74 lines
2.2 KiB
C
74 lines
2.2 KiB
C
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#include <glib.h>
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#include <stdint.h>
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#include <sys/types.h>
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#include "allocator.h"
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struct arena_link {
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// TODO:
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// For efficiency, we should probably allocate the arena links in
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// their own slice, and link to a block directly. That can be
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// implemented later, though, with no change in interface.
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struct arena_link *next; // It is crucial that this be the first item; so that
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// any arena link can be casted to struct arena_link**.
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size_t free;
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size_t used;
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uint8_t rest[];
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} ;
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struct arena {
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struct arena_link *head;
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size_t block_size;
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};
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arena_t new_arena(size_t block_size) {
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struct arena *ret = g_new(struct arena, 1);
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struct arena_link *link = (struct arena_link*)g_malloc0(sizeof(struct arena_link) + block_size);
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link->free = block_size;
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link->used = 0;
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link->next = NULL;
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ret->head = link;
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ret->block_size = 0;
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return ret;
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}
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void* arena_malloc(arena_t arena, size_t size) {
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if (size <= arena->head->free) {
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// fast path..
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void* ret = arena->head->rest + arena->head->used;
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arena->head->used += size;
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arena->head->free -= size;
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return ret;
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} else if (size > arena->block_size) {
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// We need a new, dedicated block for it, because it won't fit in a standard sized one.
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// This involves some annoying casting...
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void* link = g_malloc(size + sizeof(struct arena_link*));
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*(struct arena_link**)link = arena->head->next;
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arena->head->next = (struct arena_link*)link;
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return (void*)((uint8_t*)link + sizeof(struct arena_link*));
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} else {
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// we just need to allocate an ordinary new block.
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struct arena_link *link = (struct arena_link*)g_malloc0(sizeof(struct arena_link) + arena->block_size);
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link->free = arena->block_size - size;
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link->used = size;
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link->next = arena->head;
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arena->head = link;
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return link->rest;
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}
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}
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void delete_arena(arena_t arena) {
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struct arena_link *link = arena->head;
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while (link) {
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struct arena_link *next = link->next;
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// Even in the case of a special block, without the full arena
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// header, this is correct, because the next pointer is the first
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// in the structure.
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g_free(link);
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link = next;
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}
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g_free(arena);
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}
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