Refactor OpenDocument formats to be in the zip hierarchy to prevent m…

…ultiple format matches

src/FileSignatures/Formats/OpenDocument.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.IO;
+using System.Text;
+
+namespace FileSignatures.Formats;
+
+/// <summary>
+/// Specifies the format of an OpenDocument file.
+/// </summary>
+public abstract class OpenDocument : Zip
+{
+    private const int SubsignatureOffset = 30;
+
+    protected OpenDocument(byte[] subsignature, string mediaType, string extension) : base(SubsignatureOffset + subsignature.Length, mediaType, extension)
+    {
+        Subsignature = new ReadOnlyCollection<byte>(subsignature); ;
+    }
+
+    /// <summary>
+    /// Gets the subsignature of the OpenDocument file.
+    /// This will be the media type in byte format e.g. 'mimetypeapplication/vnd.oasis.opendocument.presentation'
+    /// </summary>
+    public ReadOnlyCollection<byte> Subsignature { get; }
+
+    public override bool IsMatch(Stream stream)
+    {
+        if (!base.IsMatch(stream))
+            return false;
+
+        stream.Position = SubsignatureOffset;
+
+        for (int i = 0; i < Subsignature.Count; i++)
+        {
+            var b = stream.ReadByte();
+            if (b != Subsignature[i])
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}

src/FileSignatures/Formats/OpenDocumentPresentation.cs

@@ -1,15 +1,15 @@
 namespace FileSignatures.Formats
 {
     /// <summary>
-    /// Specifies the format of a OffsetFileFormat file.
+    /// Specifies the format of a OpenDocument Presentation file.
     /// </summary>
-    public class OpenDocumentPresentation : FileFormat
+    public class OpenDocumentPresentation : OpenDocument
     {
-        public OpenDocumentPresentation() : base(new byte[] {
+        public OpenDocumentPresentation() : base([
             0x6D, 0x69, 0x6D, 0x65, 0x74, 0x79, 0x70, 0x65, 0x61, 0x70, 0x70, 0x6C, 0x69, 0x63, 0x61, 0x74, 0x69, 0x6F, 0x6E,
             0x2F, 0x76, 0x6E, 0x64, 0x2E, 0x6F, 0x61, 0x73, 0x69, 0x73, 0x2E, 0x6F, 0x70, 0x65, 0x6E, 0x64, 0x6F, 0x63, 0x75,
             0x6D, 0x65, 0x6E, 0x74, 0x2E, 0x70, 0x72, 0x65, 0x73, 0x65, 0x6E, 0x74, 0x61, 0x74, 0x69, 0x6F, 0x6E
-        }, "application/vnd.oasis.opendocument.presentation", "odp", 30)
+        ], "application/vnd.oasis.opendocument.presentation", "odp")
         {
         }
     }

src/FileSignatures/Formats/OpenDocumentSpreadsheet.cs

@@ -3,13 +3,13 @@
     /// <summary>
     /// Specifies the format of a OffsetFileFormat file.
     /// </summary>
-    public class OpenDocumentSpreadsheet : FileFormat
+    public class OpenDocumentSpreadsheet : OpenDocument
     {
-        public OpenDocumentSpreadsheet() : base(new byte[] {
+        public OpenDocumentSpreadsheet() : base([
             0x6D, 0x69, 0x6D, 0x65, 0x74, 0x79, 0x70, 0x65, 0x61, 0x70, 0x70, 0x6C, 0x69, 0x63, 0x61, 0x74, 0x69, 0x6F,
             0x6E, 0x2F, 0x76, 0x6E, 0x64, 0x2E, 0x6F, 0x61, 0x73, 0x69, 0x73, 0x2E, 0x6F, 0x70, 0x65, 0x6E, 0x64, 0x6F,
             0x63, 0x75, 0x6D, 0x65, 0x6E, 0x74, 0x2E, 0x73, 0x70, 0x72, 0x65, 0x61, 0x64, 0x73, 0x68, 0x65, 0x65, 0x74
-        }, "application/vnd.oasis.opendocument.spreadsheet", "ods", 30)
+        ], "application/vnd.oasis.opendocument.spreadsheet", "ods")
         {
         }
     }

src/FileSignatures/Formats/OpenDocumentText.cs

@@ -3,13 +3,13 @@
     /// <summary>
     /// Specifies the format of a OpenDocumentText file.
     /// </summary>
-    public class OpenDocumentText : FileFormat
+    public class OpenDocumentText : OpenDocument
     {
-        public OpenDocumentText() : base(new byte[] {
+        public OpenDocumentText() : base([
             0x6D, 0x69, 0x6D, 0x65, 0x74, 0x79, 0x70, 0x65, 0x61, 0x70, 0x70, 0x6C, 0x69, 0x63, 0x61, 0x74,
             0x69, 0x6F, 0x6E, 0x2F, 0x76, 0x6E, 0x64, 0x2E, 0x6F, 0x61, 0x73, 0x69, 0x73, 0x2E, 0x6F, 0x70,
             0x65, 0x6E, 0x64, 0x6F, 0x63, 0x75, 0x6D, 0x65, 0x6E, 0x74, 0x2E, 0x74, 0x65, 0x78, 0x74
-        }, "application/vnd.oasis.opendocument.text", "odt", 30)
+        ], "application/vnd.oasis.opendocument.text", "odt")
         {
         }
     }