Add AniChunk

src/ImageSharp/Formats/Ani/AniChunk.cs

@@ -0,0 +1,38 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+#nullable disable
+using System.Buffers;
+using SixLabors.ImageSharp.Formats.Png;
+
+namespace SixLabors.ImageSharp.Formats.Ani;
+
+internal readonly struct AniChunk
+{
+    public AniChunk(int length, AniChunkType type, IMemoryOwner<byte> data = null)
+    {
+        this.Length = length;
+        this.Type = type;
+        this.Data = data;
+    }
+
+    /// <summary>
+    /// Gets the length.
+    /// An unsigned integer giving the number of bytes in the chunk's
+    /// data field. The length counts only the data field, not itself,
+    /// the chunk type code, or the CRC. Zero is a valid length
+    /// </summary>
+    public int Length { get; }
+
+    /// <summary>
+    /// Gets the chunk type.
+    /// The value is the equal to the UInt32BigEndian encoding of its 4 ASCII characters.
+    /// </summary>
+    public AniChunkType Type { get; }
+
+    /// <summary>
+    /// Gets the data bytes appropriate to the chunk type, if any.
+    /// This field can be of zero length or null.
+    /// </summary>
+    public IMemoryOwner<byte> Data { get; }
+}

src/ImageSharp/Formats/Ani/AniChunkType.cs

@@ -0,0 +1,11 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Ani;
+
+internal enum AniChunkType : uint
+{
+    Seq = 0x73_65_71_20,
+    Rate = 0x72_61_74_65,
+    List = 0x4C_49_53_54
+}

src/ImageSharp/Formats/Ani/AniConstants.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Ani;
+
+internal static class AniConstants
+{
+    /// <summary>
+    /// The list of mime types that equate to an ani.
+    /// </summary>
+    /// <remarks>
+    /// See <see href="https://en.wikipedia.org/wiki/ICO_(file_format)#MIME_type"/>
+    /// </remarks>
+    public static readonly IEnumerable<string> MimeTypes = [];
+
+    /// <summary>
+    /// The list of file extensions that equate to an ani.
+    /// </summary>
+    public static readonly IEnumerable<string> FileExtensions = ["ani"];
+
+}

src/ImageSharp/Formats/Ani/AniDecoderCore.cs

@@ -1,50 +1,206 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Buffers;
+using System.Buffers.Binary;
+using System.Runtime.CompilerServices;
 using SixLabors.ImageSharp.Formats.Icon;
+using SixLabors.ImageSharp.Formats.Png;
 using SixLabors.ImageSharp.IO;
+using SixLabors.ImageSharp.Memory.Internals;
+using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.Metadata;
 
 namespace SixLabors.ImageSharp.Formats.Ani;
 
 internal class AniDecoderCore : ImageDecoderCore
 {
+    /// <summary>
+    /// The general decoder options.
+    /// </summary>
+    private readonly Configuration configuration;
+
+    /// <summary>
+    /// The stream to decode from.
+    /// </summary>
+    private BufferedReadStream currentStream = null!;
+
+    private AniHeader header;
+
     public AniDecoderCore(DecoderOptions options)
-        : base(options)
-    {
-    }
+        : base(options) => this.configuration = options.Configuration;
 
     protected override Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken cancellationToken)
     {
-        this.ReadHeader(stream);
-        Span<byte> buffer = stackalloc byte[4];
-        _ = stream.Read(buffer);
-        uint type = BitConverter.ToUInt32(buffer);
-        switch (type)
+        this.currentStream = stream;
+        this.ReadHeader();
+        ImageMetadata metadata = new();
+        AniMetadata aniMetadata = metadata.GetAniMetadata();
+        Image<TPixel>? image = null;
+
+        Span<byte> buffer = stackalloc byte[20];
+
+        try
         {
-            case 0x73_65_71_20: // seq
-                break;
-            case 0x72_61_74_65: // rate
-                break;
-            case 0x4C_49_53_54: // list
-                break;
-            default:
-                break;
+            while (this.TryReadChunk(buffer, out AniChunk chunk))
+            {
+                try
+                {
+                    switch (chunk.Type)
+                    {
+                        case AniChunkType.Seq:
+
+                            break;
+                        case AniChunkType.Rate:
+
+                            break;
+                        case AniChunkType.List:
+
+                            break;
+                        default:
+                            break;
+                    }
+                }
+                finally
+                {
+                    chunk.Data?.Dispose();
+                }
+            }
         }
+        catch
+        {
+            image?.Dispose();
+            throw;
+        }
+
 
