src/bitops.c

   1 #include "redis.h"
   2
   3 /* -----------------------------------------------------------------------------
   4  * Helpers and low level bit functions.
   5  * -------------------------------------------------------------------------- */
   6
   7 /* This helper function used by GETBIT / SETBIT parses the bit offset arguemnt
   8  * making sure an error is returned if it is negative or if it overflows
   9  * Redis 512 MB limit for the string value. */
  10 static int getBitOffsetFromArgument(redisClient *c, robj *o, size_t *offset) {
  11     long long loffset;
  12     char *err = "bit offset is not an integer or out of range";
  13
  14     if (getLongLongFromObjectOrReply(c,o,&loffset,err) != REDIS_OK)
  15         return REDIS_ERR;
  16
  17     /* Limit offset to 512MB in bytes */
  18     if ((loffset < 0) || ((unsigned long long)loffset >> 3) >= (512*1024*1024))
  19     {
  20         addReplyError(c,err);
  21         return REDIS_ERR;
  22     }
  23
  24     *offset = (size_t)loffset;
  25     return REDIS_OK;
  26 }
  27
  28 /* Count number of bits set in the binary array pointed by 's' and long
  29  * 'count' bytes. The implementation of this function is required to
  30  * work with a input string length up to 512 MB. */
  31 long popcount(void *s, long count) {
  32     long bits = 0;
  33     unsigned char *p;
  34     uint32_t *p4 = s;
  35     static const unsigned char bitsinbyte[256] = {0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,4,5,5,6,5,6,6,7,5,6,6,7,6,7,7,8};
  36
  37     /* Count bits 16 bytes at a time */
  38     while(count>=16) {
  39         uint32_t aux1, aux2, aux3, aux4;
  40
  41         aux1 = *p4++;
  42         aux2 = *p4++;
  43         aux3 = *p4++;
  44         aux4 = *p4++;
  45         count -= 16;
  46
  47         aux1 = aux1 - ((aux1 >> 1) & 0x55555555);
  48         aux1 = (aux1 & 0x33333333) + ((aux1 >> 2) & 0x33333333);
  49         aux2 = aux2 - ((aux2 >> 1) & 0x55555555);
  50         aux2 = (aux2 & 0x33333333) + ((aux2 >> 2) & 0x33333333);
  51         aux3 = aux3 - ((aux3 >> 1) & 0x55555555);
  52         aux3 = (aux3 & 0x33333333) + ((aux3 >> 2) & 0x33333333);
  53         aux4 = aux4 - ((aux4 >> 1) & 0x55555555);
  54         aux4 = (aux4 & 0x33333333) + ((aux4 >> 2) & 0x33333333);
  55         bits += ((((aux1 + (aux1 >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24) +
  56                 ((((aux2 + (aux2 >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24) +
  57                 ((((aux3 + (aux3 >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24) +
  58                 ((((aux4 + (aux4 >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24);
  59     }
  60     /* Count the remaining bytes */
  61     p = (unsigned char*)p4;
  62     while(count--) bits += bitsinbyte[*p++];
  63     return bits;
  64 }
  65
  66 /* -----------------------------------------------------------------------------
  67  * Bits related string commands: GETBIT, SETBIT, BITCOUNT, BITOP.
