More copy-less

Author: longfin

Bencodex/Decoder.cs

@@ -4,6 +4,7 @@
 using System.Globalization;
 using System.IO;
 using System.Numerics;
+using System.Runtime.CompilerServices;
 using System.Text;
 using Bencodex.Misc;
 using Bencodex.Types;
@@ -12,7 +13,6 @@ namespace Bencodex
 {
     internal sealed class Decoder
     {
-        private readonly byte[] _tinyBuffer = new byte[1];
         private readonly Stream _stream;
         private readonly IndirectValue.Loader? _indirectValueLoader;
         private byte _lastRead;
@@ -74,7 +74,7 @@ private IValue DecodeValue()
                     return ReadTextAfterPrefix();
 
                 case 0x6c: // 'l'
-                    var indirElements = new List<IndirectValue>();
+                    var indirBuilder = ImmutableArray.CreateBuilder<IndirectValue>();
                     while (true)
                     {
                         byte b = ReadByte() ?? throw new DecodingException(
@@ -87,17 +87,17 @@ private IValue DecodeValue()
                         else if (b == indir)
                         {
                             Fingerprint fp = DecodeFingerprint();
-                            indirElements.Add(new IndirectValue(fp));
+                            indirBuilder.Add(new IndirectValue(fp));
                             continue;
                         }
 
                         Back();
                         IValue element = DecodeValue();
-                        indirElements.Add(new IndirectValue(element));
+                        indirBuilder.Add(new IndirectValue(element));
                     }
 
                     return new Bencodex.Types.List(
-                        indirElements.ToImmutableArray(),
+                        indirBuilder.MoveToImmutable().AsSpan(),
                         _indirectValueLoader
                     );
 
@@ -255,15 +255,15 @@ private byte[] Read(byte[] buffer)
                 return _lastRead;
             }
 
-            int read = _stream.Read(_tinyBuffer, 0, 1);
+            int read = _stream.ReadByte();
             if (read > 0)
             {
-                _lastRead = _tinyBuffer[0];
+                _lastRead = (byte)read;
             }
 
             _offset++;
             _didBack = false;
-            return read == 0 ? (byte?)null : _tinyBuffer[0];
+            return read == -1 ? (byte?)null : _lastRead;
         }
 
         private void Back()
@@ -363,12 +363,7 @@ Func<string, IFormatProvider, T> converter
         )
         {
             byte[] buffer = ReadDigits(takeMinusSign, delimiter);
-            var digits = new char[buffer.Length];
-            for (int i = 0; i < buffer.Length; i++)
-            {
-                digits[i] = (char)buffer[i];
-            }
-
+            var digits = Unsafe.As<byte[], char[]>(ref buffer);
             return converter(new string(digits), CultureInfo.InvariantCulture);
         }
 
@@ -399,7 +394,7 @@ Func<string, IFormatProvider, T> converter
         private Binary ReadBinary()
         {
             (byte[] bytes, _) = ReadByteArray();
-            return new Binary(bytes);
+            return new Binary(bytes.AsSpan());
         }
 
         private Text ReadTextAfterPrefix()

Bencodex/Types/Binary.cs

@@ -30,13 +30,24 @@ namespace Bencodex.Types
         private readonly int?[] _hashCode;
         private readonly ImmutableArray<byte>?[] _digest;
 
-        public Binary(ImmutableArray<byte> value)
+        public Binary(ReadOnlySpan<byte> value)
         {
-            _value = value;
+            var builder = ImmutableArray.CreateBuilder<byte>(value.Length);
+            foreach (byte b in value)
+            {
+                builder.Add(b);
+            }
+
+            _value = builder.MoveToImmutable();
             _hashCode = new int?[1];
             _digest = new[] { (ImmutableArray<byte>?)null };
         }
 
+        public Binary(ImmutableArray<byte> value)
+            : this(value.AsSpan())
+        {
+        }
+
         public Binary(params byte[] value)
             : this(value is byte[] bytes
                 ? ImmutableArray.Create(bytes)
@@ -90,7 +101,7 @@ public Fingerprint Fingerprint
         public string Inspection => Inspect(true);
 
         public static implicit operator Binary(ImmutableArray<byte> bytes) =>
-            new Binary(bytes);
+            new Binary(bytes.AsSpan());
 
         public static implicit operator ImmutableArray<byte>(Binary binary) =>
             binary.ByteArray;
@@ -179,7 +190,7 @@ byte ParseNibble(char hex)
                 bytes.Add((byte)(ParseNibble(upper) << 4 | ParseNibble(lower)));
             }
 
-            return new Binary(bytes.MoveToImmutable());
+            return new Binary(bytes.MoveToImmutable().AsSpan());
         }
 
 #if !NETSTANDARD2_0
@@ -225,8 +236,7 @@ public static Binary FromBase64(ReadOnlySpan<char> base64)
         public static Binary FromBase64(string base64)
         {
             byte[] bytes = Convert.FromBase64String(base64);
-            ImmutableArray<byte> moved = Unsafe.As<byte[], ImmutableArray<byte>>(ref bytes);
-            return new Binary(moved);
+            return new Binary(bytes.AsSpan());
         }
 
         bool IEquatable<ImmutableArray<byte>>.Equals(ImmutableArray<byte> other) =>
@@ -325,10 +335,10 @@ public byte[] ToByteArray()
         {
             if (ByteArray.IsDefaultOrEmpty)
             {
-                return new byte[0];
+                return Array.Empty<byte>();
             }
 
-            return ByteArray.ToBuilder().ToArray();
+            return ByteArray.ToArray();
         }
 
         /// <summary>