = zmalloc(outlen+1)) == NULL) return 0;
    comprlen = lzf_compress(obj->ptr, sdslen(obj->ptr), out, outlen);
    if (comprlen == 0) {
        zfree(out);
        return 0;
    }
    /* Data compressed! Let's save it on disk */
    byte = (REDIS_RDB_ENCVAL<<6)|REDIS_RDB_ENC_LZF;
    if (fwrite(&byte,1,1,fp) == 0) goto writeerr;
    if (rdbSaveLen(fp,comprlen) == -1) goto writeerr;
    if (rdbSaveLen(fp,sdslen(obj->ptr)) == -1) goto writeerr;
    if (fwrite(out,comprlen,1,fp) == 0) goto writeerr;
    zfree(out);
    return comprlen;

writeerr:
    zfree(out);
    return -1;
}

/* Save a string objet as [len][data] on disk. If the object is a string
 * representation of an integer value we try to safe it in a special form */
static int rdbSaveStringObject(FILE *fp, robj *obj) {
    size_t len = sdslen(obj->ptr);
    int enclen;

    /* Try integer encoding */
    if (len <= 11) {
        unsigned char buf[5];
        if ((enclen = rdbTryIntegerEncoding(obj->ptr,buf)) > 0) {
            if (fwrite(buf,enclen,1,fp) == 0) return -1;
            return 0;
        }
    }

    /* Try LZF compression - under 20 bytes it's unable to compress even
     * aaaaaaaaaaaaaaaaaa so skip it */
    if (1 && len > 20) {
        int retval;

        retval = rdbSaveLzfStringObject(fp,obj);
        if (retval == -1) return -1;
        if (retval > 0) return 0;
        /* retval == 0 means data can't be compressed, save the old way */
    }

    /* Store verbatim */
    if (rdbSaveLen(fp,len) == -1) return -1;
    if (len && fwrite(obj->ptr,len,1,fp) == 0) return -1;
    return 0;
}

/* Save the DB on disk. Return REDIS_ERR on error, REDIS_OK on success */
static int rdbSave(char *filename) {
    dictIterator *di = NULL;
    dictEntry *de;
    FILE *fp;
    char tmpfile[256];
    int j;
    time_t now = time(NULL);

    snprintf(tmpfile,256,"temp-%d.%ld.rdb",(int)time(NULL),(long int)random());
    fp = fopen(tmpfile,"w");
    if (!fp) {
        redisLog(REDIS_WARNING, "Failed saving the DB: %s", strerror(errno));
        return REDIS_ERR;
    }
    if (fwrite("REDIS0001",9,1,fp) == 0) goto werr;
    for (j = 0; j < server.dbnum; j++) {
        redisDb *db = server.db+j;
        dict *d = db->dict;
        if (dictSize(d) == 0) continue;
        di = dictGetIterator(d);
        if (!di) {
            fclose(fp);
            return REDIS_ERR;
        }

        /* Write the SELECT DB opcode */
        if (rdbSaveType(fp,REDIS_SELECTDB) == -1) goto werr;
        if (rdbSaveLen(fp,j) == -1) goto werr;

        /* Iterate this DB writing every entry */
        while((de = dictNext(di)) != NULL) {
            robj *key = dictGetEntryKey(de);
            robj *o = dictGetEntryVal(de);
            time_t expiretime = getExpire(db,key);

            /* Save the expire time */
            if (expiretime != -1) {
                /* If this key is already expired skip it */
                if (expiretime < now) continue;
                if (rdbSaveType(fp,REDIS_EXPIRETIME) == -1) goto werr;
                if (rdbSaveTime(fp,expiretime) == -1) goto werr;
            }
            /* Save the key and associated value */
            if (rdbSaveType(fp,o->type) == -1) goto werr;
            if (rdbSaveStringObject(fp,key) == -1) goto werr;
            if (o->type == REDIS_STRING) {
                /* Save a string value */
                if (rdbSaveStringObject(fp,o) == -1) goto werr;
            } else if (o->type == REDIS_LIST) {
                /* Save a list value */
                list *list = o->ptr;
                listNode *ln;

                listRewind(list);
                if (rdbSaveLen(fp,listLength(list)) == -1) goto werr;
                while((ln = listYield(list))) {
                    robj *eleobj = listNodeValue(ln);

                    if (rdbSaveStringObject(fp,eleobj) == -1) goto werr;
                }
            } else if (o->type == REDIS_SET) {
                /* Save a set value */
                dict *set = o->ptr;
                dictIterator *di = dictGetIterator(set);
                dictEntry *de;

                if (!set) oom("dictGetIteraotr");
                if (rdbSaveLen(fp,dictSize(set)) == -1) goto werr;
                while((de = dictNext(di)) != NULL) {
                    robj *eleobj = dictGetEntryKey(de);

                    if (rdbSaveStringObject(fp,eleobj) == -1) goto werr;
                }
                dictReleaseIterator(di);
            } else {
                assert(0 != 0);
            }
        }
        dictReleaseIterator(di);
    }
    /* EOF opcode */
    if (rdbSaveType(fp,REDIS_EOF) == -1) goto werr;

    /* Make sure data will not remain on the OS's output buffers */
    fflush(fp);
    fsync(fileno(fp));
    fclose(fp);
    
    /* Use RENAME to make sure the DB file is changed atomically only
     * if the generate DB file is ok. */
    if (rename(tmpfile,filename) == -1) {
        redisLog(REDIS_WARNING,"Error moving temp DB file on the final destionation: %s", strerror(errno));
        unlink(tmpfile);
        return REDIS_ERR;
    }
    redisLog(REDIS_NOTICE,"DB saved on disk");
    server.dirty = 0;
    server.lastsave = time(NULL);
    return REDIS_OK;

werr:
    fclose(fp);
    unlink(tmpfile);
    redisLog(REDIS_WARNING,"Write error saving DB on disk: %s", strerror(errno));
    if (di) dictReleaseIterator(di);
    return REDIS_ERR;
}

static int rdbSaveBackground(char *filename) {
    pid_t childpid;

    if (server.bgsaveinprogress) return REDIS_ERR;
    if ((childpid = fork()) == 0) {
        /* Child */
        close(server.fd);
        if (rdbSave(filename) == REDIS_OK) {
            exit(0);
        } else {
            exit(1);
        }
    } else {
        /* Parent */
        if (childpid == -1) {
            redisLog(REDIS_WARNING,"Can't save in background: fork: %s",
                strerror(errno));
            return REDIS_ERR;
        }
        redisLog(REDIS_NOTICE,"Background saving started by pid %d",childpid);
        server.bgsaveinprogress = 1;
        server.bgsavechildpid = childpid;
        return REDIS_OK;
    }
    return REDIS_OK; /* unreached */
}

static int rdbLoadType(FILE *fp) {
    unsigned char type;
    if (fread(&type,1,1,fp) == 0) return -1;
    return type;
}

static time_t rdbLoadTime(FILE *fp) {
    int32_t t32;
    if (fread(&t32,4,1,fp) == 0) return -1;
    return (time_t) t32;
}

/* Load an encoded length from the DB, see the REDIS_RDB_* defines on the top
 * of this file for a description of how this are stored on disk.
 *
 * isencoded is set to 1 if the readed length is not actually a length but
 * an "encoding type", check the above comments for more info */
static uint32_t rdbLoadLen(FILE *fp, int rdbver, int *isencoded) {
    unsigned char buf[2];
    uint32_t len;

    if (isencoded) *isencoded = 0;
    if (rdbver == 0) {
        if (fread(&len,4,1,fp) == 0) return REDIS_RDB_LENERR;
        return ntohl(len);
    } else {
        int type;

        if (fread(buf,1,1,fp) == 0) return REDIS_RDB_LENERR;
        type = (buf[0]&0xC0)>>6;
        if (type == REDIS_RDB_6BITLEN) {
            /* Read a 6 bit len */
            return buf[0]&0x3F;
        } else if (type == REDIS_RDB_ENCVAL) {
            /* Read a 6 bit len encoding type */
            if (isencoded) *isencoded = 1;
            return buf[0]&0x3F;
        } else if (type == REDIS_RDB_14BITLEN) {
            /* Read a 14 bit len */
            if (fread(buf+1,1,1,fp) == 0) return REDIS_RDB_LENERR;
            return ((buf[0]&0x3F)<<8)|buf[1];
        } else {
            /* Read a 32 bit len */
            if (fread(&len,4,1,fp) == 0) return REDIS_RDB_LENERR;
            return ntohl(len);
        }
    }
}

static robj *rdbLoadIntegerObject(FILE *fp, int enctype) {
    unsigned char enc[4];
    long long val;

    if (enctype == REDIS_RDB_ENC_INT8) {
        if (fread(enc,1,1,fp) == 0) return NULL;
        val = (signed char)enc[0];
    } else if (enctype == REDIS_RDB_ENC_INT16) {
        uint16_t v;
        if (fread(enc,2,1,fp) == 0) return NULL;
        v = enc[0]|(enc[1]<<8);
        val = (int16_t)v;
    } else if (enctype == REDIS_RDB_ENC_INT32) {
        uint32_t v;
        if (fread(enc,4,1,fp) == 0) return NULL;
        v = enc[0]|(enc[1]<<8)|(enc[2]<<16)|(enc[3]<<24);
        val = (int32_t)v;
    } else {
        val = 0; /* anti-warning */
        assert(0!=0);
    }
    return createObject(REDIS_STRING,sdscatprintf(sdsempty(),"%lld",val));
}

static robj *rdbLoadLzfStringObject(FILE*fp, int rdbver) {
    unsigned int len, clen;
    unsigned char *c = NULL;
    sds val = NULL;

