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/*
** 2012-02-08
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** SQLite4-compatible varint implementation.
*/
#include "lsmInt.h"
/*************************************************************************
** The following is a copy of the varint.c module from SQLite 4.
*/
/*
** Decode the varint in z[]. Write the integer value into *pResult and
** return the number of bytes in the varint.
*/
static int lsmSqlite4GetVarint64(const unsigned char *z, u64 *pResult){
unsigned int x;
if( z[0]<=240 ){
*pResult = z[0];
return 1;
}
if( z[0]<=248 ){
*pResult = (z[0]-241)*256 + z[1] + 240;
return 2;
}
if( z[0]==249 ){
*pResult = 2288 + 256*z[1] + z[2];
return 3;
}
if( z[0]==250 ){
*pResult = (z[1]<<16) + (z[2]<<8) + z[3];
return 4;
}
x = (z[1]<<24) + (z[2]<<16) + (z[3]<<8) + z[4];
if( z[0]==251 ){
*pResult = x;
return 5;
}
if( z[0]==252 ){
*pResult = (((u64)x)<<8) + z[5];
return 6;
}
if( z[0]==253 ){
*pResult = (((u64)x)<<16) + (z[5]<<8) + z[6];
return 7;
}
if( z[0]==254 ){
*pResult = (((u64)x)<<24) + (z[5]<<16) + (z[6]<<8) + z[7];
return 8;
}
*pResult = (((u64)x)<<32) +
(0xffffffff & ((z[5]<<24) + (z[6]<<16) + (z[7]<<8) + z[8]));
return 9;
}
/*
** Write a 32-bit unsigned integer as 4 big-endian bytes.
*/
static void lsmVarintWrite32(unsigned char *z, unsigned int y){
z[0] = (unsigned char)(y>>24);
z[1] = (unsigned char)(y>>16);
z[2] = (unsigned char)(y>>8);
z[3] = (unsigned char)(y);
}
/*
** Write a varint into z[]. The buffer z[] must be at least 9 characters
** long to accommodate the largest possible varint. Return the number of
** bytes of z[] used.
*/
static int lsmSqlite4PutVarint64(unsigned char *z, u64 x){
unsigned int w, y;
if( x<=240 ){
z[0] = (unsigned char)x;
return 1;
}
if( x<=2287 ){
y = (unsigned int)(x - 240);
z[0] = (unsigned char)(y/256 + 241);
z[1] = (unsigned char)(y%256);
return 2;
}
if( x<=67823 ){
y = (unsigned int)(x - 2288);
z[0] = 249;
z[1] = (unsigned char)(y/256);
z[2] = (unsigned char)(y%256);
return 3;
}
y = (unsigned int)x;
w = (unsigned int)(x>>32);
if( w==0 ){
if( y<=16777215 ){
z[0] = 250;
z[1] = (unsigned char)(y>>16);
z[2] = (unsigned char)(y>>8);
z[3] = (unsigned char)(y);
return 4;
}
z[0] = 251;
lsmVarintWrite32(z+1, y);
return 5;
}
if( w<=255 ){
z[0] = 252;
z[1] = (unsigned char)w;
lsmVarintWrite32(z+2, y);
return 6;
}
if( w<=32767 ){
z[0] = 253;
z[1] = (unsigned char)(w>>8);
z[2] = (unsigned char)w;
lsmVarintWrite32(z+3, y);
return 7;
}
if( w<=16777215 ){
z[0] = 254;
z[1] = (unsigned char)(w>>16);
z[2] = (unsigned char)(w>>8);
z[3] = (unsigned char)w;
lsmVarintWrite32(z+4, y);
return 8;
}
z[0] = 255;
lsmVarintWrite32(z+1, w);
lsmVarintWrite32(z+5, y);
return 9;
}
/*
** End of SQLite 4 code.
*************************************************************************/
int lsmVarintPut64(u8 *aData, i64 iVal){
return lsmSqlite4PutVarint64(aData, (u64)iVal);
}
int lsmVarintGet64(const u8 *aData, i64 *piVal){
return lsmSqlite4GetVarint64(aData, (u64 *)piVal);
}
int lsmVarintPut32(u8 *aData, int iVal){
return lsmSqlite4PutVarint64(aData, (u64)iVal);
}
int lsmVarintGet32(u8 *z, int *piVal){
u64 i;
int ret;
if( z[0]<=240 ){
*piVal = z[0];
return 1;
}
if( z[0]<=248 ){
*piVal = (z[0]-241)*256 + z[1] + 240;
return 2;
}
if( z[0]==249 ){
*piVal = 2288 + 256*z[1] + z[2];
return 3;
}
if( z[0]==250 ){
*piVal = (z[1]<<16) + (z[2]<<8) + z[3];
return 4;
}
ret = lsmSqlite4GetVarint64(z, &i);
*piVal = (int)i;
return ret;
}
int lsmVarintLen32(int n){
u8 aData[9];
return lsmVarintPut32(aData, n);
}
int lsmVarintLen64(i64 n){
u8 aData[9];
return lsmVarintPut64(aData, n);
}
/*
** The argument is the first byte of a varint. This function returns the
** total number of bytes in the entire varint (including the first byte).
*/
int lsmVarintSize(u8 c){
if( c<241 ) return 1;
if( c<249 ) return 2;
return (int)(c - 246);
}
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