shared source/sscli20/jscript/engine/dowhile.cs

   1 // ==++==
   2 //
   3 //
   4 //    Copyright (c) 2006 Microsoft Corporation.  All rights reserved.
   5 //
   6 //    The use and distribution terms for this software are contained in the file
   7 //    named license.txt, which can be found in the root of this distribution.
   8 //    By using this software in any fashion, you are agreeing to be bound by the
   9 //    terms of this license.
  10 //
  11 //    You must not remove this notice, or any other, from this software.
  12 //
  13 //
  14 // ==--==
  15
  16 namespace Microsoft.JScript {
  17
  18     using System;
  19     using System.Collections;
  20     using System.Reflection;
  21     using System.Reflection.Emit;
  22
  23     internal sealed class DoWhile : AST{
  24       private AST body;
  25       private AST condition;
  26       private Completion completion;
  27
  28       internal DoWhile(Context context, AST body, AST condition)
  29         : base(context) {
  30         this.body = body;
  31         this.condition = condition;
  32         this.completion = new Completion();
  33       }
  34
  35       internal override Object Evaluate(){
  36         this.completion.Continue = 0;
  37         this.completion.Exit = 0;
  38         this.completion.value = null;
  39         do{
  40           Completion c = (Completion)this.body.Evaluate();
  41           if (c.value != null)
  42             this.completion.value = c.value;
  43           if (c.Continue > 1){
  44             this.completion.Continue = c.Continue - 1;
  45             break;
  46           }
  47           if (c.Exit > 0){
  48             this.completion.Exit = c.Exit - 1;
  49             break;
  50           }
  51           if (c.Return)
  52             return c;
  53         }while (Convert.ToBoolean(this.condition.Evaluate()) == true);
  54         return this.completion;
  55       }
  56
  57       internal override AST PartiallyEvaluate(){
  58         ScriptObject current_scope = Globals.ScopeStack.Peek();
  59         while (current_scope is WithObject) current_scope = current_scope.GetParent();
  60         if (current_scope is FunctionScope){
  61           FunctionScope scope = (FunctionScope)current_scope;
  62           BitArray before = scope.DefinedFlags;
  63           this.body = this.body.PartiallyEvaluate();
  64           scope.DefinedFlags = before; //The body may have a continue in it
  65           this.condition = this.condition.PartiallyEvaluate();
  66           scope.DefinedFlags = before;
  67           //This is very pessimistic, but the potential presence of break/continue/return/throw
  68           //inside the loop presents complications that are hard to resolve naively.
  69         }else{
  70           this.body = this.body.PartiallyEvaluate();
  71           this.condition = this.condition.PartiallyEvaluate();
  72         }
  73         IReflect conditiontype = this.condition.InferType(null);
  74         if (conditiontype is FunctionPrototype || conditiontype == Typeob.ScriptFunction)
  75           this.context.HandleError(JSError.SuspectLoopCondition);
  76         return this;
  77       }
  78
  79       internal override void TranslateToIL(ILGenerator il, Type rtype){
  80         //This assumes that rtype == Void.class
  81         Label loop_start = il.DefineLabel();
  82         Label condition_start = il.DefineLabel();
  83         Label loop_end = il.DefineLabel();
  84         compilerGlobals.BreakLabelStack.Push(loop_end);
  85         compilerGlobals.ContinueLabelStack.Push(condition_start);
  86         il.MarkLabel(loop_start);
  87         this.body.TranslateToIL(il, Typeob.Void);
  88         il.MarkLabel(condition_start);
  89         this.context.EmitLineInfo(il);
  90         this.condition.TranslateToConditionalBranch(il, true, loop_start, false);
  91         il.MarkLabel(loop_end);
  92         compilerGlobals.BreakLabelStack.Pop();
  93         compilerGlobals.ContinueLabelStack.Pop();
  94       }
  95
  96       internal override void TranslateToILInitializer(ILGenerator il){
  97         this.body.TranslateToILInitializer(il);
  98         this.condition.TranslateToILInitializer(il);
  99       }
 100
 101       internal override Context GetFirstExecutableContext(){
 102         return this.body.GetFirstExecutableContext();
 103       }
 104
 105     }
 106
 107 }