Refactor codebase to utilize Span<byte> and ReadOnlySpan<byte> for improved memory efficiency. Introduced utility methods in BinaryOperations and MemoryOperations for big-endian and little-endian data handling. Updated NetConvert to use BinaryPrimitives for network byte order conversions. Marked several methods as obsolete to guide towards new span-based APIs. Refactored AudioEncoder and SCTP-related classes for enhanced performance and reduced memory overhead. Overall, these changes optimize memory usage and improve performance across the codebase.

Author: Paulo Morgado

src/app/Media/Codecs/AudioEncoder.cs

@@ -18,6 +18,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using SIPSorceryMedia.Abstractions;
+using SIPSorcery.Sys;
 using Concentus.Enums;
 
 namespace SIPSorcery.Media
@@ -121,16 +122,13 @@ public byte[] EncodeAudio(short[] pcm, AudioFormat format)
             }
             else if (format.Codec == AudioCodecsEnum.L16)
             {
-                // When netstandard2.1 can be used.
-                //return MemoryMarshal.Cast<short, byte>(pcm)
-
                 // Put on the wire in network byte order (big endian).
-                return pcm.SelectMany(x => new byte[] { (byte)(x >> 8), (byte)(x) }).ToArray();
+                return MemoryOperations.ToBigEndianBytes(pcm);
             }
             else if (format.Codec == AudioCodecsEnum.PCM_S16LE)
             {
                 // Put on the wire as little endian.
-                return pcm.SelectMany(x => new byte[] { (byte)(x), (byte)(x >> 8) }).ToArray();
+                return MemoryOperations.ToLittleEndianBytes(pcm);
             }
             else if (format.Codec == AudioCodecsEnum.OPUS)
             {
@@ -148,7 +146,7 @@ public byte[] EncodeAudio(short[] pcm, AudioFormat format)
 
                 byte[] encodedSample = new byte[pcm.Length];
                 int encodedLength = _opusEncoder.Encode(pcmFloat, pcmFloat.Length / format.ChannelCount, encodedSample, encodedSample.Length);
-                return encodedSample.Take(encodedLength).ToArray();
+                return encodedSample.AsSpan(0, encodedLength).ToArray();
             }
             else
             {
@@ -174,7 +172,7 @@ public short[] DecodeAudio(byte[] encodedSample, AudioFormat format)
                 short[] decodedPcm = new short[encodedSample.Length * 2];
                 int decodedSampleCount = _g722Decoder.Decode(_g722DecoderState, decodedPcm, encodedSample, encodedSample.Length);
 
-                return decodedPcm.Take(decodedSampleCount).ToArray();
+                return decodedPcm.AsSpan(0, decodedSampleCount).ToArray();
             }
             if (format.Codec == AudioCodecsEnum.G729)
             {

src/app/Media/Codecs/G729Encoder.cs

@@ -55,7 +55,7 @@ public class G729Encoder : Ld8k
          * Initialization of the coder.
          */
 
-        private byte[] _leftover = new byte[0];
+        private byte[] _leftover = Array.Empty<byte>();
 
         /**
          * Init the Ld8k Coder

src/core/SIP/Channels/SIPClientWebSocketChannel.cs

@@ -376,7 +376,7 @@ private void MonitorReceiveTasks()
                         if (receiveTask.IsCompleted)
                         {
                             logger.LogDebug("Client web socket connection to {ServerUri} received {BytesReceived} bytes.", conn.ServerUri, receiveTask.Result.Count);
-                            //SIPMessageReceived(this, conn.LocalEndPoint, conn.RemoteEndPoint, conn.ReceiveBuffer.Take(receiveTask.Result.Count).ToArray()).Wait();
+                            //SIPMessageReceived(this, conn.LocalEndPoint, conn.RemoteEndPoint, conn.ReceiveBuffer.AsSpan(0, receiveTask.Result.Count).ToArray()).Wait();
                             ExtractSIPMessages(this, conn, conn.ReceiveBuffer, receiveTask.Result.Count);
                             conn.ReceiveTask = conn.Client.ReceiveAsync(conn.ReceiveBuffer, m_cts.Token);
                         }

