/************************************************************
* mm/mm_malloc.c
*
* Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
* COPYRIGHT OWNER 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.
*
************************************************************/
/************************************************************
* Included Files
************************************************************/
/* Special definitions when we operate in the normal vs. the
* host-pc test environement.
*/
#include <assert.h>
#include "mm_environment.h"
#include "mm_internal.h"
/************************************************************
* Pre-processor Definitions
************************************************************/
#ifndef NULL
# define NULL ((void*)0)
#endif
/************************************************************
* Type Definitions
************************************************************/
/************************************************************
* Private Data
************************************************************/
/************************************************************
* Public Data
************************************************************/
/************************************************************
* Private Functions
************************************************************/
/************************************************************
* Public Functions
************************************************************/
/************************************************************
* malloc
*
* Description:
* Find the smallest chunk that satisfies the request.
* Take the memory from that chunk, save the remaining,
* smaller chunk (if any).
*
* 8-byte alignment of the allocated data is assured.
*
************************************************************/
FAR void *malloc(size_t size)
{
FAR struct mm_freenode_s *node;
void *ret = NULL;
int ndx;
/* Handle bad sizes */
if (size <= 0)
{
return NULL;
}
/* Adjust the size to account for (1) the size of the allocated
* node and (2) to make sure that it is an even multiple of
* our granule size.
*/
size = MM_ALIGN_UP(size + SIZEOF_MM_ALLOCNODE);
/* We need to hold the MM semaphore while we muck with the
* nodelist.
*/
mm_takesemaphore();
/* Get the location in the node list to start the search.
* Special case really big alloctions
*/
if (size >= MM_MAX_CHUNK)
{
ndx = MM_NNODES-1;
}
else
{
/* Convert the request size into a nodelist index */
ndx = mm_size2ndx(size);
}
/* Search for a large enough chunk in the list of nodes.
* This list is ordered by size, but will have occasional
* zero sized nodes as we visit other g_nodelist[] entries.
*/
for (node = g_nodelist[ndx].flink;
node && node->size < size;
node = node->flink);
/* If we found a node with non-zero size, then this is one
* to use. Since the list is ordered, we know that is must be
* best fitting chunk available.
*/
if (node)
{
FAR struct mm_freenode_s *remainder;
FAR struct mm_freenode_s *next;
size_t remaining;
/* Remove the node. There must be a predecessor, but there may
* not be a successor node.
*/
DEBUGASSERT(node->blink);
node->blink->flink = node->flink;
if (node->flink)
{
node->flink->blink = node->blink;
}
/* Check if we have to split the free node into one of the
* allocated size and another smaller freenode. In some
* cases, the remaining bytes can be smaller (they may be
* SIZEOF_MM_ALLOCNODE). In that case, we will just carry
* the few wasted bytes at the end of the allocation.
*/
remaining = node->size - size;
if (remaining >= SIZEOF_MM_FREENODE)
{
/* Get a pointer to the next node in physical memory */
next = (FAR struct mm_freenode_s*)(((char*)node) + node->size);
/* Create the remainder node */
remainder = (FAR struct mm_freenode_s*)(((char*)node) + size);
remainder->size = remaining;
remainder->preceding = size;
/* Adjust the size of the node under consideration */
node->size = size;
/* Adjust the 'preceding' size of the (old) next node,
* preserving the allocated flag.
*/
next->preceding = remaining | (next->preceding & MM_ALLOC_BIT);
/* Add the remainder back into the nodelist */
mm_addfreechunk(remainder);
}
/* Handle the case of an exact size match */
node->preceding |= MM_ALLOC_BIT;
ret = (void*)((char*)node + SIZEOF_MM_ALLOCNODE);
}
mm_givesemaphore();
mvdbg("Allocated %p, size %d\n", ret, size);
return ret;
}
