Buffered Decoding.

src/ImageSharp/Common/Extensions/StreamExtensions.cs

@@ -2,11 +2,9 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Buffers;
 using System.IO;
 using SixLabors.ImageSharp.Memory;
-#if !SUPPORTS_SPAN_STREAM
-using System.Buffers;
-#endif
 
 namespace SixLabors.ImageSharp
 {
@@ -40,7 +38,7 @@ public static int Read(this Stream stream, Span<byte> buffer, int offset, int co
         /// Skips the number of bytes in the given stream.
         /// </summary>
         /// <param name="stream">The stream.</param>
-        /// <param name="count">The count.</param>
+        /// <param name="count">A byte offset relative to the origin parameter.</param>
         public static void Skip(this Stream stream, int count)
         {
             if (count < 1)
@@ -50,14 +48,16 @@ public static void Skip(this Stream stream, int count)
 
             if (stream.CanSeek)
             {
-                stream.Seek(count, SeekOrigin.Current); // Position += count;
+                stream.Seek(count, SeekOrigin.Current);
+                return;
             }
-            else
+
+            byte[] buffer = ArrayPool<byte>.Shared.Rent(count);
+            try
             {
-                var foo = new byte[count];
                 while (count > 0)
                 {
-                    int bytesRead = stream.Read(foo, 0, count);
+                    int bytesRead = stream.Read(buffer, 0, count);
                     if (bytesRead == 0)
                     {
                         break;
@@ -66,6 +66,10 @@ public static void Skip(this Stream stream, int count)
                     count -= bytesRead;
                 }
             }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buffer);
+            }
         }
 
         public static void Read(this Stream stream, IManagedByteBuffer buffer)

src/ImageSharp/Formats/Bmp/BmpDecoder.cs

@@ -3,6 +3,7 @@
 
 using System.IO;
 using System.Threading.Tasks;
+using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -29,65 +30,71 @@ public sealed class BmpDecoder : IImageDecoder, IBmpDecoderOptions, IImageInfoDe
         public RleSkippedPixelHandling RleSkippedPixelHandling { get; set; } = RleSkippedPixelHandling.Black;
 
         /// <inheritdoc/>
-        public async Task<Image<TPixel>> DecodeAsync<TPixel>(Configuration configuration, Stream stream)
-           where TPixel : unmanaged, IPixel<TPixel>
+        public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
+            where TPixel : unmanaged, IPixel<TPixel>
         {
             Guard.NotNull(stream, nameof(stream));
 
             var decoder = new BmpDecoderCore(configuration, this);
 
             try
             {
-                return await decoder.DecodeAsync<TPixel>(stream).ConfigureAwait(false);
+                using var bufferedStream = new BufferedReadStream(stream);
+                return decoder.Decode<TPixel>(bufferedStream);
             }
             catch (InvalidMemoryOperationException ex)
             {
                 Size dims = decoder.Dimensions;
 
-                throw new InvalidImageContentException($"Can not decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}. This error can happen for very large RLE bitmaps, which are not supported.", ex);
+                throw new InvalidImageContentException($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}. This error can happen for very large RLE bitmaps, which are not supported.", ex);
             }
         }
 
+        /// <inheritdoc />
+        public Image Decode(Configuration configuration, Stream stream)
+            => this.Decode<Rgba32>(configuration, stream);
+
         /// <inheritdoc/>
-        public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
-            where TPixel : unmanaged, IPixel<TPixel>
+        public async Task<Image<TPixel>> DecodeAsync<TPixel>(Configuration configuration, Stream stream)
+           where TPixel : unmanaged, IPixel<TPixel>
         {
             Guard.NotNull(stream, nameof(stream));
 
             var decoder = new BmpDecoderCore(configuration, this);
 
             try
             {
-                return decoder.Decode<TPixel>(stream);
+                using var bufferedStream = new BufferedReadStream(stream);
+                return await decoder.DecodeAsync<TPixel>(bufferedStream).ConfigureAwait(false);
             }
             catch (InvalidMemoryOperationException ex)
             {
                 Size dims = decoder.Dimensions;
 
-                throw new InvalidImageContentException($"Can not decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}. This error can happen for very large RLE bitmaps, which are not supported.", ex);
+                throw new InvalidImageContentException($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}. This error can happen for very large RLE bitmaps, which are not supported.", ex);
             }
         }
 
         /// <inheritdoc />
-        public Image Decode(Configuration configuration, Stream stream) => this.Decode<Rgba32>(configuration, stream);
-
-        /// <inheritdoc />
-        public async Task<Image> DecodeAsync(Configuration configuration, Stream stream) => await this.DecodeAsync<Rgba32>(configuration, stream).ConfigureAwait(false);
+        public async Task<Image> DecodeAsync(Configuration configuration, Stream stream)
+            => await this.DecodeAsync<Rgba32>(configuration, stream).ConfigureAwait(false);
 
         /// <inheritdoc/>
         public IImageInfo Identify(Configuration configuration, Stream stream)
         {
             Guard.NotNull(stream, nameof(stream));
 