src/core/SIP/Channels/SIPWebSocketChannel.cs

@@ -122,7 +122,7 @@ protected override void OnError(ErrorEventArgs e)
 
             public void Send(byte[] buffer, int offset, int length)
             {
-                base.Send(buffer.Skip(offset).Take(length).ToArray());
+                base.Send(buffer.AsSpan(offset, length).ToArray());
             }
         }
 

src/net/DtlsSrtp/DtlsSrtpTransport.cs

@@ -18,6 +18,7 @@
 
 using System;
 using System.Collections.Concurrent;
+using System.ComponentModel;
 using Microsoft.Extensions.Logging;
 using Org.BouncyCastle.Tls;
 using SIPSorcery.Sys;
@@ -482,11 +483,15 @@ public int GetSendLimit()
             return this._sendLimit;
         }
 
-        public void WriteToRecvStream(byte[] buf)
+        [Obsolete("Use WriteToRecvStream(ReadOnlySpan<byte>) instead.", false)]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public void WriteToRecvStream(byte[] buf) => WriteToRecvStream(buf.AsSpan());
+
+        public void WriteToRecvStream(ReadOnlySpan<byte> buf)
         {
             if (!_isClosed)
             {
-                _chunks.Add(buf);
+                _chunks.Add(buf.ToArray());
             }
         }
 

src/net/HEP/HepPacket.cs

@@ -316,7 +316,7 @@ public static byte[] GetBytes(SIPEndPoint srcEndPoint, SIPEndPoint dstEndPoint,
                 Buffer.BlockCopy(BitConverter.GetBytes((ushort)offset), 0, packetBuffer, 4, 2);
             }
 
-            return packetBuffer.Take(offset).ToArray();
+            return packetBuffer.AsSpan(0, offset).ToArray();
         }
     }
 }

src/net/RTCP/RTCPCompoundPacket.cs

@@ -298,7 +298,7 @@ public static bool TryParse(
                 }
                 else
                 {
-                    var buffer = packet.Skip(offset).ToArray();
+                    var buffer = packet.AsSpan(offset).ToArray();
 
                     // The payload type field is the second byte in the RTCP header.
                     byte packetTypeID = buffer[1];

src/net/RTCP/RTCPTWCCFeedback.cs

@@ -180,12 +180,12 @@ public RTCPTWCCFeedback(ReadOnlySpan<byte> packet)
             packet = packet.Slice(RTCPHeader.HEADER_BYTES_LENGTH);
 
             // Parse sender and media SSRCs
-            SenderSSRC = ReadUInt32(ref packet);
-            MediaSSRC = ReadUInt32(ref packet);
+            SenderSSRC = BinaryOperations.ReadUInt32BigEndian(ref packet);
+            MediaSSRC = BinaryOperations.ReadUInt32BigEndian(ref packet);
 
             // Parse Base Sequence Number and Packet Status Count
-            BaseSequenceNumber = ReadUInt16(ref packet);
-            PacketStatusCount = ReadUInt16(ref packet);
+            BaseSequenceNumber = BinaryOperations.ReadUInt16BigEndian(ref packet);
+            PacketStatusCount = BinaryOperations.ReadUInt16BigEndian(ref packet);
 
             // Parse Reference Time and Feedback Packet Count
             ReferenceTime = ParseReferenceTime(ref packet, out byte fbCount);
@@ -271,38 +271,6 @@ private uint ParseReferenceTime(ref ReadOnlySpan<byte> packet, out byte fbCount)
             return (uint)((b1 << 16) | (b2 << 8) | b3);
         }
 
