Don't allocate arrays when copying streams (#1510)

- Use the array pool
- Use Span to copy native memory
- Fixes #1509

binding/Binding/SKManagedStream.cs

@@ -1,8 +1,5 @@
 using System;
-using System.Buffers;
 using System.IO;
-using System.Runtime.InteropServices;
-using System.Text;
 
 namespace SkiaSharp
 {
@@ -90,18 +87,25 @@ namespace SkiaSharp
 
 		private IntPtr OnReadManagedStream (IntPtr buffer, IntPtr size)
 		{
-			byte[] managedBuffer;
-			using (var reader = new BinaryReader (stream, Encoding.UTF8, true)) {
-				managedBuffer = reader.ReadBytes ((int)size);
-			}
-			var result = managedBuffer.Length;
-			if (buffer != IntPtr.Zero) {
-				Marshal.Copy (managedBuffer, 0, buffer, result);
-			}
-			if (!stream.CanSeek && (int)size > 0 && result <= (int)size) {
+			if (buffer == IntPtr.Zero)
+				throw new ArgumentNullException (nameof (buffer));
+			if ((int)size < 0)
+				throw new ArgumentOutOfRangeException (nameof (size));
+
+			if (size == IntPtr.Zero)
+				return IntPtr.Zero;
+
+			using var managedBuffer = Utils.RentArray<byte> ((int)size);
+			var len = stream.Read (managedBuffer.Array, 0, managedBuffer.Length);
+
+			var src = managedBuffer.Span.Slice (0, len);
+			var dst = buffer.AsSpan (managedBuffer.Length);
+			src.CopyTo (dst);
+
+			if (!stream.CanSeek && (int)size > 0 && len <= (int)size)
 				isAsEnd = true;
-			}
-			return (IntPtr)result;
+
+			return (IntPtr)len;
 		}
 
 		protected override IntPtr OnRead (IntPtr buffer, IntPtr size)

samples/Basic/UWP/SkiaSharpSample/SkiaSharpSample.csproj

@@ -17,7 +17,7 @@
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <PackageCertificateKeyFile>..\..\..\AppStoreCertificates\SkiaSharpSample_TemporaryKey.pfx</PackageCertificateKeyFile>
-    <PackageCertificateThumbprint>D3578B78019FED6AEE572B23C1723D44951E0BF9</PackageCertificateThumbprint>
+    <PackageCertificateThumbprint>5FC604ABEDFB78C8B4E57214FEB937949F44ABE4</PackageCertificateThumbprint>
     <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
     <LangVersion>8.0</LangVersion>
   </PropertyGroup>

samples/Basic/Uno/SkiaSharpSample.UWP/SkiaSharpSample.UWP.csproj

@@ -17,7 +17,7 @@
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <PackageCertificateKeyFile>..\..\..\AppStoreCertificates\SkiaSharpSample_TemporaryKey.pfx</PackageCertificateKeyFile>
-    <PackageCertificateThumbprint>D3578B78019FED6AEE572B23C1723D44951E0BF9</PackageCertificateThumbprint>
+    <PackageCertificateThumbprint>5FC604ABEDFB78C8B4E57214FEB937949F44ABE4</PackageCertificateThumbprint>
     <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
     <LangVersion>8.0</LangVersion>
   </PropertyGroup>

samples/Basic/Xamarin.Forms/SkiaSharpSample.UWP/SkiaSharpSample.UWP.csproj

@@ -17,7 +17,7 @@
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <PackageCertificateKeyFile>..\..\..\AppStoreCertificates\SkiaSharpSample_TemporaryKey.pfx</PackageCertificateKeyFile>
-    <PackageCertificateThumbprint>D3578B78019FED6AEE572B23C1723D44951E0BF9</PackageCertificateThumbprint>
+    <PackageCertificateThumbprint>5FC604ABEDFB78C8B4E57214FEB937949F44ABE4</PackageCertificateThumbprint>
     <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
     <LangVersion>8.0</LangVersion>
   </PropertyGroup>

