88 lines
2.3 KiB
C
88 lines
2.3 KiB
C
#include "arena_allocator.h"
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#include <assert.h>
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#include <stddef.h>
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#include <stdlib.h>
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#define DEFAUL_REGION_SIZE 1048576 /* 8 * 1024 * 1024 = 8MB */
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Region *new_region(size_t capacity) {
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if (capacity < DEFAUL_REGION_SIZE) {
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capacity = DEFAUL_REGION_SIZE;
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}
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Region *region = malloc(capacity + sizeof(Region));
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assert(region != NULL);
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*region = (Region){.next = NULL, .capacity = capacity, .cursor = 0};
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return region;
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}
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Arena arena_init(Arena *parent, size_t capacity) {
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Region *region = new_region(capacity);
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if (parent != NULL) {
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// Allocate new arena in parent to reduce likelyhood of loss
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Arena *current_arena = arena_alloc(parent, sizeof(Arena));
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*current_arena =
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(Arena){.begin = region, .end = region, .child = NULL, .sibling = NULL};
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// if parent has no children this arena is now it's child
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if (parent->child == NULL) {
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parent->child = current_arena;
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return *current_arena;
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}
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// Push the arena onto the first childs sibling list
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current_arena->sibling = parent->child;
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parent->child = current_arena;
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return *current_arena;
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}
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// This is the root of the arena tree
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Arena arena = {
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.begin = region, .end = region, .child = NULL, .sibling = NULL};
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return arena;
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}
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void arena_deinit(Arena *arena) {
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if (arena == NULL) {
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return;
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}
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// Recursively deinit children
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while (arena->child != NULL) {
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Arena *current_child = arena->child;
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arena->child = current_child->sibling;
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arena_deinit(current_child);
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}
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// actually free the data
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assert(arena->begin != NULL && arena->end != NULL);
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Region *region = arena->begin;
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while (region != NULL) {
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Region *next_region = region->next;
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free(region);
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region = next_region;
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}
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*arena = (Arena){.begin = NULL, .end = NULL};
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}
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void *arena_alloc(Arena *arena, size_t size) {
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// TODO: only align when needed
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size = (size + 7) & ~7; // align size increase to multiple of 8
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Region *region = arena->end;
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assert(region != NULL);
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if (region->cursor + size > region->capacity) {
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region->next = new_region(size);
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arena->end = region->next;
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region = region->next;
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}
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void *result = ®ion->data[region->cursor];
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region->cursor += size;
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return result;
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}
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// void *arena_clear(Arena *arena) {
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// arena->size = 0;
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// return arena->data;
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// }
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