-        private List<TWCCPacketStatusType> ParseStatusChunks(byte[] packet, ref int offset)
-        {
-            var statusSymbols = new List<TWCCPacketStatusType>();
-            int remainingStatuses = PacketStatusCount;
-
-            while (remainingStatuses > 0)
-            {
-                if (offset + 2 > packet.Length)
-                {
-                    throw new ArgumentException($"Packet truncated during status chunk parsing. Expected {remainingStatuses} more statuses.");
-                }
-
-                var chunk = ReadUInt16(packet, ref offset);
-                var chunkType = chunk >> 14;
-
-                switch (chunkType)
-                {
-                    case 0: // Run Length Chunk
-                        ParseRunLengthChunk(chunk, statusSymbols, ref remainingStatuses);
-                        break;
-                    case 2: // Two-bit Status Vector
-                        ParseTwoBitStatusVector(chunk, statusSymbols, ref remainingStatuses);
-                        break;
-                    case 3: // One-bit Status Vector
-                        ParseOneBitStatusVector(chunk, statusSymbols, ref remainingStatuses);
-                        break;
-                }
-            }
-
-            return statusSymbols;
-        }
-
         private List<TWCCPacketStatusType> ParseStatusChunks(ref ReadOnlySpan<byte> packet)
         {
             var statusSymbols = new List<TWCCPacketStatusType>();
@@ -315,7 +283,7 @@ private List<TWCCPacketStatusType> ParseStatusChunks(ref ReadOnlySpan<byte> pack
                     throw new ArgumentException($"Packet truncated during status chunk parsing. Expected {remainingStatuses} more statuses.");
                 }
 
-                var chunk = ReadUInt16(ref packet);
+                var chunk = BinaryOperations.ReadUInt16BigEndian(ref packet);
                 var chunkType = chunk >> 14;
 
                 switch (chunkType)
@@ -600,15 +568,15 @@ private void WriteBytesCore(Span<byte> buffer)
             buffer = buffer.Slice(RTCPHeader.HEADER_BYTES_LENGTH);
 
             // Write Sender and Media SSRC.
-            WriteUInt32(ref buffer, SenderSSRC);
-            WriteUInt32(ref buffer, MediaSSRC);
+            BinaryOperations.WriteUInt32BigEndian(ref buffer, SenderSSRC);
+            BinaryOperations.WriteUInt32BigEndian(ref buffer, MediaSSRC);
 
             // Write Base Sequence Number and Packet Status Count.
-            WriteUInt16(ref buffer, BaseSequenceNumber);
-            WriteUInt16(ref buffer, PacketStatusCount);
+            BinaryOperations.WriteUInt16BigEndian(ref buffer, BaseSequenceNumber);
+            BinaryOperations.WriteUInt16BigEndian(ref buffer, PacketStatusCount);
 
             // Build the 32-bit word for ReferenceTime and FeedbackPacketCount.
-            WriteUInt32(ref buffer, (ReferenceTime << 8) | FeedbackPacketCount);
+            BinaryOperations.WriteUInt32BigEndian(ref buffer, (ReferenceTime << 8) | FeedbackPacketCount);
 
             for (var i = 0; i < PacketStatuses.Count;)
             {
@@ -646,7 +614,7 @@ private void WriteBytesCore(Span<byte> buffer)
 
                     var chunk = (ushort)(statusBits << 12);
                     chunk |= (ushort)(runLength & 0x0FFF);
-                    WriteUInt16(ref buffer, chunk);
+                    BinaryOperations.WriteUInt16BigEndian(ref buffer, chunk);
                     i += runLength;
             }
                 else
@@ -677,7 +645,7 @@ private void WriteBytesCore(Span<byte> buffer)
 
