139 lines
4.0 KiB
C
139 lines
4.0 KiB
C
/****************************************************************************
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* mm/iob/iob_contig.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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 <string.h>
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#include <sys/param.h>
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#include <assert.h>
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#include <errno.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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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: iob_contig
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*
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* Description:
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* Ensure that there is'len' bytes of contiguous space at the beginning
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* of the I/O buffer chain starting at 'iob'.
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*
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****************************************************************************/
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int iob_contig(FAR struct iob_s *iob, unsigned int len)
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{
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FAR struct iob_s *next;
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unsigned int ncopy;
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/* We can't make more contiguous space that the size of one I/O buffer.
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* If you get this assertion and really need that much contiguous data,
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* then you will need to increase CONFIG_IOB_BUFSIZE.
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*/
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DEBUGASSERT(len <= CONFIG_IOB_BUFSIZE);
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/* Check if there is already sufficient, contiguous space at the beginning
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* of the packet
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*/
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if (len <= iob->io_len)
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{
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/* Yes we are good */
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return 0;
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}
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/* Can we get the required amount of contiguous data by just packing the
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* head I/0 buffer?
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*/
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else if (len <= iob->io_pktlen)
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{
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/* Yes.. First eliminate any leading offset */
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if (iob->io_offset > 0)
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{
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memcpy(iob->io_data, &iob->io_data[iob->io_offset], iob->io_len);
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iob->io_offset = 0;
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}
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/* Then move what we need from the next I/O buffer(s) */
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do
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{
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/* Get the next I/O buffer in the chain */
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next = iob->io_flink;
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DEBUGASSERT(next != NULL);
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/* Copy what we need or what we can from the next buffer */
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ncopy = len - iob->io_len;
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ncopy = MIN(ncopy, next->io_len);
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memcpy(&iob->io_data[iob->io_len],
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&next->io_data[next->io_offset], ncopy);
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/* Adjust counts and offsets */
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iob->io_len += ncopy;
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next->io_offset += ncopy;
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next->io_len -= ncopy;
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/* Handle a (improbable) case where we just emptied the second
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* buffer in the chain.
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*/
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if (next->io_len == 0)
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{
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iob->io_flink = iob_free(next);
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}
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}
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while (len > iob->io_len);
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/* This should always succeed because we know that:
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*
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* pktlen >= CONFIG_IOB_BUFSIZE >= len
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*/
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return 0;
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}
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/* Otherwise, the request for contiguous data is larger then the entire
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* packet. We can't do that without extending the I/O buffer chain with
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* garbage (which would probably not be what the caller wants).
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*/
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else
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{
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ioberr("ERROR: pktlen=%u < requested len=%u\n", iob->io_pktlen, len);
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return -ENOSPC;
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}
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}
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