Introduce ScopedBuffer

MetadataExtractor/Formats/Apple/BplistReader.cs

@@ -1,7 +1,5 @@
 // Copyright (c) Drew Noakes and contributors. All Rights Reserved. Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
 
-using System.Buffers;
-
 namespace MetadataExtractor.Formats.Apple;
 
 /// <summary>
@@ -123,12 +121,9 @@ static object HandleInt(ref BufferReader reader, byte marker)
 
         static Dictionary<byte, byte> HandleDict(ref BufferReader reader, byte count)
         {
-            var keyRefs = ArrayPool<byte>.Shared.Rent(count);
+            Span<byte> keyRefs = stackalloc byte[count]; // count is a byte (0-255)
 
-            for (int j = 0; j < count; j++)
-            {
-                keyRefs[j] = reader.GetByte();
-            }
+            reader.GetBytes(keyRefs);
 
             Dictionary<byte, byte> map = [];
 
@@ -137,8 +132,6 @@ static Dictionary<byte, byte> HandleDict(ref BufferReader reader, byte count)
                 map.Add(keyRefs[j], reader.GetByte());
             }
 
-            ArrayPool<byte>.Shared.Return(keyRefs);
-
             return map;
         }
 

MetadataExtractor/IO/BufferReader.Indexed.cs

@@ -1,6 +1,5 @@
 // Copyright (c) Drew Noakes and contributors. All Rights Reserved. Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
 
-using System.Buffers;
 using System.Buffers.Binary;
 
 namespace MetadataExtractor.IO;
@@ -178,33 +177,22 @@ public readonly double GetDouble64(int index)
 
     public readonly string GetString(int index, int bytesRequested, Encoding encoding)
     {
+        if (bytesRequested < 0)
+            throw new ArgumentOutOfRangeException(nameof(bytesRequested), "Must be zero or greater.");
+
         // This check is important on .NET Framework
         if (bytesRequested is 0)
         {
             return "";
         }
-        else if (bytesRequested < 256)
-        {
-            Span<byte> bytes = stackalloc byte[bytesRequested];
-
-            GetBytes(index, bytes);
-
-            return encoding.GetString(bytes);
-        }
-        else
-        {
-            byte[] bytes = ArrayPool<byte>.Shared.Rent(bytesRequested);
-
-            Span<byte> span = bytes.AsSpan(0, bytesRequested);
 
-            GetBytes(index, span);
+        using var buffer = bytesRequested <= ScopedBuffer.MaxStackBufferSize
+            ? new ScopedBuffer(stackalloc byte[bytesRequested])
+            : new ScopedBuffer(bytesRequested);
 
-            var s = encoding.GetString(span);
+        GetBytes(index, buffer);
 
-            ArrayPool<byte>.Shared.Return(bytes);
-
-            return s;
-        }
+        return encoding.GetString(buffer);
     }
 
     private readonly void ValidateIndex(int index, int bytesRequested)

MetadataExtractor/IO/BufferReader.Sequential.cs

@@ -114,17 +114,20 @@ public ulong GetUInt64()
 
     public string GetString(int bytesRequested, Encoding encoding)
     {
+        if (bytesRequested < 0)
+            throw new ArgumentOutOfRangeException(nameof(bytesRequested), "Must be zero or greater.");
+
         // This check is important on .NET Framework
         if (bytesRequested is 0)
             return "";
 
-        Span<byte> bytes = bytesRequested <= 256
-            ? stackalloc byte[bytesRequested]
-            : new byte[bytesRequested];
+        using var buffer = bytesRequested <= ScopedBuffer.MaxStackBufferSize
+            ? new ScopedBuffer(stackalloc byte[bytesRequested])
+            : new ScopedBuffer(bytesRequested);
 
-        GetBytes(bytes);
+        GetBytes(buffer);
 
-        return encoding.GetString(bytes);
+        return encoding.GetString(buffer);
     }
 
     public StringValue GetNullTerminatedStringValue(int maxLengthBytes, Encoding? encoding = null, bool moveToMaxLength = false)

MetadataExtractor/IO/IndexedReader.cs

@@ -1,7 +1,5 @@
 // Copyright (c) Drew Noakes and contributors. All Rights Reserved. Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
 
-
-using System.Buffers;
 using System.Buffers.Binary;
 
 namespace MetadataExtractor.IO
@@ -320,33 +318,22 @@ public double GetDouble64(int index)
         /// <exception cref="IOException"/>
         public string GetString(int index, int bytesRequested, Encoding encoding)
         {
+            if (bytesRequested < 0)
+                throw new ArgumentOutOfRangeException(nameof(bytesRequested), "Must be zero or greater.");
+
             // This check is important on .NET Framework
             if (bytesRequested is 0)
             {
                 return "";
             }
-            else if (bytesRequested < 256)
-            {
-                Span<byte> bytes = stackalloc byte[bytesRequested];
 
