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// Copyright 2019 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 STREAMING_CAST_PACKET_UTIL_H_
#define STREAMING_CAST_PACKET_UTIL_H_
#include <utility>
#include "absl/types/span.h"
#include "osp_base/big_endian.h"
#include "streaming/cast/ssrc.h"
namespace openscreen {
namespace cast_streaming {
// Reads a field from the start of the given span and advances the span to point
// just after the field.
template <typename Integer>
inline Integer ConsumeField(absl::Span<const uint8_t>* in) {
const Integer result = ReadBigEndian<Integer>(in->data());
in->remove_prefix(sizeof(Integer));
return result;
}
// Writes a field at the start of the given span and advances the span to point
// just after the field.
template <typename Integer>
inline void AppendField(Integer value, absl::Span<uint8_t>* out) {
WriteBigEndian<Integer>(value, out->data());
out->remove_prefix(sizeof(Integer));
}
// Returns a bitmask for a field having the given number of bits. For example,
// FieldBitmask<uint8_t>(5) returns 0b00011111.
template <typename Integer>
constexpr Integer FieldBitmask(unsigned field_size_in_bits) {
return (Integer{1} << field_size_in_bits) - 1;
}
// Reserves |num_bytes| from the beginning of the given span, returning the
// reserved space.
inline absl::Span<uint8_t> ReserveSpace(int num_bytes,
absl::Span<uint8_t>* out) {
const absl::Span<uint8_t> reserved = out->subspan(0, num_bytes);
out->remove_prefix(num_bytes);
return reserved;
}
// Performs a quick-scan of the packet data for the purposes of routing it to an
// appropriate parser. Identifies whether the packet is a RTP packet, RTCP
// packet, or unknown; and provides the originator's SSRC. This only performs a
// very quick scan of the packet data, and does not guarantee that a full parse
// will later succeed.
enum class ApparentPacketType { UNKNOWN, RTP, RTCP };
std::pair<ApparentPacketType, Ssrc> InspectPacketForRouting(
absl::Span<const uint8_t> packet);
} // namespace cast_streaming
} // namespace openscreen
#endif // STREAMING_CAST_PACKET_UTIL_H_
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