    if ((clen = rdbLoadLen(fp,rdbver,NULL)) == REDIS_RDB_LENERR) return NULL;
    if ((len = rdbLoadLen(fp,rdbver,NULL)) == REDIS_RDB_LENERR) return NULL;
    if ((c = zmalloc(clen)) == NULL) goto err;
    if ((val = sdsnewlen(NULL,len)) == NULL) goto err;
    if (fread(c,clen,1,fp) == 0) goto err;
    if (lzf_decompress(c,clen,val,len) == 0) goto err;
    zfree(c);
    return createObject(REDIS_STRING,val);
err:
    zfree(c);
    sdsfree(val);
    return NULL;
}

static robj *rdbLoadStringObject(FILE*fp, int rdbver) {
    int isencoded;
    uint32_t len;
    sds val;

    len = rdbLoadLen(fp,rdbver,&isencoded);
    if (isencoded) {
        switch(len) {
        case REDIS_RDB_ENC_INT8:
        case REDIS_RDB_ENC_INT16:
        case REDIS_RDB_ENC_INT32:
            return tryObjectSharing(rdbLoadIntegerObject(fp,len));
        case REDIS_RDB_ENC_LZF:
            return tryObjectSharing(rdbLoadLzfStringObject(fp,rdbver));
        default:
            assert(0!=0);
        }
    }

    if (len == REDIS_RDB_LENERR) return NULL;
    val = sdsnewlen(NULL,len);
    if (len && fread(val,len,1,fp) == 0) {
        sdsfree(val);
        return NULL;
    }
    return tryObjectSharing(createObject(REDIS_STRING,val));
}

static int rdbLoad(char *filename) {
    FILE *fp;
    robj *keyobj = NULL;
    uint32_t dbid;
    int type, retval, rdbver;
    dict *d = server.db[0].dict;
    redisDb *db = server.db+0;
    char buf[1024];
    time_t expiretime = -1, now = time(NULL);

    fp = fopen(filename,"r");
    if (!fp) return REDIS_ERR;
    if (fread(buf,9,1,fp) == 0) goto eoferr;
    buf[9] = '\0';
    if (memcmp(buf,"REDIS",5) != 0) {
        fclose(fp);
        redisLog(REDIS_WARNING,"Wrong signature trying to load DB from file");
        return REDIS_ERR;
    }
    rdbver = atoi(buf+5);
    if (rdbver > 1) {
        fclose(fp);
        redisLog(REDIS_WARNING,"Can't handle RDB format version %d",rdbver);
        return REDIS_ERR;
    }
    while(1) {
        robj *o;

        /* Read type. */
        if ((type = rdbLoadType(fp)) == -1) goto eoferr;
        if (type == REDIS_EXPIRETIME) {
            if ((expiretime = rdbLoadTime(fp)) == -1) goto eoferr;
            /* We read the time so we need to read the object type again */
            if ((type = rdbLoadType(fp)) == -1) goto eoferr;
        }
        if (type == REDIS_EOF) break;
        /* Handle SELECT DB opcode as a special case */
        if (type == REDIS_SELECTDB) {
            if ((dbid = rdbLoadLen(fp,rdbver,NULL)) == REDIS_RDB_LENERR)
                goto eoferr;
            if (dbid >= (unsigned)server.dbnum) {
                redisLog(REDIS_WARNING,"FATAL: Data file was created with a Redis server configured to handle more than %d databases. Exiting\n", server.dbnum);
                exit(1);
            }
            db = server.db+dbid;
            d = db->dict;
            continue;
        }
        /* Read key */
        if ((keyobj = rdbLoadStringObject(fp,rdbver)) == NULL) goto eoferr;

        if (type == REDIS_STRING) {
            /* Read string value */
            if ((o = rdbLoadStringObject(fp,rdbver)) == NULL) goto eoferr;
        } else if (type == REDIS_LIST || type == REDIS_SET) {
            /* Read list/set value */
            uint32_t listlen;

            if ((listlen = rdbLoadLen(fp,rdbver,NULL)) == REDIS_RDB_LENERR)
                goto eoferr;
            o = (type == REDIS_LIST) ? createListObject() : createSetObject();
            /* Load every single element of the list/set */
            while(listlen--) {
                robj *ele;

                if ((ele = rdbLoadStringObject(fp,rdbver)) == NULL) goto eoferr;
                if (type == REDIS_LIST) {
                    if (!listAddNodeTail((list*)o->ptr,ele))
                        oom("listAddNodeTail");
                } else {
                    if (dictAdd((dict*)o->ptr,ele,NULL) == DICT_ERR)
                        oom("dictAdd");
                }
            }
        } else {
            assert(0 != 0);
        }
        /* Add the new object in the hash table */
        retval = dictAdd(d,keyobj,o);
        if (retval == DICT_ERR) {
            redisLog(REDIS_WARNING,"Loading DB, duplicated key (%s) found! Unrecoverable error, exiting now.", keyobj->ptr);
            exit(1);
        }
        /* Set the expire time if needed */
        if (expiretime != -1) {
            setExpire(db,keyobj,expiretime);
            /* Delete this key if already expired */
            if (expiretime < now) deleteKey(db,keyobj);
            expiretime = -1;
        }
        keyobj = o = NULL;
    }
    fclose(fp);
    return REDIS_OK;

eoferr: /* unexpected end of file is handled here with a fatal exit */
    if (keyobj) decrRefCount(keyobj);
    redisLog(REDIS_WARNING,"Short read or OOM loading DB. Unrecoverable error, exiting now.");
    exit(1);
    return REDIS_ERR; /* Just to avoid warning */
}

/*================================== Commands =============================== */

static void authCommand(redisClient *c) {
    if (!server.requirepass || !strcmp(c->argv[1]->ptr, server.requirepass)) {
      c->authenticated = 1;
      addReply(c,shared.ok);
    } else {
      c->authenticated = 0;
      addReply(c,shared.err);
    }
}

static void pingCommand(redisClient *c) {
    addReply(c,shared.pong);
}

static void echoCommand(redisClient *c) {
    addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",
        (int)sdslen(c->argv[1]->ptr)));
    addReply(c,c->argv[1]);
    addReply(c,shared.crlf);
}

/*=================================== Strings =============================== */

static void setGenericCommand(redisClient *c, int nx) {
    int retval;

    retval = dictAdd(c->db->dict,c->argv[1],c->argv[2]);
    if (retval == DICT_ERR) {
        if (!nx) {
            dictReplace(c->db->dict,c->argv[1],c->argv[2]);
            incrRefCount(c->argv[2]);
        } else {
            addReply(c,shared.czero);
            return;
        }
    } else {
        incrRefCount(c->argv[1]);
        incrRefCount(c->argv[2]);
    }
    server.dirty++;
    removeExpire(c->db,c->argv[1]);
    addReply(c, nx ? shared.cone : shared.ok);
}

static void setCommand(redisClient *c) {
    setGenericCommand(c,0);
}

static void setnxCommand(redisClient *c) {
    setGenericCommand(c,1);
}

static void getCommand(redisClient *c) {
    robj *o = lookupKeyRead(c->db,c->argv[1]);

    if (o == NULL) {
        addReply(c,shared.nullbulk);
    } else {
        if (o->type != REDIS_STRING) {
            addReply(c,shared.wrongtypeerr);
        } else {
            addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",(int)sdslen(o->ptr)));
            addReply(c,o);
            addReply(c,shared.crlf);
        }
    }
}

static void getSetCommand(redisClient *c) {
    getCommand(c);
    if (dictAdd(c->db->dict,c->argv[1],c->argv[2]) == DICT_ERR) {
        dictReplace(c->db->dict,c->argv[1],c->argv[2]);
    } else {
        incrRefCount(c->argv[1]);
    }
    incrRefCount(c->argv[2]);
    server.dirty++;
    removeExpire(c->db,c->argv[1]);
}

static void mgetCommand(redisClient *c) {
    int j;
  
    addReplySds(c,sdscatprintf(sdsempty(),"*%d\r\n",c->argc-1));
    for (j = 1; j < c->argc; j++) {
        robj *o = lookupKeyRead(c->db,c->argv[j]);
        if (o == NULL) {
            addReply(c,shared.nullbulk);
        } else {
            if (o->type != REDIS_STRING) {
                addReply(c,shared.nullbulk);
            } else {
                addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",(int)sdslen(o->ptr)));
                addReply(c,o);
                addReply(c,shared.crlf);
            }
        }
    }
}

static void incrDecrCommand(redisClient *c, long long incr) {
    long long value;
    int retval;
    robj *o;
    
    o = lookupKeyWrite(c->db,c->argv[1]);
    if (o == NULL) {
        value = 0;
    } else {
        if (o->type != REDIS_STRING) {
            value = 0;
        } else {
            char *eptr;

            value = strtoll(o->ptr, &eptr, 10);
        }
    }

    value += incr;
    o = createObject(REDIS_STRING,sdscatprintf(sdsempty(),"%lld",value));
    retval = dictAdd(c->db->dict,c->argv[1],o);
    if (retval == DICT_ERR) {
        dictReplace(c->db->dict,c->argv[1],o);
        removeExpire(c->db,c->argv[1]);
    } else {
        incrRefCount(c->argv[1]);
    }
    server.dirty++;
    addReply(c,shared.colon);
    addReply(c,o);
    addReply(c,shared.crlf);
}

static void incrCommand(redisClient *c) {
    incrDecrCommand(c,1);
}

static void decrCommand(redisClient *c) {
    incrDecrCommand(c,-1);
}

static void incrbyCommand(redisClient *c) {
    long long incr = strtoll(c->argv[2]->ptr, NULL, 10);
    incrDecrCommand(c,incr);
}

static void decrbyCommand(redisClient *c) {
    long long incr = strtoll(c->argv[2]->ptr, NULL, 10);
    incrDecrCommand(c,-incr);
}