samples/Gallery/UWP/SkiaSharpSample/SkiaSharpSample.csproj

@@ -17,7 +17,7 @@
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <PackageCertificateKeyFile>..\..\..\AppStoreCertificates\SkiaSharpSample_TemporaryKey.pfx</PackageCertificateKeyFile>
-    <PackageCertificateThumbprint>D3578B78019FED6AEE572B23C1723D44951E0BF9</PackageCertificateThumbprint>
+    <PackageCertificateThumbprint>5FC604ABEDFB78C8B4E57214FEB937949F44ABE4</PackageCertificateThumbprint>
     <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
     <LangVersion>8.0</LangVersion>
   </PropertyGroup>

samples/Gallery/Uno/SkiaSharpSample.UWP/SkiaSharpSample.UWP.csproj

@@ -17,7 +17,7 @@
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <PackageCertificateKeyFile>..\..\..\AppStoreCertificates\SkiaSharpSample_TemporaryKey.pfx</PackageCertificateKeyFile>
-    <PackageCertificateThumbprint>D3578B78019FED6AEE572B23C1723D44951E0BF9</PackageCertificateThumbprint>
+    <PackageCertificateThumbprint>5FC604ABEDFB78C8B4E57214FEB937949F44ABE4</PackageCertificateThumbprint>
     <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
     <LangVersion>8.0</LangVersion>
   </PropertyGroup>

samples/Gallery/Xamarin.Forms/UWP/UWP.csproj

@@ -17,7 +17,7 @@
     <FileAlignment>512</FileAlignment>
     <ProjectTypeGuids>{A5A43C5B-DE2A-4C0C-9213-0A381AF9435A};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <PackageCertificateKeyFile>..\..\..\AppStoreCertificates\SkiaSharpSample_TemporaryKey.pfx</PackageCertificateKeyFile>
-    <PackageCertificateThumbprint>D3578B78019FED6AEE572B23C1723D44951E0BF9</PackageCertificateThumbprint>
+    <PackageCertificateThumbprint>5FC604ABEDFB78C8B4E57214FEB937949F44ABE4</PackageCertificateThumbprint>
     <RestoreProjectStyle>PackageReference</RestoreProjectStyle>
     <LangVersion>8.0</LangVersion>
   </PropertyGroup>

tests/Tests/SKManagedStreamTest.cs

@@ -124,6 +124,34 @@ namespace SkiaSharp.Tests
 			}
 		}
 
+		[SkippableTheory]
+		[InlineData(1024, 0, 0, 0)]
+		[InlineData(1024, 1, 1, 1)]
+		[InlineData(1024, 10, 10, 10)]
+		[InlineData(1024, 100, 100, 100)]
+		[InlineData(1024, 1000, 1000, 1000)]
+		[InlineData(1024, 10000, 1024, 1024)]
+		public void ReadIsCorrect(int dataSize, int readSize, int finalPos, int expectedReadSize)
+		{
+			var data = new byte[dataSize];
+			for (var i = 0; i < data.Length; i++)
+			{
+				data[i] = (byte)(i % byte.MaxValue);
+			}
+
+			var stream = new MemoryStream(data);
+			var managedStream = new SKManagedStream(stream);
+
+			var buffer = new byte[dataSize * 2];
+
+			var actualReadSize = managedStream.Read(buffer, readSize);
+
+			Assert.Equal(expectedReadSize, actualReadSize);
+			Assert.Equal(finalPos, managedStream.Position);
+			Assert.Equal(data.Take(readSize), buffer.Take(actualReadSize));
+			Assert.All(buffer.Skip(actualReadSize), i => Assert.Equal(0, i));
+		}
+
 		[SkippableFact]
 		public void ManagedStreamReadsChunkCorrectly()
 		{