Introduce ISymbolWriter.Write

This mostly cleans up the code to make it easier to understand. `ISymbolWriter.GetDebugHeader` no longer actually writes the symbols, there's a new `Write` method for just that.

The assembly writer calls `Write` first and then the image writer calls `GetDebugHeader` when it's needed.

This is partially taken from jbevain#617.

Mono.Cecil.Cil/PortablePdb.cs

@@ -305,10 +305,10 @@ public void Write (MethodDebugInformation info)
 			pdb_metadata.AddMethodDebugInformation (info);
 		}
 
-		public ImageDebugHeader GetDebugHeader ()
+		public void Write ()
 		{
 			if (IsEmbedded)
-				return new ImageDebugHeader ();
+				return;
 
 			WritePdbFile ();
 
@@ -317,6 +317,12 @@ public ImageDebugHeader GetDebugHeader ()
 				var buffer = new byte [8192];
 				CryptoService.CopyStreamChunk (writer.BaseStream, final_stream.value, buffer, (int)writer.BaseStream.Length);
 			}
+		}
+
+		public ImageDebugHeader GetDebugHeader ()
+		{
+			if (IsEmbedded)
+				return new ImageDebugHeader ();
 
 			ImageDebugHeaderEntry codeViewEntry;
 			{
@@ -548,8 +554,14 @@ public ImageDebugHeader GetDebugHeader ()
 			return new ImageDebugHeader (debugHeaderEntries);
 		}
 
+		public void Write ()
+		{
+			writer.Write ();
+		}
+
 		public void Dispose ()
 		{
+			writer.Dispose ();
 		}
 	}
 

Mono.Cecil.Cil/Symbols.cs

@@ -1115,6 +1115,7 @@ public interface ISymbolWriter : IDisposable {
 		ISymbolReaderProvider GetReaderProvider ();
 		ImageDebugHeader GetDebugHeader ();
 		void Write (MethodDebugInformation info);
+		void Write ();
 	}
 
 	public interface ISymbolWriterProvider {

Mono.Cecil.PE/ImageWriter.cs

@@ -50,7 +50,7 @@ sealed class ImageWriter : BinaryStreamWriter {
 
 		internal long debug_header_entries_position;
 
-		ImageWriter (ModuleDefinition module, string runtime_version, MetadataBuilder metadata, Disposable<Stream> stream, bool metadataOnly = false, ImageDebugHeader debugHeader = null)
+		ImageWriter (ModuleDefinition module, string runtime_version, MetadataBuilder metadata, Disposable<Stream> stream, bool metadataOnly = false)
 			: base (stream.value)
 		{
 			this.module = module;
@@ -63,18 +63,26 @@ sealed class ImageWriter : BinaryStreamWriter {
 
 			this.pe64 = module.Architecture == TargetArchitecture.AMD64 || module.Architecture == TargetArchitecture.IA64 || module.Architecture == TargetArchitecture.ARM64;
 			this.has_reloc = module.Architecture == TargetArchitecture.I386;
+			this.GetDebugHeader ();
 			this.GetWin32Resources ();
+			this.BuildTextMap ();
+			this.sections = (ushort)(has_reloc ? 2 : 1); // text + reloc?
+		}
+
+		void GetDebugHeader ()
+		{
+			var symbol_writer = metadata.symbol_writer;
+			if (symbol_writer != null)
+				debug_header = symbol_writer.GetDebugHeader ();
 
-			debug_header = debugHeader;
 			if (module.HasDebugHeader) {
 				var header = module.GetDebugHeader ();
 				var deterministic = header.GetDeterministicEntry ();
-				if (deterministic != null)
-					debug_header = debug_header.AddDeterministicEntry ();
-			}
+				if (deterministic == null)
+					return;
 
