util/array: Add array_realloc for wl_array

array_realloc will grow the array for the target size like wl_insert_add, but
will also shrink the array if the target size is sufficiently smaller than the
current allocation.
This commit is contained in:
Kenny Levinsen 2022-08-18 11:51:21 +02:00
parent 9ab819684d
commit 724aa38fc2
2 changed files with 34 additions and 0 deletions

View File

@ -27,4 +27,9 @@ bool set_remove(uint32_t values[], size_t *len, size_t cap, uint32_t target);
*/ */
void array_remove_at(struct wl_array *arr, size_t offset, size_t size); void array_remove_at(struct wl_array *arr, size_t offset, size_t size);
/**
* Grow or shrink the array to fit the specifized size.
*/
bool array_realloc(struct wl_array *arr, size_t size);
#endif #endif

View File

@ -55,3 +55,32 @@ void array_remove_at(struct wl_array *arr, size_t offset, size_t size) {
memmove(&data[offset], &data[offset + size], arr->size - offset - size); memmove(&data[offset], &data[offset + size], arr->size - offset - size);
arr->size -= size; arr->size -= size;
} }
bool array_realloc(struct wl_array *arr, size_t size) {
// If the size is less than 1/4th of the allocation size, we shrink it.
// 1/4th is picked to provide hysteresis, without which an array with size
// arr->alloc would constantly reallocate if an element is added and then
// removed continously.
size_t alloc;
if (arr->alloc > 0 && size > arr->alloc / 4) {
alloc = arr->alloc;
} else {
alloc = 16;
}
while (alloc < size) {
alloc *= 2;
}
if (alloc == arr->alloc) {
return true;
}
void *data = realloc(arr->data, alloc);
if (data == NULL) {
return false;
}
arr->data = data;
arr->alloc = alloc;
return true;
}