From 86c5d0c1506c5bb8a938dec22fc673d35a449bfc Mon Sep 17 00:00:00 2001 From: Bruce Hill Date: Sun, 7 Feb 2021 14:10:19 -0800 Subject: [PATCH] Stabilized randomization so it doesn't reshuffle when reloading the same dir (but it still will if the dir contents change) --- bb.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/bb.c b/bb.c index da5f423..24b9515 100644 --- a/bb.c +++ b/bb.c @@ -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; }