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/****************************************************************************
* net/iob/iob_trimhead.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>
#if defined(CONFIG_DEBUG) && defined(CONFIG_NET_IOB_DEBUG)
/* Force debug output (from this file only) */
# undef CONFIG_DEBUG_NET
# define CONFIG_DEBUG_NET 1
#endif
#include <assert.h>
#include <debug.h>
#include <nuttx/net/iob.h>
#include "iob.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#ifndef NULL
# define NULL ((FAR void *)0)
#endif
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: iob_trimhead
*
* Description:
* Remove bytes from the beginning of an I/O chain. Emptied I/O buffers
* are freed and, hence, the beginning of the chain may change.
*
****************************************************************************/
FAR struct iob_s *iob_trimhead(FAR struct iob_s *iob, unsigned int trimlen)
{
uint16_t pktlen;
nllvdbg("iob=%p trimlen=%d\n", iob, trimlen);
if (iob && trimlen > 0)
{
/* Trim from the head of the I/IO buffer chain */
pktlen = iob->io_pktlen;
while (trimlen > 0 && iob != NULL)
{
/* Do we trim this entire I/O buffer away? */
nllvdbg("iob=%p io_len=%d pktlen=%d trimlen=%d\n",
iob, iob->io_len, pktlen, trimlen);
if (iob->io_len <= trimlen)
{
FAR struct iob_s *next;
/* Decrement the trim length and packet length by the full
* data size.
*/
pktlen -= iob->io_len;
trimlen -= iob->io_len;
iob->io_len = 0;
iob->io_offset = 0;
/* Check if this was the last entry in the chain */
next = iob->io_flink;
if (!next)
{
/* Yes.. break out of the loop returning the empty
* I/O buffer chain containing only one empty entry.
*/
DEBUGASSERT(pktlen == 0);
break;
}
/* Free this entry and set the next I/O buffer as the head */
nllvdbg("iob=%p: Freeing\n", iob);
(void)iob_free(iob);
iob = next;
}
else
{
/* No, then just take what we need from this I/O buffer and
* stop the trim.
*/
pktlen -= trimlen;
iob->io_len -= trimlen;
iob->io_offset += trimlen;
trimlen = 0;
}
}
/* Adjust the pktlen by the number of bytes removed from the head
* of the I/O buffer chain.
*/
iob->io_pktlen = pktlen;
}
return iob;
}
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