/* ========================= Type agnostic commands ========================= */

static void delCommand(redisClient *c) {
    int deleted = 0, j;

    for (j = 1; j < c->argc; j++) {
        if (deleteKey(c->db,c->argv[j])) {
            server.dirty++;
            deleted++;
        }
    }
    switch(deleted) {
    case 0:
        addReply(c,shared.czero);
        break;
    case 1:
        addReply(c,shared.cone);
        break;
    default:
        addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",deleted));
        break;
    }
}

static void existsCommand(redisClient *c) {
    addReply(c,lookupKeyRead(c->db,c->argv[1]) ? shared.cone : shared.czero);
}

static void selectCommand(redisClient *c) {
    int id = atoi(c->argv[1]->ptr);
    
    if (selectDb(c,id) == REDIS_ERR) {
        addReplySds(c,sdsnew("-ERR invalid DB index\r\n"));
    } else {
        addReply(c,shared.ok);
    }
}

static void randomkeyCommand(redisClient *c) {
    dictEntry *de;
   
    while(1) {
        de = dictGetRandomKey(c->db->dict);
        if (!de || expireIfNeeded(c->db,dictGetEntryKey(de)) == 0) break;
    }
    if (de == NULL) {
        addReply(c,shared.plus);
        addReply(c,shared.crlf);
    } else {
        addReply(c,shared.plus);
        addReply(c,dictGetEntryKey(de));
        addReply(c,shared.crlf);
    }
}

static void keysCommand(redisClient *c) {
    dictIterator *di;
    dictEntry *de;
    sds pattern = c->argv[1]->ptr;
    int plen = sdslen(pattern);
    int numkeys = 0, keyslen = 0;
    robj *lenobj = createObject(REDIS_STRING,NULL);

    di = dictGetIterator(c->db->dict);
    if (!di) oom("dictGetIterator");
    addReply(c,lenobj);
    decrRefCount(lenobj);
    while((de = dictNext(di)) != NULL) {
        robj *keyobj = dictGetEntryKey(de);

        sds key = keyobj->ptr;
        if ((pattern[0] == '*' && pattern[1] == '\0') ||
            stringmatchlen(pattern,plen,key,sdslen(key),0)) {
            if (expireIfNeeded(c->db,keyobj) == 0) {
                if (numkeys != 0)
                    addReply(c,shared.space);
                addReply(c,keyobj);
                numkeys++;
                keyslen += sdslen(key);
            }
        }
    }
    dictReleaseIterator(di);
    lenobj->ptr = sdscatprintf(sdsempty(),"$%lu\r\n",keyslen+(numkeys ? (numkeys-1) : 0));
    addReply(c,shared.crlf);
}

static void dbsizeCommand(redisClient *c) {
    addReplySds(c,
        sdscatprintf(sdsempty(),":%lu\r\n",dictSize(c->db->dict)));
}

static void lastsaveCommand(redisClient *c) {
    addReplySds(c,
        sdscatprintf(sdsempty(),":%lu\r\n",server.lastsave));
}

static void typeCommand(redisClient *c) {
    robj *o;
    char *type;

    o = lookupKeyRead(c->db,c->argv[1]);
    if (o == NULL) {
        type = "+none";
    } else {
        switch(o->type) {
        case REDIS_STRING: type = "+string"; break;
        case REDIS_LIST: type = "+list"; break;
        case REDIS_SET: type = "+set"; break;
        default: type = "unknown"; break;
        }
    }
    addReplySds(c,sdsnew(type));
    addReply(c,shared.crlf);
}

static void saveCommand(redisClient *c) {
    if (server.bgsaveinprogress) {
        addReplySds(c,sdsnew("-ERR background save in progress\r\n"));
        return;
    }
    if (rdbSave(server.dbfilename) == REDIS_OK) {
        addReply(c,shared.ok);
    } else {
        addReply(c,shared.err);
    }
}

static void bgsaveCommand(redisClient *c) {
    if (server.bgsaveinprogress) {
        addReplySds(c,sdsnew("-ERR background save already in progress\r\n"));
        return;
    }
    if (rdbSaveBackground(server.dbfilename) == REDIS_OK) {
        addReply(c,shared.ok);
    } else {
        addReply(c,shared.err);
    }
}

static void shutdownCommand(redisClient *c) {
    redisLog(REDIS_WARNING,"User requested shutdown, saving DB...");
    if (server.bgsaveinprogress) {
        redisLog(REDIS_WARNING,"There is a live saving child. Killing it!");
        kill(server.bgsavechildpid,SIGKILL);
    }
    if (rdbSave(server.dbfilename) == REDIS_OK) {
        if (server.daemonize)
            unlink(server.pidfile);
        redisLog(REDIS_WARNING,"%zu bytes used at exit",zmalloc_used_memory());
        redisLog(REDIS_WARNING,"Server exit now, bye bye...");
        exit(1);
    } else {
        redisLog(REDIS_WARNING,"Error trying to save the DB, can't exit"); 
        addReplySds(c,sdsnew("-ERR can't quit, problems saving the DB\r\n"));
    }
}

static void renameGenericCommand(redisClient *c, int nx) {
    robj *o;

    /* To use the same key as src and dst is probably an error */
    if (sdscmp(c->argv[1]->ptr,c->argv[2]->ptr) == 0) {
        addReply(c,shared.sameobjecterr);
        return;
    }

    o = lookupKeyWrite(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.nokeyerr);
        return;
    }
    incrRefCount(o);
    deleteIfVolatile(c->db,c->argv[2]);
    if (dictAdd(c->db->dict,c->argv[2],o) == DICT_ERR) {
        if (nx) {
            decrRefCount(o);
            addReply(c,shared.czero);
            return;
        }
        dictReplace(c->db->dict,c->argv[2],o);
    } else {
        incrRefCount(c->argv[2]);
    }
    deleteKey(c->db,c->argv[1]);
    server.dirty++;
    addReply(c,nx ? shared.cone : shared.ok);
}

static void renameCommand(redisClient *c) {
    renameGenericCommand(c,0);
}

static void renamenxCommand(redisClient *c) {
    renameGenericCommand(c,1);
}

static void moveCommand(redisClient *c) {
    robj *o;
    redisDb *src, *dst;
    int srcid;

    /* Obtain source and target DB pointers */
    src = c->db;
    srcid = c->db->id;
    if (selectDb(c,atoi(c->argv[2]->ptr)) == REDIS_ERR) {
        addReply(c,shared.outofrangeerr);
        return;
    }
    dst = c->db;
    selectDb(c,srcid); /* Back to the source DB */

    /* If the user is moving using as target the same
     * DB as the source DB it is probably an error. */
    if (src == dst) {
        addReply(c,shared.sameobjecterr);
        return;
    }

    /* Check if the element exists and get a reference */
    o = lookupKeyWrite(c->db,c->argv[1]);
    if (!o) {
        addReply(c,shared.czero);
        return;
    }

    /* Try to add the element to the target DB */
    deleteIfVolatile(dst,c->argv[1]);
    if (dictAdd(dst->dict,c->argv[1],o) == DICT_ERR) {
        addReply(c,shared.czero);
        return;
    }
    incrRefCount(c->argv[1]);
    incrRefCount(o);

    /* OK! key moved, free the entry in the source DB */
    deleteKey(src,c->argv[1]);
    server.dirty++;
    addReply(c,shared.cone);
}

/* =================================== Lists ================================ */
static void pushGenericCommand(redisClient *c, int where) {
    robj *lobj;
    list *list;

    lobj = lookupKeyWrite(c->db,c->argv[1]);
    if (lobj == NULL) {
        lobj = createListObject();
        list = lobj->ptr;
        if (where == REDIS_HEAD) {
            if (!listAddNodeHead(list,c->argv[2])) oom("listAddNodeHead");
        } else {
            if (!listAddNodeTail(list,c->argv[2])) oom("listAddNodeTail");
        }
        dictAdd(c->db->dict,c->argv[1],lobj);
        incrRefCount(c->argv[1]);
        incrRefCount(c->argv[2]);
    } else {
        if (lobj->type != REDIS_LIST) {
            addReply(c,shared.wrongtypeerr);
            return;
        }
        list = lobj->ptr;
        if (where == REDIS_HEAD) {
            if (!listAddNodeHead(list,c->argv[2])) oom("listAddNodeHead");
        } else {
            if (!listAddNodeTail(list,c->argv[2])) oom("listAddNodeTail");
        }
        incrRefCount(c->argv[2]);
    }
    server.dirty++;
    addReply(c,shared.ok);
}

static void lpushCommand(redisClient *c) {
    pushGenericCommand(c,REDIS_HEAD);
}

static void rpushCommand(redisClient *c) {
    pushGenericCommand(c,REDIS_TAIL);
}

static void llenCommand(redisClient *c) {
    robj *o;
    list *l;
    
    o = lookupKeyRead(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.czero);
        return;
    } else {
        if (o->type != REDIS_LIST) {
            addReply(c,shared.wrongtypeerr);
        } else {
            l = o->ptr;
            addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",listLength(l)));
        }
    }
}

static void lindexCommand(redisClient *c) {
    robj *o;
    int index = atoi(c->argv[2]->ptr);
    
    o = lookupKeyRead(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.nullbulk);
    } else {
        if (o->type != REDIS_LIST) {
            addReply(c,shared.wrongtypeerr);
        } else {
            list *list = o->ptr;
            listNode *ln;
            
            ln = listIndex(list, index);
            if (ln == NULL) {
                addReply(c,shared.nullbulk);
            } else {
                robj *ele = listNodeValue(ln);
                addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",(int)sdslen(ele->ptr)));
                addReply(c,ele);
                addReply(c,shared.crlf);
            }
        }
    }
}

