iterators.cs

C#编译器源代码。Micorsoft开放源代码

//
// iterators.cs: Support for implementing iterators
//
// Author:
//   Miguel de Icaza ([e-mail])
//
// (C) 2003 Ximian, Inc.
//
// TODO:
//    Flow analysis for Yield.
//    Emit calls to base object constructor.
//
// Generics note:
//    Current should be defined to return T, and IEnumerator.Current returns object
//

using System;
using System.Collections;
using System.Reflection;
using System.Reflection.Emit;

namespace Mono.CSharp {

	public interface IIteratorContainer {

		//
		// Invoked if a yield statement is found in the body
		//
		void SetYields ();
	}
	
	public class Yield : Statement {
		Expression expr;
		ArrayList finally_blocks;

		public Yield (Expression expr, Location l)
		{
			this.expr = expr;
			loc = l;
		}

		public static bool CheckContext (EmitContext ec, Location loc)
		{
			if (ec.InFinally) {
				Report.Error (1625, loc, "Cannot yield in the body of a " +
					      "finally clause");
				return false;
			} 
			
			if (ec.InUnsafe) {
				Report.Error (1629, loc, "Unsafe code may not appear in iterators");
				return false;
			}
			if (ec.InCatch){
				Report.Error (1631, loc, "Cannot yield a value in the body of a catch clause");
				return false;
			}

			AnonymousContainer am = ec.CurrentAnonymousMethod;
			if ((am != null) && !am.IsIterator){
				Report.Error (1621, loc, "The yield statement cannot be used inside anonymous method blocks");
				return false;
			}

			if (ec.CurrentBranching.InTryWithCatch ()) {
				Report.Error (1626, loc, "Cannot yield a value in the body of a " +
					"try block with a catch clause");
				return false;
			}
			return true;
		}
		
		public override bool Resolve (EmitContext ec)
		{
			expr = expr.Resolve (ec);
			if (expr == null)
				return false;

			if (!CheckContext (ec, loc))
				return false;

			Iterator iterator = ec.CurrentIterator;

			if (expr.Type != iterator.IteratorType){
				expr = Convert.ImplicitConversionRequired (
					ec, expr, iterator.IteratorType, loc);
				if (expr == null)
					return false;
			}

			ec.CurrentBranching.StealFinallyClauses (ref finally_blocks);
			return true;
		}

		protected override void DoEmit (EmitContext ec)
		{
			ec.CurrentIterator.MarkYield (ec, expr, finally_blocks);
		}
	}

	public class YieldBreak : Statement {

		public YieldBreak (Location l)
		{
			loc = l;
		}

		public override bool Resolve (EmitContext ec)
		{
			if (!Yield.CheckContext (ec, loc))
				return false;

			ec.CurrentBranching.CurrentUsageVector.Goto ();
			return true;
		}

		protected override void DoEmit (EmitContext ec)
		{
			ec.CurrentIterator.EmitYieldBreak (ec.ig);
		}
	}

	public class Iterator : Class {
		protected ToplevelBlock original_block;
		protected ToplevelBlock block;

		Type iterator_type;
		TypeExpr iterator_type_expr;
		bool is_enumerable;
		public readonly bool IsStatic;

		//
		// The state as we generate the iterator
		//
		Label move_next_ok, move_next_error;
		ArrayList resume_points = new ArrayList ();
		int pc;
		
		//
		// Context from the original method
		//
		TypeContainer container;
		Type this_type;
		InternalParameters parameters;
		IMethodData orig_method;

		MoveNextMethod move_next_method;
		Constructor ctor;
		CaptureContext cc;

		protected enum State {
			Uninitialized	= -2,
			After,
			Running
		}

		static int proxy_count;

		public void EmitYieldBreak (ILGenerator ig)
		{
			ig.Emit (OpCodes.Ldarg_0);
			IntConstant.EmitInt (ig, (int) State.After);
			ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);
			ig.Emit (OpCodes.Br, move_next_error);
		}

		public void EmitMoveNext (EmitContext ec)
		{
			ILGenerator ig = ec.ig;

			move_next_ok = ig.DefineLabel ();
			move_next_error = ig.DefineLabel ();

			LocalBuilder retval = ec.GetTemporaryLocal (TypeManager.int32_type);

			ig.BeginExceptionBlock ();

			Label dispatcher = ig.DefineLabel ();
			ig.Emit (OpCodes.Br, dispatcher);

			ResumePoint entry_point = new ResumePoint (null);
			resume_points.Add (entry_point);
			entry_point.Define (ig);

			ec.EmitTopBlock (orig_method, original_block, parameters);

			EmitYieldBreak (ig);

			ig.MarkLabel (dispatcher);

			Label [] labels = new Label [resume_points.Count];
			for (int i = 0; i < labels.Length; i++)
				labels [i] = ((ResumePoint) resume_points [i]).Label;

			ig.Emit (OpCodes.Ldarg_0);
			ig.Emit (OpCodes.Ldfld, pc_field.FieldBuilder);
			ig.Emit (OpCodes.Switch, labels);