-                GetBytes(index, bytes);
+            using var buffer = bytesRequested <= ScopedBuffer.MaxStackBufferSize
+                ? new ScopedBuffer(stackalloc byte[bytesRequested])
+                : new ScopedBuffer(bytesRequested);
 
-                return encoding.GetString(bytes);
-            }
-            else
-            {
-                byte[] bytes = ArrayPool<byte>.Shared.Rent(bytesRequested);
+            GetBytes(index, buffer);
 
-                Span<byte> span = bytes.AsSpan(0, bytesRequested);
-
-                GetBytes(index, span);
-
-                var s = encoding.GetString(span);
-
-                ArrayPool<byte>.Shared.Return(bytes);
-
-                return s;
-            }
+            return encoding.GetString(buffer);
         }
 
         /// <summary>

MetadataExtractor/IO/ScopedBuffer.cs

@@ -0,0 +1,43 @@
+// Copyright (c) Drew Noakes and contributors. All Rights Reserved. Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
+
+using System.Buffers;
+
+namespace MetadataExtractor.IO;
+
+internal ref struct ScopedBuffer
+{
+    public const int MaxStackBufferSize = 256;
+
+    private byte[]? _rentedBuffer;
+    private readonly Span<byte> _span;
+
+    public ScopedBuffer(int size)
+    {
+        _rentedBuffer = ArrayPool<byte>.Shared.Rent(size);
+        _span = _rentedBuffer.AsSpan(0, size);
+    }
+
+    public ScopedBuffer(Span<byte> span)
+    {
+        _span = span;
+    }
+
+    public readonly Span<byte> Span => _span;
+
+    public static implicit operator Span<byte>(ScopedBuffer bufferScope)
+    {
+        return bufferScope._span;
+    }
+
+    public static implicit operator ReadOnlySpan<byte>(ScopedBuffer bufferScope)
+    {
+        return bufferScope._span;
+    }
+
+    public void Dispose()
+    {
+        if (_rentedBuffer is null) return;
+
+        ArrayPool<byte>.Shared.Return(_rentedBuffer);
+    }
+}

MetadataExtractor/IO/SequentialReader.cs

@@ -1,6 +1,5 @@
 // Copyright (c) Drew Noakes and contributors. All Rights Reserved. Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
 
-using System.Buffers;
 using System.Buffers.Binary;
 
 namespace MetadataExtractor.IO
@@ -221,33 +220,22 @@ public float GetS15Fixed16()
         /// <exception cref="IOException"/>
         public string GetString(int bytesRequested, Encoding encoding)
         {
+            if (bytesRequested < 0)
+                throw new ArgumentOutOfRangeException(nameof(bytesRequested), "Must be zero or greater.");
+
             // This check is important on .NET Framework
             if (bytesRequested is 0)
             {
                 return "";
             }
-            else if (bytesRequested < 256)
-            {
-                Span<byte> bytes = stackalloc byte[bytesRequested];
-
-                GetBytes(bytes);
-
-                return encoding.GetString(bytes);
-            }
-            else
-            {
-                byte[] bytes = ArrayPool<byte>.Shared.Rent(bytesRequested);
-
-                Span<byte> span = bytes.AsSpan(0, bytesRequested);
 
-                GetBytes(span);
+            using var buffer = bytesRequested <= ScopedBuffer.MaxStackBufferSize
+                ? new ScopedBuffer(stackalloc byte[bytesRequested])
+                : new ScopedBuffer(bytesRequested);
 
-                var s = encoding.GetString(span);
+            GetBytes(buffer);
 
-                ArrayPool<byte>.Shared.Return(bytes);
-
-                return s;
-            }
+            return encoding.GetString(buffer);
         }
 
         public StringValue GetStringValue(int bytesRequested, Encoding? encoding = null)

MetadataExtractor/Util/DateUtil.cs

@@ -18,7 +18,7 @@ public static bool IsValidTime(int hours, int minutes, int seconds)
                minutes is >= 0 and < 60
                && seconds is >= 0 and < 60;
 
-#if NET8_0 || NETSTANDARD2_1
+#if NET8_0_OR_GREATER || NETSTANDARD2_1
         private static readonly DateTime _unixEpoch = DateTime.UnixEpoch;
 #else
         private static readonly DateTime _unixEpoch = new(1970, 1, 1, 0, 0, 0);