Use memory allocator for alpha chunk and for the bitreader data

src/ImageSharp/Formats/WebP/AlphaDecoder.cs

@@ -23,7 +23,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <param name="alphaChunkHeader">The first byte of the alpha image stream contains information on ow to decode the stream.</param>
         /// <param name="memoryAllocator">Used for allocating memory during decoding.</param>
         /// <param name="configuration">The configuration.</param>
-        public AlphaDecoder(int width, int height, byte[] data, byte alphaChunkHeader, MemoryAllocator memoryAllocator, Configuration configuration)
+        public AlphaDecoder(int width, int height, IMemoryOwner<byte> data, byte alphaChunkHeader, MemoryAllocator memoryAllocator, Configuration configuration)
         {
             this.Width = width;
             this.Height = height;
@@ -116,7 +116,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <summary>
         /// Gets the (maybe compressed) alpha data.
         /// </summary>
-        private byte[] Data { get; }
+        private IMemoryOwner<byte> Data { get; }
 
         /// <summary>
         /// Gets the Vp8L decoder which is used to de compress the alpha channel, if needed.
@@ -137,7 +137,8 @@ namespace SixLabors.ImageSharp.Formats.WebP
         {
             if (this.Compressed is false)
             {
-                if (this.Data.Length < (this.Width * this.Height))
+                Span<byte> dataSpan = this.Data.Memory.Span;
+                if (dataSpan.Length < (this.Width * this.Height))
                 {
                     WebPThrowHelper.ThrowImageFormatException("not enough data in the ALPH chunk");
                 }
@@ -145,11 +146,11 @@ namespace SixLabors.ImageSharp.Formats.WebP
                 Span<byte> alphaSpan = this.Alpha.Memory.Span;
                 if (this.AlphaFilterType == WebPAlphaFilterType.None)
                 {
-                    this.Data.AsSpan(0, this.Width * this.Height).CopyTo(alphaSpan);
+                    dataSpan.Slice(0, this.Width * this.Height).CopyTo(alphaSpan);
                     return;
                 }
 
-                Span<byte> deltas = this.Data.AsSpan();
+                Span<byte> deltas = dataSpan;
                 Span<byte> dst = alphaSpan;
                 Span<byte> prev = null;
                 for (int y = 0; y < this.Height; ++y)
@@ -305,6 +306,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
         public void Dispose()
         {
             this.Vp8LDec?.Dispose();
+            this.Data.Dispose();
             this.Alpha?.Dispose();
         }
     }

src/ImageSharp/Formats/WebP/BitReaderBase.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Buffers;
 using System.IO;
 
 using SixLabors.ImageSharp.Memory;
@@ -11,12 +12,12 @@ namespace SixLabors.ImageSharp.Formats.WebP
     /// <summary>
     /// Base class for VP8 and VP8L bitreader.
     /// </summary>
-    internal abstract class BitReaderBase
+    internal abstract class BitReaderBase : IDisposable
     {
         /// <summary>
         /// Gets or sets the raw encoded image data.
         /// </summary>
-        public byte[] Data { get; set; }
+        public IMemoryOwner<byte> Data { get; set; }
 
         /// <summary>
         /// Copies the raw encoded image data from the stream into a byte array.
@@ -26,24 +27,28 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <param name="memoryAllocator">Used for allocating memory during reading data from the stream.</param>
         protected void ReadImageDataFromStream(Stream input, int bytesToRead, MemoryAllocator memoryAllocator)
         {
-            using (var ms = new MemoryStream())
+            this.Data = memoryAllocator.Allocate<byte>(bytesToRead);
+            Span<byte> dataSpan = this.Data.Memory.Span;
+
             using (IManagedByteBuffer buffer = memoryAllocator.AllocateManagedByteBuffer(4096))
             {
                 Span<byte> bufferSpan = buffer.GetSpan();
                 int read;
                 while (bytesToRead > 0 && (read = input.Read(buffer.Array, 0, Math.Min(bufferSpan.Length, bytesToRead))) > 0)
                 {
-                    ms.Write(buffer.Array, 0, read);
+                    buffer.Array.AsSpan(0, read).CopyTo(dataSpan);
                     bytesToRead -= read;
+                    dataSpan = dataSpan.Slice(read);
                 }
 
                 if (bytesToRead > 0)
                 {
                     WebPThrowHelper.ThrowImageFormatException("image file has insufficient data");
                 }
-
-                this.Data = ms.ToArray();
             }
         }
+
+        /// <inheritdoc/>
+        public void Dispose() => this.Data?.Dispose();
     }
 }

