nes-proj/os/lib/heapmem.h
2017-09-29 22:18:48 +02:00

168 lines
5.7 KiB
C

/*
* Copyright (c) 2005, Nicolas Tsiftes
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the author nor the names of the contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/**
* \addtogroup mem
* @{
*/
/**
* \defgroup heapmem heapmem: Dynamic heap memory allocator
*
* The heapmem module is a dynamic heap memory allocator similar to
* malloc() in standard C. The heap memory is managed in a block of
* static memory, whose size is determined at compile-time by setting
* HEAPMEM_CONF_ARENA_SIZE parameter. By default, the heap memory is
* only 1 bytes, which entails that this parameter must be set
* explicitly in order to be possible to use this module.
*
* Each allocated memory object is referred to as a "chunk". The
* allocator manages free chunks in a double-linked list. While this
* adds some memory overhead compared to a single-linked list, it
* improves the performance of list management.
*
* Internally, allocated chunks can be retrieved using the pointer to
* the allocated memory returned by heapmem_alloc() and
* heapmem_realloc(), because the chunk structure immediately precedes
* the memory of the chunk.
*
* \note This module does not contain a corresponding function to the
* standard C function calloc().
*
* \note Dynamic memory should be used carefully on
* memory-constrained, embedded systems, because fragmentation
* may be induced through various allocation/deallocation
* patterns, and no guarantees are given regarding the
* availability of memory.
*
* @{
*/
/**
* \file
* Header file for the dynamic heap memory allocator.
* \author
* Nicolas Tsiftes <nvt@acm.org>
*/
#ifndef HEAPMEM_H
#define HEAPMEM_H
#include <stdlib.h>
typedef struct heapmem_stats {
size_t allocated;
size_t overhead;
size_t available;
size_t footprint;
size_t chunks;
} heapmem_stats_t;
#if HEAPMEM_DEBUG
#define heapmem_alloc(size) heapmem_alloc_debug((size), __FILE__, __LINE__)
#define heapmem_realloc(ptr, size) heapmem_realloc_debug((ptr), (size), __FILE__, __LINE__)
#define heapmem_free(ptr) heapmem_free_debug((ptr), __FILE__, __LINE__)
void *heapmem_alloc_debug(size_t size,
const char *file, const unsigned line);
void *heapmem_realloc_debug(void *ptr, size_t size,
const char *file, const unsigned line);
void heapmem_free_debug(void *ptr,
const char *file, const unsigned line);
#else
/**
* \brief Allocate a chunk of memory in the heap.
* \param size The number of bytes to allocate.
* \return A pointer to the allocated memory chunk,
* or NULL if the allocation failed.
*
* \sa heapmem_realloc
* \sa heapmem_free
*/
void *heapmem_alloc(size_t size);
/**
* \brief Reallocate a chunk of memory in the heap.
* \param ptr A pointer to a chunk that has been allocated using
* heapmem_alloc() or heapmem_realloc().
* \param size The number of bytes to allocate.
* \return A pointer to the allocated memory chunk,
* or NULL if the allocation failed.
*
* \note If ptr is NULL, this function behaves the same as heapmem_alloc.
* \note If ptr is not NULL and size is zero, the function deallocates
* the chunk and returns NULL.
*
* \sa heapmem_alloc
* \sa heapmem_free
*/
void *heapmem_realloc(void *ptr, size_t size);
/**
* \brief Deallocate a chunk of memory.
* \param ptr A pointer to a chunk that has been allocated using
* heapmem_alloc() or heapmem_realloc().
*
* \note If ptr is NULL, this function will return immediately without
* without performing any action.
*
* \sa heapmem_alloc
* \sa heapmem_realloc
*/
void heapmem_free(void *ptr);
#endif /* HEAMMEM_DEBUG */
/**
* \brief Obtain internal heapmem statistics regarding the
* allocated chunks.
* \param stats A pointer to an object of type heapmem_stats_t, which
* will be filled when calling this function.
*
* This function makes it possible to gain visibility into the internal
* structure of the heap. One can thus obtain information regarding
* the amount of memory allocated, overhead used for memory management,
* and the number of chunks allocated. By using this information, developers
* can tune their software to use the heapmem allocator more efficiently.
*
*/
void heapmem_stats(heapmem_stats_t *stats);
#endif /* !HEAPMEM_H */
/** @} */
/** @} */