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