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// Copyright 2016 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.
#ifndef CAST_STREAMING_FRAME_ID_H_
#define CAST_STREAMING_FRAME_ID_H_
#include <stdint.h>
#include <sstream>
#include "cast/streaming/expanded_value_base.h"
namespace cast {
namespace streaming {
// Forward declaration (see below).
class FrameId;
// Convenience operator overloads for logging.
std::ostream& operator<<(std::ostream& out, const FrameId rhs);
// Unique identifier for a frame in a RTP media stream. FrameIds are truncated
// to 8-bit values in RTP and RTCP headers, and then expanded back by the other
// endpoint when parsing the headers.
//
// Usage example:
//
// // Distance/offset math.
// FrameId first = FrameId::first();
// FrameId second = first + 1;
// FrameId third = second + 1;
// int64_t offset = third - first;
// FrameId fourth = second + offset;
//
// // Logging convenience.
// OSP_DLOG_INFO << "The current frame is " << fourth;
class FrameId : public ExpandedValueBase<int64_t, FrameId> {
public:
// The "null" FrameId constructor. Represents a FrameId field that has not
// been set and/or a "not applicable" indicator.
constexpr FrameId() : FrameId(std::numeric_limits<int64_t>::min()) {}
// Allow copy construction and assignment.
constexpr FrameId(const FrameId&) = default;
constexpr FrameId& operator=(const FrameId&) = default;
// Returns true if this is the special value representing null.
constexpr bool is_null() const { return *this == FrameId(); }
// Distance operator.
int64_t operator-(FrameId rhs) const {
OSP_DCHECK(!is_null());
OSP_DCHECK(!rhs.is_null());
return value_ - rhs.value_;
}
// Operators to compute advancement by incremental amounts.
FrameId operator+(int64_t rhs) const {
OSP_DCHECK(!is_null());
return FrameId(value_ + rhs);
}
FrameId operator-(int64_t rhs) const {
OSP_DCHECK(!is_null());
return FrameId(value_ - rhs);
}
FrameId& operator+=(int64_t rhs) {
OSP_DCHECK(!is_null());
return (*this = (*this + rhs));
}
FrameId& operator-=(int64_t rhs) {
OSP_DCHECK(!is_null());
return (*this = (*this - rhs));
}
FrameId& operator++() {
OSP_DCHECK(!is_null());
++value_;
return *this;
}
FrameId& operator--() {
OSP_DCHECK(!is_null());
--value_;
return *this;
}
FrameId operator++(int) {
OSP_DCHECK(!is_null());
return FrameId(value_++);
}
FrameId operator--(int) {
OSP_DCHECK(!is_null());
return FrameId(value_--);
}
// The identifier for the first frame in a stream.
static constexpr FrameId first() { return FrameId(0); }
private:
friend class ExpandedValueBase<int64_t, FrameId>;
friend std::ostream& operator<<(std::ostream& out, const FrameId rhs);
constexpr explicit FrameId(int64_t value) : ExpandedValueBase(value) {}
// Accessor used by ostream output function.
constexpr int64_t value() const { return value_; }
};
} // namespace streaming
} // namespace cast
#endif // CAST_STREAMING_FRAME_ID_H_
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