# Fossil

Check-in [726ab361]

 ```207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 ``` ```*/ static int digit_count(int v){ unsigned int i, x; for(i=1, x=64; v>=x; i++, x <<= 6){} return i; } /* ** Compute a 32-bit checksum on the N-byte buffer. Return the result. */ static unsigned int checksum(const char *zIn, size_t N){ const unsigned char *z = (const unsigned char *)zIn; 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); default: ; } return sum3; } /* ** 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. ``` ``` > > > > > > | > > > > > > > > > > > > > > > > > > > > > > > > > > | | | < | | | | | | | | | | | | | | | | | > > | | | | | ``` ```207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 ``` ```*/ 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 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 sum = 0; assert( (3&(sqlite3_uint64)z)==0 ); /* Four-byte alignment */ if( 0==*(char*)&byteOrderTest ){ /* This is a big-endian machine */ while( z=4003000 while( z=1300 while( z= 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 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. ```