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
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+++ b/nuttx/mm/mm_shrinkchunk.c
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+/****************************************************************************
+ * 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);
+    }
+}