149 lines
5.1 KiB
C
149 lines
5.1 KiB
C
/****************************************************************************
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* net/iob/iob_trimhead.c
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*
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* Copyright (C) 2014 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 <nuttx/net/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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/****************************************************************************
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* Private Types
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****************************************************************************/
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/****************************************************************************
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* Private Data
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****************************************************************************/
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/****************************************************************************
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* Public Data
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****************************************************************************/
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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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{
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FAR struct iob_s *entry;
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uint8_t flags;
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uint16_t pktlen;
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uint16_t vtag;
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void *priv;
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unsigned int len;
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if (iob && trimlen > 0)
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{
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/* Save information from the head of the chain (in case the
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* head is removed).
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*/
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flags = iob->io_flags;
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pktlen = iob->io_pktlen;
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vtag = iob->io_vtag;
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priv = iob->io_priv;
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/* Trim from the head of the I/IO buffer chain */
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entry = iob;
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len = trimlen;
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while (entry != NULL)
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{
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/* Do we trim this entire I/O buffer away? */
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if (entry->io_len <= len)
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{
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/* Decrement the trim length by the full data size */
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pktlen -= entry->io_len;
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len -= entry->io_len;
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/* Free this one and set the next I/O buffer as the head */
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iob = (FAR struct iob_s *)entry->io_link.flink;
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iob_free(entry);
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/* Continue with the new buffer head */
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entry = iob;
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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 -= len;
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entry->io_len -= len;
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entry->io_offset += len;
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len = 0;
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}
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}
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/* Restore the state to the head of the chain (which may not be
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* the same I/O buffer chain head that we started with).
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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. A special case is where we delete the
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* entire chain: len > 0 and iob == NULL.
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*/
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iob->io_flags = flags;
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iob->io_pktlen = pktlen;
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iob->io_vtag = vtag;
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iob->io_priv = priv;
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}
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return iob;
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}
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