incubator-nuttx/mm/umm_heap/umm_memalign.c

/****************************************************************************
 * mm/umm_heap/umm_memalign.c
 *
 *   Copyright (C) 2007, 2009, 2011, 2013-2015 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 <nuttx/config.h>

#include <stdlib.h>
#include <unistd.h>

#include <nuttx/mm/mm.h>

#include "umm_heap/umm_heap.h"

/****************************************************************************
 * Public 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)
{
#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)
  FAR void *brkaddr;
  FAR void *mem;

  /* Loop until we successfully allocate the memory or until an error
   * occurs. If we fail to allocate memory on the first pass, then call
   * sbrk to extend the heap by one page.  This may require several
   * passes if more the size of the allocation is more than one page.
   *
   * An alternative would be to increase the size of the heap by the
   * full requested allocation in sbrk().  Then the loop should never
   * execute more than twice (but more memory than we need may be
   * allocated).
   */

  do
    {
      mem = mm_memalign(USR_HEAP, alignment, size);
      if (!mem)
        {
          brkaddr = sbrk(size);
          if (brkaddr == (FAR void *)-1)
            {
              return NULL;
            }
        }
    }
  while (mem == NULL);

  return mem;
#else
  return mm_memalign(USR_HEAP, alignment, size);
#endif
}