arena.c File Reference

#include <stddef.h>
#include <string.h>
#include <htils/arena.h>
#include <htils/assert.h>
#include <htils/basictypes.h>

Macros
#define	__STDC_WANT_LIB_EXT1__   1
#define	MIN(a, b)   ((a < b) ? a : b)
#define	MAX(a, b)   ((a > b) ? a : b)
#define	ALIGN_POW2(num, pow)    (((u64)(num) + ((u64)(pow) - 1)) & (~((u64)(pow) - 1)))
	Aligns a number to a power of 2, if pow is a power of two.
#define	ARENA_BASE_POS   (sizeof(arena_t))
#define	ARENA_ALIGNMENT   (_Alignof(max_align_t))

Functions
arena_t *	arena_new (u64 reserve_size, u64 commit_size)
	Create a new arena.
void	arena_free (arena_t *arena)
	Free an arena.
void *	__arena_alloc (struct arena *arena, u64 size)
	Allocate a chunk of memory to the arena.
void *	__arena_alloc_zeroed (struct arena *arena, u64 size)
	Allocate a chunk of zeroed memory to the arena.
void	__arena_dealloc (struct arena *arena, u64 size)
	Deallocate a chunk of memory from the arena.
void	arena_dealloc_to (arena_t *arena, u64 pos)
	Set arena position to @pos.
void	arena_clear (arena_t *arena)
	Clear the arena.
temp_arena_t	temp_arena_new (arena_t *arena)
	Create a new temp_arena.
void	temp_arena_free (temp_arena_t temp)
	Free a temp_arena.

Macro Definition Documentation

__STDC_WANT_LIB_EXT1__

#define __STDC_WANT_LIB_EXT1__   1

ALIGN_POW2

#define ALIGN_POW2	(		num,
			pow
	)		(((u64)(num) + ((u64)(pow) - 1)) & (~((u64)(pow) - 1)))

Aligns a number to a power of 2, if pow is a power of two.

By adding pow - 1 to the number, and then masking out the rest to align properly.

Parameters

num	The number to align.
pow	The power of 2 to align to.

ARENA_ALIGNMENT

#define ARENA_ALIGNMENT   (_Alignof(max_align_t))

The alignment of an arena, which is the alignment of max_align_t.

ARENA_BASE_POS

#define ARENA_BASE_POS   (sizeof(arena_t))

The base position of an arena.

MAX

#define MAX	(		a,
			b
	)		((a > b) ? a : b)

MIN

#define MIN	(		a,
			b
	)		((a < b) ? a : b)

Function Documentation

__arena_alloc()

void * __arena_alloc	(	struct arena *	arena,
		u64	size
	)

Allocate a chunk of memory to the arena.

Note

This function is not meant to be run directly, and is called by the arena_alloc() macro.

Through basically pushing the position forwards and returning a small chunk of memory from the committed heap.

Parameters

arena	The arena to allocate from.
size	The size of the chunk to allocate.

Precondition

• arena and size must be valid and cannot be null.
• size must be greater than 0.

Returns

A pointer to the allocated chunk.

See also

arena_alloc()

__arena_alloc_zeroed()

void * __arena_alloc_zeroed	(	struct arena *	arena,
		u64	size
	)

Allocate a chunk of zeroed memory to the arena.

Note

This function is not meant to be run directly, and is called by the arena_alloc_zeroed() macro.

Through basically pushing the position forwards and returning a small chunk of memory from the committed heap.

Parameters

arena	The arena to allocate from.
size	The size of the chunk to allocate.

Precondition

• arena and size must be valid and cannot be null.
• size must be greater than 0.

Returns

A pointer to the allocated chunk.

See also

arena_alloc()

__arena_dealloc()

void __arena_dealloc	(	struct arena *	arena,
		u64	size
	)

Deallocate a chunk of memory from the arena.

Note

This function is not meant to be run directly, and is called by the arena_dealloc() macro.

Through basically popping back the position, so that it may be reused for other allocations.

Parameters

arena	The arena to deallocate from.
size	The size of the chunk to deallocate.

Precondition

• arena and size must be valid and cannot be null.
• size must be greater than 0.

See also

arena_dealloc()

arena_clear()

void arena_clear

(

arena_t *

arena

)

Clear the arena.

Pops the arena to the base position of ARENA_BASE_POS using arena_dealloc_to(), then flushes the commit position using mem_decommit() and mem_commit().

Parameters

arena

The arena to clear.

Precondition

arena must be valid and cannot be null.

See also

arena_dealloc_to()

arena_dealloc_to()

void arena_dealloc_to	(	arena_t *	arena,
		u64	pos
	)

Set arena position to @pos.

Through setting the position of the arena to pos, useful for clearing or removing a chunk of data you know you dont need any more. Uses __arena_dealloc() internally.

Parameters

arena	The arena to deallocate from.
pos	The position to deallocate to.

Precondition

• arena and pos must be valid and cannot be null.
• pos must be greater than 0.

See also

__arena_dealloc()

arena_free()

void arena_free

(

arena_t *

arena

)

Free an arena.

Frees an arena using munmap() or VirtualFree(), depending on system, this is rarely needed cause the kernel usually frees these pages for you, but its useful if you use multiple arenas..

Parameters

arena

The arena to free.

Precondition

arena must be valid and cannot be null.

See also

munmap(), VirtualFree()

arena_new()

arena_t * arena_new	(	u64	reserve_size,
		u64	commit_size
	)

Create a new arena.

Initializes a new arena using mmap() or VirtualAlloc(), depending on system.

Parameters

reserve_size	The size of the arena to reserve.
commit_size	The size of the arena to commit.

Precondition

• reserve_size must be greater than 0.
• commit_size must be greater than 0 and less than or equal to reserve_size.

Returns

A pointer to the new arena.

See also

mmap(), VirtualAlloc()

temp_arena_free()

void temp_arena_free

(

temp_arena_t

temp

)

Free a temp_arena.

By popping the arena back to the position it was at when the temp arena was initialized using temp_arena_new().

Parameters

temp	The temp_arena to free.

Precondition

temp must be valid and cannot be null.

See also

temp_arena_new()

temp_arena_new()

temp_arena_t temp_arena_new

(

arena_t *

arena

)

Create a new temp_arena.

Through saving a snapshot of the current pos param of the arena, to then pop back to when you run temp_arena_free().

Parameters

arena

The arena to create the temporary arena from.

Precondition

arena must be valid and cannot be null.

®return The new temp_arena.

See also

temp_arena_free()