1 files changed, 208 insertions, 0 deletions
diff --git a/nuttx/mm/mm_memalign.c b/nuttx/mm/mm_memalign.c
new file mode 100644
index 000000000..87547c96b
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+++ b/nuttx/mm/mm_memalign.c
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+/****************************************************************************
+ * mm/mm_memalign.c
+ *
+ *   Copyright (C) 2007, 2009, 2011 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 <assert.h>
+
+#include "mm_environment.h"
+#include "mm_internal.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Global Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: memalign
+ *
+ * Description:
+ *   memalign requests more than enough space from malloc, finds a region
+ *   within that chunk that meets the alignment request and then frees any
+ *   leading or trailing space. 
+ *
+ *   The alignment argument must be a power of two (not checked).  8-byte
+ *   alignment is guaranteed by normal malloc calls.
+ *
+ ****************************************************************************/
+
+FAR void *memalign(size_t alignment, size_t size)
+{
+  FAR struct mm_allocnode_s *node;
+  size_t rawchunk;
+  size_t alignedchunk;
+  size_t mask = (size_t)(alignment - 1);
+  size_t allocsize;
+
+  /* If this requested alignement less than or equal to the natural alignment
+   * of malloc, then just let malloc do the work.
+   */
+
+  if (alignment <= MM_MIN_CHUNK)
+    {
+      return malloc(size);
+    }
+
+  /* Adjust the size to account for (1) the size of the allocated node, (2)
+   * to make sure that it is an even multiple of our granule size, and to
+   * include the alignment amount.
+   *
+   * Notice that we increase the allocation size by twice the requested
+   * alignment.  We do this so that there will be at least two valid
+   * alignment points within the allocated memory.
+   *
+   * NOTE:  These are sizes given to malloc and not chunk sizes. They do
+   * not include SIZEOF_MM_ALLOCNODE.
+   */
+
+  size      = MM_ALIGN_UP(size);   /* Make multiples of our granule size */
+  allocsize = size + 2*alignment;  /* Add double full alignment size */
+
+  /* Then malloc that size */
+
+  rawchunk = (size_t)malloc(allocsize);
+  if (rawchunk == 0)
+    {
+      return NULL;
+    }
+
+  /* We need to hold the MM semaphore while we muck with the chunks and
+   * nodelist.
+   */
+
+  mm_takesemaphore();
+
+  /* Get the node associated with the allocation and the next node after
+   * the allocation.
+   */
+
+  node = (FAR struct mm_allocnode_s*)(rawchunk - SIZEOF_MM_ALLOCNODE);
+
+  /* Find the aligned subregion */
+
+  alignedchunk = (rawchunk + mask) & ~mask;
+
+  /* Check if there is free space at the beginning of the aligned chunk */
+
+  if (alignedchunk != rawchunk)
+    {
+      FAR struct mm_allocnode_s *newnode;
+      FAR struct mm_allocnode_s *next;
+      size_t precedingsize;
+
+      /* Get the node the next node after the allocation. */
+
+      next = (FAR struct mm_allocnode_s*)((char*)node + node->size);
+
+      /* Make sure that there is space to convert the preceding mm_allocnode_s
+       * into an mm_freenode_s.  I think that this should always be true
+       */
+
+      DEBUGASSERT(alignedchunk >= rawchunk + 8);
+
+      newnode = (FAR struct mm_allocnode_s*)(alignedchunk - SIZEOF_MM_ALLOCNODE);
+
+      /* Preceding size is full size of the new 'node,' including
+       * SIZEOF_MM_ALLOCNODE
+       */
+
+      precedingsize = (size_t)newnode - (size_t)node;
+
+      /* If we were unlucky, then the alignedchunk can lie in such a position
+       * that precedingsize < SIZEOF_NODE_FREENODE.  We can't let that happen
+       * because we are going to cast 'node' to struct mm_freenode_s below.
+       * This is why we allocated memory large enough to support two
+       * alignment points.  In this case, we will simply use the second
+       * alignment point.
+       */
+
+      if (precedingsize < SIZEOF_MM_FREENODE)
+        {
+          alignedchunk += alignment;
+          newnode       = (FAR struct mm_allocnode_s*)(alignedchunk - SIZEOF_MM_ALLOCNODE);
+          precedingsize = (size_t)newnode - (size_t)node;
+        }
+
+      /* Set up the size of the new node */
+
+      newnode->size = (size_t)next - (size_t)newnode;
+      newnode->preceding = precedingsize | MM_ALLOC_BIT;
+
+      /* Reduce the size of the original chunk and mark it not allocated, */
+
+      node->size = precedingsize;
+      node->preceding &= ~MM_ALLOC_BIT;
+
+      /* Fix the preceding size of the next node */
+
+      next->preceding = newnode->size | (next->preceding & MM_ALLOC_BIT);
+
+      /* Convert the newnode chunk size back into malloc-compatible size by
+       * subtracting the header size SIZEOF_MM_ALLOCNODE.
+       */
+
+      allocsize = newnode->size - SIZEOF_MM_ALLOCNODE;
+
+      /* Add the original, newly freed node to the free nodelist */
+
+      mm_addfreechunk((FAR struct mm_freenode_s *)node);
+
+      /* Replace the original node with the newlay realloaced,
+       * aligned node
+       */
+
+      node = newnode;
+    }
+
+  /* Check if there is free space at the end of the aligned chunk */
+
+  if (allocsize > size)
+    {
+      /* Shrink the chunk by that much -- remember, mm_shrinkchunk wants
+       * internal chunk sizes that include SIZEOF_MM_ALLOCNODE, and not the
+       * malloc-compatible sizes that we have.
+       */
+
+      mm_shrinkchunk(node, size + SIZEOF_MM_ALLOCNODE);
+    }
+
+  mm_givesemaphore();
+  return (FAR void*)alignedchunk;
+}