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