-			this.BuildTextMap ();
-			this.sections = (ushort)(has_reloc ? 2 : 1); // text + reloc?
+				debug_header = debug_header.AddDeterministicEntry ();
+			}
 		}
 
 		void GetWin32Resources ()
@@ -90,9 +98,9 @@ void GetWin32Resources ()
 			}
 		}
 
-		public static ImageWriter CreateWriter (ModuleDefinition module, MetadataBuilder metadata, Disposable<Stream> stream, ImageDebugHeader debugHeader)
+		public static ImageWriter CreateWriter (ModuleDefinition module, MetadataBuilder metadata, Disposable<Stream> stream)
 		{
-			var writer = new ImageWriter (module, module.runtime_version, metadata, stream, metadataOnly: false, debugHeader: debugHeader);
+			var writer = new ImageWriter (module, module.runtime_version, metadata, stream, metadataOnly: false);
 			writer.BuildSections ();
 			return writer;
 		}

Mono.Cecil/AssemblyWriter.cs

@@ -118,11 +118,10 @@ static void Write (ModuleDefinition module, Disposable<Stream> stream, WriterPar
 					metadata.SetSymbolWriter (symbol_writer);
 					BuildMetadata (module, metadata);
 
-					ImageDebugHeader debugHeader = null;
 					if (symbol_writer != null)
-						debugHeader = symbol_writer.GetDebugHeader ();
+						symbol_writer.Write ();
 
-					var writer = ImageWriter.CreateWriter (module, metadata, stream, debugHeader);
+					var writer = ImageWriter.CreateWriter (module, metadata, stream);
 					stream.value.SetLength (0);
 					writer.WriteImage ();
 

Test/Mono.Cecil.Tests/PortablePdbTests.cs

@@ -708,6 +708,11 @@ public void Write (MethodDebugInformation info)
 				symbol_writer.Write (info);
 			}
 
+			public void Write ()
+			{
+				symbol_writer.Write ();
+			}
+
 			public void Dispose ()
 			{
 				symbol_writer.Dispose ();

symbols/mdb/Mono.Cecil.Mdb/MdbWriter.cs

@@ -167,6 +167,12 @@ public ImageDebugHeader GetDebugHeader ()
 			return new ImageDebugHeader ();
 		}
 
+		public void Write ()
+		{
+			// Can't write it here since we need the final module MVID - which is only computed
+			// after the entire image of the assembly is written (since it's computed from the hash of that)
+		}
+
 		public void Dispose ()
 		{
 			writer.WriteSymbolFile (module.Mvid);

symbols/pdb/Mono.Cecil.Pdb/NativePdbWriter.cs

@@ -28,6 +28,9 @@ public class NativePdbWriter : ISymbolWriter {
 		readonly Dictionary<string, SymDocumentWriter> documents;
 		readonly Dictionary<ImportDebugInformation, MetadataToken> import_info_to_parent;
 
+		ImageDebugDirectory debug_directory;
+		byte [] debug_info;
+
 		internal NativePdbWriter (ModuleDefinition module, SymWriter writer)
 		{
 			this.module = module;
@@ -44,16 +47,7 @@ public ISymbolReaderProvider GetReaderProvider ()
 
 		public ImageDebugHeader GetDebugHeader ()
 		{
-			var entry_point = module.EntryPoint;
-			if (entry_point != null)
-				writer.SetUserEntryPoint (entry_point.MetadataToken.ToInt32 ());
-
-			ImageDebugDirectory directory;
-			var data = writer.GetDebugInfo (out directory);
-			directory.TimeDateStamp = (int) module.timestamp;
-
-			writer.Close ();
-			return new ImageDebugHeader (new ImageDebugHeaderEntry (directory, data));
+			return new ImageDebugHeader (new ImageDebugHeaderEntry (debug_directory, debug_info));
 		}
 
 		public void Write (MethodDebugInformation info)
@@ -259,6 +253,18 @@ SymDocumentWriter GetDocument (Document document)
 			return doc_writer;
 		}
 
+		public void Write ()
+		{
+			var entry_point = module.EntryPoint;
+			if (entry_point != null)
+				writer.SetUserEntryPoint (entry_point.MetadataToken.ToInt32 ());
+
+			debug_info = writer.GetDebugInfo (out debug_directory);
+			debug_directory.TimeDateStamp = (int)module.timestamp;
+
+			writer.Close ();
+		}
+
 		public void Dispose ()
 		{
 		}