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+
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-
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-
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-
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|
*/
static int digit_count(int v){
unsigned int i, x;
for(i=1, x=64; v>=x; i++, x <<= 6){}
return i;
}
#ifdef __GNUC__
# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
#else
# define GCC_VERSION 0
#endif
/*
** Compute a 32-bit checksum on the N-byte buffer. Return the result.
** Compute a 32-bit big-endian checksum on the N-byte buffer. If the
** buffer is not a multiple of 4 bytes length, compute the sum that would
** have occurred if the buffer was padded with zeros to the next multiple
** of four bytes.
*/
static unsigned int checksum(const char *zIn, size_t N){
static const int byteOrderTest = 1;
const unsigned char *z = (const unsigned char *)zIn;
const unsigned char *zEnd = (const unsigned char*)&zIn[N&~3];
unsigned sum0 = 0;
unsigned sum1 = 0;
unsigned sum2 = 0;
unsigned sum3 = 0;
while(N >= 16){
sum0 += ((unsigned)z[0] + z[4] + z[8] + z[12]);
sum1 += ((unsigned)z[1] + z[5] + z[9] + z[13]);
sum2 += ((unsigned)z[2] + z[6] + z[10]+ z[14]);
sum3 += ((unsigned)z[3] + z[7] + z[11]+ z[15]);
z += 16;
N -= 16;
}
while(N >= 4){
sum0 += z[0];
sum1 += z[1];
sum2 += z[2];
sum3 += z[3];
z += 4;
N -= 4;
}
sum3 += (sum2 << 8) + (sum1 << 16) + (sum0 << 24);
switch(N){
case 3: sum3 += (z[2] << 8);
case 2: sum3 += (z[1] << 16);
case 1: sum3 += (z[0] << 24);
unsigned sum = 0;
assert( (3&(sqlite3_uint64)z)==0 ); /* Four-byte alignment */
if( 0==*(char*)&byteOrderTest ){
/* This is a big-endian machine */
while( z<zEnd ){
sum += *(unsigned*)z;
z += 4;
}
}else{
/* A little-endian machine */
#if GCC_VERSION>=4003000
while( z<zEnd ){
sum += __builtin_bswap32(*(unsigned*)z);
z += 4;
}
#elif defined(_MSC_VER) && _MSC_VER>=1300
while( z<zEnd ){
sum += _byteswap_ulong(*(unsigned*)z);
z += 4;
}
#else
unsigned sum0 = 0;
unsigned sum1 = 0;
unsigned sum2 = 0;
while(N >= 16){
sum0 += ((unsigned)z[0] + z[4] + z[8] + z[12]);
sum1 += ((unsigned)z[1] + z[5] + z[9] + z[13]);
sum2 += ((unsigned)z[2] + z[6] + z[10]+ z[14]);
sum += ((unsigned)z[3] + z[7] + z[11]+ z[15]);
z += 16;
N -= 16;
}
while(N >= 4){
sum0 += z[0];
sum1 += z[1];
sum2 += z[2];
sum += z[3];
z += 4;
N -= 4;
}
sum += (sum2 << 8) + (sum1 << 16) + (sum0 << 24);
#endif
}
switch(N&3){
case 3: sum += (z[2] << 8);
case 2: sum += (z[1] << 16);
case 1: sum += (z[0] << 24);
default: ;
}
return sum3;
return sum;
}
/*
** Create a new delta.
**
** The delta is written into a preallocated buffer, zDelta, which
** should be at least 60 bytes longer than the target file, zOut.
|