			Label end = ig.DefineLabel ();

			ig.MarkLabel (move_next_error);
			ig.Emit (OpCodes.Ldc_I4_0); 
			ig.Emit (OpCodes.Stloc, retval);
			ig.Emit (OpCodes.Leave, end);

			ig.MarkLabel (move_next_ok);
			ig.Emit (OpCodes.Ldc_I4_1);
			ig.Emit (OpCodes.Stloc, retval);
			ig.Emit (OpCodes.Leave, end);

			ig.BeginFaultBlock ();

			ig.Emit (OpCodes.Ldarg_0);
			ig.Emit (OpCodes.Callvirt, dispose.MethodBuilder);

			ig.EndExceptionBlock ();

			ig.MarkLabel (end);
			ig.Emit (OpCodes.Ldloc, retval);
			ig.Emit (OpCodes.Ret);
		}

		public void EmitDispose (EmitContext ec)
		{
			ILGenerator ig = ec.ig;

			Label end = ig.DefineLabel ();
			Label dispatcher = ig.DefineLabel ();
			ig.Emit (OpCodes.Br, dispatcher);

			Label [] labels = new Label [resume_points.Count];
			for (int i = 0; i < labels.Length; i++) {
				ResumePoint point = (ResumePoint) resume_points [i];

				if (point.FinallyBlocks == null) {
					labels [i] = end;
					continue;
				}

				labels [i] = ig.DefineLabel ();
				ig.MarkLabel (labels [i]);

				ig.BeginExceptionBlock ();
				ig.BeginFinallyBlock ();

				foreach (ExceptionStatement stmt in point.FinallyBlocks) {
					if (stmt != null)
						stmt.EmitFinally (ec);
				}

				ig.EndExceptionBlock ();
				ig.Emit (OpCodes.Br, end);
			}
			
			ig.MarkLabel (dispatcher);
			ig.Emit (OpCodes.Ldarg_0);
			ig.Emit (OpCodes.Ldfld, pc_field.FieldBuilder);
			ig.Emit (OpCodes.Switch, labels);

			ig.Emit (OpCodes.Ldarg_0);
			IntConstant.EmitInt (ig, (int) State.After);
			ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);

			ig.MarkLabel (end);
		}

		protected class ResumePoint
		{
			public Label Label;
			public readonly ExceptionStatement[] FinallyBlocks;

			public ResumePoint (ArrayList list)
			{
				if (list != null) {
					FinallyBlocks = new ExceptionStatement [list.Count];
					list.CopyTo (FinallyBlocks, 0);
				}
			}

			public void Define (ILGenerator ig)
			{
				Label = ig.DefineLabel ();
				ig.MarkLabel (Label);
			}
		}

		//
		// Called back from Yield
		//
		public void MarkYield (EmitContext ec, Expression expr,
				       ArrayList finally_blocks)
		{
			ILGenerator ig = ec.ig;

			// Store the new current
			ig.Emit (OpCodes.Ldarg_0);
			expr.Emit (ec);
			ig.Emit (OpCodes.Stfld, current_field.FieldBuilder);

			// increment pc
			pc++;
			ig.Emit (OpCodes.Ldarg_0);
			IntConstant.EmitInt (ig, pc);
			ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);

			// Return ok
			ig.Emit (OpCodes.Br, move_next_ok);

			ResumePoint point = new ResumePoint (finally_blocks);
			resume_points.Add (point);
			point.Define (ig);
		}

		public void MarkFinally (EmitContext ec, ArrayList finally_blocks)
		{
			ILGenerator ig = ec.ig;

			// increment pc
			pc++;
			ig.Emit (OpCodes.Ldarg_0);
			IntConstant.EmitInt (ig, pc);
			ig.Emit (OpCodes.Stfld, pc_field.FieldBuilder);

			ResumePoint point = new ResumePoint (finally_blocks);
			resume_points.Add (point);
			point.Define (ig);
		}

		private static MemberName MakeProxyName (string name, Location loc)
		{
			int pos = name.LastIndexOf ('.');
			if (pos > 0)
				name = name.Substring (pos + 1);

			return new MemberName ("<" + name + ">__" + (proxy_count++), loc);
		}

		//
		// Our constructor
		//
		public Iterator (IMethodData m_container, TypeContainer container,
				 InternalParameters parameters,
				 int modifiers)
			: base (container.NamespaceEntry, container, MakeProxyName (m_container.MethodName.Name, m_container.Location),
				(modifiers & Modifiers.UNSAFE) | Modifiers.PRIVATE, null)
		{
			this.orig_method = m_container;

			this.container = container;
			this.parameters = parameters;
			this.original_block = orig_method.Block;
			this.block = new ToplevelBlock (orig_method.Block, parameters.Parameters, orig_method.Location);

