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====== 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 malloc’d first before being passed to ''%%arena_init()%%''.

<code c>
typedef struct {
    unsigned char* buf;
    size_t buf_sz;
    size_t offset_cur;
    size_t offset_prev;
} ArenaAllocator;
</code>

===== 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.

<code c>
void arena_init(ArenaAllocator *allocator, size_t buf_sz);

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

==== arena_free ====

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

<code c>
void arena_free(ArenaAllocator *allocator);

/* Usage */
arena_free(allocator);
allocator = NULL;
</code>

==== 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

<code c>
void arena_clear(ArenaAllocator *allocator);
</code>

==== *arena_malloc ====

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

<code c>
void *arena_malloc(ArenaAllocator* allocator, size_t size);
</code>

==== 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.

<code c>
void arena_resize_buf(ArenaAllocator *allocator, size_t new_sz);
</code>

==== *arena_resize ====

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

<code c>
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);
</code>

===== Macros =====

==== arena_sz ====

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

<code c>
#define arena_sz(a) (a)->buf_sz
</code>

===== Pool Allocator =====

A pool-based allocator for chunks of the same size. Useful for quickly allocating and using memory of the same size without worrying about order; most operations are ''%%O(1)%%''

===== Structs =====

==== PoolAllocator ====

Represents a pool allocator. ''%%PoolAllocator%%'' holds its own buffer, but managing its size is left to the user. Like most structs in ''%%libflint%%'', it must be malloc’d first before being passed to ''%%pool_init()%%''.

<code c>
typedef struct {
    unsigned char *buf;
    size_t buf_sz;
    size_t chunk_size;

    List *free_list;
} PoolAllocator;
</code>

===== Functions =====

==== pool_init ====

Initializes the ''%%PoolAllocator%%''. The struct must first be created by the user using ''%%malloc()%%'', see the example below.

  * ''%%buf_sz%%'': Size of the underlying buffer in bytes
  * ''%%chunk_sz%%'': Size of each chunk in bytes
  * ''%%chunk_align%%'': The alignment of the chunks. The''%%LF_DEFAULT_ALIGNMENT%%'' macro is available as a good default for basic types

<code c>
void pool_init(PoolAllocator *allocator, size_t buf_sz, size_t chunk_sz, size_t chunk_align);

/* Usage */
PoolAllocator *pool = malloc(sizeof(PoolAllocator));
pool_init(pool, 64, 16, LF_DEFAULT_ALIGNMENT);
</code>

==== pool_free ====

Return a single chunk back to the pool. ''%%ptr%%'' is a pointer to the allocated chunk.

<code c>
void pool_free(PoolAllocator *allocator, void *ptr);
</code>

==== pool_free_all ====

Returns all chunks back to the pool. Any pointers received before this call are now invalid and must be reasigned with ''%%pool_alloc%%'' or set to ''%%NULL%%''.

<code c>
void pool_free_all(PoolAllocator *allocator);
</code>

==== pool_alloc ====

Allocate a chunk from the pool. Returns ''%%NULL%%'' on failure.

<code c>
void *pool_alloc(PoolAllocator *allocator);
</code>

==== pool_destroy ====

Destroys the underlying buffer and ''%%List%%'' in ''%%allocator%%'', then frees it. User is responsible for setting ''%%allocator%%'' to ''%%NULL%%'' afterwards.

<code c>
void pool_destroy(PoolAllocator *allocator);
</code>

===== Macros =====

==== pool_count_available ====

Returns the amount of chunks left available in the pool

<code c>
#define pool_count_available(x) (x)->free_list->size
</code>

==== LF_DEFAULT_ALIGNMENT ====

The default alignment for allocators. Use this as a simple default (defaults to 16 bytes on amd64 systems) when storing basic types

<code c>
#ifndef DEFAULT_ALIGNMENT
#define LF_DEFAULT_ALIGNMENT (2*sizeof(void*))
#endif // DEFAULT_ALIGNMENT
</code>
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