mem.c File Reference

Dynamic memory manager.

This is a lightweight replacement for the standard C library malloc().

If you want to use the standard C library malloc() instead, define MEM_LIBC_MALLOC to 1 in your lwipopts.h

To let mem_malloc() use pools (prevents fragmentation and is much faster than a heap but might waste some memory), define MEM_USE_POOLS to 1, define MEM_USE_CUSTOM_POOLS to 1 and create a file "lwippools.h" that includes a list of pools like this (more pools can be added between _START and _END):

Define three pools with sizes 256, 512, and 1512 bytes LWIP_MALLOC_MEMPOOL_START LWIP_MALLOC_MEMPOOL(20, 256) LWIP_MALLOC_MEMPOOL(10, 512) LWIP_MALLOC_MEMPOOL(5, 1512) LWIP_MALLOC_MEMPOOL_END

#include "lwip/opt.h"
#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/sys.h"
#include "lwip/stats.h"
#include "lwip/err.h"
#include <string.h>

Data Structures
struct	mem
	The heap is made up as a list of structs of this type. More...

Macros
#define	LWIP_MEM_ALLOC_DECL_PROTECT()
#define	LWIP_MEM_ALLOC_PROTECT()
#define	LWIP_MEM_ALLOC_UNPROTECT()
#define	LWIP_MEM_FREE_DECL_PROTECT()
	concurrent access protection More...
#define	LWIP_MEM_FREE_PROTECT()   sys_mutex_lock(&mem_mutex)
#define	LWIP_MEM_FREE_UNPROTECT()   sys_mutex_unlock(&mem_mutex)
#define	LWIP_RAM_HEAP_POINTER   ram_heap
#define	MEM_SIZE_ALIGNED   LWIP_MEM_ALIGN_SIZE(MEM_SIZE)
#define	MIN_SIZE   12
	All allocated blocks will be MIN_SIZE bytes big, at least! MIN_SIZE can be overridden to suit your needs. More...
#define	MIN_SIZE_ALIGNED   LWIP_MEM_ALIGN_SIZE(MIN_SIZE)
#define	SIZEOF_STRUCT_MEM   LWIP_MEM_ALIGN_SIZE(sizeof(struct mem))

Functions
void *	mem_calloc (mem_size_t count, mem_size_t size)
	Contiguously allocates enough space for count objects that are size bytes of memory each and returns a pointer to the allocated memory. More...
void	mem_free (void *rmem)
	Put a struct mem back on the heap. More...
void	mem_init (void)
	Zero the heap and initialize start, end and lowest-free. More...
void *	mem_malloc (mem_size_t size)
	Adam's mem_malloc() plus solution for bug #17922 Allocate a block of memory with a minimum of 'size' bytes. More...
void *	mem_trim (void *rmem, mem_size_t newsize)
	Shrink memory returned by mem_malloc(). More...
static void	plug_holes (struct mem *mem)
	"Plug holes" by combining adjacent empty struct mems. More...

Variables
static struct mem *	lfree
	pointer to the lowest free block, this is used for faster search More...
static u8_t *	ram
	pointer to the heap (ram_heap): for alignment, ram is now a pointer instead of an array More...
static struct mem *	ram_end
	the last entry, always unused! More...
u8_t	ram_heap [MEM_SIZE_ALIGNED+(2 *SIZEOF_STRUCT_MEM)+MEM_ALIGNMENT]
	If you want to relocate the heap to external memory, simply define LWIP_RAM_HEAP_POINTER as a void-pointer to that location. More...

#define LWIP_MEM_ALLOC_DECL_PROTECT

(

)

Referenced by mem_malloc().

#define LWIP_MEM_ALLOC_PROTECT

(

)

Referenced by mem_malloc().

#define LWIP_MEM_ALLOC_UNPROTECT

(

)

Referenced by mem_malloc().

#define LWIP_MEM_FREE_DECL_PROTECT

(

)

concurrent access protection

Referenced by mem_free(), and mem_trim().

#define LWIP_MEM_FREE_PROTECT

(

)

sys_mutex_lock(&mem_mutex)

Referenced by mem_free(), and mem_trim().

#define LWIP_MEM_FREE_UNPROTECT

(

)

sys_mutex_unlock(&mem_mutex)

Referenced by mem_free(), and mem_trim().

#define LWIP_RAM_HEAP_POINTER   ram_heap

Referenced by mem_init().

#define MEM_SIZE_ALIGNED   LWIP_MEM_ALIGN_SIZE(MEM_SIZE)

Referenced by mem_init(), mem_malloc(), mem_trim(), and plug_holes().

#define MIN_SIZE   12

All allocated blocks will be MIN_SIZE bytes big, at least! MIN_SIZE can be overridden to suit your needs.

Smaller values save space, larger values could prevent too small blocks to fragment the RAM too much.

#define MIN_SIZE_ALIGNED   LWIP_MEM_ALIGN_SIZE(MIN_SIZE)

Referenced by mem_malloc(), and mem_trim().

#define SIZEOF_STRUCT_MEM   LWIP_MEM_ALIGN_SIZE(sizeof(struct mem))

Referenced by mem_free(), mem_init(), mem_malloc(), and mem_trim().

void* mem_calloc	(	mem_size_t	count,
		mem_size_t	size
	)

Contiguously allocates enough space for count objects that are size bytes of memory each and returns a pointer to the allocated memory.