static void lsetCommand(redisClient *c) {
    robj *o;
    int index = atoi(c->argv[2]->ptr);
    
    o = lookupKeyWrite(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.nokeyerr);
    } else {
        if (o->type != REDIS_LIST) {
            addReply(c,shared.wrongtypeerr);
        } else {
            list *list = o->ptr;
            listNode *ln;
            
            ln = listIndex(list, index);
            if (ln == NULL) {
                addReply(c,shared.outofrangeerr);
            } else {
                robj *ele = listNodeValue(ln);

                decrRefCount(ele);
                listNodeValue(ln) = c->argv[3];
                incrRefCount(c->argv[3]);
                addReply(c,shared.ok);
                server.dirty++;
            }
        }
    }
}

static void popGenericCommand(redisClient *c, int where) {
    robj *o;

    o = lookupKeyWrite(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.nullbulk);
    } else {
        if (o->type != REDIS_LIST) {
            addReply(c,shared.wrongtypeerr);
        } else {
            list *list = o->ptr;
            listNode *ln;

            if (where == REDIS_HEAD)
                ln = listFirst(list);
            else
                ln = listLast(list);

            if (ln == NULL) {
                addReply(c,shared.nullbulk);
            } else {
                robj *ele = listNodeValue(ln);
                addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",(int)sdslen(ele->ptr)));
                addReply(c,ele);
                addReply(c,shared.crlf);
                listDelNode(list,ln);
                server.dirty++;
            }
        }
    }
}

static void lpopCommand(redisClient *c) {
    popGenericCommand(c,REDIS_HEAD);
}

static void rpopCommand(redisClient *c) {
    popGenericCommand(c,REDIS_TAIL);
}

static void lrangeCommand(redisClient *c) {
    robj *o;
    int start = atoi(c->argv[2]->ptr);
    int end = atoi(c->argv[3]->ptr);

    o = lookupKeyRead(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.nullmultibulk);
    } else {
        if (o->type != REDIS_LIST) {
            addReply(c,shared.wrongtypeerr);
        } else {
            list *list = o->ptr;
            listNode *ln;
            int llen = listLength(list);
            int rangelen, j;
            robj *ele;

            /* convert negative indexes */
            if (start < 0) start = llen+start;
            if (end < 0) end = llen+end;
            if (start < 0) start = 0;
            if (end < 0) end = 0;

            /* indexes sanity checks */
            if (start > end || start >= llen) {
                /* Out of range start or start > end result in empty list */
                addReply(c,shared.emptymultibulk);
                return;
            }
            if (end >= llen) end = llen-1;
            rangelen = (end-start)+1;

            /* Return the result in form of a multi-bulk reply */
            ln = listIndex(list, start);
            addReplySds(c,sdscatprintf(sdsempty(),"*%d\r\n",rangelen));
            for (j = 0; j < rangelen; j++) {
                ele = listNodeValue(ln);
                addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",(int)sdslen(ele->ptr)));
                addReply(c,ele);
                addReply(c,shared.crlf);
                ln = ln->next;
            }
        }
    }
}

static void ltrimCommand(redisClient *c) {
    robj *o;
    int start = atoi(c->argv[2]->ptr);
    int end = atoi(c->argv[3]->ptr);
    
    o = lookupKeyWrite(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.nokeyerr);
    } else {
        if (o->type != REDIS_LIST) {
            addReply(c,shared.wrongtypeerr);
        } else {
            list *list = o->ptr;
            listNode *ln;
            int llen = listLength(list);
            int j, ltrim, rtrim;

            /* convert negative indexes */
            if (start < 0) start = llen+start;
            if (end < 0) end = llen+end;
            if (start < 0) start = 0;
            if (end < 0) end = 0;

            /* indexes sanity checks */
            if (start > end || start >= llen) {
                /* Out of range start or start > end result in empty list */
                ltrim = llen;
                rtrim = 0;
            } else {
                if (end >= llen) end = llen-1;
                ltrim = start;
                rtrim = llen-end-1;
            }

            /* Remove list elements to perform the trim */
            for (j = 0; j < ltrim; j++) {
                ln = listFirst(list);
                listDelNode(list,ln);
            }
            for (j = 0; j < rtrim; j++) {
                ln = listLast(list);
                listDelNode(list,ln);
            }
            addReply(c,shared.ok);
            server.dirty++;
        }
    }
}

static void lremCommand(redisClient *c) {
    robj *o;
    
    o = lookupKeyWrite(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.czero);
    } else {
        if (o->type != REDIS_LIST) {
            addReply(c,shared.wrongtypeerr);
        } else {
            list *list = o->ptr;
            listNode *ln, *next;
            int toremove = atoi(c->argv[2]->ptr);
            int removed = 0;
            int fromtail = 0;

            if (toremove < 0) {
                toremove = -toremove;
                fromtail = 1;
            }
            ln = fromtail ? list->tail : list->head;
            while (ln) {
                robj *ele = listNodeValue(ln);

                next = fromtail ? ln->prev : ln->next;
                if (sdscmp(ele->ptr,c->argv[3]->ptr) == 0) {
                    listDelNode(list,ln);
                    server.dirty++;
                    removed++;
                    if (toremove && removed == toremove) break;
                }
                ln = next;
            }
            addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",removed));
        }
    }
}

/* ==================================== Sets ================================ */

static void saddCommand(redisClient *c) {
    robj *set;

    set = lookupKeyWrite(c->db,c->argv[1]);
    if (set == NULL) {
        set = createSetObject();
        dictAdd(c->db->dict,c->argv[1],set);
        incrRefCount(c->argv[1]);
    } else {
        if (set->type != REDIS_SET) {
            addReply(c,shared.wrongtypeerr);
            return;
        }
    }
    if (dictAdd(set->ptr,c->argv[2],NULL) == DICT_OK) {
        incrRefCount(c->argv[2]);
        server.dirty++;
        addReply(c,shared.cone);
    } else {
        addReply(c,shared.czero);
    }
}

static void sremCommand(redisClient *c) {
    robj *set;

    set = lookupKeyWrite(c->db,c->argv[1]);
    if (set == NULL) {
        addReply(c,shared.czero);
    } else {
        if (set->type != REDIS_SET) {
            addReply(c,shared.wrongtypeerr);
            return;
        }
        if (dictDelete(set->ptr,c->argv[2]) == DICT_OK) {
            server.dirty++;
            addReply(c,shared.cone);
        } else {
            addReply(c,shared.czero);
        }
    }
}

static void smoveCommand(redisClient *c) {
    robj *srcset, *dstset;

    srcset = lookupKeyWrite(c->db,c->argv[1]);
    dstset = lookupKeyWrite(c->db,c->argv[2]);

    /* If the source key does not exist return 0, if it's of the wrong type
     * raise an error */
    if (srcset == NULL || srcset->type != REDIS_SET) {
        addReply(c, srcset ? shared.wrongtypeerr : shared.czero);
        return;
    }
    /* Error if the destination key is not a set as well */
    if (dstset && dstset->type != REDIS_SET) {
        addReply(c,shared.wrongtypeerr);
        return;
    }
    /* Remove the element from the source set */
    if (dictDelete(srcset->ptr,c->argv[3]) == DICT_ERR) {
        /* Key not found in the src set! return zero */
        addReply(c,shared.czero);
        return;
    }
    server.dirty++;
    /* Add the element to the destination set */
    if (!dstset) {
        dstset = createSetObject();
        dictAdd(c->db->dict,c->argv[2],dstset);
        incrRefCount(c->argv[2]);
    }
    if (dictAdd(dstset->ptr,c->argv[3],NULL) == DICT_OK)
        incrRefCount(c->argv[3]);
    addReply(c,shared.cone);
}

static void sismemberCommand(redisClient *c) {
    robj *set;

    set = lookupKeyRead(c->db,c->argv[1]);
    if (set == NULL) {
        addReply(c,shared.czero);
    } else {
        if (set->type != REDIS_SET) {
            addReply(c,shared.wrongtypeerr);
            return;
        }
        if (dictFind(set->ptr,c->argv[2]))
            addReply(c,shared.cone);
        else
            addReply(c,shared.czero);
    }
}

static void scardCommand(redisClient *c) {
    robj *o;
    dict *s;
    
    o = lookupKeyRead(c->db,c->argv[1]);
    if (o == NULL) {
        addReply(c,shared.czero);
        return;
    } else {
        if (o->type != REDIS_SET) {
            addReply(c,shared.wrongtypeerr);
        } else {
            s = o->ptr;
            addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",
                dictSize(s)));
        }
    }
}

static int qsortCompareSetsByCardinality(const void *s1, const void *s2) {
    dict **d1 = (void*) s1, **d2 = (void*) s2;

    return dictSize(*d1)-dictSize(*d2);
}

static void sinterGenericCommand(redisClient *c, robj **setskeys, int setsnum, robj *dstkey) {
    dict **dv = zmalloc(sizeof(dict*)*setsnum);
    dictIterator *di;
    dictEntry *de;
    robj *lenobj = NULL, *dstset = NULL;
    int j, cardinality = 0;

    if (!dv) oom("sinterGenericCommand");
    for (j = 0; j < setsnum; j++) {
        robj *setobj;

        setobj = dstkey ?
                    lookupKeyWrite(c->db,setskeys[j]) :
                    lookupKeyRead(c->db,setskeys[j]);
        if (!setobj) {
            zfree(dv);
            if (dstkey) {
                deleteKey(c->db,dstkey);
                addReply(c,shared.ok);
            } else {
                addReply(c,shared.nullmultibulk);
            }
            return;
        }
        if (setobj->type != REDIS_SET) {
            zfree(dv);
            addReply(c,shared.wrongtypeerr);
            return;
        }
        dv[j] = setobj->ptr;
    }
    /* Sort sets from the smallest to largest, this will improve our
     * algorithm's performace */
    qsort(dv,setsnum,sizeof(dict*),qsortCompareSetsByCardinality);

