memory.c File Reference

Implementation of arena allocator and growable array utilities. More...

#include "memory.h"
#include <stdarg.h>
#include <stdio.h>
#include <stdnoreturn.h>
#include <string.h>
#include <stdint.h>

Include dependency graph for memory.c:

Functions
noreturn void	die (const char *fmt,...)
	Prints a fatal error message and exits the program.
void *	xmalloc (size_t size)
	Allocates memory and checks for allocation failure. If !size it will still return a valid pointer that can be freed.
void *	xcalloc (size_t nr, size_t size)
	Allocates zero-init memory and checks for allocation failure. If !size it will still return a valid pointer.
char *	xstrdup (const char *str)
	Duplicates a string and checks for allocation failure.
Buffer *	buffer_create (size_t s, size_t alignment)
	Creates a new aligned buffer for the arena allocator.
int	arena_allocator_init (ArenaAllocator *arena, size_t initial_size)
	Initializes an ArenaAllocator with a specified initial buffer size.
void *	arena_alloc (ArenaAllocator *arena, size_t size, size_t alignment)
	Allocates memory from the arena allocator with automatic buffer growth.
void *	arena_realloc (ArenaAllocator *arena, void *ptr, size_t old_size, size_t new_size, size_t alignment)
	Reallocates memory from the arena allocator.
void	arena_reset (ArenaAllocator *arena)
	Resets the arena allocator, making all buffers reusable.
void	arena_destroy (ArenaAllocator *arena)
	Frees all buffers and resets the arena allocator.
size_t	arena_get_total_allocated (ArenaAllocator *arena)
	Returns the total number of bytes allocated across all buffers.
void	arena_print_stats (ArenaAllocator *arena)
	Prints statistics about the arena allocator to stderr.
char *	arena_strdup (ArenaAllocator *arena, const char *src)
	Duplicates a null-terminated string into arena-allocated memory.
bool	growable_array_init (GrowableArray *arr, ArenaAllocator *arena, size_t initial_capacity, size_t item_size)
	Initializes a GrowableArray backed by an arena allocator.
void *	growable_array_push (GrowableArray *arr)
	Pushes a new element onto the growable array, resizing if necessary.

Detailed Description

Implementation of arena allocator and growable array utilities.

This module implements a memory arena allocator that reduces overhead by allocating large buffers and serving sequential allocations from them. It also provides a growable array type that uses the arena for backing storage.

Features:

• Dynamic buffer sizing with growth factor.
• Aligned allocations.
• Reset and free all buffers at once.
• Debug print support for allocations and frees.

See also

memory.h

Function Documentation

arena_alloc()

void * arena_alloc	(	ArenaAllocator *	arena,
		size_t	size,
		size_t	alignment
	)

Allocates memory from the arena allocator with automatic buffer growth.

Allocates memory from the arena.

Attempts to allocate aligned memory from current buffers. If insufficient space, it moves to the next buffer or allocates a new one.

Large allocations create dedicated buffers.

Parameters

arena	Pointer to the ArenaAllocator.
size	Number of bytes to allocate.
alignment	Memory alignment requirement.

Returns

Pointer to allocated memory or NULL on failure.

arena_allocator_init()

int arena_allocator_init	(	ArenaAllocator *	arena,
		size_t	initial_size
	)

Initializes an ArenaAllocator with a specified initial buffer size.

Initializes an arena allocator.

Allocates the first buffer and sets initial parameters.

Parameters

arena	Pointer to the ArenaAllocator to initialize.
initial_size	Initial buffer size to allocate (will be clamped to minimum size).

Returns

0 on success, -1 on failure.

arena_destroy()

void arena_destroy

(

ArenaAllocator *

arena

)

Frees all buffers and resets the arena allocator.

Frees all memory used by the arena.

Parameters

arena

Pointer to the ArenaAllocator to destroy.

arena_get_total_allocated()

size_t arena_get_total_allocated

(

ArenaAllocator *

arena

)

Returns the total number of bytes allocated across all buffers.

Gets the total number of bytes allocated across all buffers.

Parameters

arena

Pointer to the ArenaAllocator.

