A proposal and implementation for an initial postMessage interface. These in...

webkit/plugins/ppapi/message_channel.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "webkit/plugins/ppapi/message_channel.h"
+
+#include <cstdlib>
+#include <string>
+
+#include "base/logging.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebBindings.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebDocument.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebElement.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebPluginContainer.h"
+#include "webkit/plugins/ppapi/npapi_glue.h"
+#include "webkit/plugins/ppapi/ppapi_plugin_instance.h"
+#include "webkit/plugins/ppapi/var.h"
+
+using WebKit::WebBindings;
+
+namespace webkit {
+
+namespace ppapi {
+
+namespace {
+
+const char kPostMessage[] = "postMessage";
+
+// Helper function to get the MessageChannel that is associated with an
+// NPObject*.
+MessageChannel& ToMessageChannel(NPObject* object) {
+  return *(static_cast<MessageChannel::MessageChannelNPObject*>(object)->
+      message_channel);
+}
+
+// Helper function to determine if a given identifier is equal to kPostMessage.
+bool IdentifierIsPostMessage(NPIdentifier identifier) {
+  return WebBindings::getStringIdentifier(kPostMessage) == identifier;
+}
+
+// Converts the given PP_Var to an NPVariant, returning true on success.
+// False means that the given variant is invalid. In this case, the result
+// NPVariant will be set to a void one.
+//
+// The contents of the PP_Var will NOT be copied, so you need to ensure that
+// the PP_Var remains valid while the resultant NPVariant is in use.
+//
+// Note:  This is largely copied from var.cc so that we don't depend on code
+//        which will be removed.  TODO(dmichael) remove this comment when var
+//        is removed.
+bool PPVarToNPVariantNoCopy(PP_Var var, NPVariant* result) {
+  switch (var.type) {
+    case PP_VARTYPE_UNDEFINED:
+      VOID_TO_NPVARIANT(*result);
+      break;
+    case PP_VARTYPE_NULL:
+      NULL_TO_NPVARIANT(*result);
+      break;
+    case PP_VARTYPE_BOOL:
+      BOOLEAN_TO_NPVARIANT(var.value.as_bool, *result);
+      break;
+    case PP_VARTYPE_INT32:
+      INT32_TO_NPVARIANT(var.value.as_int, *result);
+      break;
+    case PP_VARTYPE_DOUBLE:
+      DOUBLE_TO_NPVARIANT(var.value.as_double, *result);
+      break;
+    case PP_VARTYPE_STRING: {
+      scoped_refptr<StringVar> string(StringVar::FromPPVar(var));
+      if (!string) {
+        VOID_TO_NPVARIANT(*result);
+        return false;
+      }
+      const std::string& value = string->value();
+      STRINGN_TO_NPVARIANT(value.c_str(), value.size(), *result);
+      break;
+    }
+    case PP_VARTYPE_OBJECT:
+      // Objects are not currently supported.
+      DCHECK(false);
+      VOID_TO_NPVARIANT(*result);
+      return false;
+    default:
+      VOID_TO_NPVARIANT(*result);
+      return false;
+  }
+  return true;
+}
+
+//------------------------------------------------------------------------------
+// Implementations of NPClass functions.  These are here to:
+// - Implement postMessage behavior.
+// - Forward calls to the 'passthrough' object to allow backwards-compatibility
+//   with GetInstanceObject() objects.
+//------------------------------------------------------------------------------
+NPObject* MessageChannelAllocate(NPP npp, NPClass* the_class) {
+  return new MessageChannel::MessageChannelNPObject;
+}
+
+void MessageChannelDeallocate(NPObject* object) {
+  MessageChannel::MessageChannelNPObject* instance =
+      static_cast<MessageChannel::MessageChannelNPObject*>(object);
+  delete instance;
+}
+
+bool MessageChannelHasMethod(NPObject* np_obj, NPIdentifier name) {
+  if (!np_obj)
+    return false;
+
+  // We only handle a function called postMessage.
+  if (IdentifierIsPostMessage(name))
+    return true;
+
+  // Other method names we will pass to the passthrough object, if we have one.
+  NPObject* passthrough = ToMessageChannel(np_obj).passthrough_object();
+  if (passthrough)
+    return WebBindings::hasMethod(NULL, passthrough, name);
+  return false;
+}
+
+bool MessageChannelInvoke(NPObject* np_obj, NPIdentifier name,
+                          const NPVariant* args, uint32 arg_count,
+                          NPVariant* result) {
+  if (!np_obj)
+    return false;
+
+  // We only handle a function called postMessage.
+  if (IdentifierIsPostMessage(name) && (arg_count == 1)) {
+    MessageChannel& message_channel(ToMessageChannel(np_obj));
+    PP_Var argument(Var::NPVariantToPPVar(message_channel.instance(),
+                                          &args[0]));
+    message_channel.PostMessageToNative(argument);
+    return true;
+  }
+  // Other method calls we will pass to the passthrough object, if we have one.
+  NPObject* passthrough = ToMessageChannel(np_obj).passthrough_object();
+  if (passthrough) {
+    return WebBindings::invoke(NULL, passthrough, name, args, arg_count,
+                               result);
+  }
+  return false;
+}
+
+bool MessageChannelInvokeDefault(NPObject* np_obj,
+                                 const NPVariant* args,
+                                 uint32 arg_count,
+                                 NPVariant* result) {
+  if (!np_obj)
+    return false;
+
+  // Invoke on the passthrough object, if we have one.