    /* The first thing we should output is the total number of elements...
     * since this is a multi-bulk write, but at this stage we don't know
     * the intersection set size, so we use a trick, append an empty object
     * to the output list and save the pointer to later modify it with the
     * right length */
    if (!dstkey) {
        lenobj = createObject(REDIS_STRING,NULL);
        addReply(c,lenobj);
        decrRefCount(lenobj);
    } else {
        /* If we have a target key where to store the resulting set
         * create this key with an empty set inside */
        dstset = createSetObject();
    }

    /* Iterate all the elements of the first (smallest) set, and test
     * the element against all the other sets, if at least one set does
     * not include the element it is discarded */
    di = dictGetIterator(dv[0]);
    if (!di) oom("dictGetIterator");

    while((de = dictNext(di)) != NULL) {
        robj *ele;

        for (j = 1; j < setsnum; j++)
            if (dictFind(dv[j],dictGetEntryKey(de)) == NULL) break;
        if (j != setsnum)
            continue; /* at least one set does not contain the member */
        ele = dictGetEntryKey(de);
        if (!dstkey) {
            addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",sdslen(ele->ptr)));
            addReply(c,ele);
            addReply(c,shared.crlf);
            cardinality++;
        } else {
            dictAdd(dstset->ptr,ele,NULL);
            incrRefCount(ele);
        }
    }
    dictReleaseIterator(di);

    if (dstkey) {
        /* Store the resulting set into the target */
        deleteKey(c->db,dstkey);
        dictAdd(c->db->dict,dstkey,dstset);
        incrRefCount(dstkey);
    }

    if (!dstkey) {
        lenobj->ptr = sdscatprintf(sdsempty(),"*%d\r\n",cardinality);
    } else {
        addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",
            dictSize((dict*)dstset->ptr)));
        server.dirty++;
    }
    zfree(dv);
}

static void sinterCommand(redisClient *c) {
    sinterGenericCommand(c,c->argv+1,c->argc-1,NULL);
}

static void sinterstoreCommand(redisClient *c) {
    sinterGenericCommand(c,c->argv+2,c->argc-2,c->argv[1]);
}

#define REDIS_OP_UNION 0
#define REDIS_OP_DIFF 1

static void sunionDiffGenericCommand(redisClient *c, robj **setskeys, int setsnum, robj *dstkey, int op) {
    dict **dv = zmalloc(sizeof(dict*)*setsnum);
    dictIterator *di;
    dictEntry *de;
    robj *dstset = NULL;
    int j, cardinality = 0;

    if (!dv) oom("sunionDiffGenericCommand");
    for (j = 0; j < setsnum; j++) {
        robj *setobj;

        setobj = dstkey ?
                    lookupKeyWrite(c->db,setskeys[j]) :
                    lookupKeyRead(c->db,setskeys[j]);
        if (!setobj) {
            dv[j] = NULL;
            continue;
        }
        if (setobj->type != REDIS_SET) {
            zfree(dv);
            addReply(c,shared.wrongtypeerr);
            return;
        }
        dv[j] = setobj->ptr;
    }

    /* We need a temp set object to store our union. If the dstkey
     * is not NULL (that is, we are inside an SUNIONSTORE operation) then
     * this set object will be the resulting object to set into the target key*/
    dstset = createSetObject();

    /* Iterate all the elements of all the sets, add every element a single
     * time to the result set */
    for (j = 0; j < setsnum; j++) {
        if (op == REDIS_OP_DIFF && j == 0 && !dv[j]) break; /* result set is empty */
        if (!dv[j]) continue; /* non existing keys are like empty sets */

        di = dictGetIterator(dv[j]);
        if (!di) oom("dictGetIterator");

        while((de = dictNext(di)) != NULL) {
            robj *ele;

            /* dictAdd will not add the same element multiple times */
            ele = dictGetEntryKey(de);
            if (op == REDIS_OP_UNION || j == 0) {
                if (dictAdd(dstset->ptr,ele,NULL) == DICT_OK) {
                    incrRefCount(ele);
                    cardinality++;
                }
            } else if (op == REDIS_OP_DIFF) {
                if (dictDelete(dstset->ptr,ele) == DICT_OK) {
                    cardinality--;
                }
            }
        }
        dictReleaseIterator(di);

        if (op == REDIS_OP_DIFF && cardinality == 0) break; /* result set is empty */
    }

    /* Output the content of the resulting set, if not in STORE mode */
    if (!dstkey) {
        addReplySds(c,sdscatprintf(sdsempty(),"*%d\r\n",cardinality));
        di = dictGetIterator(dstset->ptr);
        if (!di) oom("dictGetIterator");
        while((de = dictNext(di)) != NULL) {
            robj *ele;

            ele = dictGetEntryKey(de);
            addReplySds(c,sdscatprintf(sdsempty(),
                    "$%d\r\n",sdslen(ele->ptr)));
            addReply(c,ele);
            addReply(c,shared.crlf);
        }
        dictReleaseIterator(di);
    } else {
        /* If we have a target key where to store the resulting set
         * create this key with the result set inside */
        deleteKey(c->db,dstkey);
        dictAdd(c->db->dict,dstkey,dstset);
        incrRefCount(dstkey);
    }

    /* Cleanup */
    if (!dstkey) {
        decrRefCount(dstset);
    } else {
        addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",
            dictSize((dict*)dstset->ptr)));
        server.dirty++;
    }
    zfree(dv);
}

static void sunionCommand(redisClient *c) {
    sunionDiffGenericCommand(c,c->argv+1,c->argc-1,NULL,REDIS_OP_UNION);
}

static void sunionstoreCommand(redisClient *c) {
    sunionDiffGenericCommand(c,c->argv+2,c->argc-2,c->argv[1],REDIS_OP_UNION);
}

static void sdiffCommand(redisClient *c) {
    sunionDiffGenericCommand(c,c->argv+1,c->argc-1,NULL,REDIS_OP_DIFF);
}

static void sdiffstoreCommand(redisClient *c) {
    sunionDiffGenericCommand(c,c->argv+2,c->argc-2,c->argv[1],REDIS_OP_DIFF);
}

static void flushdbCommand(redisClient *c) {
    server.dirty += dictSize(c->db->dict);
    dictEmpty(c->db->dict);
    dictEmpty(c->db->expires);
    addReply(c,shared.ok);
}

static void flushallCommand(redisClient *c) {
    server.dirty += emptyDb();
    addReply(c,shared.ok);
    rdbSave(server.dbfilename);
    server.dirty++;
}

redisSortOperation *createSortOperation(int type, robj *pattern) {
    redisSortOperation *so = zmalloc(sizeof(*so));
    if (!so) oom("createSortOperation");
    so->type = type;
    so->pattern = pattern;
    return so;
}

/* Return the value associated to the key with a name obtained
 * substituting the first occurence of '*' in 'pattern' with 'subst' */
robj *lookupKeyByPattern(redisDb *db, robj *pattern, robj *subst) {
    char *p;
    sds spat, ssub;
    robj keyobj;
    int prefixlen, sublen, postfixlen;
    /* Expoit the internal sds representation to create a sds string allocated on the stack in order to make this function faster */
    struct {
        long len;
        long free;
        char buf[REDIS_SORTKEY_MAX+1];
    } keyname;

    spat = pattern->ptr;
    ssub = subst->ptr;
    if (sdslen(spat)+sdslen(ssub)-1 > REDIS_SORTKEY_MAX) return NULL;
    p = strchr(spat,'*');
    if (!p) return NULL;

    prefixlen = p-spat;
    sublen = sdslen(ssub);
    postfixlen = sdslen(spat)-(prefixlen+1);
    memcpy(keyname.buf,spat,prefixlen);
    memcpy(keyname.buf+prefixlen,ssub,sublen);
    memcpy(keyname.buf+prefixlen+sublen,p+1,postfixlen);
    keyname.buf[prefixlen+sublen+postfixlen] = '\0';
    keyname.len = prefixlen+sublen+postfixlen;

    keyobj.refcount = 1;
    keyobj.type = REDIS_STRING;
    keyobj.ptr = ((char*)&keyname)+(sizeof(long)*2);

    /* printf("lookup '%s' => %p\n", keyname.buf,de); */
    return lookupKeyRead(db,&keyobj);
}

/* sortCompare() is used by qsort in sortCommand(). Given that qsort_r with
 * the additional parameter is not standard but a BSD-specific we have to
 * pass sorting parameters via the global 'server' structure */
static int sortCompare(const void *s1, const void *s2) {
    const redisSortObject *so1 = s1, *so2 = s2;
    int cmp;

    if (!server.sort_alpha) {
        /* Numeric sorting. Here it's trivial as we precomputed scores */
        if (so1->u.score > so2->u.score) {
            cmp = 1;
        } else if (so1->u.score < so2->u.score) {
            cmp = -1;
        } else {
            cmp = 0;
        }
    } else {
        /* Alphanumeric sorting */
        if (server.sort_bypattern) {
            if (!so1->u.cmpobj || !so2->u.cmpobj) {
                /* At least one compare object is NULL */
                if (so1->u.cmpobj == so2->u.cmpobj)
                    cmp = 0;
                else if (so1->u.cmpobj == NULL)
                    cmp = -1;
                else
                    cmp = 1;
            } else {
                /* We have both the objects, use strcoll */
                cmp = strcoll(so1->u.cmpobj->ptr,so2->u.cmpobj->ptr);
            }
        } else {
            /* Compare elements directly */
            cmp = strcoll(so1->obj->ptr,so2->obj->ptr);
        }
    }
    return server.sort_desc ? -cmp : cmp;
}

