Testable code

src/ImageSharp/Formats/Jpeg/Common/Decoder/ProfileResolver.cs

@@ -0,0 +1,59 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+
+namespace SixLabors.ImageSharp.Formats.Jpeg.Common.Decoder
+{
+    /// <summary>
+    /// Provides methods for identifying metadata and color profiles within jpeg images.
+    /// </summary>
+    internal static class ProfileResolver
+    {
+        /// <summary>
+        /// Describes the EXIF specific markers
+        /// </summary>
+        public static readonly byte[] JFifMarker = ToAsciiBytes("JFIF\0");
+
+        /// <summary>
+        /// Describes the EXIF specific markers
+        /// </summary>
+        public static readonly byte[] IccMarker = ToAsciiBytes("ICC_PROFILE\0");
+
+        /// <summary>
+        /// Describes the ICC specific markers
+        /// </summary>
+        public static readonly byte[] ExifMarker = ToAsciiBytes("Exif\0\0");
+
+        /// <summary>
+        /// Describes Adobe specific markers <see href="http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe"/>
+        /// </summary>
+        public static readonly byte[] AdobeMarker = ToAsciiBytes("Adobe");
+
+        /// <summary>
+        /// Returns a value indicating whether the passed bytes are a match to the profile identifer
+        /// </summary>
+        /// <param name="bytesToCheck">The bytes to check</param>
+        /// <param name="profileIdentifier">The profile identifier</param>
+        /// <returns>The <see cref="bool"/></returns>
+        public static bool IsProfile(Span<byte> bytesToCheck, Span<byte> profileIdentifier)
+        {
+            return bytesToCheck.Length >= profileIdentifier.Length
+                   && bytesToCheck.Slice(0, profileIdentifier.Length).SequenceEqual(profileIdentifier);
+        }
+
+        // No Encoding.ASCII nor Linq.Select on NetStandard 1.1
+        private static byte[] ToAsciiBytes(string str)
+        {
+            int length = str.Length;
+            byte[] bytes = new byte[length];
+            char[] chars = str.ToCharArray();
+            for (int i = 0; i < length; i++)
+            {
+                bytes[i] = (byte)chars[i];
+            }
+
+            return bytes;
+        }
+    }
+}

src/ImageSharp/Formats/Jpeg/GolangPort/OrigJpegConstants.cs

@@ -25,49 +25,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.GolangPort
         /// </summary>
         public static readonly IEnumerable<string> FileExtensions = new[] { "jpg", "jpeg", "jfif" };
 
-        /// <summary>
-        /// Descibes the various header identifers for metadata profiles
-        /// </summary>
-        /// <remarks>
-        /// Encoding ASCII isn't available for NetStandard 1.1
-        /// </remarks>
-        internal static class ProfileIdentifiers
-        {
-            /// <summary>
-            /// Describes the EXIF specific markers
-            /// </summary>
-            public static readonly byte[] JFifMarker = ToAsciiBytes("JFIF\0");
-
-            /// <summary>
-            /// Describes the EXIF specific markers
-            /// </summary>
-            public static readonly byte[] IccMarker = ToAsciiBytes("ICC_PROFILE\0");
-
-            /// <summary>
-            /// Describes the ICC specific markers
-            /// </summary>
-            public static readonly byte[] ExifMarker = ToAsciiBytes("Exif\0\0");
-
-            /// <summary>
-            /// Describes Adobe specific markers <see href="http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe"/>
-            /// </summary>
-            public static readonly byte[] AdobeMarker = ToAsciiBytes("Adobe");
-
-            // No Linq Select on NetStandard 1.1
-            private static byte[] ToAsciiBytes(string str)
-            {
-                int length = str.Length;
-                byte[] bytes = new byte[length];
-                char[] chars = str.ToCharArray();
-                for (int i = 0; i < length; i++)
-                {
-                    bytes[i] = (byte)chars[i];
-                }
-
-                return bytes;
-            }
-        }
-
         /// <summary>
         /// Describes common Jpeg markers
         /// </summary>
@@ -208,32 +165,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.GolangPort
             public const byte APP15 = 0xef;
         }
 
-        /// <summary>
-        /// Contains JFIF specific markers
-        /// </summary>
-        public static class JFif
-        {
-            /// <summary>
-            /// Represents J in ASCII
-            /// </summary>
-            public const byte J = 0x4A;
-
-            /// <summary>
-            /// Represents F in ASCII
-            /// </summary>
-            public const byte F = 0x46;
-
-            /// <summary>
-            /// Represents I in ASCII
-            /// </summary>
-            public const byte I = 0x49;
-
-            /// <summary>
-            /// Represents the null "0" marker
-            /// </summary>
-            public const byte Null = 0x0;
-        }
-
         /// <summary>
         /// Describes Adobe specific markers <see href="http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/JPEG.html#Adobe"/>
         /// </summary>

src/ImageSharp/Formats/Jpeg/GolangPort/OrigJpegDecoderCore.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System;
 using System.Collections.Generic;
 using System.IO;
 
@@ -395,18 +394,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.GolangPort
             this.InitDerivedMetaDataProperties();
         }
 
