/****************************************************************************
* mm/mm_shrinkchunk.c
*
* Copyright (C) 2007, 2009, 1013 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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
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*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <assert.h>
#include <nuttx/mm.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: mm_shrinkchunk
*
* Description:
* Reduce the size of the chunk specified by the node structure to the
* specified size. this internal logic is used both from memalign to
* dispose of any trailing memory in the aligned allocation and also by
* realloc when there is a request to reduce the size of an allocation.
*
* NOTES:
* (1) size is the whole chunk size (payload and header)
* (2) the caller must hold the MM semaphore.
*
****************************************************************************/
void mm_shrinkchunk(FAR struct mm_heap_s *heap,
FAR struct mm_allocnode_s *node, size_t size)
{
FAR struct mm_freenode_s *next;
/* Get a reference to the next node */
next = (FAR struct mm_freenode_s*)((char*)node + node->size);
/* Check if it is free */
if ((next->preceding & MM_ALLOC_BIT) == 0)
{
FAR struct mm_allocnode_s *andbeyond;
FAR struct mm_freenode_s *newnode;
/* Get the chunk next the next node (which could be the tail chunk) */
andbeyond = (FAR struct mm_allocnode_s*)((char*)next + next->size);
/* Remove the next node. There must be a predecessor, but there may
* not be a successor node.
*/
DEBUGASSERT(next->blink);
next->blink->flink = next->flink;
if (next->flink)
{
next->flink->blink = next->blink;
}
/* Create a new chunk that will hold both the next chunk and the
* tailing memory from the aligned chunk.
*/
newnode = (FAR struct mm_freenode_s*)((char*)node + size);
/* Set up the size of the new node */
newnode->size = next->size + node->size - size;
newnode->preceding = size;
node->size = size;
andbeyond->preceding = newnode->size | (andbeyond->preceding & MM_ALLOC_BIT);
/* Add the new node to the freenodelist */
mm_addfreechunk(heap, newnode);
}
/* The next chunk is allocated. Try to free the end portion at the end
* chunk to be shrunk.
*/
else if (node->size >= size + SIZEOF_MM_FREENODE)
{
FAR struct mm_freenode_s *newnode;
/* Create a new chunk that will hold both the next chunk and the
* tailing memory from the aligned chunk.
*/
newnode = (FAR struct mm_freenode_s*)((char*)node + size);
/* Set up the size of the new node */
newnode->size = node->size - size;
newnode->preceding = size;
node->size = size;
next->preceding = newnode->size | MM_ALLOC_BIT;
/* Add the new node to the freenodelist */
mm_addfreechunk(heap, newnode);
}
}
