50 lines
1.8 KiB
C
50 lines
1.8 KiB
C
/* This heap algorithm uses two different data structures: blocks and holes.
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* Blocks: Contiguous areas of memory containing user data
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* Holes: Special kind of blocks that are not in use, this is the result
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* of free() operation. Those spaces lend to a common problem called "Fragmentation";
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* where malloc() cannot use those spaces anymore because they are too small for any
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* kind of program. Any modern OS must have a solution to avoid this problem, but to keep
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* things simple as possible i wont implement anything like that.
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* Blocks/holes contains informations like the magic number(error checking), the type of
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* chunk(hole or block) and the size, while the footer contains only a pointer to the header
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* (and obviously an error checking flag).
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*/
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#ifndef KHEAP_H
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#define KHEAP_H
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#define KHEAP_START 0xC0000000 // starting location can be different
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#define KHEAP_INITIAL_SIZE 0x100000
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#define HEAP_INDEX_SIZE 0x20000
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#define HEAP_MAGIC 0x123890AB
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#define HEAP_MIN_SIZE 0x70000
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#include <stdint.h>
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#include "ordered_list.h"
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// Data structure for single block/hole
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typedef struct {
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uint32_t magic; // Magic number for error checking
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uint8_t is_hole; // 1 if its an hole, 0 for a block
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uint32_t size; // Size of the block
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} header_t;
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typedef struct {
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uint32_t magic;
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header_t *header; // Pointer to the head
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} footer_t;
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typedef struct {
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ordered_list_t index;
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uint32_t start_address; // Start of allocated space
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uint32_t end_address; // End of allocated space
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uint32_t max_address; // Maximum size, heap can be expanded to
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uint8_t supervisor;
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uint8_t readonly;
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} heap_t;
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// Heap functions
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heap_t *create_heap(uint32_t start, uint32_t end, uint32_t max, uint8_t supervisor, uint8_t readonly);
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void *alloc(uint32_t size, uint8_t page_align, heap_t *heap);
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void free(void *p, heap_t *heap);
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#endif |