ES6: Adding support for size to Set and Map

Section 15.14.5.10 and 15.16.5.7 in the October 26, 2012 ES6 draft,
http://wiki.ecmascript.org/doku.php?id=harmony:specification_drafts

This adds a getter for "size" to Set.prototype and Map.prototype which reflects
the number of elements in the Set and Map respectively.

BUG=v8:2395

Review URL: https://codereview.chromium.org/11360089
Patch from Erik Arvidsson <arv@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12875 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/collection.js

@@ -88,6 +88,15 @@ function SetDelete(key) {
 }
 
 
+function SetGetSize() {
+  if (!IS_SET(this)) {
+    throw MakeTypeError('incompatible_method_receiver',
+                        ['Set.prototype.size', this]);
+  }
+  return %SetGetSize(this);
+}
+
+
 function MapConstructor() {
   if (%_IsConstructCall()) {
     %MapInitialize(this);
@@ -145,6 +154,15 @@ function MapDelete(key) {
 }
 
 
+function MapGetSize() {
+  if (!IS_MAP(this)) {
+    throw MakeTypeError('incompatible_method_receiver',
+                        ['Map.prototype.size', this]);
+  }
+  return %MapGetSize(this);
+}
+
+
 function WeakMapConstructor() {
   if (%_IsConstructCall()) {
     %WeakMapInitialize(this);
@@ -215,6 +233,7 @@ function WeakMapDelete(key) {
   %SetProperty($Map.prototype, "constructor", $Map, DONT_ENUM);
 
   // Set up the non-enumerable functions on the Set prototype object.
+  InstallGetter($Set.prototype, "size", SetGetSize);
   InstallFunctions($Set.prototype, DONT_ENUM, $Array(
     "add", SetAdd,
     "has", SetHas,
@@ -222,6 +241,7 @@ function WeakMapDelete(key) {
   ));
 
   // Set up the non-enumerable functions on the Map prototype object.
+  InstallGetter($Map.prototype, "size", MapGetSize);
   InstallFunctions($Map.prototype, DONT_ENUM, $Array(
     "get", MapGet,
     "set", MapSet,

src/runtime.cc

@@ -783,6 +783,15 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_SetDelete) {
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_SetGetSize) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(JSSet, holder, 0);
+  Handle<ObjectHashSet> table(ObjectHashSet::cast(holder->table()));
+  return Smi::FromInt(table->NumberOfElements());
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_MapInitialize) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 1);
@@ -842,6 +851,15 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_MapSet) {
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_MapGetSize) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(JSMap, holder, 0);
+  Handle<ObjectHashTable> table(ObjectHashTable::cast(holder->table()));
+  return Smi::FromInt(table->NumberOfElements());
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_WeakMapInitialize) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 1);

src/runtime.h

@@ -302,6 +302,7 @@ namespace internal {
   F(SetAdd, 2, 1) \
   F(SetHas, 2, 1) \
   F(SetDelete, 2, 1) \
+  F(SetGetSize, 1, 1) \
   \
   /* Harmony maps */ \
   F(MapInitialize, 1, 1) \
@@ -309,6 +310,7 @@ namespace internal {
   F(MapHas, 2, 1) \
   F(MapDelete, 2, 1) \
   F(MapSet, 3, 1) \
+  F(MapGetSize, 1, 1) \
   \
   /* Harmony weakmaps */ \
   F(WeakMapInitialize, 1, 1) \

src/v8natives.js

@@ -60,6 +60,16 @@ function InstallFunctions(object, attributes, functions) {
   %ToFastProperties(object);
 }
 
+
+// Helper function to install a getter only property.
+function InstallGetter(object, name, getter) {
+  %FunctionSetName(getter, name);
+  %FunctionRemovePrototype(getter);
+  %DefineOrRedefineAccessorProperty(object, name, getter, null, DONT_ENUM);
+  %SetNativeFlag(getter);
+}
+
+
 // Prevents changes to the prototype of a built-in function.
 // The "prototype" property of the function object is made non-configurable,
 // and the prototype object is made non-extensible. The latter prevents

test/mjsunit/harmony/collections.js

@@ -314,3 +314,44 @@ TestBogusReceivers(bogusReceiversTestSet);
 // There is a proposed stress-test available at the es-discuss mailing list
 // which cannot be reasonably automated.  Check it out by hand if you like:
 // https://mail.mozilla.org/pipermail/es-discuss/2011-May/014096.html
+
+
+// Set and Map size getters
+var setSizeDescriptor = Object.getOwnPropertyDescriptor(Set.prototype, 'size');
+assertEquals(undefined, setSizeDescriptor.value);
+assertEquals(undefined, setSizeDescriptor.set);
+assertTrue(setSizeDescriptor.get instanceof Function);
+assertEquals(undefined, setSizeDescriptor.get.prototype);
+assertFalse(setSizeDescriptor.enumerable);
+assertTrue(setSizeDescriptor.configurable);
+
+var s = new Set();
+assertFalse(s.hasOwnProperty('size'));
+for (var i = 0; i < 10; i++) {
+  assertEquals(i, s.size);
+  s.add(i);
+}
+for (var i = 9; i >= 0; i--) {
+  s.delete(i);
+  assertEquals(i, s.size);
+}
+
+
+var mapSizeDescriptor = Object.getOwnPropertyDescriptor(Map.prototype, 'size');
+assertEquals(undefined, mapSizeDescriptor.value);
+assertEquals(undefined, mapSizeDescriptor.set);
+assertTrue(mapSizeDescriptor.get instanceof Function);
+assertEquals(undefined, mapSizeDescriptor.get.prototype);
+assertFalse(mapSizeDescriptor.enumerable);
+assertTrue(mapSizeDescriptor.configurable);
+
+var m = new Map();
+assertFalse(m.hasOwnProperty('size'));
+for (var i = 0; i < 10; i++) {
+  assertEquals(i, m.size);
+  m.set(i, i);
+}
+for (var i = 9; i >= 0; i--) {
+  m.delete(i);
+  assertEquals(i, m.size);
+}