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Small performance improvement on the variable-length integer decoder:

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sqlite3GetVarint().

FossilOrigin-Name: 5df2bf62fcd4dfdaa195062dddbd5ce5420bc239b2649ac8f547e0db34e7f0bb
This commit is contained in:
drh
2019-04-17 12:07:08 +00:00
parent 7e427337fe
commit 698c86f40d
3 changed files with 14 additions and 24 deletions
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24
src/util.c
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@@ -918,23 +918,12 @@ int sqlite3PutVarint(unsigned char *p, u64 v){
u8 sqlite3GetVarint(const unsigned char *p, u64 *v){
u32 a,b,s;
a = *p;
/* a: p0 (unmasked) */
if (!(a&0x80))
{
*v = a;
if( ((signed char*)p)[0]>=0 ){
*v = *p;
return 1;
}
p++;
b = *p;
/* b: p1 (unmasked) */
if (!(b&0x80))
{
a &= 0x7f;
a = a<<7;
a |= b;
*v = a;
if( ((signed char*)p)[1]>=0 ){
*v = ((u32)(p[0]&0x7f)<<7) | p[1];
return 2;
}
@@ -942,8 +931,9 @@ u8 sqlite3GetVarint(const unsigned char *p, u64 *v){
assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );
assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );
p++;
a = a<<14;
a = ((u32)p[0])<<14;
b = p[1];
p += 2;
a |= *p;
/* a: p0<<14 | p2 (unmasked) */
if (!(a&0x80))