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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_BYTE_BUFFER_QUEUE_H_
#define THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_BYTE_BUFFER_QUEUE_H_
#include "base/containers/span.h"
#include "base/dcheck_is_on.h"
#include "third_party/blink/renderer/modules/modules_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/deque.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"
namespace blink {
// A ByteBufferQueue is a byte buffer with O(1) append and O(n) read operations.
// Clients can append entire byte buffers then copy data out across buffer
// boundaries using |ReadInto|.
class MODULES_EXPORT ByteBufferQueue final {
DISALLOW_NEW();
public:
// Number of bytes that can be read.
wtf_size_t size() const { return size_; }
// True if size() == 0.
bool empty() const { return size_ == 0; }
// Copies data into the given byte span. This will cause bytes to be consumed
// so that the next call to ReadInto will return different bytes.
// Returns the number of bytes written to |buffer_out|.
wtf_size_t ReadInto(base::span<uint8_t> buffer_out);
// Appends the contents of a byte buffer. This takes ownership of the buffer.
void Append(Vector<uint8_t> buffer);
// Clear stored buffers.
void Clear();
private:
#if DCHECK_IS_ON()
void CheckInvariants() const;
#endif
// Number of bytes that can be read.
// |Append()| adds to this number.
// |ReadInto()| subtracts from this number.
// Invariant: |size_| = sum of |deque_of_buffers_| element sizes -
// |front_buffer_offset_|.
wtf_size_t size_ = 0;
// Double-ended queue of byte buffers.
// |Append()| pushes to the right.
// |ReadInto()| pops from the left (if an entire buffer has been read).
// Invariant: No element in |deque_of_buffers_| is empty.
Deque<Vector<uint8_t>> deque_of_buffers_;
// The offset from which to start reading the buffer at the front of
// |deque_of_buffers_|.
// Invariants:
// - If |deque_of_buffers_| is empty, |front_buffer_offset_| = 0.
// - Otherwise, |front_buffer_offset_| < |deque_of_buffers_|.front().size().
wtf_size_t front_buffer_offset_ = 0;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_BYTE_BUFFER_QUEUE_H_
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