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- /****************************************************************************
- * mm/iob/iob_contig.c
- *
- * Copyright (C) 2014 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 <string.h>
- #include <assert.h>
- #include <errno.h>
- #include <debug.h>
- #include <nuttx/mm/iob.h>
- #include "iob.h"
- /****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
- #ifndef MIN
- # define MIN(a,b) ((a) < (b) ? (a) : (b))
- #endif
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: iob_contig
- *
- * Description:
- * Ensure that there is'len' bytes of contiguous space at the beginning
- * of the I/O buffer chain starting at 'iob'.
- *
- ****************************************************************************/
- int iob_contig(FAR struct iob_s *iob, unsigned int len)
- {
- FAR struct iob_s *next;
- unsigned int ncopy;
- /* We can't make more contiguous space that the size of one I/O buffer.
- * If you get this assertion and really need that much contiguous data,
- * then you will need to increase CONFIG_IOB_BUFSIZE.
- */
- DEBUGASSERT(len <= CONFIG_IOB_BUFSIZE);
- /* Check if there is already sufficient, contiguous space at the beginning
- * of the packet
- */
- if (len <= iob->io_len)
- {
- /* Yes we are good */
- return 0;
- }
- /* Can we get the required amount of contiguous data by just packing the
- * head I/0 buffer?
- */
- else if (len <= iob->io_pktlen)
- {
- /* Yes.. First eliminate any leading offset */
- if (iob->io_offset > 0)
- {
- memcpy(iob->io_data, &iob->io_data[iob->io_offset], iob->io_len);
- iob->io_offset = 0;
- }
- /* Then move what we need from the next I/O buffer(s) */
- do
- {
- /* Get the next I/O buffer in the chain */
- next = iob->io_flink;
- DEBUGASSERT(next != NULL);
- /* Copy what we need or what we can from the next buffer */
- ncopy = len - iob->io_len;
- ncopy = MIN(ncopy, next->io_len);
- memcpy(&iob->io_data[iob->io_len],
- &next->io_data[next->io_offset], ncopy);
- /* Adjust counts and offsets */
- iob->io_len += ncopy;
- next->io_offset += ncopy;
- next->io_len -= ncopy;
- /* Handle a (improbable) case where we just emptied the second
- * buffer in the chain.
- */
- if (next->io_len == 0)
- {
- iob->io_flink = iob_free(next);
- }
- }
- while (len > iob->io_len);
- /* This should always succeed because we know that:
- *
- * pktlen >= CONFIG_IOB_BUFSIZE >= len
- */
- return 0;
- }
- /* Otherwise, the request for contiguous data is larger then the entire
- * packet. We can't do that without extending the I/O buffer chain with
- * garbage (which would probably not be what the caller wants).
- */
- else
- {
- ioberr("ERROR: pktlen=%u < requested len=%u\n", iob->io_pktlen, len);
- return -ENOSPC;
- }
- }
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