-            return new BmpDecoderCore(configuration, this).Identify(stream);
+            using var bufferedStream = new BufferedReadStream(stream);
+            return new BmpDecoderCore(configuration, this).Identify(bufferedStream);
         }
 
         /// <inheritdoc/>
         public Task<IImageInfo> IdentifyAsync(Configuration configuration, Stream stream)
         {
             Guard.NotNull(stream, nameof(stream));
 
-            return new BmpDecoderCore(configuration, this).IdentifyAsync(stream);
+            using var bufferedStream = new BufferedReadStream(stream);
+            return new BmpDecoderCore(configuration, this).IdentifyAsync(bufferedStream);
         }
     }
 }

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -4,10 +4,8 @@
 using System;
 using System.Buffers;
 using System.Buffers.Binary;
-using System.IO;
 using System.Numerics;
 using System.Runtime.CompilerServices;
-using System.Threading.Tasks;
 using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
@@ -62,7 +60,7 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
         /// <summary>
         /// The stream to decode from.
         /// </summary>
-        private Stream stream;
+        private BufferedReadStream stream;
 
         /// <summary>
         /// The metadata.
@@ -120,7 +118,7 @@ public BmpDecoderCore(Configuration configuration, IBmpDecoderOptions options)
         public Size Dimensions => new Size(this.infoHeader.Width, this.infoHeader.Height);
 
         /// <inheritdoc />
-        public Image<TPixel> Decode<TPixel>(Stream stream)
+        public Image<TPixel> Decode<TPixel>(BufferedReadStream stream)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             try
@@ -199,7 +197,7 @@ public Image<TPixel> Decode<TPixel>(Stream stream)
         }
 
         /// <inheritdoc />
-        public IImageInfo Identify(Stream stream)
+        public IImageInfo Identify(BufferedReadStream stream)
         {
             this.ReadImageHeaders(stream, out _, out _);
             return new ImageInfo(new PixelTypeInfo(this.infoHeader.BitsPerPixel), this.infoHeader.Width, this.infoHeader.Height, this.metadata);
@@ -1355,7 +1353,7 @@ private void ReadFileHeader()
         /// </summary>
         /// <returns>Bytes per color palette entry. Usually 4 bytes, but in case of Windows 2.x bitmaps or OS/2 1.x bitmaps
         /// the bytes per color palette entry's can be 3 bytes instead of 4.</returns>
-        private int ReadImageHeaders(Stream stream, out bool inverted, out byte[] palette)
+        private int ReadImageHeaders(BufferedReadStream stream, out bool inverted, out byte[] palette)
         {
             this.stream = stream;
 

src/ImageSharp/Formats/Gif/GifDecoder.cs

@@ -1,9 +1,9 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
-using System;
 using System.IO;
 using System.Threading.Tasks;
+using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.PixelFormats;
@@ -26,54 +26,66 @@ public sealed class GifDecoder : IImageDecoder, IGifDecoderOptions, IImageInfoDe
         public FrameDecodingMode DecodingMode { get; set; } = FrameDecodingMode.All;
 
         /// <inheritdoc/>
-        public async Task<Image<TPixel>> DecodeAsync<TPixel>(Configuration configuration, Stream stream)
+        public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             var decoder = new GifDecoderCore(configuration, this);
 
             try
             {
-                return await decoder.DecodeAsync<TPixel>(stream).ConfigureAwait(false);
+                using var bufferedStream = new BufferedReadStream(stream);
+                return decoder.Decode<TPixel>(bufferedStream);
             }
             catch (InvalidMemoryOperationException ex)
             {
                 Size dims = decoder.Dimensions;
 
-                GifThrowHelper.ThrowInvalidImageContentException($"Can not decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}.", ex);
+                GifThrowHelper.ThrowInvalidImageContentException($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}.", ex);
 
                 // Not reachable, as the previous statement will throw a exception.
                 return null;
             }
         }
 
+        /// <inheritdoc />
+        public Image Decode(Configuration configuration, Stream stream)
+            => this.Decode<Rgba32>(configuration, stream);
+
         /// <inheritdoc/>
-        public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
+        public async Task<Image<TPixel>> DecodeAsync<TPixel>(Configuration configuration, Stream stream)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             var decoder = new GifDecoderCore(configuration, this);
 
             try
             {
-                return decoder.Decode<TPixel>(stream);
+                using var bufferedStream = new BufferedReadStream(stream);
+                return await decoder.DecodeAsync<TPixel>(bufferedStream).ConfigureAwait(false);
             }
             catch (InvalidMemoryOperationException ex)
             {
                 Size dims = decoder.Dimensions;
 
-                GifThrowHelper.ThrowInvalidImageContentException($"Can not decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}.", ex);
+                GifThrowHelper.ThrowInvalidImageContentException($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}.", ex);
 
                 // Not reachable, as the previous statement will throw a exception.
                 return null;
             }
         }
 