Returns

Total allocated bytes, or 0 if arena is NULL.

arena_print_stats()

void arena_print_stats

(

ArenaAllocator *

arena

)

Prints statistics about the arena allocator to stderr.

Prints statistics about arena memory usage.

Includes number of buffers, total allocated memory, current buffer and offset, and the planned size for the next buffer.

Parameters

arena

Pointer to the ArenaAllocator.

arena_realloc()

void * arena_realloc	(	ArenaAllocator *	arena,
		void *	ptr,
		size_t	old_size,
		size_t	new_size,
		size_t	alignment
	)

Reallocates memory from the arena allocator.

WARNING: This implementation has limitations due to arena allocator design:

• Can only shrink or grow the MOST RECENTLY allocated block in the current buffer
• Cannot reclaim space from shrunk allocations
• Falls back to allocate-and-copy for other cases

Parameters

arena	Pointer to the ArenaAllocator.
ptr	Pointer to previously allocated memory (can be NULL).
old_size	Size of the previous allocation (required for validation).
new_size	New size requested.
alignment	Memory alignment requirement.

Returns

Pointer to reallocated memory or NULL on failure.

arena_reset()

void arena_reset

(

ArenaAllocator *

arena

)

Resets the arena allocator, making all buffers reusable.

Resets the arena, keeping buffers but making them empty.

Does not free memory; resets the current allocation offset and buffer pointer.

Parameters

arena

Pointer to the ArenaAllocator to reset.

arena_strdup()

char * arena_strdup	(	ArenaAllocator *	arena,
		const char *	src
	)

Duplicates a null-terminated string into arena-allocated memory.

Duplicates a string into arena-managed memory.

Parameters

arena	Pointer to the ArenaAllocator.
src	Null-terminated source string.

Returns

Pointer to the duplicated string in arena memory, or NULL on failure.

buffer_create()

Buffer * buffer_create	(	size_t	s,
		size_t	alignment
	)

Creates a new aligned buffer for the arena allocator.

Creates a new buffer with given size and alignment.

Allocates memory for a Buffer struct plus usable space aligned according to the alignment.

Parameters

s	Size of usable memory requested.s
alignment	Alignment requirement for the usable memory.

Returns

Pointer to the new Buffer on success, or NULL on failure.

die()

noreturn void die	(	const char *	fmt,
			...
	)

Prints a fatal error message and exits the program.

Parameters

fmt	Format string for the error message.
...	Additional arguments for the format string.

growable_array_init()

bool growable_array_init	(	GrowableArray *	arr,
		ArenaAllocator *	arena,
		size_t	initial_capacity,
		size_t	item_size
	)

Initializes a GrowableArray backed by an arena allocator.

Initializes a growable array using an arena allocator.

Allocates initial storage for the array and sets metadata.

Parameters

arr	Pointer to the GrowableArray to initialize.
arena	Pointer to the ArenaAllocator for backing storage.
initial_capacity	Initial number of elements to allocate space for.
item_size	Size in bytes of each element.

Returns

true on success, false on failure.

growable_array_push()

void * growable_array_push

(

GrowableArray *

arr

)

Pushes a new element onto the growable array, resizing if necessary.

Pushes a new element onto the growable array.

Automatically doubles the array capacity and copies existing elements into new arena memory when full.

Parameters

arr	Pointer to the GrowableArray.

Returns

Pointer to the newly allocated element slot, or NULL on failure.

xcalloc()

void * xcalloc	(	size_t	nr,
		size_t	size
	)

Allocates zero-init memory and checks for allocation failure. If !size it will still return a valid pointer.

Parameters

nr	Number of elements to allocate.
size	Size of each element.

Returns

Pointer to the allocated memory on success.

xmalloc()

void * xmalloc

(

size_t

size

)

Allocates memory and checks for allocation failure. If !size it will still return a valid pointer that can be freed.

Parameters

size	Number of bytes to allocate.

Returns

Pointer to the allocated memory on success.

xstrdup()

char * xstrdup

(

const char *

str

)

Duplicates a string and checks for allocation failure.

Parameters

str	The string to duplicate.

Returns

Pointer to the duplicated string on success.