X-Git-Url: https://git.saurik.com/redis.git/blobdiff_plain/48a32944e6b5e30754701109ff23d85a418d3d4d..f0d962c0eca870e3fd2a4529de321db217c2e9fe:/src/ziplist.c?ds=sidebyside diff --git a/src/ziplist.c b/src/ziplist.c index 4ecd1885..31e61633 100644 --- a/src/ziplist.c +++ b/src/ziplist.c @@ -52,12 +52,23 @@ * String value with length less than or equal to 16383 bytes (14 bits). * |10______|qqqqqqqq|rrrrrrrr|ssssssss|tttttttt| - 5 bytes * String value with length greater than or equal to 16384 bytes. - * |1100____| - 1 byte + * |11000000| - 1 byte * Integer encoded as int16_t (2 bytes). - * |1101____| - 1 byte + * |11010000| - 1 byte * Integer encoded as int32_t (4 bytes). - * |1110____| - 1 byte + * |11100000| - 1 byte * Integer encoded as int64_t (8 bytes). + * |11110000| - 1 byte + * Integer encoded as 24 bit signed (3 bytes). + * |11111110| - 1 byte + * Integer encoded as 8 bit signed (1 byte). + * |1111xxxx| - (with xxxx between 0000 and 1101) immediate 4 bit integer. + * Unsigned integer from 0 to 12. The encoded value is actually from + * 1 to 13 because 0000 and 1111 can not be used, so 1 should be + * subtracted from the encoded 4 bit value to obtain the right value. + * |11111111| - End of ziplist. + * + * All the integers are represented in little endian byte order. */ #include @@ -75,16 +86,27 @@ #define ZIP_BIGLEN 254 /* Different encoding/length possibilities */ +#define ZIP_STR_MASK 0xc0 +#define ZIP_INT_MASK 0x30 #define ZIP_STR_06B (0 << 6) #define ZIP_STR_14B (1 << 6) #define ZIP_STR_32B (2 << 6) #define ZIP_INT_16B (0xc0 | 0<<4) #define ZIP_INT_32B (0xc0 | 1<<4) #define ZIP_INT_64B (0xc0 | 2<<4) +#define ZIP_INT_24B (0xc0 | 3<<4) +#define ZIP_INT_8B 0xfe +/* 4 bit integer immediate encoding */ +#define ZIP_INT_IMM_MASK 0x0f +#define ZIP_INT_IMM_MIN 0xf1 /* 11110001 */ +#define ZIP_INT_IMM_MAX 0xfd /* 11111101 */ +#define ZIP_INT_IMM_VAL(v) (v & ZIP_INT_IMM_MASK) + +#define INT24_MAX 0x7fffff +#define INT24_MIN (-INT24_MAX - 1) -/* Macro's to determine type */ -#define ZIP_IS_STR(enc) (((enc) & 0xc0) < 0xc0) -#define ZIP_IS_INT(enc) (!ZIP_IS_STR(enc) && ((enc) & 0x30) < 0x30) +/* Macro to determine type */ +#define ZIP_IS_STR(enc) (((enc) & ZIP_STR_MASK) < ZIP_STR_MASK) /* Utility macros */ #define ZIPLIST_BYTES(zl) (*((uint32_t*)(zl))) @@ -110,61 +132,27 @@ typedef struct zlentry { unsigned char *p; } zlentry; -/* Return the encoding pointer to by 'p'. */ -static unsigned int zipEntryEncoding(unsigned char *p) { - /* String encoding: 2 MSBs */ - unsigned char b = p[0] & 0xc0; - if (b < 0xc0) { - return b; - } else { - /* Integer encoding: 4 MSBs */ - return p[0] & 0xf0; - } - assert(NULL); - return 0; -} +/* Extract the encoding from the byte pointed by 'ptr' and set it into + * 'encoding'. */ +#define ZIP_ENTRY_ENCODING(ptr, encoding) do { \ + (encoding) = (ptr[0]); \ + if ((encoding) < ZIP_STR_MASK) (encoding) &= ZIP_STR_MASK; \ +} while(0) /* Return bytes needed to store integer encoded by 'encoding' */ static unsigned int zipIntSize(unsigned char encoding) { switch(encoding) { - case ZIP_INT_16B: return sizeof(int16_t); - case ZIP_INT_32B: return sizeof(int32_t); - case ZIP_INT_64B: return sizeof(int64_t); + case ZIP_INT_8B: return 1; + case ZIP_INT_16B: return 2; + case ZIP_INT_24B: return 3; + case ZIP_INT_32B: return 4; + case ZIP_INT_64B: return 8; + default: return 0; /* 4 bit immediate */ } assert(NULL); return 