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/****************************************************************************
* net/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>
#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 <string.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/net/iob.h>
#include "iob.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#ifndef MIN
# define MIN(a,b) ((a) < (b) ? (a) : (b))
#endif
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* 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 && next->io_len > 0);
/* 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
{
ndbg("ERROR: pktlen=%u < requested len=%u\n", iob->io_pktlen, len);
return -ENOSPC;
}
}
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