119 lines
3.7 KiB
C
119 lines
3.7 KiB
C
/****************************************************************************
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* mm/iob/iob_trimhead.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 <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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* 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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unsigned int 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/O 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);
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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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