add ReceptionReport

Sources/RTCP/ReceptionReport.swift

@@ -0,0 +1,201 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftRTC open source project
+//
+// Copyright (c) 2024 ngRTC and the SwiftRTC project authors
+// Licensed under MIT License
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftRTC project authors
+//
+// SPDX-License-Identifier: MIT
+//
+//===----------------------------------------------------------------------===//
+import NIOCore
+import Shared
+
+let recptionReportLength: Int = 24
+let fractionLostOffset: Int = 4
+let totalLostOffset: Int = 5
+let lastSeqOffset: Int = 8
+let jitterOffset: Int = 12
+let lastSrOffset: Int = 16
+let delayOffset: Int = 20
+
+/// A ReceptionReport block conveys statistics on the reception of RTP packets
+/// from a single synchronization source.
+public struct ReceptionReport: Equatable {
+    /// The SSRC identifier of the source to which the information in this
+    /// reception report block pertains.
+    public var ssrc: UInt32
+    /// The fraction of RTP data packets from source SSRC lost since the
+    /// previous SR or RR packet was sent, expressed as a fixed point
+    /// number with the binary point at the left edge of the field.
+    public var fractionLost: UInt8
+    /// The total number of RTP data packets from source SSRC that have
+    /// been lost since the beginning of reception.
+    public var totalLost: UInt32
+    /// The least significant 16 bits contain the highest sequence number received
+    /// in an RTP data packet from source SSRC, and the most significant 16 bits extend
+    /// that sequence number with the corresponding count of sequence number cycles.
+    public var lastSequenceNumber: UInt32
+    /// An estimate of the statistical variance of the RTP data packet
+    /// interarrival time, measured in timestamp units and expressed as an
+    /// unsigned integer.
+    public var jitter: UInt32
+    /// The middle 32 bits out of 64 in the NTP timestamp received as part of
+    /// the most recent RTCP sender report (SR) packet from source SSRC. If no
+    /// SR has been received yet, the field is set to zero.
+    public var lastSenderReport: UInt32
+    /// The delay, expressed in units of 1/65536 seconds, between receiving the
+    /// last SR packet from source SSRC and sending this reception report block.
+    /// If no SR packet has been received yet from SSRC, the field is set to zero.
+    public var delay: UInt32
+}
+
+extension ReceptionReport: Packet {
+    public func header() -> Header {
+        Header()
+    }
+
+    public func destinationSsrc() -> [UInt32] {
+        []
+    }
+
+    public func rawSize() -> Int {
+        recptionReportLength
+    }
+}
+
+extension ReceptionReport: Unmarshal {
+    /// unmarshal decodes the ReceptionReport from binary
+    public static func unmarshal(_ buf: ByteBuffer) throws -> (Self, Int) {
+        if buf.readableBytes < recptionReportLength {
+            throw RtcpError.errPacketTooShort
+        }
+
+        /*
+         *  0                   1                   2                   3
+         *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+         * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+         * |                              SSRC                             |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * | fraction lost |       cumulative number of packets lost       |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * |           extended highest sequence number received           |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * |                      interarrival jitter                      |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * |                         last SR (LSR)                         |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * |                   delay since last SR (DLSR)                  |
+         * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+         */
+        var reader = buf.slice()
+        guard let ssrc: UInt32 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+        guard let fractionLost: UInt8 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+
+        guard let t0: UInt8 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+        guard let t1: UInt8 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+        guard let t2: UInt8 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+        // TODO: The type of `total_lost` should be `i32`, per the RFC:
+        // The total number of RTP data packets from source SSRC_n that have
+        // been lost since the beginning of reception.  This number is
+        // defined to be the number of packets expected less the number of
+        // packets actually received, where the number of packets received
+        // includes any which are late or duplicates.  Thus, packets that
+        // arrive late are not counted as lost, and the loss may be negative
+        // if there are duplicates.  The number of packets expected is
+        // defined to be the extended last sequence number received, as
+        // defined next, less the initial sequence number received.  This may
+        // be calculated as shown in Appendix A.3.
+        let totalLost: UInt32 = UInt32(t2) | UInt32(t1) << 8 | UInt32(t0) << 16
+
+        guard let lastSequenceNumber: UInt32 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+        guard let jitter: UInt32 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+        guard let lastSenderReport: UInt32 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+        guard let delay: UInt32 = reader.readInteger() else {
+            throw RtcpError.errPacketTooShort
+        }
+
+        return (
+            ReceptionReport(
+                ssrc: ssrc,
+                fractionLost: fractionLost,
+                totalLost: totalLost,
+                lastSequenceNumber: lastSequenceNumber,
+                jitter: jitter,
+                lastSenderReport: lastSenderReport,
+                delay: delay
+            ), reader.readerIndex
+        )
+    }
+}
+
+extension ReceptionReport: MarshalSize {
+    public func marshalSize() -> Int {
+        let l = self.rawSize()
+        // align to 32-bit boundary
+        return l + getPadding(l)
+    }
+}
+
+extension ReceptionReport: Marshal {
+    /// marshal_to encodes the ReceptionReport in binary
+    public func marshalTo(_ buf: inout ByteBuffer) throws -> Int {
+        /*
+         *  0                   1                   2                   3
+         *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+         * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+         * |                              SSRC                             |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * | fraction lost |       cumulative number of packets lost       |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * |           extended highest sequence number received           |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * |                      interarrival jitter                      |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * |                         last SR (LSR)                         |
+         * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+         * |                   delay since last SR (DLSR)                  |
+         * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+         */
+        buf.writeInteger(self.ssrc)
+
+        buf.writeInteger(self.fractionLost)
+
+        // pack TotalLost into 24 bits
+        if self.totalLost >= (1 << 25) {
+            throw RtcpError.errInvalidTotalLost
+        }
+
+        buf.writeInteger(UInt8((self.totalLost >> 16) & 0xFF))
+        buf.writeInteger(UInt8((self.totalLost >> 8) & 0xFF))
+        buf.writeInteger(UInt8(self.totalLost & 0xFF))
+
+        buf.writeInteger(self.lastSequenceNumber)
+        buf.writeInteger(self.jitter)
+        buf.writeInteger(self.lastSenderReport)
+        buf.writeInteger(self.delay)
+
+        putPadding(&buf, self.rawSize())
+
+        return self.marshalSize()
+    }
+}