diff options
Diffstat (limited to 'nuttx/mm/mm_shrinkchunk.c')
-rw-r--r-- | nuttx/mm/mm_shrinkchunk.c | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/nuttx/mm/mm_shrinkchunk.c b/nuttx/mm/mm_shrinkchunk.c new file mode 100644 index 000000000..e538e43ed --- /dev/null +++ b/nuttx/mm/mm_shrinkchunk.c @@ -0,0 +1,139 @@ +/**************************************************************************** + * mm/mm_shrinkchunk.c + * + * Copyright (C) 2007, 2009 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 + * 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 + ****************************************************************************/ + +#include "mm_environment.h" +#include "mm_internal.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_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(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(newnode); + } +} |