  68  * -------------------------------------------------------------------------- */
  69
  70 #define BITOP_AND   0
  71 #define BITOP_OR    1
  72 #define BITOP_XOR   2
  73 #define BITOP_NOT   3
  74
  75 /* SETBIT key offset bitvalue */
  76 void setbitCommand(redisClient *c) {
  77     robj *o;
  78     char *err = "bit is not an integer or out of range";
  79     size_t bitoffset;
  80     int byte, bit;
  81     int byteval, bitval;
  82     long on;
  83
  84     if (getBitOffsetFromArgument(c,c->argv[2],&bitoffset) != REDIS_OK)
  85         return;
  86
  87     if (getLongFromObjectOrReply(c,c->argv[3],&on,err) != REDIS_OK)
  88         return;
  89
  90     /* Bits can only be set or cleared... */
  91     if (on & ~1) {
  92         addReplyError(c,err);
  93         return;
  94     }
  95
  96     o = lookupKeyWrite(c->db,c->argv[1]);
  97     if (o == NULL) {
  98         o = createObject(REDIS_STRING,sdsempty());
  99         dbAdd(c->db,c->argv[1],o);
 100     } else {
 101         if (checkType(c,o,REDIS_STRING)) return;
 102
 103         /* Create a copy when the object is shared or encoded. */
 104         if (o->refcount != 1 || o->encoding != REDIS_ENCODING_RAW) {
 105             robj *decoded = getDecodedObject(o);
 106             o = createStringObject(decoded->ptr, sdslen(decoded->ptr));
 107             decrRefCount(decoded);
 108             dbOverwrite(c->db,c->argv[1],o);
 109         }
 110     }
 111
 112     /* Grow sds value to the right length if necessary */
 113     byte = bitoffset >> 3;
 114     o->ptr = sdsgrowzero(o->ptr,byte+1);
 115
 116     /* Get current values */
 117     byteval = ((char*)o->ptr)[byte];
 118     bit = 7 - (bitoffset & 0x7);
 119     bitval = byteval & (1 << bit);
 120
 121     /* Update byte with new bit value and return original value */
 122     byteval &= ~(1 << bit);
 123     byteval |= ((on & 0x1) << bit);
 124     ((char*)o->ptr)[byte] = byteval;
 125     signalModifiedKey(c->db,c->argv[1]);
 126     server.dirty++;
 127     addReply(c, bitval ? shared.cone : shared.czero);
 128 }
 129
 130 /* GETBIT key offset */
 131 void getbitCommand(redisClient *c) {
 132     robj *o;
 133     char llbuf[32];
 134     size_t bitoffset;
 135     size_t byte, bit;
 136     size_t bitval = 0;
 137
 138     if (getBitOffsetFromArgument(c,c->argv[2],&bitoffset) != REDIS_OK)
 139         return;
 140
 141     if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
 142         checkType(c,o,REDIS_STRING)) return;
 143
 144     byte = bitoffset >> 3;
 145     bit = 7 - (bitoffset & 0x7);
 146     if (o->encoding != REDIS_ENCODING_RAW) {
 147         if (byte < (size_t)ll2string(llbuf,sizeof(llbuf),(long)o->ptr))
 148             bitval = llbuf[byte] & (1 << bit);
 149     } else {
 150         if (byte < sdslen(o->ptr))
 151             bitval = ((char*)o->ptr)[byte] & (1 << bit);
 152     }
 153
 154     addReply(c, bitval ? shared.cone : shared.czero);
 155 }
 156
 157 /* BITOP op_name target_key src_key1 src_key2 src_key3 ... src_keyN */
 158 void bitopCommand(redisClient *c) {
 159     char *opname = c->argv[1]->ptr;
 160     robj *o, *targetkey = c->argv[2];
 161     long op, j, numkeys;
 162     unsigned char **src; /* Array of source strings pointers. */
 163     long *len, maxlen = 0; /* Array of length of src strings, and max len. */
 164     unsigned char *res = NULL; /* Resulting string. */
 165
 166     /* Parse the operation name. */
 167     if ((opname[0] == 'a' || opname[0] == 'A') && !strcasecmp(opname,"and"))
 168         op = BITOP_AND;
 169     else if((opname[0] == 'o' || opname[0] == 'O') && !strcasecmp(opname,"or"))
 170         op = BITOP_OR;
 171     else if((opname[0] == 'x' || opname[0] == 'X') && !strcasecmp(opname,"xor"))
 172         op = BITOP_XOR;
 173     else if((opname[0] == 'n' || opname[0] == 'N') && !strcasecmp(opname,"not"))
 174         op = BITOP_NOT;
 175     else {
 176         addReply(c,shared.syntaxerr);
 177         return;
 178     }
 179
 180     /* Sanity check: NOT accepts only a single key argument. */
 181     if (op == BITOP_NOT && c->argc != 4) {
 182         addReplyError(c,"BITOP NOT must be called with a single source key.");