0; } -/* Decode the encoded length pointed by 'p'. If a pointer to 'lensize' is - * provided, it is set to the number of bytes required to encode the length. */ -static unsigned int zipDecodeLength(unsigned char *p, unsigned int *lensize) { - unsigned char encoding = zipEntryEncoding(p); - unsigned int len = 0; - - if (ZIP_IS_STR(encoding)) { - switch(encoding) { - case ZIP_STR_06B: - len = p[0] & 0x3f; - if (lensize) *lensize = 1; - break; - case ZIP_STR_14B: - len = ((p[0] & 0x3f) << 8) | p[1]; - if (lensize) *lensize = 2; - break; - case ZIP_STR_32B: - len = (p[1] << 24) | (p[2] << 16) | (p[3] << 8) | p[4]; - if (lensize) *lensize = 5; - break; - default: - assert(NULL); - } - } else { - len = zipIntSize(encoding); - if (lensize) *lensize = 1; - } - return len; -} - /* Encode the length 'l' writing it in 'p'. If p is NULL it just returns * the amount of bytes required to encode such a length. */ static unsigned int zipEncodeLength(unsigned char *p, unsigned char encoding, unsigned int rawlen) { @@ -201,18 +189,33 @@ static unsigned int zipEncodeLength(unsigned char *p, unsigned char encoding, un return len; } -/* Decode the length of the previous element stored at "p". */ -static unsigned int zipPrevDecodeLength(unsigned char *p, unsigned int *lensize) { - unsigned int len = *p; - if (len < ZIP_BIGLEN) { - if (lensize) *lensize = 1; - } else { - if (lensize) *lensize = 1+sizeof(len); - memcpy(&len,p+1,sizeof(len)); - memrev32ifbe(&len); - } - return len; -} +/* Decode the length encoded in 'ptr'. The 'encoding' variable will hold the + * entries encoding, the 'lensize' variable will hold the number of bytes + * required to encode the entries length, and the 'len' variable will hold the + * entries length. */ +#define ZIP_DECODE_LENGTH(ptr, encoding, lensize, len) do { \ + ZIP_ENTRY_ENCODING((ptr), (encoding)); \ + if ((encoding) < ZIP_STR_MASK) { \ + if ((encoding) == ZIP_STR_06B) { \ + (lensize) = 1; \ + (len) = (ptr)[0] & 0x3f; \ + } else if ((encoding) == ZIP_STR_14B) { \ + (lensize) = 2; \ + (len) = (((ptr)[0] & 0x3f) << 8) | (ptr)[1]; \ + } else if (encoding == ZIP_STR_32B) { \ + (lensize) = 5; \ + (len) = ((ptr)[1] << 24) | \ + ((ptr)[2] << 16) | \ + ((ptr)[3] << 8) | \ + ((ptr)[4]); \ + } else { \ + assert(NULL); \ + } \ + } else { \ + (lensize) = 1; \ + (len) = zipIntSize(encoding); \ + } \ +} while(0); /* Encode the length of the previous entry and write it to "p". Return the * number of bytes needed to encode this length if "p" is NULL. */ @@ -241,12 +244,43 @@ static void zipPrevEncodeLengthForceLarge(unsigned char *p, unsigned int len) { memrev32ifbe(p+1); } -/* Return the difference in number of bytes needed to store the new length - * "len" on the entry pointed to by "p". */ +/* Decode the number of bytes required to store the length of the previous + * element, from the perspective of the entry pointed to by 'ptr'. */ +#define ZIP_DECODE_PREVLENSIZE(ptr, prevlensize) do { \ + if ((ptr)[0] < ZIP_BIGLEN) { \ + (prevlensize) = 1; \ + } else { \ + (prevlensize) = 5; \ + } \ +} while(0); + +/* Decode the length of the previous element, from the perspective of the entry + * pointed to by 'ptr'. */ +#define ZIP_DECODE_PREVLEN(ptr, prevlensize, prevlen) do { \ + ZIP_DECODE_PREVLENSIZE(ptr, prevlensize); \ + if ((prevlensize) == 1) { \ + (prevlen) = (ptr)[0]; \ + } else if ((prevlensize) == 5) { \ + assert(sizeof((prevlensize)) == 