86 lines
2.4 KiB
C
86 lines
2.4 KiB
C
#include "arena.h"
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#include <string.h>
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Arena *
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arena_init(void *mem, ptrdiff_t size) {
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Arena *arena = mem;
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arena->mem = arena + 1;
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arena->top = arena->mem;
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arena->lim = arena->mem + size;
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return arena;
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}
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static void *
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align_forward(void *ptr, ptrdiff_t align) {
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return (void *)(((uintptr_t)ptr + align - 1) & ~(align - 1));
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}
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static void
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arena_oom(Arena *arena, ptrdiff_t size, ptrdiff_t align) {
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loge("Out of memory in arena %p: requested size %ld, align %ld", arena, size, align);
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BP();
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}
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void *
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arena_alloc_aligned(Arena *arena, ptrdiff_t size, ptrdiff_t align) {
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uintptr_t start = (uintptr_t) align_forward(arena->top, align);
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if (start + size > (uintptr_t) arena->lim) {
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arena_oom(arena, size, align);
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return NULL;
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}
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memset((void *)start, 0, size);
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arena->top = (void *)(start + size);
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return (void *)start;
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}
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void *
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arena_realloc_aligned(Arena *arena, void *ptr, ptrdiff_t old_size, ptrdiff_t new_size, ptrdiff_t align) {
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if (ptr) {
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// check that pointer was allocated in this arena
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ASSERT((uintptr_t) ptr >= (uintptr_t) arena->mem);
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ASSERT((uintptr_t) ptr < (uintptr_t) arena->lim);
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ASSERT((uintptr_t) ptr + old_size <= (uintptr_t) arena->top);
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}
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void *result = NULL;
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if (false && ptr && (uintptr_t) ptr + old_size == (uintptr_t) arena->top) {
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// The block is at the top of the arena, so we can just attempt to extend it.
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if ((uintptr_t) ptr + new_size <= (uintptr_t) arena->lim) {
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// clear new memory
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memset((char *) ptr + old_size, 0, new_size - old_size);
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arena->top = ((char *) ptr + new_size);
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result = ptr;
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}
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else {
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arena_oom(arena, new_size, align);
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}
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}
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else {
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result = arena_alloc_aligned(arena, new_size, align);
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if (result) {
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if (ptr) {
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memcpy(result, ptr, old_size);
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}
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}
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else {
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arena_oom(arena, new_size, align);
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}
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}
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return result;
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}
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void
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arena_clear(Arena *arena) {
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arena_clear_overwrite(arena);
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arena->top = arena->mem;
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}
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void arena_clear_overwrite_with(Arena *arena, u8 value) {
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memset(arena->mem, value, (uintptr_t) arena->top - (uintptr_t) arena->mem);
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arena->top = arena->mem;
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}
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void arena_clear_overwrite(Arena *arena) {
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arena_clear_overwrite_with(arena, 0xCC);
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}
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