Implement API functions for handling the AccessorDescriptor

Implement API functions for handling the AccessorDescriptor

Patch by Peter Varga.

BUG=none
TEST=cctest/test-api/DefineAndLookupGetterSetter

[Mads Ager (chromium), 2011-07-12 07:09:41]

__defineGetter__ and friends are not part of the standard and i would prefer not
to expose them through the API. It is very easy to use these from C++ already so
I don't see a lot of value in exposing them:


#include <assert.h>
#include <stdio.h>
#include <v8.h>


v8::Handle<v8::Value> CompileAndRun(const char* code) {
  v8::Handle<v8::Script> script =
      v8::Script::Compile(v8::String::New(code));
  return script->Run();
}

v8::Handle<v8::Function> GetGlobalFunction(const char* name) {
  v8::Handle<v8::Value> function = CompileAndRun(name);
  assert(function->IsFunction());
  return v8::Handle<v8::Function>::Cast(function);
}

int main() {
  v8::HandleScope handle_scope;
  v8::Persistent<v8::Context> context = v8::Context::New();
  context->Enter();

  // Create object.
  v8::Handle<v8::Object> object = v8::Object::New();

  // Extract __defineGetter__ function.
  v8::Handle<v8::Function> define_getter =
      GetGlobalFunction("__defineGetter__");

  // Define a getter on the object.
  v8::Handle<v8::String> name = v8::String::New("x");
  v8::Handle<v8::Value> getter = CompileAndRun("(function() { return 42; })");
  v8::Handle<v8::Value> args[] = { name, getter };
  define_getter->Call(object, 2, args);

  // Get the property and verify the result.
  v8::Handle<v8::Value> value = object->Get(name);
  assert(value->Int32Value() == 42);

  context->Exit();
  context.Dispose();
}

[Peter Varga, 2011-07-12 08:40:13]

Thank you for the reply.

We are already using a similar solution for handling a property's getter/setter
but I just try to avoid the overhead of the "CompileAndRun" of a JS code with
this patch.
Since we store the "define_getter" function in a Persistent handle, the
destruction of the wrapper object causes more performance decrease.

After all I can accept the rejection because these AccessorDescriptor handler
functions actually are not part of the ECMA.