/* The SORT command is the most complex command in Redis. Warning: this code
 * is optimized for speed and a bit less for readability */
static void sortCommand(redisClient *c) {
    list *operations;
    int outputlen = 0;
    int desc = 0, alpha = 0;
    int limit_start = 0, limit_count = -1, start, end;
    int j, dontsort = 0, vectorlen;
    int getop = 0; /* GET operation counter */
    robj *sortval, *sortby = NULL;
    redisSortObject *vector; /* Resulting vector to sort */

    /* Lookup the key to sort. It must be of the right types */
    sortval = lookupKeyRead(c->db,c->argv[1]);
    if (sortval == NULL) {
        addReply(c,shared.nokeyerr);
        return;
    }
    if (sortval->type != REDIS_SET && sortval->type != REDIS_LIST) {
        addReply(c,shared.wrongtypeerr);
        return;
    }

    /* Create a list of operations to perform for every sorted element.
     * Operations can be GET/DEL/INCR/DECR */
    operations = listCreate();
    listSetFreeMethod(operations,zfree);
    j = 2;

    /* Now we need to protect sortval incrementing its count, in the future
     * SORT may have options able to overwrite/delete keys during the sorting
     * and the sorted key itself may get destroied */
    incrRefCount(sortval);

    /* The SORT command has an SQL-alike syntax, parse it */
    while(j < c->argc) {
        int leftargs = c->argc-j-1;
        if (!strcasecmp(c->argv[j]->ptr,"asc")) {
            desc = 0;
        } else if (!strcasecmp(c->argv[j]->ptr,"desc")) {
            desc = 1;
        } else if (!strcasecmp(c->argv[j]->ptr,"alpha")) {
            alpha = 1;
        } else if (!strcasecmp(c->argv[j]->ptr,"limit") && leftargs >= 2) {
            limit_start = atoi(c->argv[j+1]->ptr);
            limit_count = atoi(c->argv[j+2]->ptr);
            j+=2;
        } else if (!strcasecmp(c->argv[j]->ptr,"by") && leftargs >= 1) {
            sortby = c->argv[j+1];
            /* If the BY pattern does not contain '*', i.e. it is constant,
             * we don't need to sort nor to lookup the weight keys. */
            if (strchr(c->argv[j+1]->ptr,'*') == NULL) dontsort = 1;
            j++;
        } else if (!strcasecmp(c->argv[j]->ptr,"get") && leftargs >= 1) {
            listAddNodeTail(operations,createSortOperation(
                REDIS_SORT_GET,c->argv[j+1]));
            getop++;
            j++;
        } else if (!strcasecmp(c->argv[j]->ptr,"del") && leftargs >= 1) {
            listAddNodeTail(operations,createSortOperation(
                REDIS_SORT_DEL,c->argv[j+1]));
            j++;
        } else if (!strcasecmp(c->argv[j]->ptr,"incr") && leftargs >= 1) {
            listAddNodeTail(operations,createSortOperation(
                REDIS_SORT_INCR,c->argv[j+1]));
            j++;
        } else if (!strcasecmp(c->argv[j]->ptr,"get") && leftargs >= 1) {
            listAddNodeTail(operations,createSortOperation(
                REDIS_SORT_DECR,c->argv[j+1]));
            j++;
        } else {
            decrRefCount(sortval);
            listRelease(operations);
            addReply(c,shared.syntaxerr);
            return;
        }
        j++;
    }

    /* Load the sorting vector with all the objects to sort */
    vectorlen = (sortval->type == REDIS_LIST) ?
        listLength((list*)sortval->ptr) :
        dictSize((dict*)sortval->ptr);
    vector = zmalloc(sizeof(redisSortObject)*vectorlen);
    if (!vector) oom("allocating objects vector for SORT");
    j = 0;
    if (sortval->type == REDIS_LIST) {
        list *list = sortval->ptr;
        listNode *ln;

        listRewind(list);
        while((ln = listYield(list))) {
            robj *ele = ln->value;
            vector[j].obj = ele;
            vector[j].u.score = 0;
            vector[j].u.cmpobj = NULL;
            j++;
        }
    } else {
        dict *set = sortval->ptr;
        dictIterator *di;
        dictEntry *setele;

        di = dictGetIterator(set);
        if (!di) oom("dictGetIterator");
        while((setele = dictNext(di)) != NULL) {
            vector[j].obj = dictGetEntryKey(setele);
            vector[j].u.score = 0;
            vector[j].u.cmpobj = NULL;
            j++;
        }
        dictReleaseIterator(di);
    }
    assert(j == vectorlen);

    /* Now it's time to load the right scores in the sorting vector */
    if (dontsort == 0) {
        for (j = 0; j < vectorlen; j++) {
            if (sortby) {
                robj *byval;

                byval = lookupKeyByPattern(c->db,sortby,vector[j].obj);
                if (!byval || byval->type != REDIS_STRING) continue;
                if (alpha) {
                    vector[j].u.cmpobj = byval;
                    incrRefCount(byval);
                } else {
                    vector[j].u.score = strtod(byval->ptr,NULL);
                }
            } else {
                if (!alpha) vector[j].u.score = strtod(vector[j].obj->ptr,NULL);
            }
        }
    }

    /* We are ready to sort the vector... perform a bit of sanity check
     * on the LIMIT option too. We'll use a partial version of quicksort. */
    start = (limit_start < 0) ? 0 : limit_start;
    end = (limit_count < 0) ? vectorlen-1 : start+limit_count-1;
    if (start >= vectorlen) {
        start = vectorlen-1;
        end = vectorlen-2;
    }
    if (end >= vectorlen) end = vectorlen-1;

    if (dontsort == 0) {
        server.sort_desc = desc;
        server.sort_alpha = alpha;
        server.sort_bypattern = sortby ? 1 : 0;
        if (sortby && (start != 0 || end != vectorlen-1))
            pqsort(vector,vectorlen,sizeof(redisSortObject),sortCompare, start,end);
        else
            qsort(vector,vectorlen,sizeof(redisSortObject),sortCompare);
    }

    /* Send command output to the output buffer, performing the specified
     * GET/DEL/INCR/DECR operations if any. */
    outputlen = getop ? getop*(end-start+1) : end-start+1;
    addReplySds(c,sdscatprintf(sdsempty(),"*%d\r\n",outputlen));
    for (j = start; j <= end; j++) {
        listNode *ln;
        if (!getop) {
            addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",
                sdslen(vector[j].obj->ptr)));
            addReply(c,vector[j].obj);
            addReply(c,shared.crlf);
        }
        listRewind(operations);
        while((ln = listYield(operations))) {
            redisSortOperation *sop = ln->value;
            robj *val = lookupKeyByPattern(c->db,sop->pattern,
                vector[j].obj);

            if (sop->type == REDIS_SORT_GET) {
                if (!val || val->type != REDIS_STRING) {
                    addReply(c,shared.nullbulk);
                } else {
                    addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",
                        sdslen(val->ptr)));
                    addReply(c,val);
                    addReply(c,shared.crlf);
                }
            } else if (sop->type == REDIS_SORT_DEL) {
                /* TODO */
            }
        }
    }

    /* Cleanup */
    decrRefCount(sortval);
    listRelease(operations);
    for (j = 0; j < vectorlen; j++) {
        if (sortby && alpha && vector[j].u.cmpobj)
            decrRefCount(vector[j].u.cmpobj);
    }
    zfree(vector);
}

static void infoCommand(redisClient *c) {
    sds info;
    time_t uptime = time(NULL)-server.stat_starttime;
    
    info = sdscatprintf(sdsempty(),
        "redis_version:%s\r\n"
        "uptime_in_seconds:%d\r\n"
        "uptime_in_days:%d\r\n"
        "connected_clients:%d\r\n"
        "connected_slaves:%d\r\n"
        "used_memory:%zu\r\n"
        "changes_since_last_save:%lld\r\n"
        "bgsave_in_progress:%d\r\n"
        "last_save_time:%d\r\n"
        "total_connections_received:%lld\r\n"
        "total_commands_processed:%lld\r\n"
        "role:%s\r\n"
        ,REDIS_VERSION,
        uptime,
        uptime/(3600*24),
        listLength(server.clients)-listLength(server.slaves),
        listLength(server.slaves),
        server.usedmemory,
        server.dirty,
        server.bgsaveinprogress,
        server.lastsave,
        server.stat_numconnections,
        server.stat_numcommands,
        server.masterhost == NULL ? "master" : "slave"
    );
    if (server.masterhost) {
        info = sdscatprintf(info,
            "master_host:%s\r\n"
            "master_port:%d\r\n"
            "master_link_status:%s\r\n"
            "master_last_io_seconds_ago:%d\r\n"
            ,server.masterhost,
            server.masterport,
            (server.replstate == REDIS_REPL_CONNECTED) ?
                "up" : "down",
            (int)(time(NULL)-server.master->lastinteraction)
        );
    }
    addReplySds(c,sdscatprintf(sdsempty(),"$%d\r\n",sdslen(info)));
    addReplySds(c,info);
    addReply(c,shared.crlf);
}

static void monitorCommand(redisClient *c) {
    /* ignore MONITOR if aleady slave or in monitor mode */
    if (c->flags & REDIS_SLAVE) return;

    c->flags |= (REDIS_SLAVE|REDIS_MONITOR);
    c->slaveseldb = 0;
    if (!listAddNodeTail(server.monitors,c)) oom("listAddNodeTail");
    addReply(c,shared.ok);
}

/* ================================= Expire ================================= */
static int removeExpire(redisDb *db, robj *key) {
    if (dictDelete(db->expires,key) == DICT_OK) {
        return 1;
    } else {
        return 0;
    }
}

static int setExpire(redisDb *db, robj *key, time_t when) {
    if (dictAdd(db->expires,key,(void*)when) == DICT_ERR) {
        return 0;
    } else {
        incrRefCount(key);
        return 1;
    }
}

