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Bit-related string operations moved to bitop.c
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All the general string operations are implemented in t_string.c, however
the bit operations, while targeting the string type, are better served
in a specific file where we have the implementations of the following
four commands and helper functions:

    GETBIT
    SETBIT
    BITOP
    BITCOUNT

In the future this file will probably contain more code related to
making the BITOP and BITCOUNT operations faster.
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@antirez
antirez committed May 24, 2012
1 parent a3f2b48 commit 760e776
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Showing 3 changed files with 260 additions and 249 deletions.
2 changes: 1 addition & 1 deletion src/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,7 @@ QUIET_LINK = @printf ' %b %b\n' $(LINKCOLOR)LINK$(ENDCOLOR) $(BINCOLOR)$@$(EN
endif

REDIS_SERVER_NAME= redis-server
REDIS_SERVER_OBJ= adlist.o ae.o anet.o dict.o redis.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o
REDIS_SERVER_OBJ= adlist.o ae.o anet.o dict.o redis.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o bitop.o
REDIS_CLI_NAME= redis-cli
REDIS_CLI_OBJ= anet.o sds.o adlist.o redis-cli.o zmalloc.o release.o anet.o ae.o
REDIS_BENCHMARK_NAME= redis-benchmark
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259 changes: 259 additions & 0 deletions src/bitop.c
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@@ -0,0 +1,259 @@
#include "redis.h"

/* -----------------------------------------------------------------------------
* Bits related string commands: GETBIT, SETBIT, BITCOUNT, BITOP.
* -------------------------------------------------------------------------- */

#define BITOP_AND 0
#define BITOP_OR 1
#define BITOP_XOR 2
#define BITOP_NOT 3

/* This helper function used by GETBIT / SETBIT parses the bit offset arguemnt
* making sure an error is returned if it is negative or if it overflows
* Redis 512 MB limit for the string value. */
static int getBitOffsetFromArgument(redisClient *c, robj *o, size_t *offset) {
long long loffset;
char *err = "bit offset is not an integer or out of range";

if (getLongLongFromObjectOrReply(c,o,&loffset,err) != REDIS_OK)
return REDIS_ERR;

/* Limit offset to 512MB in bytes */
if ((loffset < 0) || ((unsigned long long)loffset >> 3) >= (512*1024*1024))
{
addReplyError(c,err);
return REDIS_ERR;
}

*offset = (size_t)loffset;
return REDIS_OK;
}

/* SETBIT key offset bitvalue */
void setbitCommand(redisClient *c) {
robj *o;
char *err = "bit is not an integer or out of range";
size_t bitoffset;
int byte, bit;
int byteval, bitval;
long on;

if (getBitOffsetFromArgument(c,c->argv[2],&bitoffset) != REDIS_OK)
return;

if (getLongFromObjectOrReply(c,c->argv[3],&on,err) != REDIS_OK)
return;

/* Bits can only be set or cleared... */
if (on & ~1) {
addReplyError(c,err);
return;
}

o = lookupKeyWrite(c->db,c->argv[1]);
if (o == NULL) {
o = createObject(REDIS_STRING,sdsempty());
dbAdd(c->db,c->argv[1],o);
} else {
if (checkType(c,o,REDIS_STRING)) return;

/* Create a copy when the object is shared or encoded. */
if (o->refcount != 1 || o->encoding != REDIS_ENCODING_RAW) {
robj *decoded = getDecodedObject(o);
o = createStringObject(decoded->ptr, sdslen(decoded->ptr));
decrRefCount(decoded);
dbOverwrite(c->db,c->argv[1],o);
}
}

/* Grow sds value to the right length if necessary */
byte = bitoffset >> 3;
o->ptr = sdsgrowzero(o->ptr,byte+1);

/* Get current values */
byteval = ((char*)o->ptr)[byte];
bit = 7 - (bitoffset & 0x7);
bitval = byteval & (1 << bit);

/* Update byte with new bit value and return original value */
byteval &= ~(1 << bit);
byteval |= ((on & 0x1) << bit);
((char*)o->ptr)[byte] = byteval;
signalModifiedKey(c->db,c->argv[1]);
server.dirty++;
addReply(c, bitval ? shared.cone : shared.czero);
}

/* GETBIT key offset */
void getbitCommand(redisClient *c) {
robj *o;
char llbuf[32];
size_t bitoffset;
size_t byte, bit;
size_t bitval = 0;

if (getBitOffsetFromArgument(c,c->argv[2],&bitoffset) != REDIS_OK)
return;

if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
checkType(c,o,REDIS_STRING)) return;

byte = bitoffset >> 3;
bit = 7 - (bitoffset & 0x7);
if (o->encoding != REDIS_ENCODING_RAW) {
if (byte < (size_t)ll2string(llbuf,sizeof(llbuf),(long)o->ptr))
bitval = llbuf[byte] & (1 << bit);
} else {
if (byte < sdslen(o->ptr))
bitval = ((char*)o->ptr)[byte] & (1 << bit);
}

addReply(c, bitval ? shared.cone : shared.czero);
}

/* BITOP op_name target_key src_key1 src_key2 src_key3 ... src_keyN */
void bitopCommand(redisClient *c) {
char *opname = c->argv[1]->ptr;
robj *o, *targetkey = c->argv[2];
long op, j, numkeys;
unsigned char **src; /* Array of source strings pointers. */
long *len, maxlen = 0; /* Array of length of src strings, and max len. */
unsigned char *res = NULL; /* Resulting string. */

