cdsa/cdsa_utilities/bufferfifo.cpp

   1 /*
   2  * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 //
  20 // bufferfifo - a Sink that queues data in a FIFO of buffers for retrieval
  21 //
  22 #include "bufferfifo.h"
  23 #include <Security/memutils.h>
  24
  25
  26 namespace Security {
  27
  28
  29 //
  30 // On destruction, throw away all queued buffers (that haven't been picked up)
  31 //
  32 BufferFifo::~BufferFifo()
  33 {
  34     while (!mBuffers.empty()) {
  35         delete mBuffers.front();
  36         mBuffers.pop();
  37     }
  38 }
  39
  40
  41 //
  42 // This is the put function of a Sink. We store the data in at most two buffers:
  43 // First we append to the last (partially filled) one; then we allocate a new one
  44 // (if needed) to hold the rest.
  45 //
  46 void BufferFifo::consume(const void *data, size_t size)
  47 {
  48     // step 1: fill the rearmost (partially filled) buffer
  49     if (size > 0 && !mBuffers.empty()) {
  50         Buffer *current = mBuffers.back();
  51         size_t length = current->put(data, size);
  52         data = LowLevelMemoryUtilities::increment(data, length);
  53         size -= length;
  54     }
  55     // step 2: if there's anything left, make a new buffer and fill it
  56     if (size > 0) {     // not done
  57         Buffer *current = new Buffer(max(bufferLength, size));
  58         mBuffers.push(current);
  59         assert(current->available() >= size);
  60         current->put(data, size);
  61     }
  62 }
  63
  64
  65 //
  66 // Pull the first (FI) buffer off the queue and deliver it.
  67 // We retain no memory of it; it belongs to the caller now.
  68 //
  69 Buffer *BufferFifo::pop()
  70 {
  71     assert(!mBuffers.empty());
  72     Buffer *top = mBuffers.front();
  73     mBuffers.pop();
  74     return top;
  75 }
  76
  77
  78 }       // end namespace Security