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Overview
| Comment: | Small performance improvement on the variable-length integer decoder: sqlite3GetVarint(). |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA3-256: |
5df2bf62fcd4dfdaa195062dddbd5ce5 |
| User & Date: | drh 2019-04-17 12:07:08 |
Context
|
2019-04-17
| ||
| 12:29 | In the "pgidx" command of the showdb utility, try to identify orphaned pages and show when pages have been zeroed out. check-in: eed701ef user: drh tags: trunk | |
| 12:07 | Small performance improvement on the variable-length integer decoder: sqlite3GetVarint(). check-in: 5df2bf62 user: drh tags: trunk | |
| 11:34 | Faster and smaller implementation of sqlite3StrICmp(). check-in: 7ac500fb user: drh tags: trunk | |
Changes
Changes to src/util.c.
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/*
** Read a 64-bit variable-length integer from memory starting at p[0].
** Return the number of bytes read. The value is stored in *v.
*/
u8 sqlite3GetVarint(const unsigned char *p, u64 *v){
u32 a,b,s;
a = *p;
/* a: p0 (unmasked) */
if (!(a&0x80))
{
*v = a;
return 1;
}
p++;
b = *p;
/* b: p1 (unmasked) */
if (!(b&0x80))
{
a &= 0x7f;
a = a<<7;
a |= b;
*v = a;
return 2;
}
/* Verify that constants are precomputed correctly */
assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );
assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );
p++;
a = a<<14;
a |= *p;
/* a: p0<<14 | p2 (unmasked) */
if (!(a&0x80))
{
a &= SLOT_2_0;
b &= 0x7f;
b = b<<7;
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/*
** Read a 64-bit variable-length integer from memory starting at p[0].
** Return the number of bytes read. The value is stored in *v.
*/
u8 sqlite3GetVarint(const unsigned char *p, u64 *v){
u32 a,b,s;
if( ((signed char*)p)[0]>=0 ){
*v = *p;
return 1;
}
if( ((signed char*)p)[1]>=0 ){
*v = ((u32)(p[0]&0x7f)<<7) | p[1];
return 2;
}
/* Verify that constants are precomputed correctly */
assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );
assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );
a = ((u32)p[0])<<14;
b = p[1];
p += 2;
a |= *p;
/* a: p0<<14 | p2 (unmasked) */
if (!(a&0x80))
{
a &= SLOT_2_0;
b &= 0x7f;
b = b<<7;
|