Add detectors for mp4/m4v. Fix multiple choice checking and add skipping

Author: adamhathcock

FileTypeChecker.Tests/FIleTypeValidatorTests.cs

@@ -87,6 +87,7 @@ public void GetFileType_ShouldReturnFileExtension(string filePath, string expect
         [TestCase("./files/test.7z", "7-Zip File Format")]
         [TestCase("./files/test.bz2", "BZIP2 file")]
         [TestCase("./files/test.gz", "GZIP compressed file")]
+        [TestCase("./files/test.mp4", "MP4 file")]
         public void GetFileType_ShouldReturnFileName(string filePath, string expectedFileTypeName)
         {
             using var fileStream = File.OpenRead(filePath);

FileTypeChecker.Tests/FileTypeChecker.Tests.csproj

@@ -67,6 +67,8 @@
     <None Update="files\test.bz2">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Update="files\test.mp4">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
-
 </Project>

FileTypeChecker.Tests/files/test.mp4

@@ -13,19 +13,23 @@ public abstract class FileType : IFileType
         private string extension;
         private byte[][] bytes;
 
-        public FileType(string name, string extension, byte[] magicBytes)
+        public FileType(string name, string extension, byte[] magicBytes, int skipBytes = 0)
         {
             this.Name = name;
             this.Extension = extension;
-            this.Bytes = new byte[][] { magicBytes };
+            this.Bytes = new[] { magicBytes };
+            SkipBytes = skipBytes;
         }
 
-        public FileType(string name, string extension, byte[][] magicBytesJaggedArray)
+        public FileType(string name, string extension, byte[][] magicBytesJaggedArray, int skipBytes = 0)
         {
             this.Name = name;
             this.Extension = extension;
             this.Bytes = magicBytesJaggedArray;
+            SkipBytes = skipBytes;
         }
+        
+        public int SkipBytes { get; }
 
         /// <inheritdoc />
         public string Name
@@ -79,11 +83,27 @@ public bool DoesMatchWith(Stream stream, bool resetPosition = true)
                 stream.Position = 0;
             }
 
-            return CompareBytes(stream);
+            var buffer = new byte[20];
+            stream.Read(buffer, 0, buffer.Length);
+            return CompareBytes(buffer);
+        }
+        
+        public bool DoesMatchWith(byte[] buffer)
+        {
+            return CompareBytes(buffer);
         }
 
 
-        protected bool CompareBytes(Stream stream)
-            => this.Bytes.Any(x => x.All(b => stream.ReadByte() == b));
+        protected bool CompareBytes(byte[] buffer)
+        {
+            foreach (var x in this.Bytes)
+            {
+                if (buffer.Skip(SkipBytes).Take(x.Length).SequenceEqual(x)) 
+                {
+                    return true;
+                }
+            }
+            return false;
+        }
     }
 }

FileTypeChecker/Abstracts/FileType.cs

@@ -48,7 +48,7 @@ private static ICollection<IFileType> Types
         /// <param name="fileContent">File to check as stream.</param>
         /// <returns>If current type is supported</returns>
         /// <exception cref="System.ArgumentException"></exception>
-        /// <exception cref="System.A rgumentNullException"></exception>
+        /// <exception cref="System.ArgumentNullException"></exception>
         /// <exception cref="System.NotSupportedException"></exception>
         /// <exception cref="System.ObjectDisposedException"></exception>
         public static bool IsTypeRecognizable(Stream fileContent)

FileTypeChecker/FileTypeValidator.cs

@@ -0,0 +1,17 @@
+using FileTypeChecker.Abstracts;
+
+namespace FileTypeChecker.Types
+{
+    public class M4v : FileType, IFileType
+    {
+        private static readonly string name = "M4v file";
+        private static readonly string extension = "m4v";
+
+        private static readonly byte[][] magicBytesJaggedArray =
+            {new byte[] {0x66, 0x74, 0x79, 0x70, 0x6D, 0x70, 0x34, 0x32}};
+
+        public M4v() : base(name, extension, magicBytesJaggedArray, 4)
+        {
+        }
+    }
+}

FileTypeChecker/Types/M4v.cs

@@ -0,0 +1,16 @@
+using FileTypeChecker.Abstracts;
+
+namespace FileTypeChecker.Types
+{
+    public class Mp4 : FileType, IFileType
+    {
+        private static readonly string name = "MP4 file";
+        private static readonly string extension = "mp4";
+        private static readonly byte[][] magicBytesJaggedArray = { new byte[] { 0x66, 0x74 , 0x79 , 0x70 , 0x4D , 0x53 , 0x4E , 0x56 }, 
+            new byte[] { 0x66, 0x74 , 0x79 , 0x70 , 0x69 , 0x73 , 0x6F , 0x6D }};
+
+        public Mp4() : base(name, extension, magicBytesJaggedArray, 4)
+        {
+        }
+    }
+}