 183         return;
 184     }
 185
 186     /* Lookup keys, and store pointers to the string objects into an array. */
 187     numkeys = c->argc - 3;
 188     src = zmalloc(sizeof(unsigned char*) * numkeys);
 189     len = zmalloc(sizeof(long) * numkeys);
 190     for (j = 0; j < numkeys; j++) {
 191         o = lookupKeyRead(c->db,c->argv[j+3]);
 192         /* Handle non-existing keys as empty strings. */
 193         if (o == NULL) {
 194             src[j] = NULL;
 195             len[j] = 0;
 196             continue;
 197         }
 198         /* Return an error if one of the keys is not a string. */
 199         if (checkType(c,o,REDIS_STRING)) {
 200             zfree(src);
 201             zfree(len);
 202             return;
 203         }
 204         src[j] = o->ptr;
 205         len[j] = sdslen(o->ptr);
 206         if (len[j] > maxlen) maxlen = len[j];
 207     }
 208
 209     /* Compute the bit operation, if at least one string is not empty. */
 210     if (maxlen) {
 211         res = (unsigned char*) sdsnewlen(NULL,maxlen);
 212         unsigned char output, byte;
 213         long i;
 214
 215         for (j = 0; j < maxlen; j++) {
 216             output = (len[0] <= j) ? 0 : src[0][j];
 217             if (op == BITOP_NOT) output = ~output;
 218             for (i = 1; i < numkeys; i++) {
 219                 byte = (len[i] <= j) ? 0 : src[i][j];
 220                 switch(op) {
 221                 case BITOP_AND: output &= byte; break;
 222                 case BITOP_OR:  output |= byte; break;
 223                 case BITOP_XOR: output ^= byte; break;
 224                 }
 225             }
 226             res[j] = output;
 227         }
 228     }
 229     zfree(src);
 230     zfree(len);
 231
 232     /* Store the computed value into the target key */
 233     if (maxlen) {
 234         o = createObject(REDIS_STRING,res);
 235         setKey(c->db,targetkey,o);
 236         decrRefCount(o);
 237     } else if (dbDelete(c->db,targetkey)) {
 238         signalModifiedKey(c->db,targetkey);
 239     }
 240     server.dirty++;
 241     addReplyLongLong(c,maxlen); /* Return the output string length in bytes. */
 242 }
 243
 244 /* BITCOUNT key [start end] */
 245 void bitcountCommand(redisClient *c) {
 246     robj *o;
 247     long start, end;
 248     unsigned char *p;
 249     char llbuf[32];
 250     size_t strlen;
 251
 252     /* Lookup, check for type, and return 0 for non existing keys. */
 253     if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
 254         checkType(c,o,REDIS_STRING)) return;
 255
 256     /* Set the 'p' pointer to the string, that can be just a stack allocated
 257      * array if our string was integer encoded. */
 258     if (o->encoding == REDIS_ENCODING_INT) {
 259         p = (unsigned char*) llbuf;
 260         strlen = ll2string(llbuf,sizeof(llbuf),(long)o->ptr);
 261     } else {
 262         p = (unsigned char*) o->ptr;
 263         strlen = sdslen(o->ptr);
 264     }
 265
 266     /* Parse start/end range if any. */
 267     if (c->argc == 4) {
 268         if (getLongFromObjectOrReply(c,c->argv[2],&start,NULL) != REDIS_OK)
 269             return;
 270         if (getLongFromObjectOrReply(c,c->argv[3],&end,NULL) != REDIS_OK)
 271             return;
 272         /* Convert negative indexes */
 273         if (start < 0) start = strlen+start;
 274         if (end < 0) end = strlen+end;
 275         if (start < 0) start = 0;
 276         if (end < 0) end = 0;
 277         if ((unsigned)end >= strlen) end = strlen-1;
 278     } else if (c->argc == 2) {
 279         /* The whole string. */
 280         start = 0;
 281         end = strlen-1;
 282     } else {
 283         /* Syntax error. */
 284         addReply(c,shared.syntaxerr);
 285         return;
 286     }
 287
 288     /* Precondition: end >= 0 && end < strlen, so the only condition where
 289      * zero can be returned is: start > end. */
 290     if (start > end) {
 291         addReply(c,shared.czero);
 292     } else {
 293         long bytes = end-start+1;
 294
 295         addReplyLongLong(c,popcount(p+start,bytes));
 296     }
 297 }