marCsweep/include/gc_malloc.h

66 lines
2.3 KiB
C

#ifndef GC_MALLOC_H
#define GC_MALLOC_H
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
// Generally, inline functions are preferable to macros resembling functions.
// https://www.kernel.org/doc/html/v4.10/process/coding-style.html#data-structures
#define ALIGN 8 /* Number of bytes to which chunk size is aligned */
#define OVERHEAD 1 /* Number of 8-byte segments for chunk size & flags */
#define MAGIC 2 /* Number of 8-byte segments from top of chunk to fields */
#define MIN 3 /* Minimum number of 8-byte segments for data in a chunk */
/*
* Metadata and user data for allocated memory
*
* footer: size of previous block or user data of previous block if allocated
* size: size of chunk in bytes
* merge: flag to identify when the chunk can be coalesced,
* possible values 0 (false, don't merge) or non-zero (true, do merge)
* free: flag to identify when the chunk is free,
* possible values 0 (false, allocated) or non-zero (true, chunk is free)
* next: pointer to next chunk in the free list
* prev: pointer to previous chunk in the free list
*/
struct gc_chunk {
uint64_t footer;
uint32_t size;
uint16_t merge; /* 1 = do merge, initialize to 0 */
uint16_t free; /* 0 = allocated, initialize to 1 */
struct gc_chunk *next;
struct gc_chunk *prev;
};
// Gets a pointer to the next chunk
struct gc_chunk *find_next_chunk(struct gc_chunk *curr);
// Gets a pointer to the previous chunk, ensuring that current can be coalesced
struct gc_chunk *find_prev_chunk(struct gc_chunk *curr);
// Updates chunk footer information (remember that the current chunk's footer
// data is actually part of the next chunk)
void set_footer(struct gc_chunk *curr);
// Gets footer information for the current chunk - useful for debugging
int get_footer(struct gc_chunk *curr);
// Creates a new chunk with sentinel
struct gc_chunk *init_gc_chunk(void);
// Gets a pointer to a suitable chunk from the free list, otherwise creates a
// new chunk and returns it's pointer
struct gc_chunk *find_free_chunk(size_t size);
// Coalesces chunks when merge flag is set
void merge_chunk(struct gc_chunk *curr);
// Performs allocations of SIZE bytes
void *gc_malloc(size_t size);
// Frees blocks of memory allocated by 'gc_alloc'
void gc_free(void *ptr);
#endif /* GC_MALLOC_H */