			IsStatic = (modifiers & Modifiers.STATIC) != 0;
		}

		public AnonymousContainer Host {
			get { return move_next_method; }
		}

		public bool DefineIterator ()
		{
			ec = new EmitContext (this, Mono.CSharp.Location.Null, null, null, ModFlags);
			ec.CurrentAnonymousMethod = move_next_method;
			ec.CurrentIterator = this;
			ec.InIterator = true;

			if (!CheckType ()) {
				Report.Error (1624, Location,
					"The body of `{0}' cannot be an iterator block because `{1}' is not an iterator interface type",
					orig_method.GetSignatureForError (), TypeManager.CSharpName (orig_method.ReturnType));
				return false;
			}

			for (int i = 0; i < parameters.Count; i++){
				Parameter.Modifier mod = parameters.ParameterModifier (i);
				if ((mod & (Parameter.Modifier.REF | Parameter.Modifier.OUT)) != 0){
					Report.Error (
						1623, Location,
						"Iterators cannot have ref or out parameters");
					return false;
				}

				if ((mod & Parameter.Modifier.ARGLIST) != 0) {
					Report.Error (1636, Location, "__arglist is not allowed in parameter list of iterators");
					return false;
				}

				if (parameters.ParameterType (i).IsPointer) {
					Report.Error (1637, Location, "Iterators cannot have unsafe parameters or yield types");
					return false;
				}
			}

			this_type = container.TypeBuilder;

			ArrayList list = new ArrayList ();
			if (is_enumerable)
				list.Add (new TypeExpression (
						  TypeManager.ienumerable_type, Location));
			list.Add (new TypeExpression (TypeManager.ienumerator_type, Location));
			list.Add (new TypeExpression (TypeManager.idisposable_type, Location));

			iterator_type_expr = new TypeExpression (iterator_type, Location);

			container.AddIterator (this);

			Bases = list;
			orig_method.Block = block;
			return true;
		}

		protected override bool DoDefineMembers ()
		{
			ec.InIterator = true;
			ec.CurrentIterator = this;
			ec.CurrentAnonymousMethod = move_next_method;
			ec.capture_context = cc;

			if (!base.DoDefineMembers ())
				return false;

			return true;
		}

		public override bool Define ()
		{
			if (!base.Define ())
				return false;

			ec.InIterator = true;
			ec.CurrentIterator = this;
			ec.CurrentAnonymousMethod = move_next_method;
			ec.capture_context = cc;
			ec.TypeContainer = ec.TypeContainer.Parent;

			ec.ContainerType = ec.TypeContainer.TypeBuilder;

			ec.ig = move_next_method.method.MethodBuilder.GetILGenerator ();

			if (!ctor.Define ())
				return false;

			bool unreachable;

			if (!ec.ResolveTopBlock (null, original_block, parameters, orig_method, out unreachable))
				return false;

			if (!ec.ResolveTopBlock (null, block, parameters, orig_method, out unreachable))
				return false;

			original_block.CompleteContexts ();

			cc.EmitAnonymousHelperClasses (ec);

			return true;
		}

		//
		// Returns the new block for the method, or null on failure
		//
		protected override bool DefineNestedTypes ()
		{
			Define_Fields ();
			Define_Current ();
			Define_MoveNext ();
			Define_Reset ();
			Define_Dispose ();

			Create_Block ();

			Define_Constructor ();

			if (is_enumerable)
				Define_GetEnumerator ();

			return base.DefineNestedTypes ();
		}

		Field pc_field;
		Field current_field;
		Method dispose;

		void Create_Block ()
		{
			original_block.SetHaveAnonymousMethods (Location, move_next_method);
			block.SetHaveAnonymousMethods (Location, move_next_method);

			cc = original_block.CaptureContext;

			int first = IsStatic ? 0 : 1;

			ArrayList args = new ArrayList ();
			if (!IsStatic) {
				Type t = container.TypeBuilder;
				args.Add (new Argument (
					new ThisParameterReference (t, Location)));
				cc.CaptureThis ();
			}

			args.Add (new Argument (new BoolLiteral (false, Location)));

			for (int i = 0; i < parameters.Count; i++) {
				Type t = parameters.ParameterType (i);
				string name = parameters.ParameterName (i);

				args.Add (new Argument (
					new SimpleParameterReference (t, first + i, Location)));

				cc.AddParameterToContext (move_next_method, name, t, first + i);
			}

			Expression new_expr = new New (
				new TypeExpression (TypeBuilder, Location), args, Location);

			block.AddStatement (new NoCheckReturn (new_expr, Location));
		}

		void Define_Fields ()
		{
			pc_field = new Field (
				this, TypeManager.system_int32_expr, Modifiers.PRIVATE, "$PC",
				null, null, Location);
			AddField (pc_field);

			current_field = new Field (
				this, iterator_type_expr, Modifiers.PRIVATE, "$current",
				null, null, Location);
			AddField (current_field);
		}

		void Define_Constructor ()
		{
			Parameters ctor_params;

			ArrayList list = new ArrayList ();