125 lines
3.7 KiB
C
125 lines
3.7 KiB
C
/****************************************************************************
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* mm/iob/iob_trimtail.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 <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_trimtail
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*
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* Description:
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* Remove bytes from the end of an I/O chain
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*
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****************************************************************************/
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FAR struct iob_s *iob_trimtail(FAR struct iob_s *iob, unsigned int trimlen,
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enum iob_user_e producerid)
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{
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FAR struct iob_s *entry;
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FAR struct iob_s *penultimate;
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FAR struct iob_s *last;
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int len;
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iobinfo("iob=%p pktlen=%d trimlen=%d\n", iob, iob->io_pktlen, trimlen);
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if (iob && trimlen > 0)
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{
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len = trimlen;
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/* Loop until complete the trim */
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while (len > 0)
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{
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/* Calculate the total length of the data in the I/O buffer
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* chain and find the last entry in the chain.
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*/
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penultimate = NULL;
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last = NULL;
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for (entry = iob; entry; entry = entry->io_flink)
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{
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/* Remember the last and the next to the last in the chain */
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penultimate = last;
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last = entry;
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}
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/* Trim from the last entry in the chain. Do we trim this entire
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* I/O buffer away?
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*/
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iobinfo("iob=%p len=%d vs %d\n", last, last->io_len, len);
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if (last->io_len <= len)
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{
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/* Yes.. Consume the entire buffer */
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iob->io_pktlen -= last->io_len;
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len -= last->io_len;
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last->io_len = 0;
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/* Free the last, empty buffer in the list */
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iob_free(last, producerid);
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/* There should be a buffer before this one */
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if (!penultimate)
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{
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/* No.. we just freed the head of the chain */
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return NULL;
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}
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/* Unlink the penultimate from the freed buffer */
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penultimate->io_flink = NULL;
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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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iob->io_pktlen -= len;
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last->io_len -= len;
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len = 0;
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}
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}
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}
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return iob;
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}
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