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Make map_t size deterministic; 

Currently, the amount of memory allocated for a map can sometimes be
different depending on whether it was allocated with an initial capacity
or the items were added iteratively.

This causes problems for people that want to copy data between maps that
have the same number of elements.

Now, the size of a map will always be the same for a given number of
elements, regardless of how the elements are added.

Plus this gets rid of the weird prevpo2 function.  Yay.
This commit is contained in:
bjorn 2022-06-14 16:52:19 -07:00
parent fbe54d5dca
commit af8f650a07
1 changed files with 4 additions and 10 deletions
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14
src/util.c
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@ -65,15 +65,6 @@ void* arr_alloc(void* data, size_t size) {
}
// Hashmap
static uint32_t prevpo2(uint32_t x) {
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
return x - (x >> 1);
}
static void map_rehash(map_t* map) {
map_t old = *map;
map->size <<= 1;
@ -110,7 +101,10 @@ static inline uint64_t map_find(map_t* map, uint64_t hash) {
}
void map_init(map_t* map, uint32_t n) {
map->size = prevpo2(n) + !n;
map->size = 1;
while (map->size + (map->size >> 1) < n) {
map->size <<= 1;
}
map->used = 0;
map->hashes = NULL;
map_rehash(map);