diff options
Diffstat (limited to 'src/util.c')
-rw-r--r-- | src/util.c | 125 |
1 files changed, 18 insertions, 107 deletions
diff --git a/src/util.c b/src/util.c index 58591590d..e9c7cccb0 100644 --- a/src/util.c +++ b/src/util.c @@ -1367,121 +1367,32 @@ u8 sqlite3GetVarint(const unsigned char *p, u64 *v){ ** this function assumes the single-byte case has already been handled. */ u8 sqlite3GetVarint32(const unsigned char *p, u32 *v){ - u32 a,b; + u64 v64; + u8 n; - /* The 1-byte case. Overwhelmingly the most common. Handled inline - ** by the getVarin32() macro */ - a = *p; - /* a: p0 (unmasked) */ -#ifndef getVarint32 - if (!(a&0x80)) - { - /* Values between 0 and 127 */ - *v = a; - return 1; - } -#endif + /* Assume that the single-byte case has already been handled by + ** the getVarint32() macro */ + assert( (p[0] & 0x80)!=0 ); - /* The 2-byte case */ - p++; - b = *p; - /* b: p1 (unmasked) */ - if (!(b&0x80)) - { - /* Values between 128 and 16383 */ - a &= 0x7f; - a = a<<7; - *v = a | b; + if( (p[1] & 0x80)==0 ){ + /* This is the two-byte case */ + *v = ((p[0]&0x7f)<<7) | p[1]; return 2; } - - /* The 3-byte case */ - p++; - a = a<<14; - a |= *p; - /* a: p0<<14 | p2 (unmasked) */ - if (!(a&0x80)) - { - /* Values between 16384 and 2097151 */ - a &= (0x7f<<14)|(0x7f); - b &= 0x7f; - b = b<<7; - *v = a | b; + if( (p[2] & 0x80)==0 ){ + /* This is the three-byte case */ + *v = ((p[0]&0x7f)<<14) | ((p[1]&0x7f)<<7) | p[2]; return 3; } - - /* A 32-bit varint is used to store size information in btrees. - ** Objects are rarely larger than 2MiB limit of a 3-byte varint. - ** A 3-byte varint is sufficient, for example, to record the size - ** of a 1048569-byte BLOB or string. - ** - ** We only unroll the first 1-, 2-, and 3- byte cases. The very - ** rare larger cases can be handled by the slower 64-bit varint - ** routine. - */ -#if 1 - { - u64 v64; - u8 n; - - n = sqlite3GetVarint(p-2, &v64); - assert( n>3 && n<=9 ); - if( (v64 & SQLITE_MAX_U32)!=v64 ){ - *v = 0xffffffff; - }else{ - *v = (u32)v64; - } - return n; - } - -#else - /* For following code (kept for historical record only) shows an - ** unrolling for the 3- and 4-byte varint cases. This code is - ** slightly faster, but it is also larger and much harder to test. - */ - p++; - b = b<<14; - b |= *p; - /* b: p1<<14 | p3 (unmasked) */ - if (!(b&0x80)) - { - /* Values between 2097152 and 268435455 */ - b &= (0x7f<<14)|(0x7f); - a &= (0x7f<<14)|(0x7f); - a = a<<7; - *v = a | b; - return 4; - } - - p++; - a = a<<14; - a |= *p; - /* a: p0<<28 | p2<<14 | p4 (unmasked) */ - if (!(a&0x80)) - { - /* Values between 268435456 and 34359738367 */ - a &= SLOT_4_2_0; - b &= SLOT_4_2_0; - b = b<<7; - *v = a | b; - return 5; - } - - /* We can only reach this point when reading a corrupt database - ** file. In that case we are not in any hurry. Use the (relatively - ** slow) general-purpose sqlite3GetVarint() routine to extract the - ** value. */ - { - u64 v64; - u8 n; - - p -= 4; - n = sqlite3GetVarint(p, &v64); - assert( n>5 && n<=9 ); + /* four or more bytes */ + n = sqlite3GetVarint(p, &v64); + assert( n>3 && n<=9 ); + if( (v64 & SQLITE_MAX_U32)!=v64 ){ + *v = 0xffffffff; + }else{ *v = (u32)v64; - return n; } -#endif + return n; } /* |