                         chunk |= (ushort)(statusBits << (12 - 2 * j));
                     }
-                    WriteUInt16(ref buffer, chunk);
+                    BinaryOperations.WriteUInt16BigEndian(ref buffer, chunk);
                     i += count;
                 }
             }
@@ -713,77 +681,5 @@ public override string ToString()
                    $"StatusCount={PacketStatusCount}, RefTime={ReferenceTime} (1/64 sec), " +
                    $"FbkPktCount={FeedbackPacketCount}, PacketStatuses=[{packetStatusInfo}]";
         }
-
-        #region Helper Methods
-
-        private uint ReadUInt32(byte[] buffer, ref int offset)
-        {
-            uint value = BitConverter.ToUInt32(buffer, offset);
-            if (BitConverter.IsLittleEndian)
-            {
-                value = NetConvert.DoReverseEndian(value);
-            }
-            offset += 4;
-            return value;
-        }
-
-        private uint ReadUInt32(ref ReadOnlySpan<byte> buffer)
-        {
-            var value = BinaryPrimitives.ReadUInt32BigEndian(buffer);
-            buffer = buffer.Slice(sizeof(uint));
-            return value;
-        }
-
-        private ushort ReadUInt16(byte[] buffer, ref int offset)
-        {
-            ushort value = BitConverter.ToUInt16(buffer, offset);
-            if (BitConverter.IsLittleEndian)
-            {
-                value = NetConvert.DoReverseEndian(value);
-            }
-            offset += 2;
-            return value;
-        }
-
-        private ushort ReadUInt16(ref ReadOnlySpan<byte> buffer)
-        {
-            var value = BinaryPrimitives.ReadUInt16BigEndian(buffer);
-            buffer = buffer.Slice(sizeof(ushort));
-            return value;
-        }
-
-        private void WriteUInt32(byte[] buffer, ref int offset, uint value)
-        {
-            if (BitConverter.IsLittleEndian)
-            {
-                value = NetConvert.DoReverseEndian(value);
-            }
-            Buffer.BlockCopy(BitConverter.GetBytes(value), 0, buffer, offset, 4);
-            offset += 4;
-        }
-
-        private void WriteUInt16(byte[] buffer, ref int offset, ushort value)
-        {
-            if (BitConverter.IsLittleEndian)
-            {
-                value = NetConvert.DoReverseEndian(value);
-            }
-            Buffer.BlockCopy(BitConverter.GetBytes(value), 0, buffer, offset, 2);
-            offset += 2;
-        }
-
-        private static void WriteUInt32(ref Span<byte> buffer, uint value)
-        {
-            BinaryPrimitives.WriteUInt32BigEndian(buffer, value);
-            buffer = buffer.Slice(sizeof(uint));
-        }
-
-        private static void WriteUInt16(ref Span<byte> buffer, ushort value)
-        {
-            BinaryPrimitives.WriteUInt16BigEndian(buffer, value);
-            buffer = buffer.Slice(sizeof(ushort));
-        }
-
-        #endregion
     }
 }

src/net/RTP/MediaStream.cs

@@ -280,7 +280,7 @@ public bool IsSecurityContextReady()
 
                 if (res == 0)
                 {
-                    return (true, buffer.Take(outBufLen).ToArray());
+                    return (true, buffer.AsSpan(0, outBufLen).ToArray());
                 }
                 else
                 {
@@ -467,7 +467,7 @@ 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
                     }
                     else
                     {
-                        rtpChannel.Send(RTPChannelSocketsEnum.RTP, DestinationEndPoint, rtpBuffer.Take(outBufLen).ToArray());
+                        rtpChannel.Send(RTPChannelSocketsEnum.RTP, DestinationEndPoint, rtpBuffer.AsSpan(0, outBufLen).ToArray());
                     }
                 }
 
@@ -615,7 +615,7 @@ private bool SendRtcpReport(byte[] reportBuffer)
                     }
                     else
                     {
-                        rtpChannel.Send(sendOnSocket, ControlDestinationEndPoint, sendBuffer.Take(outBufLen).ToArray());
+                        rtpChannel.Send(sendOnSocket, ControlDestinationEndPoint, sendBuffer.AsSpan(0, outBufLen).ToArray());
                     }
                 }
             }

src/net/RTP/Packetisation/H264Packetiser.cs

@@ -30,6 +30,7 @@
 // BSD 3-Clause "New" or "Revised" License, see included LICENSE.md file.
 //-----------------------------------------------------------------------------
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -74,7 +75,7 @@ public static IEnumerable<H264Nal> ParseNals(byte[] accessUnit)
                         int nalSize = endPosn - currPosn;
                         bool isLast = currPosn + nalSize == accessUnit.Length;
 
-                        yield return new H264Nal(accessUnit.Skip(currPosn).Take(nalSize).ToArray(), isLast);
+                        yield return new H264Nal(accessUnit.AsSpan(currPosn, nalSize).ToArray(), isLast);
                     }
 
                     currPosn = nalStart;
@@ -87,7 +88,7 @@ public static IEnumerable<H264Nal> ParseNals(byte[] accessUnit)
 
             if (currPosn < accessUnit.Length)
             {
-                yield return new H264Nal(accessUnit.Skip(currPosn).ToArray(), true);
+                yield return new H264Nal(accessUnit.AsSpan(currPosn).ToArray(), true);
             }
         }