Debugger: use a Map to cache mirrors.

src/debug/mirrors.js

 // Copyright 2006-2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils) {
 "use strict";
 
 // ----------------------------------------------------------------------------
 // Imports
 
 var GlobalArray = global.Array;
 var IsNaN = global.isNaN;
 var JSONStringify = global.JSON.stringify;
+var GlobalMap = global.Map;
 var MathMin = global.Math.min;
 
 // ----------------------------------------------------------------------------
 
 // Mirror hierarchy:
 // - Mirror
 //   - ValueMirror
 //     - UndefinedMirror
 //     - NullMirror
 //     - BooleanMirror
@@ skipping 42 matching lines @@
   ITERATOR_TYPE : 'iterator',
   GENERATOR_TYPE : 'generator',
 }
 
 
 // Handle id counters.
 var next_handle_ = 0;
 var next_transient_handle_ = -1;
 
 // Mirror cache.
-var mirror_cache_ = [];
+var mirror_cache_ = new GlobalMap();
 var mirror_cache_enabled_ = true;
 
 
 function MirrorCacheIsEmpty() {
-  return next_handle_ == 0 && mirror_cache_.length == 0;
+  return mirror_cache_.size === 0;
 }
 
 
 function ToggleMirrorCache(value) {
   mirror_cache_enabled_ = value;
   ClearMirrorCache();
 }
 
 
 function ClearMirrorCache(value) {
   next_handle_ = 0;
-  mirror_cache_ = [];
+  mirror_cache_.clear();
 }
 
 
 // Wrapper to check whether an object is a Promise.  The call may not work
 // if promises are not enabled.
 // TODO(yangguo): remove try-catch once promises are enabled by default.
 function ObjectIsPromise(value) {
   try {
     return IS_SPEC_OBJECT(value) &&
            !IS_UNDEFINED(%DebugGetProperty(value, builtins.$promiseStatus));
   } catch (e) {
     return false;
   }
 }
 
 
 /**
  * Returns the mirror for a specified value or object.
  *
  * @param {value or Object} value the value or object to retreive the mirror for
  * @param {boolean} transient indicate whether this object is transient and
  *    should not be added to the mirror cache. The default is not transient.
  * @returns {Mirror} the mirror reflects the passed value or object
  */
 function MakeMirror(value, opt_transient) {
   var mirror;
 
   // Look for non transient mirrors in the mirror cache.
   if (!opt_transient && mirror_cache_enabled_) {
-    for (var id in mirror_cache_) {
-      mirror = mirror_cache_[id];
-      if (mirror.value() === value) {
-        return mirror;
-      }
-      // Special check for NaN as NaN == NaN is false.
-      if (mirror.isNumber() && IsNaN(mirror.value()) &&
-          typeof value == 'number' && IsNaN(value)) {
-        return mirror;
-      }
-    }
+    if (mirror_cache_.has(value)) return mirror_cache_.get(value);
   }
 
   if (IS_UNDEFINED(value)) {
     mirror = new UndefinedMirror();
   } else if (IS_NULL(value)) {
     mirror = new NullMirror();
   } else if (IS_BOOLEAN(value)) {
     mirror = new BooleanMirror(value);
   } else if (IS_NUMBER(value)) {
     mirror = new NumberMirror(value);
@@ skipping 20 matching lines @@
   } else if (IS_MAP_ITERATOR(value) || IS_SET_ITERATOR(value)) {
     mirror = new IteratorMirror(value);
   } else if (ObjectIsPromise(value)) {
     mirror = new PromiseMirror(value);
   } else if (IS_GENERATOR(value)) {
     mirror = new GeneratorMirror(value);
   } else {
     mirror = new ObjectMirror(value, MirrorType.OBJECT_TYPE, opt_transient);
   }
 
-  if (mirror_cache_enabled_) mirror_cache_[mirror.handle()] = mirror;
+  if (mirror_cache_enabled_) mirror_cache_.set(value, mirror);
   return mirror;
 }
 
 
 /**
  * Returns the mirror for a specified mirror handle.
  *
  * @param {number} handle the handle to find the mirror for
  * @returns {Mirror or undefiend} the mirror with the requested handle or
  *     undefined if no mirror with the requested handle was found
  */
 function LookupMirror(handle) {
   if (!mirror_cache_enabled_) {
     throw MakeError(kDebugger, "Mirror cache is disabled");
   }
-  return mirror_cache_[handle];
+  for (var value of mirror_cache_.values()) {
+    if (value.handle() == handle) return value;
+  }
+  return UNDEFINED;
 }
 
 
 /**
  * Returns the mirror for the undefined value.
  *
  * @returns {Mirror} the mirror reflects the undefined value
  */
 function GetUndefinedMirror() {
   return MakeMirror(UNDEFINED);
@@ skipping 2897 matching lines @@
 // Functions needed by the debugger runtime.
 utils.InstallFunctions(utils, DONT_ENUM, [
   "ClearMirrorCache", ClearMirrorCache
 ]);
 
 // Export to debug.js
 utils.Export(function(to) {
   to.MirrorType = MirrorType;
 });
 })