diff --git a/src/ImageSharp/Formats/Png/PngChunk.cs b/src/ImageSharp/Formats/Png/PngChunk.cs index c75f9465af..1fee4a8371 100644 --- a/src/ImageSharp/Formats/Png/PngChunk.cs +++ b/src/ImageSharp/Formats/Png/PngChunk.cs @@ -1,4 +1,4 @@ -// Copyright (c) Six Labors and contributors. +// Copyright (c) Six Labors and contributors. // Licensed under the Apache License, Version 2.0. using SixLabors.Memory; @@ -10,12 +10,11 @@ namespace SixLabors.ImageSharp.Formats.Png /// internal readonly struct PngChunk { - public PngChunk(int length, PngChunkType type, IManagedByteBuffer data = null, uint crc = 0) + public PngChunk(int length, PngChunkType type, IManagedByteBuffer data = null) { this.Length = length; this.Type = type; this.Data = data; - this.Crc = crc; } /// @@ -38,20 +37,12 @@ namespace SixLabors.ImageSharp.Formats.Png /// public IManagedByteBuffer Data { get; } - /// - /// Gets a CRC (Cyclic Redundancy Check) calculated on the preceding bytes in the chunk, - /// including the chunk type code and chunk data fields, but not including the length field. - /// The CRC is always present, even for chunks containing no data - /// - public uint Crc { get; } - /// /// Gets a value indicating whether the given chunk is critical to decoding /// public bool IsCritical => this.Type == PngChunkType.Header || this.Type == PngChunkType.Palette || - this.Type == PngChunkType.Data || - this.Type == PngChunkType.End; + this.Type == PngChunkType.Data; } -} \ No newline at end of file +} diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs index 037f648f0a..19e8b62fed 100644 --- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs +++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs @@ -221,7 +221,7 @@ namespace SixLabors.ImageSharp.Formats.Png if (image is null) { - throw new ImageFormatException("PNG Image does not contain a data chunk"); + PngThrowHelper.ThrowNoData(); } return image; @@ -285,7 +285,7 @@ namespace SixLabors.ImageSharp.Formats.Png if (this.header.Width == 0 && this.header.Height == 0) { - throw new ImageFormatException("PNG Image does not contain a header chunk"); + PngThrowHelper.ThrowNoHeader(); } return new ImageInfo(new PixelTypeInfo(this.CalculateBitsPerPixel()), this.header.Width, this.header.Height, metadata); @@ -407,7 +407,8 @@ namespace SixLabors.ImageSharp.Formats.Png case PngColorType.RgbWithAlpha: return this.header.BitDepth * 4; default: - throw new NotSupportedException("Unsupported PNG color type"); + PngThrowHelper.ThrowNotSupportedColor(); + return -1; } } @@ -528,7 +529,8 @@ namespace SixLabors.ImageSharp.Formats.Png break; default: - throw new ImageFormatException("Unknown filter type."); + PngThrowHelper.ThrowUnknownFilter(); + break; } this.ProcessDefilteredScanline(scanlineSpan, image, pngMetadata); @@ -601,7 +603,8 @@ namespace SixLabors.ImageSharp.Formats.Png break; default: - throw new ImageFormatException("Unknown filter type."); + PngThrowHelper.ThrowUnknownFilter(); + break; } Span rowSpan = image.GetPixelRowSpan(this.currentRow); @@ -1119,13 +1122,9 @@ namespace SixLabors.ImageSharp.Formats.Png chunk = new PngChunk( length: length, type: type, - data: this.ReadChunkData(length), - crc: this.ReadChunkCrc()); + data: this.ReadChunkData(length)); - if (chunk.IsCritical) - { - this.ValidateChunk(chunk); - } + this.ValidateChunk(chunk); return true; } @@ -1136,6 +1135,11 @@ namespace SixLabors.ImageSharp.Formats.Png /// The . private void ValidateChunk(in PngChunk chunk) { + if (!chunk.IsCritical) + { + return; + } + Span chunkType = stackalloc byte[4]; BinaryPrimitives.WriteUInt32BigEndian(chunkType, (uint)chunk.Type); @@ -1144,25 +1148,26 @@ namespace SixLabors.ImageSharp.Formats.Png this.crc.Update(chunkType); this.crc.Update(chunk.Data.GetSpan()); - if (this.crc.Value != chunk.Crc) + uint crc = this.ReadChunkCrc(); + if (this.crc.Value != crc) { string chunkTypeName = Encoding.ASCII.GetString(chunkType); - - throw new ImageFormatException($"CRC Error. PNG {chunkTypeName} chunk is corrupt!"); + PngThrowHelper.ThrowInvalidChunkCrc(chunkTypeName); } } /// /// Reads the cycle redundancy chunk from the data. /// - /// - /// Thrown if the input stream is not valid or corrupt. - /// private uint ReadChunkCrc() { - return this.currentStream.Read(this.buffer, 0, 4) == 4 - ? BinaryPrimitives.ReadUInt32BigEndian(this.buffer) - : throw new ImageFormatException("Image stream is not valid!"); + uint crc = 0; + if (this.currentStream.Read(this.buffer, 0, 4) == 4) + { + crc = BinaryPrimitives.ReadUInt32BigEndian(this.buffer); + } + + return crc; } /// @@ -1197,9 +1202,17 @@ namespace SixLabors.ImageSharp.Formats.Png /// private PngChunkType ReadChunkType() { - return this.currentStream.Read(this.buffer, 0, 4) == 4 - ? (PngChunkType)BinaryPrimitives.ReadUInt32BigEndian(this.buffer) - : throw new ImageFormatException("Invalid PNG data."); + if (this.currentStream.Read(this.buffer, 0, 4) == 4) + { + return (PngChunkType)BinaryPrimitives.ReadUInt32BigEndian(this.buffer); + } + else + { + PngThrowHelper.ThrowInvalidChunkType(); + + // The IDE cannot detect the throw here. + return default; + } } /// diff --git a/src/ImageSharp/Formats/Png/PngThrowHelper.cs b/src/ImageSharp/Formats/Png/PngThrowHelper.cs new file mode 100644 index 0000000000..bc6093948b --- /dev/null +++ b/src/ImageSharp/Formats/Png/PngThrowHelper.cs @@ -0,0 +1,29 @@ +// Copyright (c) Six Labors and contributors. +// Licensed under the Apache License, Version 2.0. + +using System; +using System.Runtime.CompilerServices; + +namespace SixLabors.ImageSharp.Formats.Png +{ + /// + /// Cold path optimizations for throwing png format based exceptions. + /// + internal static class PngThrowHelper + { + [MethodImpl(InliningOptions.ColdPath)] + public static void ThrowNoHeader() => throw new ImageFormatException("PNG Image does not contain a header chunk"); + + [MethodImpl(InliningOptions.ColdPath)] + public static void ThrowNoData() => throw new ImageFormatException("PNG Image does not contain a data chunk"); + + public static void ThrowInvalidChunkType() => throw new ImageFormatException("Invalid PNG data."); + + [MethodImpl(InliningOptions.ColdPath)] + public static void ThrowInvalidChunkCrc(string chunkTypeName) => throw new ImageFormatException($"CRC Error. PNG {chunkTypeName} chunk is corrupt!"); + + public static void ThrowNotSupportedColor() => new NotSupportedException("Unsupported PNG color type"); + + public static void ThrowUnknownFilter() => throw new ImageFormatException("Unknown filter type."); + } +}