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Test versions of getVarint functions. The updates essentially utilize loop unrolling and some shifting/anding tricks to minimize the number of logical operations required. (CVS 5072)

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FossilOrigin-Name: 682dc24dbe82d0326377e27c5ff97db3499873b0
This commit is contained in:
shane
2008-05-01 02:47:03 +00:00
parent 4697988687
commit 356574e97a
3 changed files with 258 additions and 51 deletions
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293
src/util.c
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@@ -14,7 +14,7 @@
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.224 2008/04/28 17:41:31 shane Exp $
** $Id: util.c,v 1.225 2008/05/01 02:47:04 shane Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
@@ -533,41 +533,158 @@ int sqlite3PutVarint32(unsigned char *p, u32 v){
** Return the number of bytes read. The value is stored in *v.
*/
int sqlite3GetVarint(const unsigned char *p, u64 *v){
u32 x;
u64 x64;
int n;
unsigned char c;
if( ((c = p[0]) & 0x80)==0 ){
*v = c;
u32 a,b,s;
a = *p;
// a: p0 (unmasked)
if (!(a&0x80))
{
*v = a;
return 1;
}
x = c & 0x7f;
if( ((c = p[1]) & 0x80)==0 ){
*v = (x<<7) | c;
p++;
b = *p;
// b: p1 (unmasked)
if (!(b&0x80))
{
a &= 0x7f;
a = a<<7;
a |= b;
*v = a;
return 2;
}
x = (x<<7) | (c&0x7f);
if( ((c = p[2]) & 0x80)==0 ){
*v = (x<<7) | c;
p++;
a = a<<14;
a |= *p;
// a: p0<<14 | p2 (unmasked)
if (!(a&0x80))
{
a &= (0x7f<<14)|(0x7f);
b &= 0x7f;
b = b<<7;
a |= b;
*v = a;
return 3;
}
x = (x<<7) | (c&0x7f);
if( ((c = p[3]) & 0x80)==0 ){
*v = (x<<7) | c;
// CSE1 from below
a &= (0x7f<<14)|(0x7f);
p++;
b = b<<14;
b |= *p;
// b: p1<<14 | p3 (unmasked)
if (!(b&0x80))
{
b &= (0x7f<<14)|(0x7f);
// moved CSE1 up
// a &= (0x7f<<14)|(0x7f);
a = a<<7;
a |= b;
*v = a;
return 4;
}
x64 = (x<<7) | (c&0x7f);
n = 4;
do{
c = p[n++];
if( n==9 ){
x64 = (x64<<8) | c;
break;
}
x64 = (x64<<7) | (c&0x7f);
}while( (c & 0x80)!=0 );
*v = x64;
return n;
// a: p0<<14 | p2 (masked)
// b: p1<<14 | p3 (unmasked)
// 1:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked)
// moved CSE1 up
// a &= (0x7f<<14)|(0x7f);
b &= (0x7f<<14)|(0x7f);
s = a;
// s: p0<<14 | p2 (masked)
p++;
a = a<<14;
a |= *p;
// a: p0<<28 | p2<<14 | p4 (unmasked)
if (!(a&0x80))
{
// we can skip these cause they were (effectively) done above in calc'ing s
// a &= (0x7f<<28)|(0x7f<<14)|(0x7f);
// b &= (0x7f<<14)|(0x7f);
b = b<<7;
a |= b;
s = s>>18;
*v = ((u64)s)<<32 | a;
return 5;
}
// 2:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked)
s = s<<7;
s |= b;
// s: p0<<21 | p1<<14 | p2<<7 | p3 (masked)
p++;
b = b<<14;
b |= *p;
// b: p1<<28 | p3<<14 | p5 (unmasked)
