syncio.c read / write functions reworked for correctness and performance.

[redis.git] / src / rio.c

/* rio.c is a simple stream-oriented I/O abstraction that provides an interface
 * to write code that can consume/produce data using different concrete input
 * and output devices. For instance the same rdb.c code using the rio abstraction
 * can be used to read and write the RDB format using in-memory buffers or files.
 *
 * A rio object provides the following methods:
 *  read: read from stream.
 *  write: write to stream.
 *  tell: get the current offset.
 *
 * It is also possible to set a 'checksum' method that is used by rio.c in order
 * to compute a checksum of the data written or read, or to query the rio object
 * for the current checksum. */

#include "fmacros.h"
#include <string.h>
#include <stdio.h>
#include "rio.h"
#include "util.h"

uint64_t crc64(uint64_t crc, const unsigned char *s, uint64_t l);

/* Returns 1 or 0 for success/failure. */
static size_t rioBufferWrite(rio *r, const void *buf, size_t len) {
    r->io.buffer.ptr = sdscatlen(r->io.buffer.ptr,(char*)buf,len);
    r->io.buffer.pos += len;
    return 1;
}

/* Returns 1 or 0 for success/failure. */
static size_t rioBufferRead(rio *r, void *buf, size_t len) {
    if (sdslen(r->io.buffer.ptr)-r->io.buffer.pos < len)
        return 0; /* not enough buffer to return len bytes. */
    memcpy(buf,r->io.buffer.ptr+r->io.buffer.pos,len);
    r->io.buffer.pos += len;
    return 1;
}

/* Returns read/write position in buffer. */
static off_t rioBufferTell(rio *r) {
    return r->io.buffer.pos;
}

/* Returns 1 or 0 for success/failure. */
static size_t rioFileWrite(rio *r, const void *buf, size_t len) {
    return fwrite(buf,len,1,r->io.file.fp);
}

/* Returns 1 or 0 for success/failure. */
static size_t rioFileRead(rio *r, void *buf, size_t len) {
    return fread(buf,len,1,r->io.file.fp);
}

/* Returns read/write position in file. */
static off_t rioFileTell(rio *r) {
    return ftello(r->io.file.fp);
}

static const rio rioBufferIO = {
    rioBufferRead,
    rioBufferWrite,
    rioBufferTell,
    NULL,           /* update_checksum */
    0,              /* current checksum */
    { { NULL, 0 } } /* union for io-specific vars */
};

static const rio rioFileIO = {
    rioFileRead,
    rioFileWrite,
    rioFileTell,
    NULL,           /* update_checksum */
    0,              /* current checksum */
    { { NULL, 0 } } /* union for io-specific vars */
};

void rioInitWithFile(rio *r, FILE *fp) {
    *r = rioFileIO;
    r->io.file.fp = fp;
}

void rioInitWithBuffer(rio *r, sds s) {
    *r = rioBufferIO;
    r->io.buffer.ptr = s;
    r->io.buffer.pos = 0;
}

/* This function can be installed both in memory and file streams when checksum
 * computation is needed. */
void rioGenericUpdateChecksum(rio *r, const void *buf, size_t len) {
    r->cksum = crc64(r->cksum,buf,len);
}

/* ------------------------------ Higher level interface ---------------------------
 * The following higher level functions use lower level rio.c functions to help
 * generating the Redis protocol for the Append Only File. */

/* Write multi bulk count in the format: "*<count>\r\n". */
size_t rioWriteBulkCount(rio *r, char prefix, int count) {
    char cbuf[128];
    int clen;

    cbuf[0] = prefix;
    clen = 1+ll2string(cbuf+1,sizeof(cbuf)-1,count);
    cbuf[clen++] = '\r';
    cbuf[clen++] = '\n';
    if (rioWrite(r,cbuf,clen) == 0) return 0;
    return clen;
}

/* Write binary-safe string in the format: "$<count>\r\n<payload>\r\n". */
size_t rioWriteBulkString(rio *r, const char *buf, size_t len) {
    size_t nwritten;

    if ((nwritten = rioWriteBulkCount(r,'$',len)) == 0) return 0;
    if (len > 0 && rioWrite(r,buf,len) == 0) return 0;
    if (rioWrite(r,"\r\n",2) == 0) return 0;
    return nwritten+len+2;
}

/* Write a long long value in format: "$<count>\r\n<payload>\r\n". */
size_t rioWriteBulkLongLong(rio *r, long long l) {
    char lbuf[32];
    unsigned int llen;

    llen = ll2string(lbuf,sizeof(lbuf),l);
    return rioWriteBulkString(r,lbuf,llen);
}

/* Write a double value in the format: "$<count>\r\n<payload>\r\n" */
size_t rioWriteBulkDouble(rio *r, double d) {
    char dbuf[128];
    unsigned int dlen;

    dlen = snprintf(dbuf,sizeof(dbuf),"%.17g",d);
    return rioWriteBulkString(r,dbuf,dlen);
}