Add SaveIndex/LoadFromIndex methods to XmlDocumentationProvider.

NRefactory/ICSharpCode.NRefactory/Documentation/XmlDocumentationProvider.cs

@@ -53,7 +53,14 @@ namespace ICSharpCode.NRefactory.Documentation
 		
 		struct IndexEntry : IComparable<IndexEntry>
 		{
+			/// <summary>
+			/// Hash code of the documentation tag
+			/// </summary>
 			internal readonly int HashCode;
+			
+			/// <summary>
+			/// Position in the .xml file where the documentation starts
+			/// </summary>
 			internal readonly int PositionInFile;
 			
 			internal IndexEntry(int hashCode, int positionInFile)
@@ -70,6 +77,7 @@ namespace ICSharpCode.NRefactory.Documentation
 		
 		readonly XmlDocumentationCache cache = new XmlDocumentationCache();
 		readonly string fileName;
+		DateTime lastWriteDate;
 		IndexEntry[] index; // SORTED array of index entries
 		
 		#region Constructor / Redirection support
@@ -103,6 +111,13 @@ namespace ICSharpCode.NRefactory.Documentation
 			}
 		}
 		
+		private XmlDocumentationProvider(string fileName, DateTime lastWriteDate, IndexEntry[] index)
+		{
+			this.fileName = fileName;
+			this.lastWriteDate = lastWriteDate;
+			this.index = index;
+		}
+		
 		static string GetRedirectionTarget(string target)
 		{
 			string programFilesDir = Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles);
@@ -159,6 +174,7 @@ namespace ICSharpCode.NRefactory.Documentation
 		#region Load / Create Index
 		void ReadXmlDoc(XmlTextReader reader)
 		{
+			lastWriteDate = File.GetLastWriteTimeUtc(fileName);
 			// Open up a second file stream for the line<->position mapping
 			using (FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read | FileShare.Delete)) {
 				LinePositionMapper linePosMapper = new LinePositionMapper(fs);
@@ -225,6 +241,66 @@ namespace ICSharpCode.NRefactory.Documentation
 		}
 		#endregion
 		
+		#region Save index / Restore from index
+		// FILE FORMAT FOR BINARY DOCUMENTATION
+		// long  magic = 0x4244636f446c6d58 (identifies file type = 'XmlDocDB')
+		const long magic = 0x4244636f446c6d58;
+		// short version = 5              (file format version)
+		const short version = 5;
+		// string fileName                (full name of .xml file)
+		// long  fileDate                 (last change date of xml file in DateTime ticks)
+		// int   testHashCode = magicTestString.GetHashCode() // (check if hash-code implementation is compatible)
+		// int   entryCount               (count of entries)
+		// int   indexPointer             (points to location where index starts in the file)
+		// {
+		//   int hashcode
+		//   int positionInFile           (byte number where the docu string starts in the .xml file)
+		// }
+		
+		const string magicTestString = "XmlDoc-Test-String";
+		
+		/// <summary>
+		/// Saves the index into a binary file.
+		/// Use <see cref="LoadFromIndex"/> to load the saved file.
+		/// </summary>
+		public void SaveIndex(BinaryWriter w)
+		{
+			if (w == null)
+				throw new ArgumentNullException("w");
+			w.Write(magic);
+			w.Write(version);
+			w.Write(fileName);
+			w.Write(lastWriteDate.Ticks);
+			w.Write(magicTestString.GetHashCode());
+			w.Write(index.Length);
+			foreach (var entry in index) {
+				w.Write(entry.HashCode);
+				w.Write(entry.PositionInFile);
+			}
+		}
+		
+		/// <summary>
+		/// Restores XmlDocumentationProvider from the index file (created by <see cref="SaveIndex"/>).
+		/// </summary>
+		public static XmlDocumentationProvider LoadFromIndex(BinaryReader r)
+		{
+			if (r.ReadInt64() != magic)
+				throw new InvalidDataException("File is not a stored XmlDoc index");
+			if (r.ReadInt16() != version)
+				throw new InvalidDataException("Index file was created by incompatible version");
+			string fileName = r.ReadString();
+			DateTime lastWriteDate = new DateTime(r.ReadInt64(), DateTimeKind.Utc);
+			if (r.ReadInt32() != magicTestString.GetHashCode())
+				throw new InvalidDataException("Index file was created by another hash code algorithm");
+			int indexLength = r.ReadInt32();
+			IndexEntry[] index = new IndexEntry[indexLength];
+			for (int i = 0; i < index.Length; i++) {
+				index[i] = new IndexEntry(r.ReadInt32(), r.ReadInt32());
+			}
+			return new XmlDocumentationProvider(fileName, lastWriteDate, index);
+		}
+		#endregion
+		
 		#region GetDocumentation
 		/// <inheritdoc/>
 		public string GetDocumentation(IEntity entity)