4); \ + memcpy(&(prevlen), ((char*)(ptr)) + 1, 4); \ + memrev32ifbe(&prevlen); \ + } \ +} while(0); + +/* Return the difference in number of bytes needed to store the length of the + * previous element 'len', in the entry pointed to by 'p'. */ static int zipPrevLenByteDiff(unsigned char *p, unsigned int len) { unsigned int prevlensize; - zipPrevDecodeLength(p,&prevlensize); - return zipPrevEncodeLength(NULL,len)-prevlensize; + ZIP_DECODE_PREVLENSIZE(p, prevlensize); + return zipPrevEncodeLength(NULL, len) - prevlensize; +} + +/* Return the total number of bytes used by the entry pointed to by 'p'. */ +static unsigned int zipRawEntryLength(unsigned char *p) { + unsigned int prevlensize, encoding, lensize, len; + ZIP_DECODE_PREVLENSIZE(p, prevlensize); + ZIP_DECODE_LENGTH(p + prevlensize, encoding, lensize, len); + return prevlensize + lensize + len; } /* Check if string pointed to by 'entry' can be encoded as an integer. @@ -258,8 +292,14 @@ static int zipTryEncoding(unsigned char *entry, unsigned int entrylen, long long if (string2ll((char*)entry,entrylen,&value)) { /* Great, the string can be encoded. Check what's the smallest * of our encoding types that can hold this value. */ - if (value >= INT16_MIN && value <= INT16_MAX) { + if (value >= 0 && value <= 12) { + *encoding = ZIP_INT_IMM_MIN+value; + } else if (value >= INT8_MIN && value <= INT8_MAX) { + *encoding = ZIP_INT_8B; + } else if (value >= INT16_MIN && value <= INT16_MAX) { *encoding = ZIP_INT_16B; + } else if (value >= INT24_MIN && value <= INT24_MAX) { + *encoding = ZIP_INT_24B; } else if (value >= INT32_MIN && value <= INT32_MAX) { *encoding = ZIP_INT_32B; } else { @@ -276,10 +316,16 @@ static void zipSaveInteger(unsigned char *p, int64_t value, unsigned char encodi int16_t i16; int32_t i32; int64_t i64; - if (encoding == ZIP_INT_16B) { + if (encoding == ZIP_INT_8B) { + ((char*)p)[0] = (char)value; + } else if (encoding == ZIP_INT_16B) { i16 = value; memcpy(p,&i16,sizeof(i16)); memrev16ifbe(p); + } else if (encoding == ZIP_INT_24B) { + i32 = value<<8; + memrev32ifbe(&i32); + memcpy(p,((unsigned char*)&i32)+1,sizeof(i32)-sizeof(int8_t)); } else if (encoding == ZIP_INT_32B) { i32 = value; memcpy(p,&i32,sizeof(i32)); @@ -288,6 +334,8 @@ static void zipSaveInteger(unsigned char *p, int64_t value, unsigned char encodi i64 = value; memcpy(p,&i64,sizeof(i64)); memrev64ifbe(p); + } else if (encoding >= ZIP_INT_IMM_MIN && encoding <= ZIP_INT_IMM_MAX) { + /* Nothing to do, the value is stored in the encoding itself. */ } else { assert(NULL); } @@ -298,7 +346,9 @@ static int64_t zipLoadInteger(unsigned char *p, unsigned char encoding) { int16_t i16; int32_t i32; int64_t i64, ret = 0; - if (encoding == ZIP_INT_16B) { + if (encoding == ZIP_INT_8B) { + ret = ((char*)p)[0]; + } else if (encoding == ZIP_INT_16B) { memcpy(&i16,p,sizeof(i16)); memrev16ifbe(&i16); ret = i16; @@ -306,10 +356,17 @@ static int64_t zipLoadInteger(unsigned char *p, unsigned char encoding) { memcpy(&i32,p,sizeof(i32)); memrev32ifbe(&i32); ret = i32; + } else if (encoding == ZIP_INT_24B) { + i32 = 0; + memcpy(((unsigned char*)&i32)+1,p,sizeof(i32)-sizeof(int8_t)); + memrev32ifbe(&i32); + ret = i32>>8; } else if (encoding == ZIP_INT_64B) { memcpy(&i64,p,sizeof(i64)); memrev64ifbe(&i64); ret = i64; + } else if (encoding >= ZIP_INT_IMM_MIN && encoding <= ZIP_INT_IMM_MAX) { + ret = (encoding & ZIP_INT_IMM_MASK)-1; } else { assert(NULL); } @@ -319,20 +376,14 @@ static int64_t zipLoadInteger(unsigned char *p, unsigned char encoding) { /* Return a struct with all information about an entry. */ static zlentry zipEntry(unsigned char *p) { zlentry e; - e.prevrawlen = zipPrevDecodeLength(p,&e.prevrawlensize); - e.len = zipDecodeLength(p+e.prevrawlensize,&e.lensize); - e.headersize = e.prevrawlensize+e.lensize; - e.encoding = zipEntryEncoding(p+e.prevrawlensize); + + ZIP_DECODE_PREVLEN(p, e.prevrawlensize, e.prevrawlen); + ZIP_DECODE_LENGTH(p + e.prevrawlensize, e.encoding, e.lensize, e.len); + e.headersize = e.prevrawlensize + e.lensize; e.p = p; return e; } -/* Return the total number of bytes used by the entry at "p". */ -static unsigned int zipRawEntryLength(unsigned char *p) { - zlentry e = zipEntry(p); - return e.headersize + e.len; -} - /* Create a new empty ziplist. */ unsigned char *ziplistNew(void) { unsigned int bytes = ZIPLIST_HEADER_SIZE+1; @@ -628,10 +679,14 @@ unsigned char *ziplistNext(unsigned char *zl, unsigned char *p) { * when the *next* element is ZIP_END (there is no next entry). */ if (p[0] == ZIP_END) { return NULL; - } else { - p = p+zipRawEntryLength(p); - return (p[0] == ZIP_END) ? NULL : p; } + + p += zipRawEntryLength(p); + if (p[0] == ZIP_END) { + return NULL; + } + + return p; } /* Return pointer to previous entry in ziplist. */ @@ -718,17 +773,72 @@ unsigned int ziplistCompare(unsigned char *p, unsigned char *sstr, unsigned int return 0; } } else { - /* Try to compare encoded values */ + /* Try to compare encoded values. Don't compare encoding because + * different implementations may encoded integers differently. */ if (zipTryEncoding(sstr,slen,&sval,&sencoding)) { - if (entry.encoding == sencoding) { - zval = zipLoadInteger(p+entry.headersize,entry.encoding); - return zval == sval; - } + zval = zipLoadInteger(p+entry.headersize,entry.encoding); + return zval == sval; } } return 0; } +/* Find pointer to the entry equal to the specified entry. Skip 'skip' entries + * between every comparison. Returns NULL when the field could not be found. */ +unsigned char *ziplistFind(unsigned char *p, unsigned char *vstr, unsigned int vlen, unsigned int skip) { + int skipcnt = 0; + unsigned char vencoding = 0; + long long vll = 0; + + while (p[0] != ZIP_END) { + unsigned int prevlensize, encoding, lensize, len; + unsigned char *q; + + ZIP_DECODE_PREVLENSIZE(p, prevlensize); + ZIP_DECODE_LENGTH(p + prevlensize, encoding, lensize, len); + q = p + prevlensize + lensize; + + if (skipcnt == 0) { + /* Compare current entry with specified entry */ + if (ZIP_IS_STR(encoding)) { + if (len == vlen && memcmp(q, vstr, vlen) == 0) { + return p; + } + } else { + /* Find out if the specified entry can be encoded */ + if (vencoding == 0) { + /* UINT_MAX when the entry CANNOT be encoded */ + if (!zipTryEncoding(vstr, vlen, &vll, &vencoding)) { + vencoding = UCHAR_MAX; + } + + /* Must be non-zero by now */ + assert(vencoding); + } + + /* Compare current entry with specified entry */ + if (encoding == vencoding) { + long long ll = zipLoadInteger(q, encoding); + if (ll == vll) { + return p; + } + } + } + + /* Reset skip count */ + skipcnt = skip; + } else { + /* Skip entry */ + skipcnt--; + } + + /* Move to next entry */ + p = q + len; + } + + return NULL; +} + /* Return length of ziplist. */ unsigned int ziplistLen(unsigned char *zl) { unsigned int len = 0;