/* Return the expire time of the specified key, or -1 if no expire
 * is associated with this key (i.e. the key is non volatile) */
static time_t getExpire(redisDb *db, robj *key) {
    dictEntry *de;

    /* No expire? return ASAP */
    if (dictSize(db->expires) == 0 ||
       (de = dictFind(db->expires,key)) == NULL) return -1;

    return (time_t) dictGetEntryVal(de);
}

static int expireIfNeeded(redisDb *db, robj *key) {
    time_t when;
    dictEntry *de;

    /* No expire? return ASAP */
    if (dictSize(db->expires) == 0 ||
       (de = dictFind(db->expires,key)) == NULL) return 0;

    /* Lookup the expire */
    when = (time_t) dictGetEntryVal(de);
    if (time(NULL) <= when) return 0;

    /* Delete the key */
    dictDelete(db->expires,key);
    return dictDelete(db->dict,key) == DICT_OK;
}

static int deleteIfVolatile(redisDb *db, robj *key) {
    dictEntry *de;

    /* No expire? return ASAP */
    if (dictSize(db->expires) == 0 ||
       (de = dictFind(db->expires,key)) == NULL) return 0;

    /* Delete the key */
    server.dirty++;
    dictDelete(db->expires,key);
    return dictDelete(db->dict,key) == DICT_OK;
}

static void expireCommand(redisClient *c) {
    dictEntry *de;
    int seconds = atoi(c->argv[2]->ptr);

    de = dictFind(c->db->dict,c->argv[1]);
    if (de == NULL) {
        addReply(c,shared.czero);
        return;
    }
    if (seconds <= 0) {
        addReply(c, shared.czero);
        return;
    } else {
        time_t when = time(NULL)+seconds;
        if (setExpire(c->db,c->argv[1],when))
            addReply(c,shared.cone);
        else
            addReply(c,shared.czero);
        return;
    }
}

static void ttlCommand(redisClient *c) {
    time_t expire;
    int ttl = -1;

    expire = getExpire(c->db,c->argv[1]);
    if (expire != -1) {
        ttl = (int) (expire-time(NULL));
        if (ttl < 0) ttl = -1;
    }
    addReplySds(c,sdscatprintf(sdsempty(),":%d\r\n",ttl));
}

/* =============================== Replication  ============================= */

static int syncWrite(int fd, char *ptr, ssize_t size, int timeout) {
    ssize_t nwritten, ret = size;
    time_t start = time(NULL);

    timeout++;
    while(size) {
        if (aeWait(fd,AE_WRITABLE,1000) & AE_WRITABLE) {
            nwritten = write(fd,ptr,size);
            if (nwritten == -1) return -1;
            ptr += nwritten;
            size -= nwritten;
        }
        if ((time(NULL)-start) > timeout) {
            errno = ETIMEDOUT;
            return -1;
        }
    }
    return ret;
}

static int syncRead(int fd, char *ptr, ssize_t size, int timeout) {
    ssize_t nread, totread = 0;
    time_t start = time(NULL);

    timeout++;
    while(size) {
        if (aeWait(fd,AE_READABLE,1000) & AE_READABLE) {
            nread = read(fd,ptr,size);
            if (nread == -1) return -1;
            ptr += nread;
            size -= nread;
            totread += nread;
        }
        if ((time(NULL)-start) > timeout) {
            errno = ETIMEDOUT;
            return -1;
        }
    }
    return totread;
}

static int syncReadLine(int fd, char *ptr, ssize_t size, int timeout) {
    ssize_t nread = 0;

    size--;
    while(size) {
        char c;

        if (syncRead(fd,&c,1,timeout) == -1) return -1;
        if (c == '\n') {
            *ptr = '\0';
            if (nread && *(ptr-1) == '\r') *(ptr-1) = '\0';
            return nread;
        } else {
            *ptr++ = c;
            *ptr = '\0';
            nread++;
        }
    }
    return nread;
}

static void syncCommand(redisClient *c) {
    /* ignore SYNC if aleady slave or in monitor mode */
    if (c->flags & REDIS_SLAVE) return;

    /* SYNC can't be issued when the server has pending data to send to
     * the client about already issued commands. We need a fresh reply
     * buffer registering the differences between the BGSAVE and the current
     * dataset, so that we can copy to other slaves if needed. */
    if (listLength(c->reply) != 0) {
        addReplySds(c,sdsnew("-ERR SYNC is invalid with pending input\r\n"));
        return;
    }

    redisLog(REDIS_NOTICE,"Slave ask for synchronization");
    /* Here we need to check if there is a background saving operation
     * in progress, or if it is required to start one */
    if (server.bgsaveinprogress) {
        /* Ok a background save is in progress. Let's check if it is a good
         * one for replication, i.e. if there is another slave that is
         * registering differences since the server forked to save */
        redisClient *slave;
        listNode *ln;

        listRewind(server.slaves);
        while((ln = listYield(server.slaves))) {
            slave = ln->value;
            if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_END) break;
        }
        if (ln) {
            /* Perfect, the server is already registering differences for
             * another slave. Set the right state, and copy the buffer. */
            listRelease(c->reply);
            c->reply = listDup(slave->reply);
            if (!c->reply) oom("listDup copying slave reply list");
            c->replstate = REDIS_REPL_WAIT_BGSAVE_END;
            redisLog(REDIS_NOTICE,"Waiting for end of BGSAVE for SYNC");
        } else {
            /* No way, we need to wait for the next BGSAVE in order to
             * register differences */
            c->replstate = REDIS_REPL_WAIT_BGSAVE_START;
            redisLog(REDIS_NOTICE,"Waiting for next BGSAVE for SYNC");
        }
    } else {
        /* Ok we don't have a BGSAVE in progress, let's start one */
        redisLog(REDIS_NOTICE,"Starting BGSAVE for SYNC");
        if (rdbSaveBackground(server.dbfilename) != REDIS_OK) {
            redisLog(REDIS_NOTICE,"Replication failed, can't BGSAVE");
            addReplySds(c,sdsnew("-ERR Unalbe to perform background save\r\n"));
            return;
        }
        c->replstate = REDIS_REPL_WAIT_BGSAVE_END;
    }
    c->repldbfd = -1;
    c->flags |= REDIS_SLAVE;
    c->slaveseldb = 0;
    if (!listAddNodeTail(server.slaves,c)) oom("listAddNodeTail");
    return;
}

static void sendBulkToSlave(aeEventLoop *el, int fd, void *privdata, int mask) {
    redisClient *slave = privdata;
    REDIS_NOTUSED(el);
    REDIS_NOTUSED(mask);
    char buf[REDIS_IOBUF_LEN];
    ssize_t nwritten, buflen;

    if (slave->repldboff == 0) {
        /* Write the bulk write count before to transfer the DB. In theory here
         * we don't know how much room there is in the output buffer of the
         * socket, but in pratice SO_SNDLOWAT (the minimum count for output
         * operations) will never be smaller than the few bytes we need. */
        sds bulkcount;

        bulkcount = sdscatprintf(sdsempty(),"$%lld\r\n",(unsigned long long)
            slave->repldbsize);
        if (write(fd,bulkcount,sdslen(bulkcount)) != (signed)sdslen(bulkcount))
        {
            sdsfree(bulkcount);
            freeClient(slave);
            return;
        }
        sdsfree(bulkcount);
    }
    lseek(slave->repldbfd,slave->repldboff,SEEK_SET);
    buflen = read(slave->repldbfd,buf,REDIS_IOBUF_LEN);
    if (buflen <= 0) {
        redisLog(REDIS_WARNING,"Read error sending DB to slave: %s",
            (buflen == 0) ? "premature EOF" : strerror(errno));
        freeClient(slave);
        return;
    }
    if ((nwritten = write(fd,buf,buflen)) == -1) {
        redisLog(REDIS_DEBUG,"Write error sending DB to slave: %s",
            strerror(errno));
        freeClient(slave);
        return;
    }
    slave->repldboff += nwritten;
    if (slave->repldboff == slave->repldbsize) {
        close(slave->repldbfd);
        slave->repldbfd = -1;
        aeDeleteFileEvent(server.el,slave->fd,AE_WRITABLE);
        slave->replstate = REDIS_REPL_ONLINE;
        if (aeCreateFileEvent(server.el, slave->fd, AE_WRITABLE,
            sendReplyToClient, slave, NULL) == AE_ERR) {
            freeClient(slave);
            return;
        }
        addReplySds(slave,sdsempty());
        redisLog(REDIS_NOTICE,"Synchronization with slave succeeded");
    }
}

static void updateSalvesWaitingBgsave(int bgsaveerr) {
    listNode *ln;
    int startbgsave = 0;

    listRewind(server.slaves);
    while((ln = listYield(server.slaves))) {
        redisClient *slave = ln->value;

        if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START) {
            startbgsave = 1;
            slave->replstate = REDIS_REPL_WAIT_BGSAVE_END;
        } else if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_END) {
            struct redis_stat buf;
           
            if (bgsaveerr != REDIS_OK) {
                freeClient(slave);
                redisLog(REDIS_WARNING,"SYNC failed. BGSAVE child returned an error");
                continue;
            }
            if ((slave->repldbfd = open(server.dbfilename,O_RDONLY)) == -1 ||
                redis_fstat(slave->repldbfd,&buf) == -1) {
                freeClient(slave);
                redisLog(REDIS_WARNING,"SYNC failed. Can't open/stat DB after BGSAVE: %s", strerror(errno));
                continue;
            }
            slave->repldboff = 0;
            slave->repldbsize = buf.st_size;
            slave->replstate = REDIS_REPL_SEND_BULK;
            aeDeleteFileEvent(server.el,slave->fd,AE_WRITABLE);
            if (aeCreateFileEvent(server.el, slave->fd, AE_WRITABLE, sendBulkToSlave, slave, NULL) == AE_ERR) {
                freeClient(slave);
                continue;
            }
        }
    }
    if (startbgsave) {
        if (rdbSaveBackground(server.dbfilename) != REDIS_OK) {
            listRewind(server.slaves);
            redisLog(REDIS_WARNING,"SYNC failed. BGSAVE failed");
            while((ln = listYield(server.slaves))) {
                redisClient *slave = ln->value;

