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Optimized varint routines and tests added. (CVS 1380)

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FossilOrigin-Name: d4e0933dc72b66157164610e0b03f339bc535fb9
This commit is contained in:
drh
2004-05-14 16:50:06 +00:00
parent 10617cddf6
commit 6d2fb15475
7 changed files with 169 additions and 71 deletions
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85
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 1.81 2004/05/14 11:00:53 danielk1977 Exp $
** $Id: util.c,v 1.82 2004/05/14 16:50:06 drh Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
@@ -1139,26 +1139,92 @@ int sqlite3SafetyCheck(sqlite *db){
return 0;
}
/*
** Write a 64-bit variable-length integer to memory starting at p[0].
** The length of data write will be between 1 and 9 bytes. The number
** of bytes written is returned.
**
** A variable-length integer consists of the lower 7 bits of each byte
** for all bytes that have the 8th bit set and one byte with the 8th
** bit clear.
*/
int sqlite3PutVarint(unsigned char *p, u64 v){
int i = 0;
int i, j, n;
u8 buf[10];
n = 0;
do{
p[i++] = (v & 0x7f) | 0x80;
buf[n++] = (v & 0x7f) | 0x80;
v >>= 7;
}while( v!=0 );
p[i-1] &= 0x7f;
return i;
buf[0] &= 0x7f;
for(i=0, j=n-1; j>=0; j--, i++){
p[i] = buf[j];
}
return n;
}
/*
** 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.
*/
int sqlite3GetVarint(const unsigned char *p, u64 *v){
u64 x = p[0] & 0x7f;
int n = 0;
while( (p[n++]&0x80)!=0 ){
x |= ((u64)(p[n]&0x7f))<<(n*7);
u32 x;
u64 x64;
int n;
unsigned char c;
c = p[0];
if( (c & 0x80)==0 ){
*v = c;
return 1;
}
x = c & 0x7f;
c = p[1];
if( (c & 0x80)==0 ){
*v = (x<<7) | c;
return 2;
}
x = (x<<7) | (c&0x7f);
c = p[2];
if( (c & 0x80)==0 ){
*v = (x<<7) | c;
return 3;
}
x = (x<<7) | (c&0x7f);
c = p[3];
if( (c & 0x80)==0 ){
*v = (x<<7) | c;
return 4;
}
x64 = (x<<7) | (c&0x7f);
n = 4;
do{
c = p[n++];
x64 = (x64<<7) | (c&0x7f);
}while( (c & 0x80)!=0 );
*v = x64;
return n;
}
/*
** Read a 32-bit variable-length integer from memory starting at p[0].
** Return the number of bytes read. The value is stored in *v.
*/
int sqlite3GetVarint32(const unsigned char *p, u32 *v){
int n = 1;
unsigned char c = p[0];
u32 x = c & 0x7f;
while( (c & 0x80)!=0 ){
c = p[n++];
x = (x<<7) | (c & 0x7f);
}
*v = x;
return n;
}
/*
** Return the number of bytes that will be needed to store the given
** 64-bit integer.
*/
int sqlite3VarintLen(u64 v){
int i = 0;
do{
@@ -1167,4 +1233,3 @@ int sqlite3VarintLen(u64 v){
}while( v!=0 );
return i;
}