143 lines
4.8 KiB
C
143 lines
4.8 KiB
C
/****************************************************************************
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* mm/iob/iob_trimhead.c
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*
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* Copyright (C) 2014, 2017 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <assert.h>
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#include <debug.h>
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#include <nuttx/mm/iob.h>
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#include "iob.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#ifndef NULL
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# define NULL ((FAR void *)0)
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: iob_trimhead
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*
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* Description:
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* Remove bytes from the beginning of an I/O chain. Emptied I/O buffers
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* are freed and, hence, the beginning of the chain may change.
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*
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****************************************************************************/
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FAR struct iob_s *iob_trimhead(FAR struct iob_s *iob, unsigned int trimlen,
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enum iob_user_e producerid)
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{
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uint16_t pktlen;
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iobinfo("iob=%p trimlen=%d\n", iob, trimlen);
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if (iob && trimlen > 0)
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{
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/* Trim from the head of the I/IO buffer chain */
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pktlen = iob->io_pktlen;
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while (trimlen > 0 && iob != NULL)
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{
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/* Do we trim this entire I/O buffer away? */
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iobinfo("iob=%p io_len=%d pktlen=%d trimlen=%d\n",
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iob, iob->io_len, pktlen, trimlen);
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if (iob->io_len <= trimlen)
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{
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FAR struct iob_s *next;
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/* Decrement the trim length and packet length by the full
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* data size.
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*/
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pktlen -= iob->io_len;
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trimlen -= iob->io_len;
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/* Check if this was the last entry in the chain */
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next = iob->io_flink;
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if (next == NULL)
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{
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/* Yes.. break out of the loop returning the empty
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* I/O buffer chain containing only one empty entry.
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*/
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DEBUGASSERT(pktlen == 0);
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iob->io_len = 0;
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iob->io_offset = 0;
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break;
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}
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/* Free this entry and set the next I/O buffer as the head */
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iobinfo("iob=%p: Freeing\n", iob);
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iob_free(iob, producerid);
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iob = next;
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}
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else
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{
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/* No, then just take what we need from this I/O buffer and
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* stop the trim.
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*/
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pktlen -= trimlen;
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iob->io_len -= trimlen;
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iob->io_offset += trimlen;
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trimlen = 0;
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}
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}
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/* Adjust the pktlen by the number of bytes removed from the head
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* of the I/O buffer chain.
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*/
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iob->io_pktlen = pktlen;
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}
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return iob;
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}
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