121 lines
3.5 KiB
C++
121 lines
3.5 KiB
C++
// Copyright 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef CAST_STREAMING_FRAME_ID_H_
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#define CAST_STREAMING_FRAME_ID_H_
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#include <stdint.h>
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#include <sstream>
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#include "cast/streaming/expanded_value_base.h"
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namespace openscreen {
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namespace cast {
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// Forward declaration (see below).
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class FrameId;
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// Convenience operator overloads for logging.
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std::ostream& operator<<(std::ostream& out, const FrameId rhs);
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// Unique identifier for a frame in a RTP media stream. FrameIds are truncated
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// to 8-bit values in RTP and RTCP headers, and then expanded back by the other
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// endpoint when parsing the headers.
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//
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// Usage example:
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//
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// // Distance/offset math.
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// FrameId first = FrameId::first();
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// FrameId second = first + 1;
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// FrameId third = second + 1;
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// int64_t offset = third - first;
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// FrameId fourth = second + offset;
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//
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// // Logging convenience.
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// OSP_DLOG_INFO << "The current frame is " << fourth;
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class FrameId : public ExpandedValueBase<int64_t, FrameId> {
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public:
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// The "null" FrameId constructor. Represents a FrameId field that has not
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// been set and/or a "not applicable" indicator.
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constexpr FrameId() : FrameId(std::numeric_limits<int64_t>::min()) {}
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// Allow copy construction and assignment.
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constexpr FrameId(const FrameId&) = default;
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constexpr FrameId& operator=(const FrameId&) = default;
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// Returns true if this is the special value representing null.
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constexpr bool is_null() const { return *this == FrameId(); }
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// Distance operator.
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int64_t operator-(FrameId rhs) const {
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OSP_DCHECK(!is_null());
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OSP_DCHECK(!rhs.is_null());
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return value_ - rhs.value_;
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}
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// Operators to compute advancement by incremental amounts.
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FrameId operator+(int64_t rhs) const {
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OSP_DCHECK(!is_null());
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return FrameId(value_ + rhs);
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}
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FrameId operator-(int64_t rhs) const {
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OSP_DCHECK(!is_null());
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return FrameId(value_ - rhs);
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}
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FrameId& operator+=(int64_t rhs) {
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OSP_DCHECK(!is_null());
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return (*this = (*this + rhs));
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}
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FrameId& operator-=(int64_t rhs) {
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OSP_DCHECK(!is_null());
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return (*this = (*this - rhs));
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}
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FrameId& operator++() {
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OSP_DCHECK(!is_null());
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++value_;
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return *this;
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}
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FrameId& operator--() {
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OSP_DCHECK(!is_null());
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--value_;
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return *this;
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}
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FrameId operator++(int) {
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OSP_DCHECK(!is_null());
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return FrameId(value_++);
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}
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FrameId operator--(int) {
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OSP_DCHECK(!is_null());
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return FrameId(value_--);
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}
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// The identifier for the first frame in a stream.
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static constexpr FrameId first() { return FrameId(0); }
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// A virtual identifier, representing the frame before the first. There should
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// never actually be a frame streamed with this identifier. Instead, this is
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// used in various components to represent a "not yet seen/processed the first
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// frame" state.
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//
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// The name "leader" comes from the terminology used in tape reels, which
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// refers to the non-data-carrying segment of tape before the recording
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// begins.
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static constexpr FrameId leader() { return FrameId(-1); }
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private:
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friend class ExpandedValueBase<int64_t, FrameId>;
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friend std::ostream& operator<<(std::ostream& out, const FrameId rhs);
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constexpr explicit FrameId(int64_t value) : ExpandedValueBase(value) {}
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// Accessor used by ostream output function.
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constexpr int64_t value() const { return value_; }
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};
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} // namespace cast
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} // namespace openscreen
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#endif // CAST_STREAMING_FRAME_ID_H_
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