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initgroups_dyn allocator optimization

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Motiejus Jakštys 2022-07-20 05:37:02 +03:00
parent a5f50fd63e
commit e34ee1d66b
1 changed files with 10 additions and 2 deletions

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@ -482,6 +482,7 @@ fn initgroups_dyn(
const offset = user.additional_gids_offset;
var vit = compress.varintSliceIteratorMust(db.additional_gids[offset..]);
var gids = compress.deltaDecompressionIterator(&vit);
const remaining = vit.remaining;
// the implementation below is ported from glibc's db-initgroups.c
// even though we know the size of the groups upfront, I found it too difficult
@ -493,10 +494,17 @@ fn initgroups_dyn(
return c.NSS_STATUS_SUCCESS;
const oldsize = @intCast(usize, size.*);
const newsize_want = blk: {
// double the oldsize until it is above or equal 'remaining'
var res = oldsize;
while (res < remaining) res *= 2;
break :blk res;
};
const newsize: usize = if (limit <= 0)
2 * oldsize
newsize_want
else
math.min(@intCast(usize, limit), 2 * oldsize);
math.min(@intCast(usize, limit), newsize_want);
var buf = groupsp.*[0..oldsize];
const new_groups = state.initgroups_dyn_allocator.realloc(buf, newsize);