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Overview
Comment: | Use intrinsic byte-swapping functions to boost the performance of delta checksums. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
7338b3a9510281e7d49643f55a5c27c2 |
User & Date: | drh 2015-12-31 15:45:10.207 |
Context
2015-12-31
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15:46 | Add MIME types for C# and VB.NET. ... (check-in: 5e81f4c0 user: drh tags: trunk) | |
15:45 | Use intrinsic byte-swapping functions to boost the performance of delta checksums. ... (check-in: 7338b3a9 user: drh tags: trunk) | |
15:44 | Update the built-in SQLite to 3.10.0 beta for SQLite testing. ... (check-in: ec8394e1 user: drh tags: trunk) | |
15:18 | Use intrinsic functions to boost the performance of the delta checksum. ... (Closed-Leaf check-in: 726ab361 user: drh tags: checksum-intrinsics) | |
Changes
Changes to src/delta.c.
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207 208 209 210 211 212 213 214 | */ static int digit_count(int v){ unsigned int i, x; for(i=1, x=64; v>=x; i++, x <<= 6){} return i; } /* | > > > > > > | > > > > > | > > > > > > > > > > > > > > > > > > > > | | | | | | | | | | | | | | | | | | | | > > | | | | | | 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<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 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. |
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