if (!(b&0x80))
{
// we can skip this cause it was (effectively) done above in calc'ing s
// b &= (0x7f<<28)|(0x7f<<14)|(0x7f);
a &= (0x7f<<14)|(0x7f);
a = a<<7;
a |= b;
s = s>>18;
*v = ((u64)s)<<32 | a;
return 6;
}
p++;
a = a<<14;
a |= *p;
// a: p2<<28 | p4<<14 | p6 (unmasked)
if (!(a&0x80))
{
a &= (0x7f<<28)|(0x7f<<14)|(0x7f);
b &= (0x7f<<14)|(0x7f);
b = b<<7;
a |= b;
s = s>>11;
*v = ((u64)s)<<32 | a;
return 7;
}
// CSE2 from below
a &= (0x7f<<14)|(0x7f);
p++;
b = b<<14;
b |= *p;
// b: p3<<28 | p5<<14 | p7 (unmasked)
if (!(b&0x80))
{
b &= (0x7f<<28)|(0x7f<<14)|(0x7f);
// moved CSE2 up
// a &= (0x7f<<14)|(0x7f);
a = a<<7;
a |= b;
s = s>>4;
*v = ((u64)s)<<32 | a;
return 8;
}
p++;
a = a<<15;
a |= *p;
// a: p4<<29 | p6<<15 | p8 (unmasked)
// moved CSE2 up
// a &= (0x7f<<29)|(0x7f<<15)|(0xff);
b &= (0x7f<<14)|(0x7f);
b = b<<8;
a |= b;
s = s<<4;
b = p[-4];
b &= 0x7f;
b = b>>3;
s |= b;
*v = ((u64)s)<<32 | a;
return 9;
}
/*
@@ -578,27 +695,117 @@ int sqlite3GetVarint(const unsigned char *p, u64 *v){
** this function assumes the single-byte case has already been handled.
*/
int sqlite3GetVarint32(const unsigned char *p, u32 *v){
u32 x;
int n;
unsigned char c;
u32 a,b;
a = *p;
// a: p0 (unmasked)
#ifndef getVarint32
if( ((signed char*)p)[0]>=0 ){
*v = p[0];
if (!(a&0x80))
{
*v = a;
return 1;
}
#endif
x = p[0] & 0x7f;
if( ((signed char*)p)[1]>=0 ){
*v = (x<<7) | p[1];
p++;
b = *p;
// b: p1 (unmasked)
if (!(b&0x80))
{
a &= 0x7f;
a = a<<7;
*v = a | b;
return 2;
}
x = (x<<7) | (p[1] & 0x7f);
n = 2;
do{
x = (x<<7) | ((c = p[n++])&0x7f);
}while( (c & 0x80)!=0 && n<9 );
*v = x;
return n;
p++;
a = a<<14;
a |= *p;
// a: p0<<14 | p2 (unmasked)
if (!(a&0x80))
{
a &= (0x7f<<14)|(0x7f);
b &= 0x7f;
b = b<<7;
*v = a | b;
return 3;
}
p++;
b = b<<14;
b |= *p;
// b: p1<<14 | p3 (unmasked)
if (!(b&0x80))
{
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))
{
a &= (0x7f<<28)|(0x7f<<14)|(0x7f);
b &= (0x7f<<28)|(0x7f<<14)|(0x7f);
b = b<<7;
*v = a | b;
return 5;
}
p++;
b = b<<14;
b |= *p;
// b: p1<<28 | p3<<14 | p5 (unmasked)
if (!(b&0x80))
{
b &= (0x7f<<28)|(0x7f<<14)|(0x7f);
a &= (0x7f<<28)|(0x7f<<14)|(0x7f);
a = a<<7;
*v = a | b;
return 6;
}
p++;
a = a<<14;
a |= *p;
// a: p2<<28 | p4<<14 | p6 (unmasked)
if (!(a&0x80))
{
a &= (0x7f<<28)|(0x7f<<14)|(0x7f);
b &= (0x7f<<28)|(0x7f<<14)|(0x7f);
b = b<<7;
*v = a | b;
return 7;
}
p++;
b = b<<14;
b |= *p;
// b: p3<<28 | p5<<14 | p7 (unmasked)
if (!(b&0x80))
{
b &= (0x7f<<28)|(0x7f<<14)|(0x7f);
a &= (0x7f<<28)|(0x7f<<14)|(0x7f);
a = a<<7;
*v = a | b;
return 8;
}
p++;
a = a<<14;
a |= *p;
// a: p4<<28 | p6<<14 | p8 (unmasked)
a &= (0x7f<<28)|(0x7f<<14)|(0x7f);
b &= (0x7f<<28)|(0x7f<<14)|(0x7f);
b = b<<7;
*v = a | b;
return 9;
}
/*