mem_allocator.h File Reference

Generic interface for abstracting memory allocators. More...

#include "base/base_macros.h"
#include "base/base_types.h"

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Classes
struct	MemAllocator
	An abstract allocator interface. More...

Macros
#define	MAKE(type, count, alloc)
	Allocates and zero-initialises an array of count elements of type.
#define	MAKE_STRUCT(type, alloc)
	Allocates and zero-initialises a single instance of type.
#define	RELEASE(type, count, ptr, alloc)
	Frees a previously allocated block through the allocator.

Typedefs
typedef enum MemAllocMode	MemAllocMode
	Describes the type of memory operation being requested.
typedef void *(*	MemAllocFn) (MemAllocMode mode, void *ctx, usize size, void *old_ptr)
	The core function signature for an abstract allocator.
typedef struct MemAllocator	MemAllocator
	An abstract allocator interface.

Enumerations
enum	MemAllocMode { MEM_ALLOC_MODE_ALLOC , MEM_ALLOC_MODE_FREE , MEM_ALLOC_MODE_REALLOC , MEM_ALLOC_MODE_FREE_ALL }
	Describes the type of memory operation being requested. More...

Functions
function void *	mem_alloc (MemAllocator *alloc, usize size)
	Allocator Helper Functions.
function void *	mem_realloc (MemAllocator *alloc, void *old_ptr, usize old_size, usize new_size)
	Resizes a previously allocated block through the allocator.
function void	mem_free (MemAllocator *alloc, void *ptr, usize size)
	Frees a previously allocated block through the allocator.
function void	mem_free_all (MemAllocator *alloc)
	Clears the entire allocator in one shot (e.g. arena reset, pool reset).

Detailed Description

Generic interface for abstracting memory allocators.

Allows data structures to accept a generic allocator interface rather than hardcoding a dependency on an Arena or General Purpose Allocator. Code that takes a MemAllocator works with any backing allocator without recompilation.

Usage

// Wrap an arena in the generic interface:
MemArena     arena = mem_arena_create(MB(64));
MemAllocator alloc = mem_arena_allocator(&arena);
 
// Allocate through the interface (zero-initialized):
MyStruct *s = MAKE_STRUCT(MyStruct, &alloc);
s->x = 10;
 
// Allocate an array:
int *buf = MAKE(int, 256, &alloc);
 
// Free is a no-op for arenas, but portable for any allocator:
RELEASE(int, 256, buf, &alloc);
 
// Reset the allocator (arena clear, pool reset, etc.):
mem_free_all(&alloc);

Implementing a custom allocator

static void *
my_alloc_fn(MemAllocMode mode, void *ctx, usize size, void *old_ptr)
{
    MyAllocState *state = (MyAllocState *)ctx;
    switch (mode) {
    case MEM_ALLOC_MODE_ALLOC:   return my_alloc(state, size);
    case MEM_ALLOC_MODE_FREE:    my_free(state, old_ptr); return NULL;
    case MEM_ALLOC_MODE_REALLOC: return my_realloc(state, old_ptr, size);
    case MEM_ALLOC_MODE_FREE_ALL: my_reset(state); return NULL;
    }
    return NULL;
}
 
MemAllocator alloc = { .fn = my_alloc_fn, .ctx = &my_state };

Copyright

2026 Alfred Jijo (MIT License)

Definition in file mem_allocator.h.