memory

Custom allocators and memory functions

Arena Allocator

A simple arena-style allocator

Structs

ArenaAllocator

Represents an arena allocator. ArenaAllocator holds its own buffer, but managing its size is left to the user. Like most structs in libflint, it must be malloced first before being passed to arena_init().

typedef struct {
    unsigned char* buf;
    size_t buf_sz;
    size_t offset_cur;
    size_t offset_prev;
} ArenaAllocator;

Functions

arena_init

Initializes the ArenaAllocator. The struct must first be created by the user using malloc(), see the example below. buf_sz is the size of the underlying buffer in bytes.

void arena_init(ArenaAllocator *allocator, size_t buf_sz);

/* Usage */
ArenaAllocator *a = malloc(sizeof(ArenaAllocator));
arena_init(a, 1024);

arena_free

Frees allocator and its underlying buffer. Users should set allocator to NULL after calling arena_free().

void arena_free(ArenaAllocator *allocator);

/* Usage */
arena_free(allocator);
allocator = NULL;

arena_clear

Resets the offset markers of the arena to 0, but does not wipe the underlying buffer. Technically, any assigned pointers will still work and

void arena_clear(ArenaAllocator *allocator);

*arena_malloc

Request memory of size bytes in length from the arena. Returns NULL if the assignment failed.

void *arena_malloc(ArenaAllocator* allocator, size_t size);

arena_resize_buf

Reallocates the underlying buffer in the arena to new_sz. You can grow or shrink the arena using this function. Any pointers allocated out of the arena are invalid after using this function.

void arena_resize_buf(ArenaAllocator *allocator, size_t new_sz);

*arena_resize

Resize an allocated pointer from the arena. See the example below for a simple use case

void *arena_resize(ArenaAllocator *allocator, void *mem, size_t old_sz, size_t new_sz);

/* Usage */
int *i = arena_malloc(a, sizeof(int));
*i = 1;
long *l = arena_resize(a, i1, sizeof(int), sizeof(long));
assert(*l == 1);

Macros

arena_sz

Convenience macro for getting the size of the arena's buffer

#define arena_sz(a) (a)->buf_sz

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