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Stabilized randomization so it doesn't reshuffle when reloading the same

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dir (but it still will if the dir contents change)
This commit is contained in:
Bruce Hill 2021-02-07 14:10:19 -08:00
parent 2755cbc869
commit 86c5d0c150
1 changed files with 7 additions and 1 deletions
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8
bb.c
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@ -533,8 +533,14 @@ static int populate_files(bb_t *bb, const char *path)
globfree(&globbuf);
}
// RNG is seeded with a hash of all the inodes in the current dir
// This hash algorithm is based on Python's frozenset hashing
unsigned long seed = (unsigned long)bb->nfiles * 1927868237UL;
for (int i = 0; i < bb->nfiles; i++)
seed ^= ((bb->files[i]->info.st_ino ^ 89869747UL) ^ (bb->files[i]->info.st_ino << 16)) * 3644798167UL;
srand((unsigned int)seed);
for (int i = 0; i < bb->nfiles; i++) {
int j = rand() / (RAND_MAX / (i + 1)); // This is not optimal, but doesn't need to be
int j = rand() % (i+1); // This introduces some RNG bias, but it's not important here
bb->files[i]->shufflepos = bb->files[j]->shufflepos;
bb->files[j]->shufflepos = i;
}