memory/arena: add opportunistic free and realloc functions

This commit is contained in:
Andrei Alexeyev 2024-09-05 16:45:35 +02:00
parent 1fc752531a
commit 5e0d85af1b
No known key found for this signature in database
GPG key ID: 72D26128040B9690
2 changed files with 84 additions and 1 deletions

View file

@ -45,10 +45,15 @@ static void _arena_delete_page(MemArena *arena, MemArenaPage *page) {
_arena_dealloc_page(page);
}
static void *_arena_alloc(MemArena *arena, size_t size, size_t align) {
INLINE MemArenaPage *_arena_active_page(MemArena *arena) {
auto page = NOT_NULL(arena->pages.last);
assume(page->arena == arena);
assume(page->next == NULL);
return page;
}
static void *_arena_alloc(MemArena *arena, size_t size, size_t align) {
auto page = _arena_active_page(arena);
auto page_ofs = arena->page_offset;
size_t required, alignofs;
@ -75,6 +80,46 @@ static void *_arena_alloc(MemArena *arena, size_t size, size_t align) {
return p;
}
static bool _arena_free(MemArena *arena, void *p, size_t old_size) {
auto page = _arena_active_page(arena);
if(page->data + arena->page_offset - old_size == p) {
assert(arena->page_offset >= old_size);
arena->page_offset -= old_size;
arena->total_used -= old_size;
return true;
}
return false;
}
static void *_arena_realloc(MemArena *arena, void *p, size_t old_size, size_t new_size, size_t align) {
assert(((uintptr_t)p & (align - 1)) == 0);
if(_arena_free(arena, p, old_size)) {
void *new_p = _arena_alloc(arena, new_size, align);
if(p != new_p) {
// If free succeeded and old_size >= new_size, alloc will never make a new page
assert(old_size < new_size);
memcpy(new_p, p, old_size);
}
return new_p;
}
// Couldn't free: the allocation isn't at the tip of the page.
// If we aren't growing it, just leave it alone.
if(old_size >= new_size) {
return p;
}
void *new_p = _arena_alloc(arena, new_size, align);
memcpy(new_p, p, old_size);
return new_p;
}
void marena_init(MemArena *arena, size_t min_size) {
*arena = (MemArena) { };
_arena_new_page(arena, min_size);
@ -129,3 +174,22 @@ void *marena_alloc_aligned(MemArena *arena, size_t size, size_t align) {
return _arena_alloc(arena, size, align);
}
bool marena_free(MemArena *restrict arena, void *restrict p, size_t old_size) {
return _arena_free(arena, p, old_size);
}
void *marena_realloc(MemArena *restrict arena, void *restrict p, size_t old_size, size_t new_size) {
return _arena_realloc(arena, p, old_size, new_size, alignof(max_align_t));
}
void *marena_realloc_aligned(MemArena *restrict arena, void *restrict p, size_t old_size, size_t new_size, size_t align) {
assume(align > 0);
assume(!(align & (align - 1)));
if(align < alignof(max_align_t)) {
align = alignof(max_align_t);
}
return _arena_realloc(arena, p, old_size, new_size, align);
}

View file

@ -63,6 +63,25 @@ void *marena_alloc_aligned(MemArena *arena, size_t size, size_t alignment)
attr_returns_allocated
attr_nonnull_all;
bool marena_free(MemArena *restrict arena, void *restrict p, size_t old_size);
#define marena_assert_free(arena, p, old_size) ({ \
bool _freed = marena_free(arena, p, old_size); \
assert(_freed); \
(void)0; \
})
void *marena_realloc(MemArena *restrict arena, void *restrict p, size_t old_size, size_t new_size)
attr_alloc_size(4)
attr_nonnull(1)
attr_returns_allocated;
void *marena_realloc_aligned(MemArena *restrict arena, void *restrict p, size_t old_size, size_t new_size, size_t align)
attr_alloc_size(4)
attr_alloc_align(5)
attr_nonnull(1)
attr_returns_allocated;
INLINE void *marena_memdup(MemArena *arena, const void *buf, size_t size) {
return memcpy(marena_alloc(arena, size), buf, size);
}