         throw new NotImplementedException();
     }
 
+    private void ReadSeq()
+    {
+
+    }
+
+    private bool TryReadChunk(Span<byte> buffer, out AniChunk chunk)
+    {
+        if (!this.TryReadChunkLength(buffer, out int length))
+        {
+            // IEND
+            chunk = default;
+            return false;
+        }
+
+        while (length < 0)
+        {
+            // Not a valid chunk so try again until we reach a known chunk.
+            if (!this.TryReadChunkLength(buffer, out length))
+            {
+                // IEND
+                chunk = default;
+                return false;
+            }
+        }
+
+        AniChunkType type = this.ReadChunkType(buffer);
+
+        // A chunk might report a length that exceeds the length of the stream.
+        // Take the minimum of the two values to ensure we don't read past the end of the stream.
+        long position = this.currentStream.Position;
+        chunk = new AniChunk(
+            length: (int)Math.Min(length, this.currentStream.Length - position),
+            type: type,
+            data: this.ReadChunkData(length));
+
+        return true;
+    }
+
+
     protected override ImageInfo Identify(BufferedReadStream stream, CancellationToken cancellationToken)
     {
         throw new NotImplementedException();
     }
 
-    private void ReadHeader(Stream stream)
+    private void ReadHeader()
     {
         // Skip the identifier
-        stream.Skip(12);
+        this.currentStream.Skip(12);
         Span<byte> buffer = stackalloc byte[36];
-        _ = stream.Read(buffer);
-        AniHeader header = AniHeader.Parse(buffer);
+        _ = this.currentStream.Read(buffer);
+        this.header = AniHeader.Parse(buffer);
+    }
+
+    private void ReadSeq(Stream stream)
+    {
+        Span<byte> buffer = stackalloc byte[4];
+        int length = BinaryPrimitives.ReadInt32BigEndian(buffer);
+
     }
+
+    /// <summary>
+    /// Attempts to read the length of the next chunk.
+    /// </summary>
+    /// <param name="buffer">Temporary buffer.</param>
+    /// <param name="result">The result length. If the return type is <see langword="false"/> this parameter is passed uninitialized.</param>
+    /// <returns>
+    /// Whether the length was read.
+    /// </returns>
+    [MethodImpl(InliningOptions.ShortMethod)]
+    private bool TryReadChunkLength(Span<byte> buffer, out int result)
+    {
+        if (this.currentStream.Read(buffer, 0, 4) == 4)
+        {
+            result = BinaryPrimitives.ReadInt32BigEndian(buffer);
+
+            return true;
+        }
+
+        result = 0;
+        return false;
+    }
+
+    /// <summary>
+    /// Identifies the chunk type from the chunk.
+    /// </summary>
+    /// <param name="buffer">Temporary buffer.</param>
+    /// <exception cref="ImageFormatException">
+    /// Thrown if the input stream is not valid.
+    /// </exception>
+    [MethodImpl(InliningOptions.ShortMethod)]
+    private AniChunkType ReadChunkType(Span<byte> buffer)
+    {
+        if (this.currentStream.Read(buffer, 0, 4) == 4)
+        {
+            return (AniChunkType)BinaryPrimitives.ReadUInt32BigEndian(buffer);
+        }
+
+        PngThrowHelper.ThrowInvalidChunkType();
+
+        // The IDE cannot detect the throw here.
+        return default;
+    }
+
+    /// <summary>
+    /// Reads the chunk data from the stream.
+    /// </summary>
+    /// <param name="length">The length of the chunk data to read.</param>
+    [MethodImpl(InliningOptions.ShortMethod)]
+    private IMemoryOwner<byte> ReadChunkData(int length)
+    {
+        if (length == 0)
+        {
+            return new BasicArrayBuffer<byte>([]);
+        }
+
+        // We rent the buffer here to return it afterwards in Decode()
+        // We don't want to throw a degenerated memory exception here as we want to allow partial decoding
+        // so limit the length.
+        length = (int)Math.Min(length, this.currentStream.Length - this.currentStream.Position);
+        IMemoryOwner<byte> buffer = this.configuration.MemoryAllocator.Allocate<byte>(length, AllocationOptions.Clean);
+
+        this.currentStream.Read(buffer.GetSpan(), 0, length);
+
+        return buffer;
+    }
+
 }

