142 lines
4.9 KiB
C
142 lines
4.9 KiB
C
/****************************************************************************
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* mm/mm_heap/mm_shrinkchunk.c
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*
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* Copyright (C) 2007, 2009, 1013 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <assert.h>
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#include <nuttx/mm/mm.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: mm_shrinkchunk
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*
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* Description:
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* Reduce the size of the chunk specified by the node structure to the
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* specified size. this internal logic is used both from memalign to
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* dispose of any trailing memory in the aligned allocation and also by
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* realloc when there is a request to reduce the size of an allocation.
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*
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* NOTES:
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* (1) size is the whole chunk size (payload and header)
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* (2) the caller must hold the MM semaphore.
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*
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****************************************************************************/
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void mm_shrinkchunk(FAR struct mm_heap_s *heap,
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FAR struct mm_allocnode_s *node, size_t size)
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{
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FAR struct mm_freenode_s *next;
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DEBUGASSERT((size & MM_GRAN_MASK) == 0);
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/* Get a reference to the next node */
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next = (FAR struct mm_freenode_s *)((FAR char *)node + node->size);
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/* Check if it is free */
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if ((next->preceding & MM_ALLOC_BIT) == 0)
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{
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FAR struct mm_allocnode_s *andbeyond;
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FAR struct mm_freenode_s *newnode;
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/* Get the chunk next the next node (which could be the tail chunk) */
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andbeyond = (FAR struct mm_allocnode_s *)((FAR char *)next + next->size);
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/* Remove the next node. There must be a predecessor, but there may
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* not be a successor node.
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*/
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DEBUGASSERT(next->blink);
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next->blink->flink = next->flink;
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if (next->flink)
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{
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next->flink->blink = next->blink;
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}
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/* Create a new chunk that will hold both the next chunk and the
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* tailing memory from the aligned chunk.
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*/
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newnode = (FAR struct mm_freenode_s *)((FAR char *)node + size);
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/* Set up the size of the new node */
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newnode->size = next->size + node->size - size;
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newnode->preceding = size;
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node->size = size;
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andbeyond->preceding = newnode->size | (andbeyond->preceding & MM_ALLOC_BIT);
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/* Add the new node to the freenodelist */
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mm_addfreechunk(heap, newnode);
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}
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/* The next chunk is allocated. Try to free the end portion at the end
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* chunk to be shrunk.
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*/
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else if (node->size >= size + SIZEOF_MM_FREENODE)
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{
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FAR struct mm_freenode_s *newnode;
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/* Create a new chunk that will hold both the next chunk and the
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* tailing memory from the aligned chunk.
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*/
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newnode = (FAR struct mm_freenode_s *)((FAR char *)node + size);
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/* Set up the size of the new node */
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newnode->size = node->size - size;
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newnode->preceding = size;
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node->size = size;
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next->preceding = newnode->size | MM_ALLOC_BIT;
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/* Add the new node to the freenodelist */
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mm_addfreechunk(heap, newnode);
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}
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}
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