media/base/byte_queue.cc

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/base/byte_queue.h"
   6
   7 #include "base/logging.h"
   8
   9 namespace media {
  10
  11 // Default starting size for the queue.
  12 enum { kDefaultQueueSize = 1024 };
  13
  14 ByteQueue::ByteQueue()
  15     : buffer_(new uint8[kDefaultQueueSize]),
  16       size_(kDefaultQueueSize),
  17       offset_(0),
  18       used_(0) {
  19 }
  20
  21 ByteQueue::~ByteQueue() {}
  22
  23 void ByteQueue::Reset() {
  24   offset_ = 0;
  25   used_ = 0;
  26 }
  27
  28 void ByteQueue::Push(const uint8* data, int size) {
  29   DCHECK(data);
  30   DCHECK_GT(size, 0);
  31
  32   size_t size_needed = used_ + size;
  33
  34   // Check to see if we need a bigger buffer.
  35   if (size_needed > size_) {
  36     size_t new_size = 2 * size_;
  37     while (size_needed > new_size && new_size > size_)
  38       new_size *= 2;
  39
  40     // Sanity check to make sure we didn't overflow.
  41     CHECK_GT(new_size, size_);
  42
  43     scoped_ptr<uint8[]> new_buffer(new uint8[new_size]);
  44
  45     // Copy the data from the old buffer to the start of the new one.
  46     if (used_ > 0)
  47       memcpy(new_buffer.get(), front(), used_);
  48
  49     buffer_.reset(new_buffer.release());
  50     size_ = new_size;
  51     offset_ = 0;
  52   } else if ((offset_ + used_ + size) > size_) {
  53     // The buffer is big enough, but we need to move the data in the queue.
  54     memmove(buffer_.get(), front(), used_);
  55     offset_ = 0;
  56   }
  57
  58   memcpy(front() + used_, data, size);
  59   used_ += size;
  60 }
  61
  62 void ByteQueue::Peek(const uint8** data, int* size) const {
  63   DCHECK(data);
  64   DCHECK(size);
  65   *data = front();
  66   *size = used_;
  67 }
  68
  69 void ByteQueue::Pop(int count) {
  70   DCHECK_LE(count, used_);
  71
  72   offset_ += count;
  73   used_ -= count;
  74
  75   // Move the offset back to 0 if we have reached the end of the buffer.
  76   if (offset_ == size_) {
  77     DCHECK_EQ(used_, 0);
  78     offset_ = 0;
  79   }
  80 }
  81
  82 uint8* ByteQueue::front() const { return buffer_.get() + offset_; }
  83
  84 }  // namespace media