src/ImageSharp/Formats/Ani/AniFormat.cs

@@ -0,0 +1,34 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+
+using SixLabors.ImageSharp.Formats.Ico;
+
+namespace SixLabors.ImageSharp.Formats.Ani;
+
+
+/// <summary>
+/// Registers the image encoders, decoders and mime type detectors for the bmp format.
+/// </summary>
+public sealed class AniFormat : IImageFormat<AniMetadata>
+{
+    /// <summary>
+    /// Gets the shared instance.
+    /// </summary>
+    public static AniFormat Instance { get; } = new();
+
+    /// <inheritdoc/>
+    public AniMetadata CreateDefaultFormatMetadata() => throw new NotImplementedException();
+
+    /// <inheritdoc/>
+    public string Name => "ANI";
+
+    /// <inheritdoc/>
+    public string DefaultMimeType { get; }
+
+    /// <inheritdoc/>
+    public IEnumerable<string> MimeTypes { get; }
+
+    /// <inheritdoc/>
+    public IEnumerable<string> FileExtensions { get; }
+}

src/ImageSharp/Formats/Ani/AniMetadata.cs

@@ -1,23 +1,39 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using SixLabors.ImageSharp.Formats.Ico;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Ani;
 
-internal class AniMetadata : IFormatMetadata<AniMetadata>
+/// <summary>
+/// Provides Ani specific metadata information for the image.
+/// </summary>
+public class AniMetadata : IFormatMetadata<AniMetadata>
 {
-
+    /// <summary>
+    /// Initializes a new instance of the <see cref="AniMetadata"/> class.
+    /// </summary>
+    public AniMetadata()
+    {
+    }
+
+    /// <inheritdoc/>
     public static AniMetadata FromFormatConnectingMetadata(FormatConnectingMetadata metadata) => throw new NotImplementedException();
 
+    /// <inheritdoc/>
     public void AfterImageApply<TPixel>(Image<TPixel> destination)
         where TPixel : unmanaged, IPixel<TPixel> => throw new NotImplementedException();
 
+    /// <inheritdoc/>
     public IDeepCloneable DeepClone() => throw new NotImplementedException();
 
+    /// <inheritdoc/>
     public PixelTypeInfo GetPixelTypeInfo() => throw new NotImplementedException();
 
+    /// <inheritdoc/>
     public FormatConnectingMetadata ToFormatConnectingMetadata() => throw new NotImplementedException();
 
+    /// <inheritdoc/>
     AniMetadata IDeepCloneable<AniMetadata>.DeepClone() => throw new NotImplementedException();
 }

src/ImageSharp/Formats/Bmp/BmpRenderingIntent.cs

@@ -17,7 +17,7 @@ internal enum BmpRenderingIntent
     /// <summary>
     /// Maintains saturation. Used for business charts and other situations in which undithered colors are required.
     /// </summary>
-    LCS_GM_BUSINESS = 1,
+    LCS_GM_BUSINESS = 1,  
 
     /// <summary>
     /// Maintains colorimetric match. Used for graphic designs and named colors.

src/ImageSharp/Formats/_Generated/ImageMetadataExtensions.cs

@@ -14,6 +14,7 @@ using SixLabors.ImageSharp.Formats.Qoi;
 using SixLabors.ImageSharp.Formats.Tga;
 using SixLabors.ImageSharp.Formats.Tiff;
 using SixLabors.ImageSharp.Formats.Webp;
+using SixLabors.ImageSharp.Formats.Ani;
 
 namespace SixLabors.ImageSharp;
 
@@ -102,6 +103,26 @@ public static class ImageMetadataExtensions
     /// <returns>The new <see cref="IcoMetadata"/></returns>
     public static IcoMetadata CloneIcoMetadata(this ImageMetadata source) => source.CloneFormatMetadata(IcoFormat.Instance);
 
+    /// <summary>
+    /// Gets the <see cref="AniMetadata"/> from <paramref name="source"/>.<br/>
+    /// If none is found, an instance is created either by conversion from the decoded image format metadata
+    /// or the requested format default constructor.
+    /// This instance will be added to the metadata for future requests.
+    /// </summary>
+    /// <param name="source">The image metadata.</param>
+    /// <returns>
+    /// The <see cref="AniMetadata"/>
+    /// </returns>
+    public static AniMetadata GetAniMetadata(this ImageMetadata source) => source.GetFormatMetadata(AniFormat.Instance);
+
+    /// <summary>
+    /// Creates a new cloned instance of <see cref="IcoMetadata"/> from the <paramref name="source"/>.
+    /// The instance is created via <see cref="GetIcoMetadata(ImageMetadata)"/>
+    /// </summary>
+    /// <param name="source">The image metadata.</param>
+    /// <returns>The new <see cref="IcoMetadata"/></returns>
+    public static AniMetadata CloneAniMetadata(this ImageMetadata source) => source.CloneFormatMetadata(AniFormat.Instance);
+
     /// <summary>
     /// Gets the <see cref="JpegMetadata"/> from <paramref name="source"/>.<br/>
     /// If none is found, an instance is created either by conversion from the decoded image format metadata