                if (slave->replstate == REDIS_REPL_WAIT_BGSAVE_START)
                    freeClient(slave);
            }
        }
    }
}

static int syncWithMaster(void) {
    char buf[1024], tmpfile[256];
    int dumpsize;
    int fd = anetTcpConnect(NULL,server.masterhost,server.masterport);
    int dfd;

    if (fd == -1) {
        redisLog(REDIS_WARNING,"Unable to connect to MASTER: %s",
            strerror(errno));
        return REDIS_ERR;
    }
    /* Issue the SYNC command */
    if (syncWrite(fd,"SYNC \r\n",7,5) == -1) {
        close(fd);
        redisLog(REDIS_WARNING,"I/O error writing to MASTER: %s",
            strerror(errno));
        return REDIS_ERR;
    }
    /* Read the bulk write count */
    if (syncReadLine(fd,buf,1024,3600) == -1) {
        close(fd);
        redisLog(REDIS_WARNING,"I/O error reading bulk count from MASTER: %s",
            strerror(errno));
        return REDIS_ERR;
    }
    dumpsize = atoi(buf+1);
    redisLog(REDIS_NOTICE,"Receiving %d bytes data dump from MASTER",dumpsize);
    /* Read the bulk write data on a temp file */
    snprintf(tmpfile,256,"temp-%d.%ld.rdb",(int)time(NULL),(long int)random());
    dfd = open(tmpfile,O_CREAT|O_WRONLY,0644);
    if (dfd == -1) {
        close(fd);
        redisLog(REDIS_WARNING,"Opening the temp file needed for MASTER <-> SLAVE synchronization: %s",strerror(errno));
        return REDIS_ERR;
    }
    while(dumpsize) {
        int nread, nwritten;

        nread = read(fd,buf,(dumpsize < 1024)?dumpsize:1024);
        if (nread == -1) {
            redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s",
                strerror(errno));
            close(fd);
            close(dfd);
            return REDIS_ERR;
        }
        nwritten = write(dfd,buf,nread);
        if (nwritten == -1) {
            redisLog(REDIS_WARNING,"Write error writing to the DB dump file needed for MASTER <-> SLAVE synchrnonization: %s", strerror(errno));
            close(fd);
            close(dfd);
            return REDIS_ERR;
        }
        dumpsize -= nread;
    }
    close(dfd);
    if (rename(tmpfile,server.dbfilename) == -1) {
        redisLog(REDIS_WARNING,"Failed trying to rename the temp DB into dump.rdb in MASTER <-> SLAVE synchronization: %s", strerror(errno));
        unlink(tmpfile);
        close(fd);
        return REDIS_ERR;
    }
    emptyDb();
    if (rdbLoad(server.dbfilename) != REDIS_OK) {
        redisLog(REDIS_WARNING,"Failed trying to load the MASTER synchronization DB from disk");
        close(fd);
        return REDIS_ERR;
    }
    server.master = createClient(fd);
    server.master->flags |= REDIS_MASTER;
    server.replstate = REDIS_REPL_CONNECTED;
    return REDIS_OK;
}

static void slaveofCommand(redisClient *c) {
    if (!strcasecmp(c->argv[1]->ptr,"no") &&
        !strcasecmp(c->argv[2]->ptr,"one")) {
        if (server.masterhost) {
            sdsfree(server.masterhost);
            server.masterhost = NULL;
            if (server.master) freeClient(server.master);
            server.replstate = REDIS_REPL_NONE;
            redisLog(REDIS_NOTICE,"MASTER MODE enabled (user request)");
        }
    } else {
        sdsfree(server.masterhost);
        server.masterhost = sdsdup(c->argv[1]->ptr);
        server.masterport = atoi(c->argv[2]->ptr);
        if (server.master) freeClient(server.master);
        server.replstate = REDIS_REPL_CONNECT;
        redisLog(REDIS_NOTICE,"SLAVE OF %s:%d enabled (user request)",
            server.masterhost, server.masterport);
    }
    addReply(c,shared.ok);
}

/* ============================ Maxmemory directive  ======================== */

/* This function gets called when 'maxmemory' is set on the config file to limit
 * the max memory used by the server, and we are out of memory.
 * This function will try to, in order:
 *
 * - Free objects from the free list
 * - Try to remove keys with an EXPIRE set
 *
 * It is not possible to free enough memory to reach used-memory < maxmemory
 * the server will start refusing commands that will enlarge even more the
 * memory usage.
 */
static void freeMemoryIfNeeded(void) {
    while (server.maxmemory && zmalloc_used_memory() > server.maxmemory) {
        if (listLength(server.objfreelist)) {
            robj *o;

            listNode *head = listFirst(server.objfreelist);
            o = listNodeValue(head);
            listDelNode(server.objfreelist,head);
            zfree(o);
        } else {
            int j, k, freed = 0;

            for (j = 0; j < server.dbnum; j++) {
                int minttl = -1;
                robj *minkey = NULL;
                struct dictEntry *de;

                if (dictSize(server.db[j].expires)) {
                    freed = 1;
                    /* From a sample of three keys drop the one nearest to
                     * the natural expire */
                    for (k = 0; k < 3; k++) {
                        time_t t;

                        de = dictGetRandomKey(server.db[j].expires);
                        t = (time_t) dictGetEntryVal(de);
                        if (minttl == -1 || t < minttl) {
                            minkey = dictGetEntryKey(de);
                            minttl = t;
                        }
                    }
                    deleteKey(server.db+j,minkey);
                }
            }
            if (!freed) return; /* nothing to free... */
        }
    }
}

/* ================================= Debugging ============================== */

static void debugCommand(redisClient *c) {
    if (!strcasecmp(c->argv[1]->ptr,"segfault")) {
        *((char*)-1) = 'x';
    } else if (!strcasecmp(c->argv[1]->ptr,"object") && c->argc == 3) {
        dictEntry *de = dictFind(c->db->dict,c->argv[2]);
        robj *key, *val;

        if (!de) {
            addReply(c,shared.nokeyerr);
            return;
        }
        key = dictGetEntryKey(de);
        val = dictGetEntryVal(de);
        addReplySds(c,sdscatprintf(sdsempty(),
            "+Key at:%p refcount:%d, value at:%p refcount:%d\r\n",
                key, key->refcount, val, val->refcount));
    } else {
        addReplySds(c,sdsnew(
            "-ERR Syntax error, try DEBUG [SEGFAULT|OBJECT <key>]\r\n"));
    }
}

/* =================================== Main! ================================ */

#ifdef __linux__
int linuxOvercommitMemoryValue(void) {
    FILE *fp = fopen("/proc/sys/vm/overcommit_memory","r");
    char buf[64];

    if (!fp) return -1;
    if (fgets(buf,64,fp) == NULL) {
        fclose(fp);
        return -1;
    }
    fclose(fp);

    return atoi(buf);
}

void linuxOvercommitMemoryWarning(void) {
    if (linuxOvercommitMemoryValue() == 0) {
        redisLog(REDIS_WARNING,"WARNING overcommit_memory is set to 0! Background save may fail under low condition memory. To fix this issue add 'echo 1 > /proc/sys/vm/overcommit_memory' in your init scripts.");
    }
}
#endif /* __linux__ */

static void daemonize(void) {
    int fd;
    FILE *fp;

    if (fork() != 0) exit(0); /* parent exits */
    setsid(); /* create a new session */

    /* Every output goes to /dev/null. If Redis is daemonized but
     * the 'logfile' is set to 'stdout' in the configuration file
     * it will not log at all. */
    if ((fd = open("/dev/null", O_RDWR, 0)) != -1) {
        dup2(fd, STDIN_FILENO);
        dup2(fd, STDOUT_FILENO);
        dup2(fd, STDERR_FILENO);
        if (fd > STDERR_FILENO) close(fd);
    }
    /* Try to write the pid file */
    fp = fopen(server.pidfile,"w");
    if (fp) {
        fprintf(fp,"%d\n",getpid());
        fclose(fp);
    }
}

int main(int argc, char **argv) {
#ifdef __linux__
    linuxOvercommitMemoryWarning();
#endif

    initServerConfig();
    if (argc == 2) {
        ResetServerSaveParams();
        loadServerConfig(argv[1]);
    } else if (argc > 2) {
        fprintf(stderr,"Usage: ./redis-server [/path/to/redis.conf]\n");
        exit(1);
    } else {
        redisLog(REDIS_WARNING,"Warning: no config file specified, using the default config. In order to specify a config file use 'redis-server /path/to/redis.conf'");
    }
    initServer();
    if (server.daemonize) daemonize();
    redisLog(REDIS_NOTICE,"Server started, Redis version " REDIS_VERSION);
    if (rdbLoad(server.dbfilename) == REDIS_OK)
        redisLog(REDIS_NOTICE,"DB loaded from disk");
    if (aeCreateFileEvent(server.el, server.fd, AE_READABLE,
        acceptHandler, NULL, NULL) == AE_ERR) oom("creating file event");
    redisLog(REDIS_NOTICE,"The server is now ready to accept connections on port %d", server.port);
    aeMain(server.el);
    aeDeleteEventLoop(server.el);
    return 0;
}