src/ImageSharp/Formats/WebP/Vp8BitReader.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System;
+using System.Buffers;
 using System.Buffers.Binary;
 using System.IO;
 using System.Runtime.CompilerServices;
@@ -70,10 +70,10 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <param name="imageData">The raw encoded image data.</param>
         /// <param name="partitionLength">The partition length.</param>
         /// <param name="startPos">Start index in the data array. Defaults to 0.</param>
-        public Vp8BitReader(byte[] imageData, uint partitionLength, int startPos = 0)
+        public Vp8BitReader(IMemoryOwner<byte> imageData, uint partitionLength, int startPos = 0)
         {
             this.Data = imageData;
-            this.ImageDataSize = (uint)imageData.Length;
+            this.ImageDataSize = (uint)imageData.Memory.Length;
             this.PartitionLength = partitionLength;
             this.InitBitreader(partitionLength, startPos);
         }
@@ -184,7 +184,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
         {
             if (this.pos < this.bufferMax)
             {
-                ulong inBits = BinaryPrimitives.ReadUInt64LittleEndian(this.Data.AsSpan((int)this.pos, 8));
+                ulong inBits = BinaryPrimitives.ReadUInt64LittleEndian(this.Data.Memory.Span.Slice((int)this.pos, 8));
                 this.pos += BitsCount >> 3;
                 ulong bits = this.ByteSwap64(inBits);
                 bits >>= 64 - BitsCount;
@@ -203,7 +203,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
             if (this.pos < this.bufferEnd)
             {
                 this.bits += 8;
-                this.value = this.Data[this.pos++] | (this.value << 8);
+                this.value = this.Data.Memory.Span[(int)this.pos++] | (this.value << 8);
             }
             else if (!this.eof)
             {

src/ImageSharp/Formats/WebP/Vp8LBitReader.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System.Buffers;
 using System.IO;
 using System.Runtime.CompilerServices;
 using SixLabors.ImageSharp.Memory;
@@ -62,18 +63,19 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// Initializes a new instance of the <see cref="Vp8LBitReader"/> class.
         /// </summary>
         /// <param name="data">Lossless compressed image data.</param>
-        public Vp8LBitReader(byte[] data)
+        public Vp8LBitReader(IMemoryOwner<byte> data)
         {
             this.Data = data;
-            this.len = data.Length;
+            this.len = data.Memory.Length;
             this.value = 0;
             this.bitPos = 0;
             this.Eos = false;
 
             ulong currentValue = 0;
+            System.Span<byte> dataSpan = this.Data.Memory.Span;
             for (int i = 0; i < 8; ++i)
             {
-                currentValue |= (ulong)this.Data[i] << (8 * i);
+                currentValue |= (ulong)dataSpan[i] << (8 * i);
             }
 
             this.value = currentValue;
@@ -103,9 +105,10 @@ namespace SixLabors.ImageSharp.Formats.WebP
             }
 
             ulong currentValue = 0;
+            System.Span<byte> dataSpan = this.Data.Memory.Span;
             for (int i = 0; i < length; ++i)
             {
-                currentValue |= (ulong)this.Data[i] << (8 * i);
+                currentValue |= (ulong)dataSpan[i] << (8 * i);
             }
 
             this.value = currentValue;
@@ -200,10 +203,11 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// </summary>
         private void ShiftBytes()
         {
+            System.Span<byte> dataSpan = this.Data.Memory.Span;
             while (this.bitPos >= 8 && this.pos < this.len)
             {
                 this.value >>= 8;
-                this.value |= (ulong)this.Data[this.pos] << (Lbits - 8);
+                this.value |= (ulong)dataSpan[(int)this.pos] << (Lbits - 8);
                 ++this.pos;
                 this.bitPos -= 8;
             }

src/ImageSharp/Formats/WebP/WebPDecoderCore.cs

@@ -78,7 +78,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
             this.currentStream = stream;
 
             uint fileSize = this.ReadImageHeader();
-            WebPImageInfo imageInfo = this.ReadVp8Info();
+            using var imageInfo = this.ReadVp8Info();
             if (imageInfo.Features != null && imageInfo.Features.Animation)
             {
                 WebPThrowHelper.ThrowNotSupportedException("Animations are not supported");
@@ -186,7 +186,8 @@ namespace SixLabors.ImageSharp.Formats.WebP
             // The first two bit of it are reserved and should be 0.
             if (imageFeatures >> 6 != 0)
             {
-                WebPThrowHelper.ThrowImageFormatException("first two bits of the VP8X header are expected to be zero");
+                WebPThrowHelper.ThrowImageFormatException(
+                    "first two bits of the VP8X header are expected to be zero");
             }
 
