blob: bb61b7894d7bf2f81cf8c551d70dce19d3106c4e [file] [log] [blame]
// Copyright (c) 2010 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "media/base/seekable_buffer.h"
#include <algorithm>
#include "base/logging.h"
#include "media/base/data_buffer.h"
namespace media {
SeekableBuffer::SeekableBuffer(size_t backward_capacity,
size_t forward_capacity)
: current_buffer_offset_(0),
backward_capacity_(backward_capacity),
backward_bytes_(0),
forward_capacity_(forward_capacity),
forward_bytes_(0),
current_time_(StreamSample::kInvalidTimestamp) {
current_buffer_ = buffers_.begin();
}
SeekableBuffer::~SeekableBuffer() {
}
void SeekableBuffer::Clear() {
buffers_.clear();
current_buffer_ = buffers_.begin();
current_buffer_offset_ = 0;
backward_bytes_ = 0;
forward_bytes_ = 0;
current_time_ = StreamSample::kInvalidTimestamp;
}
size_t SeekableBuffer::Read(uint8* data, size_t size) {
DCHECK(data);
return InternalRead(data, size, true);
}
size_t SeekableBuffer::Peek(uint8* data, size_t size) {
DCHECK(data);
return InternalRead(data, size, false);
}
bool SeekableBuffer::GetCurrentChunk(const uint8** data, size_t* size) const {
BufferQueue::iterator current_buffer = current_buffer_;
size_t current_buffer_offset = current_buffer_offset_;
// Advance position if we are in the end of the current buffer.
while (current_buffer != buffers_.end() &&
current_buffer_offset >= (*current_buffer)->GetDataSize()) {
++current_buffer;
current_buffer_offset = 0;
}
if (current_buffer == buffers_.end())
return false;
*data = (*current_buffer)->GetData() + current_buffer_offset;
*size = (*current_buffer)->GetDataSize() - current_buffer_offset;
return true;
}
bool SeekableBuffer::Append(Buffer* buffer_in) {
if (buffers_.empty() && buffer_in->GetTimestamp().InMicroseconds() > 0) {
current_time_ = buffer_in->GetTimestamp();
}
// Since the forward capacity is only used to check the criteria for buffer
// full, we always append data to the buffer.
buffers_.push_back(scoped_refptr<Buffer>(buffer_in));
// After we have written the first buffer, update |current_buffer_| to point
// to it.
if (current_buffer_ == buffers_.end()) {
DCHECK_EQ(0u, forward_bytes_);
current_buffer_ = buffers_.begin();
}
// Update the |forward_bytes_| counter since we have more bytes.
forward_bytes_ += buffer_in->GetDataSize();
// Advise the user to stop append if the amount of forward bytes exceeds
// the forward capacity. A false return value means the user should stop
// appending more data to this buffer.
if (forward_bytes_ >= forward_capacity_)
return false;
return true;
}
bool SeekableBuffer::Append(const uint8* data, size_t size) {
if (size > 0) {
DataBuffer* data_buffer = new DataBuffer(size);
memcpy(data_buffer->GetWritableData(), data, size);
data_buffer->SetDataSize(size);
return Append(data_buffer);
} else {
// Return true if we have forward capacity.
return forward_bytes_ < forward_capacity_;
}
}
bool SeekableBuffer::Seek(int32 offset) {
if (offset > 0)
return SeekForward(offset);
else if (offset < 0)
return SeekBackward(-offset);
return true;
}
bool SeekableBuffer::SeekForward(size_t size) {
// Perform seeking forward only if we have enough bytes in the queue.
if (size > forward_bytes_)
return false;
// Do a read of |size| bytes.
size_t taken = InternalRead(NULL, size, true);
DCHECK_EQ(taken, size);
return true;
}
bool SeekableBuffer::SeekBackward(size_t size) {
if (size > backward_bytes_)
return false;
// Record the number of bytes taken.
size_t taken = 0;
// Loop until we taken enough bytes and rewind by the desired |size|.
while (taken < size) {
// |current_buffer_| can never be invalid when we are in this loop. It can
// only be invalid before any data is appended. The invalid case should be
// handled by checks before we enter this loop.
