shared source/sscli20/jscript/engine/for.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 For : AST{
  24       private AST initializer;
  25       private AST condition;
  26       private AST incrementer;
  27       private AST body;
  28       private Completion completion;
  29
  30       internal For(Context context, AST initializer, AST condition, AST incrementer, AST body)
  31         : base(context) {
  32         this.initializer = initializer;
  33         this.condition = condition;
  34         this.incrementer = incrementer;
  35         this.body = body;
  36         this.completion = new Completion();
  37       }
  38
  39       // no debug info for the for statement iteself
  40       internal override Object Evaluate(){
  41         this.completion.Continue = 0;
  42         this.completion.Exit = 0;
  43         this.completion.value = null;
  44         this.initializer.Evaluate();
  45         while (Convert.ToBoolean(this.condition.Evaluate()) == true){
  46           Completion c = (Completion)this.body.Evaluate();
  47           if (c.value != null)
  48             this.completion.value = c.value;
  49           if (c.Continue > 1){
  50             this.completion.Continue = c.Continue - 1;
  51             break;
  52           }
  53           if (c.Exit > 0){
  54             this.completion.Exit = c.Exit - 1;
  55             break;
  56           }
  57           if (c.Return)
  58             return c;
  59           this.incrementer.Evaluate();
  60         }
  61         return this.completion;
  62       }
  63
  64       internal override AST PartiallyEvaluate(){
  65         this.initializer = this.initializer.PartiallyEvaluate();
  66         ScriptObject current_scope = Globals.ScopeStack.Peek();
  67         while (current_scope is WithObject) current_scope = current_scope.GetParent();
  68         if (current_scope is FunctionScope){
  69           FunctionScope scope = (FunctionScope)current_scope;
  70           BitArray before = scope.DefinedFlags;
  71           this.condition = this.condition.PartiallyEvaluate();
  72           //Do not need to clear the defined flags because the condition is always completely executed if the body is reached.
  73           this.body = this.body.PartiallyEvaluate();
  74           scope.DefinedFlags = before;
  75           this.incrementer = this.incrementer.PartiallyEvaluate();
  76           scope.DefinedFlags = before;
  77         }else{
  78           this.condition = this.condition.PartiallyEvaluate();
  79           this.body = this.body.PartiallyEvaluate();
  80           this.incrementer = this.incrementer.PartiallyEvaluate();
  81         }
  82         IReflect conditiontype = this.condition.InferType(null);
  83         if (conditiontype is FunctionPrototype || conditiontype == Typeob.ScriptFunction)
  84           this.context.HandleError(JSError.SuspectLoopCondition);
  85         return this;
  86       }
  87
  88       internal override void TranslateToIL(ILGenerator il, Type rtype){
  89         //This assumes that rtype == Void.class
  90         Label body_start = il.DefineLabel();
  91         Label continue_lab = il.DefineLabel();
  92         Label first_time = il.DefineLabel();
  93         Label loop_end = il.DefineLabel();
  94         bool noCondition = false;
  95         compilerGlobals.BreakLabelStack.Push(loop_end);
  96         compilerGlobals.ContinueLabelStack.Push(continue_lab);
  97         if (!(this.initializer is EmptyLiteral)){
  98           this.initializer.context.EmitLineInfo(il);
  99           this.initializer.TranslateToIL(il, Typeob.Void);
 100         }
 101         il.MarkLabel(body_start);
 102         if (!(this.condition is ConstantWrapper) || !(this.condition.Evaluate() is bool) || !((bool)this.condition.Evaluate())){
 103           this.condition.context.EmitLineInfo(il);
 104           this.condition.TranslateToConditionalBranch(il, false, loop_end, false);
 105         }else
 106           if (this.condition.context.StartPosition + 1 == this.condition.context.EndPosition)
 107             // the for does not have a condition specified. If there is no increment as well emit debug info for the whole for
 108             noCondition = true;
 109         this.body.TranslateToIL(il, Typeob.Void);
 110         il.MarkLabel(continue_lab);
 111         if (!(this.incrementer is EmptyLiteral)){
 112           this.incrementer.context.EmitLineInfo(il);
 113           this.incrementer.TranslateToIL(il, Typeob.Void);
 114         }else if (noCondition){
 115           this.context.EmitLineInfo(il);
 116         }
 117         il.Emit(OpCodes.Br, body_start);
 118         il.MarkLabel(loop_end);
 119         compilerGlobals.BreakLabelStack.Pop();
 120         compilerGlobals.ContinueLabelStack.Pop();
 121       }
 122
 123       internal override void TranslateToILInitializer(ILGenerator il){
 124         this.initializer.TranslateToILInitializer(il);
 125         this.condition.TranslateToILInitializer(il);
 126         this.incrementer.TranslateToILInitializer(il);
 127         this.body.TranslateToILInitializer(il);
 128       }
 129     }
 130
 131 }