The allocated memory is filled with bytes of value zero.

Parameters

count	number of objects to allocate
size	size of the objects to allocate

Returns

pointer to allocated memory / NULL pointer if there is an error

References mem_malloc().

void mem_free

(

void *

rmem

)

Put a struct mem back on the heap.

Parameters

rmem	is the data portion of a struct mem as returned by a previous call to mem_malloc()

References LWIP_ASSERT, LWIP_DBG_LEVEL_SERIOUS, LWIP_DBG_LEVEL_SEVERE, LWIP_DBG_TRACE, LWIP_DEBUGF, LWIP_MEM_FREE_DECL_PROTECT, LWIP_MEM_FREE_PROTECT, LWIP_MEM_FREE_UNPROTECT, MEM_ALIGNMENT, MEM_DEBUG, MEM_STATS_DEC_USED, MEM_STATS_INC, mem::next, NULL, plug_holes(), SIZEOF_STRUCT_MEM, SYS_ARCH_DECL_PROTECT(), SYS_ARCH_PROTECT(), SYS_ARCH_UNPROTECT(), and mem::used.

Referenced by http_close_conn(), http_conn_err(), and pbuf_free().

void mem_init

(

void

)

Zero the heap and initialize start, end and lowest-free.

References ERR_OK, LWIP_ASSERT, LWIP_MEM_ALIGN, LWIP_RAM_HEAP_POINTER, MEM_ALIGNMENT, MEM_SIZE_ALIGNED, MEM_STATS_AVAIL, mem::next, mem::prev, ram, SIZEOF_STRUCT_MEM, sys_mutex_new, and mem::used.

Referenced by lwip_init().

void* mem_malloc

(

mem_size_t

size

)

Adam's mem_malloc() plus solution for bug #17922 Allocate a block of memory with a minimum of 'size' bytes.

Parameters

size	is the minimum size of the requested block in bytes.

Returns

pointer to allocated memory or NULL if no free memory was found.

Note that the returned value will always be aligned (as defined by MEM_ALIGNMENT).

References lfree, LWIP_ASSERT, LWIP_DBG_LEVEL_SERIOUS, LWIP_DEBUGF, LWIP_MEM_ALIGN_SIZE, LWIP_MEM_ALLOC_DECL_PROTECT, LWIP_MEM_ALLOC_PROTECT, LWIP_MEM_ALLOC_UNPROTECT, MEM_ALIGNMENT, MEM_DEBUG, MEM_SIZE_ALIGNED, MEM_STATS_INC, MEM_STATS_INC_USED, MIN_SIZE_ALIGNED, mem::next, next, NULL, mem::prev, S16_F, SIZEOF_STRUCT_MEM, sys_mutex_lock, sys_mutex_unlock, and mem::used.

Referenced by http_accept(), mem_calloc(), and pbuf_alloc().

void* mem_trim	(	void *	rmem,
		mem_size_t	newsize
	)

Shrink memory returned by mem_malloc().

Parameters

rmem	pointer to memory allocated by mem_malloc the is to be shrinked
newsize	required size after shrinking (needs to be smaller than or equal to the previous size)

Returns

for compatibility reasons: is always == rmem, at the moment or NULL if newsize is > old size, in which case rmem is NOT touched or freed!

References LWIP_ASSERT, LWIP_DBG_LEVEL_SEVERE, LWIP_DEBUGF, LWIP_MEM_ALIGN_SIZE, LWIP_MEM_FREE_DECL_PROTECT, LWIP_MEM_FREE_PROTECT, LWIP_MEM_FREE_UNPROTECT, MEM_DEBUG, MEM_SIZE_ALIGNED, MEM_STATS_DEC_USED, MEM_STATS_INC, MIN_SIZE_ALIGNED, mem::next, next, NULL, mem::prev, ram, SIZEOF_STRUCT_MEM, SYS_ARCH_DECL_PROTECT(), SYS_ARCH_PROTECT(), SYS_ARCH_UNPROTECT(), and mem::used.

Referenced by pbuf_realloc().

static void plug_holes ( struct mem *  mem )

static

"Plug holes" by combining adjacent empty struct mems.

After this function is through, there should not exist one empty struct mem pointing to another empty struct mem.

Parameters

mem	this points to a struct mem which just has been freed

this function is only called by mem_free() and mem_trim()

This assumes access to the heap is protected by the calling function already.

References LWIP_ASSERT, MEM_SIZE_ALIGNED, mem::next, mem::prev, and mem::used.

Referenced by mem_free().

struct mem* lfree

static

pointer to the lowest free block, this is used for faster search

Referenced by mem_malloc().

u8_t* ram

static

pointer to the heap (ram_heap): for alignment, ram is now a pointer instead of an array

Referenced by mem_init(), and mem_trim().

struct mem* ram_end

static

the last entry, always unused!

u8_t ram_heap[MEM_SIZE_ALIGNED+(2 *SIZEOF_STRUCT_MEM)+MEM_ALIGNMENT]

If you want to relocate the heap to external memory, simply define LWIP_RAM_HEAP_POINTER as a void-pointer to that location.

If so, make sure the memory at that location is big enough (see below on how that space is calculated). the heap. we need one struct mem at the end and some room for alignment