NuttX RTOS

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 212 insertions, 0 deletions

diff --git a/nuttx/mm/mm_memalign.c b/nuttx/mm/mm_memalign.c
new file mode 100644
index 000000000..b91625d0a
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+++ b/nuttx/mm/mm_memalign.c
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+/************************************************************
+ * mm_memalign.c
+ *
+ *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * 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 Gregory Nutt 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"
+
+/************************************************************
+ * Definitions
+ ************************************************************/
+
+/************************************************************
+ * Global Functions
+ ************************************************************/
+
+/************************************************************
+ * 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.
+ *
+ ************************************************************/
+
+void *memalign(size_t alignment, size_t size)
+{
+  struct mm_allocnode_s *node;
+  uint32 rawchunk;
+  uint32 alignedchunk;
+  uint32 mask = (uint32)(alignment - 1);
+  uint32 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
+   * 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.
+   * The do not include SIZEOF_MM_ALLOCNODE.
+   */
+
+  size      = MM_ALIGN_UP(size);   /* Make mutliples of our granule size */
+  allocsize = size + 2*alignment;  /* Add double full alignment size */
+
+  /* If the alignment is small
+
+  /* Then malloc that size */
+
+  rawchunk = (uint32)malloc(allocsize);
+  if (!rawchunk)
+    {
+      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 = (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)
+    {
+      struct mm_allocnode_s *newnode;
+      struct mm_allocnode_s *next;
+      uint32 precedingsize;
+
+      /* Get the node the next node after the allocation. */
+
+      next = (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 = (struct mm_allocnode_s*)(alignedchunk - SIZEOF_MM_ALLOCNODE);
+
+      /* Preceding size is full size of the new 'node,' including
+       * SIZEOF_MM_ALLOCNODE
+       */
+
+      precedingsize = (uint32)newnode - (uint32)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       = (struct mm_allocnode_s*)(alignedchunk - SIZEOF_MM_ALLOCNODE);
+          precedingsize = (uint32)newnode - (uint32)node;
+        }
+
+      /* Set up the size of the new node */
+
+      newnode->size = (uint32)next - (uint32)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((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 (void*)alignedchunk;
+}