/* Parse the operation name. */
if ((opname[0] == 'a' || opname[0] == 'A') && !strcasecmp(opname,"and"))
op = BITOP_AND;
else if((opname[0] == 'o' || opname[0] == 'O') && !strcasecmp(opname,"or"))
op = BITOP_OR;
else if((opname[0] == 'x' || opname[0] == 'X') && !strcasecmp(opname,"xor"))
op = BITOP_XOR;
else if((opname[0] == 'n' || opname[0] == 'N') && !strcasecmp(opname,"not"))
op = BITOP_NOT;
else {
addReply(c,shared.syntaxerr);
return;
}

/* Sanity check: NOT accepts only a single key argument. */
if (op == BITOP_NOT && c->argc != 4) {
addReplyError(c,"BITOP NOT must be called with a single source key.");
return;
}

/* Lookup keys, and store pointers to the string objects into an array. */
numkeys = c->argc - 3;
src = zmalloc(sizeof(unsigned char*) * numkeys);
len = zmalloc(sizeof(long) * numkeys);
for (j = 0; j < numkeys; j++) {
o = lookupKeyRead(c->db,c->argv[j+3]);
/* Handle non-existing keys as empty strings. */
if (o == NULL) {
src[j] = NULL;
len[j] = 0;
continue;
}
/* Return an error if one of the keys is not a string. */
if (checkType(c,o,REDIS_STRING)) {
zfree(src);
zfree(len);
return;
}
src[j] = o->ptr;
len[j] = sdslen(o->ptr);
if (len[j] > maxlen) maxlen = len[j];
}

/* Compute the bit operation, if at least one string is not empty. */
if (maxlen) {
res = (unsigned char*) sdsnewlen(NULL,maxlen);
unsigned char output, byte;
long i;

for (j = 0; j < maxlen; j++) {
output = (len[0] <= j) ? 0 : src[0][j];
if (op == BITOP_NOT) output = ~output;
for (i = 1; i < numkeys; i++) {
byte = (len[i] <= j) ? 0 : src[i][j];
switch(op) {
case BITOP_AND: output &= byte; break;
case BITOP_OR: output |= byte; break;
case BITOP_XOR: output ^= byte; break;
}
}
res[j] = output;
}
}
zfree(src);
zfree(len);

/* Store the computed value into the target key */
if (maxlen) {
o = createObject(REDIS_STRING,res);
setKey(c->db,targetkey,o);
decrRefCount(o);
} else if (dbDelete(c->db,targetkey)) {
signalModifiedKey(c->db,targetkey);
}
server.dirty++;
addReplyLongLong(c,maxlen); /* Return the output string length in bytes. */
}

/* BITCOUNT key [start end] */
void bitcountCommand(redisClient *c) {
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};
robj *o;
long start, end;
unsigned char *p;
char llbuf[32];
size_t strlen;

/* Lookup, check for type, and return 0 for non existing keys. */
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
checkType(c,o,REDIS_STRING)) return;

/* Set the 'p' pointer to the string, that can be just a stack allocated
* array if our string was integer encoded. */
if (o->encoding == REDIS_ENCODING_INT) {
p = (unsigned char*) llbuf;
strlen = ll2string(llbuf,sizeof(llbuf),(long)o->ptr);
} else {
p = (unsigned char*) o->ptr;
strlen = sdslen(o->ptr);
}

/* Parse start/end range if any. */
if (c->argc == 4) {
if (getLongFromObjectOrReply(c,c->argv[2],&start,NULL) != REDIS_OK)
return;
if (getLongFromObjectOrReply(c,c->argv[3],&end,NULL) != REDIS_OK)
return;
/* Convert negative indexes */
if (start < 0) start = strlen+start;
if (end < 0) end = strlen+end;
if (start < 0) start = 0;
if (end < 0) end = 0;
if ((unsigned)end >= strlen) end = strlen-1;
} else if (c->argc == 2) {
/* The whole string. */
start = 0;
end = strlen-1;
} else {
/* Syntax error. */
addReply(c,shared.syntaxerr);
return;
}

/* Precondition: end >= 0 && end < strlen, so the only condition where
* zero can be returned is: start > end. */
if (start > end) {
addReply(c,shared.czero);
} else {
long bits = 0, bytes = end-start+1;

/* We can finally count bits. */
p += start;
while(bytes--) bits += bitsinbyte[*p++];
addReplyLongLong(c,bits);
}
}
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