-        /// <summary>
-        /// Returns a value indicating whether the passed bytes are a match to the profile identifer
-        /// </summary>
-        /// <param name="bytesToCheck">The bytes to check</param>
-        /// <param name="profileIdentifier">The profile identifier</param>
-        /// <returns>The <see cref="bool"/></returns>
-        private static bool IsProfile(Span<byte> bytesToCheck, Span<byte> profileIdentifier)
-        {
-            return bytesToCheck.Length >= profileIdentifier.Length
-                && bytesToCheck.Slice(0, profileIdentifier.Length).SequenceEqual(profileIdentifier);
-        }
-
         /// <summary>
         /// Assigns derived metadata properties to <see cref="MetaData"/>, eg. horizontal and vertical resolution if it has a JFIF header.
         /// </summary>
@@ -447,7 +434,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.GolangPort
             this.InputProcessor.ReadFull(this.Temp, 0, 13);
             remaining -= 13;
 
-            if (IsProfile(this.Temp, OrigJpegConstants.ProfileIdentifiers.JFifMarker))
+            if (ProfileResolver.IsProfile(this.Temp, ProfileResolver.JFifMarker))
             {
                 this.isJFif = true;
                 this.jFifHorizontalResolution = (short)((this.Temp[8] << 8) | this.Temp[9]);
@@ -475,7 +462,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.GolangPort
             byte[] profile = new byte[remaining];
             this.InputProcessor.ReadFull(profile, 0, remaining);
 
-            if (IsProfile(profile, OrigJpegConstants.ProfileIdentifiers.ExifMarker))
+            if (ProfileResolver.IsProfile(profile, ProfileResolver.ExifMarker))
             {
                 this.isExif = true;
                 this.MetaData.ExifProfile = new ExifProfile(profile);
@@ -500,7 +487,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.GolangPort
             this.InputProcessor.ReadFull(identifier, 0, Icclength);
             remaining -= Icclength; // We have read it by this point
 
-            if (IsProfile(identifier, OrigJpegConstants.ProfileIdentifiers.IccMarker))
+            if (ProfileResolver.IsProfile(identifier, ProfileResolver.IccMarker))
             {
                 byte[] profile = new byte[remaining];
                 this.InputProcessor.ReadFull(profile, 0, remaining);
@@ -538,7 +525,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.GolangPort
             this.InputProcessor.ReadFull(this.Temp, 0, 12);
             remaining -= 12;
 
-            if (IsProfile(this.Temp, OrigJpegConstants.ProfileIdentifiers.AdobeMarker))
+            if (ProfileResolver.IsProfile(this.Temp, ProfileResolver.AdobeMarker))
             {
                 this.isAdobe = true;
                 this.adobeColorTransform = this.Temp[11];

tests/ImageSharp.Tests/Formats/Jpg/ProfileResolverTests.cs

@@ -0,0 +1,79 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Tests.Formats.Jpg
+{
+    using System.Text;
+
+    using SixLabors.ImageSharp.Formats.Jpeg.Common.Decoder;
+
+    using Xunit;
+
+    public class ProfileResolverTests
+    {
+        private static readonly byte[] JFifMarker = Encoding.ASCII.GetBytes("JFIF\0");
+        private static readonly byte[] ExifMarker = Encoding.ASCII.GetBytes("Exif\0\0");
+        private static readonly byte[] IccMarker = Encoding.ASCII.GetBytes("ICC_PROFILE\0");
+        private static readonly byte[] AdobeMarker = Encoding.ASCII.GetBytes("Adobe");
+
+        [Fact]
+        public void ProfileResolverHasCorrectJFifMarker()
+        {
+            Assert.Equal(JFifMarker, ProfileResolver.JFifMarker);
+        }
+
+        [Fact]
+        public void ProfileResolverHasCorrectExifMarker()
+        {
+            Assert.Equal(ExifMarker, ProfileResolver.ExifMarker);
+        }
+
+        [Fact]
+        public void ProfileResolverHasCorrectIccMarker()
+        {
+            Assert.Equal(IccMarker, ProfileResolver.IccMarker);
+        }
+
+        [Fact]
+        public void ProfileResolverHasCorrectAdobeMarker()
+        {
+            Assert.Equal(AdobeMarker, ProfileResolver.AdobeMarker);
+        }
+
+        [Fact]
+        public void ProfileResolverCanResolveJFifMarker()
+        {
+            Assert.True(ProfileResolver.IsProfile(JFifMarker, ProfileResolver.JFifMarker));
+        }
+
+        [Fact]
+        public void ProfileResolverCanResolveExifMarker()
+        {
+            Assert.True(ProfileResolver.IsProfile(ExifMarker, ProfileResolver.ExifMarker));
+        }
+
+        [Fact]
+        public void ProfileResolverCanResolveIccMarker()
+        {
+            Assert.True(ProfileResolver.IsProfile(IccMarker, ProfileResolver.IccMarker));
+        }
+
+        [Fact]
+        public void ProfileResolverCanResolveAdobeMarker()
+        {
+            Assert.True(ProfileResolver.IsProfile(AdobeMarker, ProfileResolver.AdobeMarker));
+        }
+
+        [Fact]
+        public void ProfileResolverCorrectlyReportsNonMarker()
+        {
+            Assert.False(ProfileResolver.IsProfile(IccMarker, ProfileResolver.AdobeMarker));
+        }
+
+        [Fact]
+        public void ProfileResolverCanHandleIncorrectLength()
+        {
+            Assert.False(ProfileResolver.IsProfile(AdobeMarker, ProfileResolver.IccMarker));
+        }
+    }
+}