+        /// <inheritdoc />
+        public async Task<Image> DecodeAsync(Configuration configuration, Stream stream)
+            => await this.DecodeAsync<Rgba32>(configuration, stream).ConfigureAwait(false);
+
         /// <inheritdoc/>
         public IImageInfo Identify(Configuration configuration, Stream stream)
         {
             Guard.NotNull(stream, nameof(stream));
 
             var decoder = new GifDecoderCore(configuration, this);
-            return decoder.Identify(stream);
+
+            using var bufferedStream = new BufferedReadStream(stream);
+            return decoder.Identify(bufferedStream);
         }
 
         /// <inheritdoc/>
@@ -82,13 +94,9 @@ public Task<IImageInfo> IdentifyAsync(Configuration configuration, Stream stream
             Guard.NotNull(stream, nameof(stream));
 
             var decoder = new GifDecoderCore(configuration, this);
-            return decoder.IdentifyAsync(stream);
-        }
 
-        /// <inheritdoc />
-        public Image Decode(Configuration configuration, Stream stream) => this.Decode<Rgba32>(configuration, stream);
-
-        /// <inheritdoc />
-        public async Task<Image> DecodeAsync(Configuration configuration, Stream stream) => await this.DecodeAsync<Rgba32>(configuration, stream).ConfigureAwait(false);
+            using var bufferedStream = new BufferedReadStream(stream);
+            return decoder.IdentifyAsync(bufferedStream);
+        }
     }
 }

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -27,7 +27,7 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
         /// <summary>
         /// The currently loaded stream.
         /// </summary>
-        private Stream stream;
+        private BufferedReadStream stream;
 
         /// <summary>
         /// The global color table.
@@ -97,7 +97,7 @@ public GifDecoderCore(Configuration configuration, IGifDecoderOptions options)
         private MemoryAllocator MemoryAllocator => this.Configuration.MemoryAllocator;
 
         /// <inheritdoc />
-        public Image<TPixel> Decode<TPixel>(Stream stream)
+        public Image<TPixel> Decode<TPixel>(BufferedReadStream stream)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             Image<TPixel> image = null;
@@ -158,7 +158,7 @@ public Image<TPixel> Decode<TPixel>(Stream stream)
         }
 
         /// <inheritdoc />
-        public IImageInfo Identify(Stream stream)
+        public IImageInfo Identify(BufferedReadStream stream)
         {
             try
             {
@@ -572,7 +572,7 @@ private void SetFrameMetadata(ImageFrameMetadata meta)
         /// Reads the logical screen descriptor and global color table blocks
         /// </summary>
         /// <param name="stream">The stream containing image data. </param>
-        private void ReadLogicalScreenDescriptorAndGlobalColorTable(Stream stream)
+        private void ReadLogicalScreenDescriptorAndGlobalColorTable(BufferedReadStream stream)
         {
             this.stream = stream;
 

src/ImageSharp/Formats/Gif/LzwDecoder.cs

@@ -3,10 +3,9 @@
 
 using System;
 using System.Buffers;
-using System.IO;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-
+using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
 
 namespace SixLabors.ImageSharp.Formats.Gif
@@ -29,7 +28,7 @@ internal sealed class LzwDecoder : IDisposable
         /// <summary>
         /// The stream to decode.
         /// </summary>
-        private readonly Stream stream;
+        private readonly BufferedReadStream stream;
 
         /// <summary>
         /// The prefix buffer.
@@ -52,8 +51,8 @@ internal sealed class LzwDecoder : IDisposable
         /// </summary>
         /// <param name="memoryAllocator">The <see cref="MemoryAllocator"/> to use for buffer allocations.</param>
         /// <param name="stream">The stream to read from.</param>
-        /// <exception cref="System.ArgumentNullException"><paramref name="stream"/> is null.</exception>
-        public LzwDecoder(MemoryAllocator memoryAllocator, Stream stream)
+        /// <exception cref="ArgumentNullException"><paramref name="stream"/> is null.</exception>
+        public LzwDecoder(MemoryAllocator memoryAllocator, BufferedReadStream stream)
         {
             this.stream = stream ?? throw new ArgumentNullException(nameof(stream));
 

src/ImageSharp/Formats/IImageDecoderInternals.cs

@@ -1,7 +1,8 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
-using System.IO;
+using System;
+using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats
@@ -21,18 +22,16 @@ internal interface IImageDecoderInternals
         /// </summary>
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="stream">The stream, where the image should be decoded from. Cannot be null.</param>
-        /// <exception cref="System.ArgumentNullException">
-        ///    <para><paramref name="stream"/> is null.</para>
-        /// </exception>
+        /// <exception cref="ArgumentNullException"><paramref name="stream"/> is null.</exception>
         /// <returns>The decoded image.</returns>
-        Image<TPixel> Decode<TPixel>(Stream stream)
+        Image<TPixel> Decode<TPixel>(BufferedReadStream stream)
             where TPixel : unmanaged, IPixel<TPixel>;
 
         /// <summary>
         /// Reads the raw image information from the specified stream.
         /// </summary>
-        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
+        /// <param name="stream">The <see cref="BufferedReadStream"/> containing image data.</param>
         /// <returns>The <see cref="IImageInfo"/>.</returns>
-        IImageInfo Identify(Stream stream);
+        IImageInfo Identify(BufferedReadStream stream);
     }
 }