             // If bit 3 is set, a ICC Profile Chunk should be present.
@@ -232,12 +233,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
             if (features.Animation)
             {
                 // TODO: Animations are not yet supported.
-                return new WebPImageInfo()
-                       {
-                           Width = width,
-                           Height = height,
-                           Features = features
-                       };
+                return new WebPImageInfo() { Width = width, Height = height, Features = features };
             }
 
             // TODO: check if VP8 or VP8L info about the dimensions match VP8X info
@@ -444,8 +440,9 @@ namespace SixLabors.ImageSharp.Formats.WebP
                 case WebPChunkType.Alpha:
                     uint alphaChunkSize = this.ReadChunkSize();
                     features.AlphaChunkHeader = (byte)this.currentStream.ReadByte();
-                    features.AlphaData = new byte[alphaChunkSize - 1];
-                    this.currentStream.Read(features.AlphaData, 0, features.AlphaData.Length);
+                    var alphaDataSize = (int)(alphaChunkSize - 1);
+                    features.AlphaData = this.memoryAllocator.Allocate<byte>(alphaDataSize);
+                    this.currentStream.Read(features.AlphaData.Memory.Span, 0, alphaDataSize);
                     break;
             }
         }

src/ImageSharp/Formats/WebP/WebPFeatures.cs

@@ -1,12 +1,15 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
+using System.Buffers;
+
 namespace SixLabors.ImageSharp.Formats.WebP
 {
     /// <summary>
     /// Image features of a VP8X image.
     /// </summary>
-    internal class WebPFeatures
+    internal class WebPFeatures : IDisposable
     {
         /// <summary>
         /// Gets or sets a value indicating whether this image has a ICC Profile.
@@ -21,7 +24,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// <summary>
         /// Gets or sets the alpha data, if an ALPH chunk is present.
         /// </summary>
-        public byte[] AlphaData { get; set; }
+        public IMemoryOwner<byte> AlphaData { get; set; }
 
         /// <summary>
         /// Gets or sets the alpha chunk header.
@@ -42,5 +45,11 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// Gets or sets a value indicating whether this image is a animation.
         /// </summary>
         public bool Animation { get; set; }
+
+        /// <inheritdoc/>
+        public void Dispose()
+        {
+            this.AlphaData?.Dispose();
+        }
     }
 }

src/ImageSharp/Formats/WebP/WebPImageInfo.cs

@@ -1,17 +1,19 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
+
 namespace SixLabors.ImageSharp.Formats.WebP
 {
-    internal class WebPImageInfo
+    internal class WebPImageInfo : IDisposable
     {
         /// <summary>
-        /// Gets or sets the bitmap width in pixels (signed integer).
+        /// Gets or sets the bitmap width in pixels.
         /// </summary>
         public uint Width { get; set; }
 
         /// <summary>
-        /// Gets or sets the bitmap height in pixels (signed integer).
+        /// Gets or sets the bitmap height in pixels.
         /// </summary>
         public uint Height { get; set; }
 
@@ -53,5 +55,13 @@ namespace SixLabors.ImageSharp.Formats.WebP
         /// Gets or sets the VP8 bitreader. Will be null, if its not a lossy image.
         /// </summary>
         public Vp8BitReader Vp8BitReader { get; set; } = null;
+
+        /// <inheritdoc/>
+        public void Dispose()
+        {
+            this.Vp8BitReader?.Dispose();
+            this.Vp8LBitReader?.Dispose();
+            this.Features?.AlphaData?.Dispose();
+        }
     }
 }

src/ImageSharp/Formats/WebP/WebPLossyDecoder.cs

@@ -1195,7 +1195,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
         {
             uint size = this.bitReader.Remaining - this.bitReader.PartitionLength;
             int startIdx = (int)this.bitReader.PartitionLength;
-            Span<byte> sz = this.bitReader.Data.AsSpan(startIdx);
+            Span<byte> sz = this.bitReader.Data.Slice(startIdx);
             int sizeLeft = (int)size;
             dec.NumPartsMinusOne = (1 << (int)this.bitReader.ReadValue(2)) - 1;
             int lastPart = dec.NumPartsMinusOne;