Security/libsecurity_utilities/lib/bufferfifo.cpp

   1 /*
   2  * Copyright (c) 2000-2004,2011,2014 Apple Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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  18  * Please see the License for the specific language governing rights and
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  22  */
  23
  24
  25 //
  26 // bufferfifo - a Sink that queues data in a FIFO of buffers for retrieval
  27 //
  28 #include "bufferfifo.h"
  29 #include <security_utilities/memutils.h>
  30
  31
  32 namespace Security {
  33
  34
  35 //
  36 // On destruction, throw away all queued buffers (that haven't been picked up)
  37 //
  38 BufferFifo::~BufferFifo()
  39 {
  40     while (!mBuffers.empty()) {
  41         delete mBuffers.front();
  42         mBuffers.pop();
  43     }
  44 }
  45
  46 void BufferFifo::clearBuffer()
  47 {
  48     while (!mBuffers.empty()) {
  49         delete mBuffers.front();
  50         mBuffers.pop();
  51     }
  52     mSize = 0;
  53 }
  54
  55 //
  56 // This is the put function of a Sink. We store the data in at most two buffers:
  57 // First we append to the last (partially filled) one; then we allocate a new one
  58 // (if needed) to hold the rest.
  59 //
  60 void BufferFifo::consume(const void *data, size_t size)
  61 {
  62     mSize += size;
  63
  64     // step 1: fill the rearmost (partially filled) buffer
  65     if (size > 0 && !mBuffers.empty()) {
  66         Buffer *current = mBuffers.back();
  67         size_t length = current->put(data, size);
  68         data = LowLevelMemoryUtilities::increment(data, length);
  69         size -= length;
  70     }
  71     // step 2: if there's anything left, make a new buffer and fill it
  72     if (size > 0) {     // not done
  73         Buffer *current = new Buffer(max(bufferLength, size));
  74         mBuffers.push(current);
  75         assert(current->available() >= size);
  76         current->put(data, size);
  77     }
  78 }
  79
  80
  81 //
  82 // Pull the first (FI) buffer off the queue and deliver it.
  83 // We retain no memory of it; it belongs to the caller now.
  84 //
  85 Buffer *BufferFifo::pop()
  86 {
  87     assert(!mBuffers.empty());
  88     Buffer *top = mBuffers.front();
  89     mBuffers.pop();
  90     return top;
  91 }
  92
  93
  94 }       // end namespace Security