Reduced intermediate allocations: Profiles

Author: gfoidl

src/ImageSharp/Metadata/Profiles/Exif/ExifReader.cs

@@ -86,10 +86,6 @@ private void GetThumbnail(uint offset)
 /// </summary>
 internal abstract class BaseExifReader
 {
-    private readonly byte[] buf8 = new byte[8];
-    private readonly byte[] buf4 = new byte[4];
-    private readonly byte[] buf2 = new byte[2];
-
     private readonly MemoryAllocator? allocator;
     private readonly Stream data;
     private List<ExifTag>? invalidTags;
@@ -528,20 +524,33 @@ private bool TryReadSpan(Span<byte> span)
         return read == length;
     }
 
-    protected ulong ReadUInt64() =>
-        this.TryReadSpan(this.buf8)
-            ? this.ConvertToUInt64(this.buf8)
+    protected ulong ReadUInt64()
+    {
+        Span<byte> buffer = stackalloc byte[8];
+
+        return this.TryReadSpan(buffer)
+            ? this.ConvertToUInt64(buffer)
             : default;
+    }
 
     // Known as Long in Exif Specification.
-    protected uint ReadUInt32() =>
-        this.TryReadSpan(this.buf4)
-            ? this.ConvertToUInt32(this.buf4)
+    protected uint ReadUInt32()
+    {
+        Span<byte> buffer = stackalloc byte[4];
+
+        return this.TryReadSpan(buffer)
+            ? this.ConvertToUInt32(buffer)
             : default;
+    }
 
-    protected ushort ReadUInt16() => this.TryReadSpan(this.buf2)
-            ? this.ConvertToShort(this.buf2)
+    protected ushort ReadUInt16()
+    {
+        Span<byte> buffer = stackalloc byte[2];
+
+        return this.TryReadSpan(buffer)
+            ? this.ConvertToShort(buffer)
             : default;
+    }
 
     private long ConvertToInt64(ReadOnlySpan<byte> buffer)
     {

src/ImageSharp/Metadata/Profiles/Exif/Values/ExifByteArray.cs

@@ -45,12 +45,12 @@ public override bool TrySetValue(object? value)
 
     private bool TrySetSignedIntArray(int[] intArrayValue)
     {
-        if (Array.FindIndex(intArrayValue, x => x < byte.MinValue || x > byte.MaxValue) > -1)
+        if (Array.FindIndex(intArrayValue, x => (uint)x > byte.MaxValue) >= 0)
         {
             return false;
         }
 
-        var value = new byte[intArrayValue.Length];
+        byte[] value = new byte[intArrayValue.Length];
         for (int i = 0; i < intArrayValue.Length; i++)
         {
             int s = intArrayValue[i];

src/ImageSharp/Metadata/Profiles/ICC/IccProfile.cs

@@ -108,10 +108,10 @@ public static IccProfileId CalculateHash(byte[] data)
         const int profileIdPos = 84;
 
         // need to copy some values because they need to be zero for the hashing
-        byte[] temp = new byte[24];
-        Buffer.BlockCopy(data, profileFlagPos, temp, 0, 4);
-        Buffer.BlockCopy(data, renderingIntentPos, temp, 4, 4);
-        Buffer.BlockCopy(data, profileIdPos, temp, 8, 16);
+        Span<byte> temp = stackalloc byte[24];
+        data.AsSpan(profileFlagPos, 4).CopyTo(temp);
+        data.AsSpan(renderingIntentPos, 4).CopyTo(temp.Slice(4));
+        data.AsSpan(profileIdPos, 16).CopyTo(temp.Slice(8));
 
         try
         {
@@ -131,9 +131,9 @@ public static IccProfileId CalculateHash(byte[] data)
         }
         finally
         {
-            Buffer.BlockCopy(temp, 0, data, profileFlagPos, 4);
-            Buffer.BlockCopy(temp, 4, data, renderingIntentPos, 4);
-            Buffer.BlockCopy(temp, 8, data, profileIdPos, 16);
+            temp.Slice(0, 4).CopyTo(data.AsSpan(profileFlagPos));
+            temp.Slice(4, 4).CopyTo(data.AsSpan(renderingIntentPos));
+            temp.Slice(8, 16).CopyTo(data.AsSpan(profileIdPos));
         }
     }