mem.c File Reference

Data Structures
struct	mem_helper
struct	mem
Functions
void *	mem_malloc (mem_size_t size)
void	mem_free (void *rmem)
void	mem_init (void)
void *	mem_realloc (void *rmem, mem_size_t newsize)
void *	mem_calloc (mem_size_t count, mem_size_t size)

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Detailed Description

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

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Function Documentation

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

void mem_free

(

void *

rmem

)

Free memory previously allocated by mem_malloc. Loads the pool number and calls memp_free with that pool number to put the element back into its pool

Parameters:

rmem

the memory element to free

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()

void mem_init

(

void

)

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

void * mem_malloc

(

mem_size_t

size

)

Allocate memory: determine the smallest pool that is big enough to contain an element of 'size' and get an element from that pool.

Parameters:

size

the size in bytes of the memory needed

Returns:

a pointer to the allocated memory or NULL if the pool is empty

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).

void* mem_realloc	(	void *	rmem,
		mem_size_t	newsize
	)

In contrast to its name, mem_realloc can only shrink memory, not expand it. Since the only use (for now) is in pbuf_realloc (which also can only shrink), this shouldn't be a problem!

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

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