DCHECK(current_buffer_ != buffers_.end());
// We try to consume at most |size| bytes in the backward direction. We also
// have to account for the offset we are in the current buffer, so take the
// minimum between the two to determine the amount of bytes to take from the
// current buffer.
size_t consumed = std::min(size - taken, current_buffer_offset_);
// Decreases the offset in the current buffer since we are rewinding.
current_buffer_offset_ -= consumed;
// Increase the amount of bytes taken in the backward direction. This
// determines when to stop the loop.
taken += consumed;
// Forward bytes increases and backward bytes decreases by the amount
// consumed in the current buffer.
forward_bytes_ += consumed;
backward_bytes_ -= consumed;
DCHECK_GE(backward_bytes_, 0u);
// The current buffer pointed by current iterator has been consumed. Move
// the iterator backward so it points to the previous buffer.
if (current_buffer_offset_ == 0) {
if (current_buffer_ == buffers_.begin())
break;
// Move the iterator backward.
--current_buffer_;
// Set the offset into the current buffer to be the buffer size as we
// are preparing for rewind for next iteration.
current_buffer_offset_ = (*current_buffer_)->GetDataSize();
}
}
UpdateCurrentTime(current_buffer_, current_buffer_offset_);
DCHECK_EQ(taken, size);
return true;
}
void SeekableBuffer::EvictBackwardBuffers() {
// Advances the iterator until we hit the current pointer.
while (backward_bytes_ > backward_capacity_) {
BufferQueue::iterator i = buffers_.begin();
if (i == current_buffer_)
break;
scoped_refptr<Buffer> buffer = *i;
backward_bytes_ -= buffer->GetDataSize();
DCHECK_GE(backward_bytes_, 0u);
buffers_.erase(i);
}
}
size_t SeekableBuffer::InternalRead(uint8* data, size_t size,
bool advance_position) {
// Counts how many bytes are actually read from the buffer queue.
size_t taken = 0;
BufferQueue::iterator current_buffer = current_buffer_;
size_t current_buffer_offset = current_buffer_offset_;
while (taken < size) {
// |current_buffer| is valid since the first time this buffer is appended
// with data.
if (current_buffer == buffers_.end())
break;
scoped_refptr<Buffer> buffer = *current_buffer;
// Find the right amount to copy from the current buffer referenced by
// |buffer|. We shall copy no more than |size| bytes in total and each
// single step copied no more than the current buffer size.
size_t copied = std::min(size - taken,
buffer->GetDataSize() - current_buffer_offset);
// |data| is NULL if we are seeking forward, so there's no need to copy.
if (data)
memcpy(data + taken, buffer->GetData() + current_buffer_offset, copied);
// Increase total number of bytes copied, which regulates when to end this
// loop.
taken += copied;
// We have read |copied| bytes from the current buffer. Advances the offset.
current_buffer_offset += copied;
// The buffer has been consumed.
if (current_buffer_offset == buffer->GetDataSize()) {
if (advance_position) {
// Next buffer may not have timestamp, so we need to update current
// timestamp before switching to the next buffer.
UpdateCurrentTime(current_buffer, current_buffer_offset);
}
BufferQueue::iterator next = current_buffer;
++next;
// If we are at the last buffer, don't advance.
if (next == buffers_.end())
break;
// Advances the iterator.
current_buffer = next;
current_buffer_offset = 0;
}
}
if (advance_position) {
// We have less forward bytes and more backward bytes. Updates these
// counters by |taken|.
forward_bytes_ -= taken;
backward_bytes_ += taken;
DCHECK_GE(forward_bytes_, 0u);
DCHECK(current_buffer_ != buffers_.end() || forward_bytes_ == 0u);
current_buffer_ = current_buffer;
current_buffer_offset_ = current_buffer_offset;
UpdateCurrentTime(current_buffer_, current_buffer_offset_);
EvictBackwardBuffers();
}
return taken;
}
void SeekableBuffer::UpdateCurrentTime(BufferQueue::iterator buffer,
size_t offset) {
// Garbage values are unavoidable, so this check will remain.
if (buffer != buffers_.end() &&
(*buffer)->GetTimestamp().InMicroseconds() > 0) {
int64 time_offset = ((*buffer)->GetDuration().InMicroseconds() *
offset) / (*buffer)->GetDataSize();
current_time_ = (*buffer)->GetTimestamp() +
base::TimeDelta::FromMicroseconds(time_offset);
}
}
} // namespace media