From 724aa38fc2de14909663cb984a9de64a561abf5f Mon Sep 17 00:00:00 2001 From: Kenny Levinsen Date: Thu, 18 Aug 2022 11:51:21 +0200 Subject: 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. --- util/array.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'util') diff --git a/util/array.c b/util/array.c index 50025b77..9da26127 100644 --- a/util/array.c +++ b/util/array.c @@ -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); 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; +} -- cgit v1.2.3