Use spans to improve performance in StreamExts.

Also avoid ReadBytes calls that allocate a buffer by either updating the stream position (if not interested in the bytes), by reusing an input buffer (if interested in the bytes), or using a stackalloc buffer to avoid the allocation (for small reads).

OpenRA.Mods.Common/AudioLoaders/OggLoader.cs

@@ -76,9 +76,7 @@ namespace OpenRA.Mods.Common.AudioLoaders
 		{
 			readonly OggFormat format;
 
-			// This buffer can be static because it can only be used by 1 instance per thread.
-			[ThreadStatic]
-			static float[] conversionBuffer;
+			float[] conversionBuffer;
 
 			public OggStream(OggFormat format)
 			{
@@ -105,13 +103,10 @@ namespace OpenRA.Mods.Common.AudioLoaders
 				// Make sure we don't have an odd count.
 				count -= count % format.reader.Channels;
 
-				// Get the buffer, creating a new one if none exists or the existing one is too small.
-				var floatBuffer = conversionBuffer ??= new float[count];
-				if (floatBuffer.Length < count)
-					floatBuffer = conversionBuffer = new float[count];
+				var floatBuffer = EnsureArraySize(ref conversionBuffer, count);
 
 				// Let NVorbis do the actual reading.
-				var samples = format.reader.ReadSamples(floatBuffer, offset, count);
+				var samples = format.reader.ReadSamples(floatBuffer);
 
 				// Move the data back to the request buffer and convert to 16-bit signed samples for OpenAL.
 				for (var i = 0; i < samples; i++)
@@ -137,6 +132,13 @@ namespace OpenRA.Mods.Common.AudioLoaders
 
 				base.Dispose(disposing);
 			}
+
+			static Span<float> EnsureArraySize(ref float[] array, int desiredSize)
+			{
+				if (array == null || array.Length < desiredSize)
+					array = new float[desiredSize];
+				return array.AsSpan(..desiredSize);
+			}
 		}
 	}
 }

OpenRA.Mods.Common/FileFormats/ImaAdpcmReader.cs

@@ -9,7 +9,7 @@
  */
 #endregion
 
-using System.IO;
+using System;
 
 namespace OpenRA.Mods.Common.FileFormats
 {
@@ -56,15 +56,14 @@ namespace OpenRA.Mods.Common.FileFormats
 			return (short)current;
 		}
 
-		public static byte[] LoadImaAdpcmSound(byte[] raw, ref int index)
+		public static byte[] LoadImaAdpcmSound(ReadOnlySpan<byte> raw, ref int index)
 		{
 			var currentSample = 0;
 			return LoadImaAdpcmSound(raw, ref index, ref currentSample);
 		}
 
-		public static byte[] LoadImaAdpcmSound(byte[] raw, ref int index, ref int currentSample)
+		public static byte[] LoadImaAdpcmSound(ReadOnlySpan<byte> raw, ref int index, ref int currentSample)
 		{
-			var s = new MemoryStream(raw);
 			var dataSize = raw.Length;
 			var outputSize = raw.Length * 4;
 
@@ -73,7 +72,7 @@ namespace OpenRA.Mods.Common.FileFormats
 
 			while (dataSize-- > 0)
 			{
-				var b = s.ReadUInt8();
+				var b = raw[offset / 4];
 
 				var t = DecodeImaAdpcmSample(b, ref index, ref currentSample);
 				output[offset++] = (byte)t;

OpenRA.Mods.Common/FileFormats/WavReader.cs

@@ -67,12 +67,12 @@ namespace OpenRA.Mods.Common.FileFormats
 						blockAlign = s.ReadInt16();
 						sampleBits = s.ReadInt16();
 						lengthInSeconds = (float)(s.Length * 8) / (channels * sampleRate * sampleBits);
-						s.ReadBytes(fmtChunkSize - 16);
+						s.Position += fmtChunkSize - 16;
 						break;
 					case "fact":
 						var chunkSize = s.ReadInt32();
 						uncompressedSize = s.ReadInt32();
-						s.ReadBytes(chunkSize - 4);
+						s.Position += chunkSize - 4;
 						break;
 					case "data":
 						dataSize = s.ReadInt32();
@@ -82,7 +82,7 @@ namespace OpenRA.Mods.Common.FileFormats
 					case "LIST":
 					case "cue ":
 						var listCueChunkSize = s.ReadInt32();
-						s.ReadBytes(listCueChunkSize);
+						s.Position += listCueChunkSize;
 						break;
 					default:
 						s.Position = s.Length; // Skip to end of stream
@@ -156,12 +156,13 @@ namespace OpenRA.Mods.Common.FileFormats
 
 				// Decode and output remaining data in this block
 				var blockOffset = 0;
+				Span<byte> chunk = stackalloc byte[4];
 				while (blockOffset < blockDataSize)
 				{
 					for (var c = 0; c < channels; c++)
 					{
 						// Decode 4 bytes (to 16 bytes of output) per channel
-						var chunk = baseStream.ReadBytes(4);
+						baseStream.ReadBytes(chunk);
 						var decoded = ImaAdpcmReader.LoadImaAdpcmSound(chunk, ref index[c], ref predictor[c]);
 
 						// Interleave output, one sample per channel

OpenRA.Mods.Common/FileFormats/WestwoodCompressedReader.cs

@@ -20,11 +20,11 @@ namespace OpenRA.Mods.Common.FileFormats
 		static readonly int[] AudWsStepTable2 = { -2, -1, 0, 1 };
 		static readonly int[] AudWsStepTable4 = { -9, -8, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 8 };
 
-		public static void DecodeWestwoodCompressedSample(byte[] input, byte[] output)
+		public static void DecodeWestwoodCompressedSample(ReadOnlySpan<byte> input, Span<byte> output)
 		{
 			if (input.Length == output.Length)
 			{
-				Array.Copy(input, output, output.Length);
+				input.CopyTo(output);
 
 				return;
 			}

OpenRA.Mods.Common/FileSystem/InstallShieldPackage.cs

@@ -73,7 +73,7 @@ namespace OpenRA.Mods.Common.FileSystem
 						var dirName = s.ReadASCII(nameLength);
 
 						// Skip to the end of the chunk
-						s.ReadBytes(chunkSize - nameLength - 6);
+						s.Position += chunkSize - nameLength - 6;
 						directories.Add(dirName, fileCount);
 					}