+  NPObject* passthrough = ToMessageChannel(np_obj).passthrough_object();
+  if (passthrough) {
+    return WebBindings::invokeDefault(NULL, passthrough, args, arg_count,
+                                      result);
+  }
+  return false;
+}
+
+bool MessageChannelHasProperty(NPObject* np_obj, NPIdentifier name) {
+  if (!np_obj)
+    return false;
+
+  // Invoke on the passthrough object, if we have one.
+  NPObject* passthrough = ToMessageChannel(np_obj).passthrough_object();
+  if (passthrough)
+    return WebBindings::hasProperty(NULL, passthrough, name);
+  return false;
+}
+
+bool MessageChannelGetProperty(NPObject* np_obj, NPIdentifier name,
+                               NPVariant* result) {
+  if (!np_obj)
+    return false;
+
+  // Don't allow getting the postMessage function.
+  if (IdentifierIsPostMessage(name))
+    return false;
+
+  // Invoke on the passthrough object, if we have one.
+  NPObject* passthrough = ToMessageChannel(np_obj).passthrough_object();
+  if (passthrough)
+    return WebBindings::getProperty(NULL, passthrough, name, result);
+  return false;
+}
+
+bool MessageChannelSetProperty(NPObject* np_obj, NPIdentifier name,
+                               const NPVariant* variant) {
+  if (!np_obj)
+    return false;
+
+  // Don't allow setting the postMessage function.
+  if (IdentifierIsPostMessage(name))
+    return false;
+
+  // Invoke on the passthrough object, if we have one.
+  NPObject* passthrough = ToMessageChannel(np_obj).passthrough_object();
+  if (passthrough)
+    return WebBindings::setProperty(NULL, passthrough, name, variant);
+  return false;
+}
+
+bool MessageChannelEnumerate(NPObject *np_obj, NPIdentifier **value,
+                             uint32_t *count) {
+  if (!np_obj)
+    return false;
+
+  // Invoke on the passthrough object, if we have one, to enumerate its
+  // properties.
+  NPObject* passthrough = ToMessageChannel(np_obj).passthrough_object();
+  if (passthrough) {
+    bool success = WebBindings::enumerate(NULL, passthrough, value, count);
+    if (success) {
+      // Add postMessage to the list and return it.
+      NPIdentifier* new_array = static_cast<NPIdentifier*>(
+          std::malloc(sizeof(NPIdentifier) * (*count + 1)));
+      std::memcpy(new_array, *value, sizeof(NPIdentifier)*(*count));
+      new_array[*count] = WebBindings::getStringIdentifier(kPostMessage);
+      std::free(*value);
+      *value = new_array;
+      ++(*count);
+      return true;
+    }
+  }
+
+  // Otherwise, build an array that includes only postMessage.
+  *value = static_cast<NPIdentifier*>(malloc(sizeof(NPIdentifier)));
+  (*value)[0] = WebBindings::getStringIdentifier(kPostMessage);
+  *count = 1;
+  return true;
+}
+
+NPClass message_channel_class = {
+  NP_CLASS_STRUCT_VERSION,
+  &MessageChannelAllocate,
+  &MessageChannelDeallocate,
+  NULL,
+  &MessageChannelHasMethod,
+  &MessageChannelInvoke,
+  &MessageChannelInvokeDefault,
+  &MessageChannelHasProperty,
+  &MessageChannelGetProperty,
+  &MessageChannelSetProperty,
+  NULL,
+  &MessageChannelEnumerate,
+};
+
+}  // namespace
+
+// MessageChannel --------------------------------------------------------------
+MessageChannel::MessageChannelNPObject::MessageChannelNPObject() {}
+
+MessageChannel::MessageChannelNPObject::~MessageChannelNPObject() {}
+
+MessageChannel::MessageChannel(PluginInstance* instance)
+    : instance_(instance),
+      passthrough_object_(NULL),
+      np_object_(NULL) {
+  VOID_TO_NPVARIANT(onmessage_invoker_);
+
+  // Now create an NPObject for receiving calls to postMessage.
+  NPObject* obj = WebBindings::createObject(NULL, &message_channel_class);
+  DCHECK(obj);
+  np_object_ = static_cast<MessageChannel::MessageChannelNPObject*>(obj);
+  np_object_->message_channel = this;
+}
+
+bool MessageChannel::EvaluateOnMessageInvoker() {
+  // If we've already evaluated the function, just return.
+  if (NPVARIANT_IS_OBJECT(onmessage_invoker_))
+    return true;
+
+  // This is the javascript code that we invoke.  It checks to see if onmessage
+  // exists, and if so, it invokes it.
+  const char invoke_onmessage_js[] =
+      "(function(module_instance, message_data) {"
+      "  if (module_instance &&"  // Only invoke if the instance is valid and
+      "      module_instance.onmessage &&"  // has a function named onmessage.
+      "      typeof(module_instance.onmessage) == 'function') {"
+      "    var message_event = document.createEvent('MessageEvent');"
+      "    message_event.initMessageEvent('message',"  // type
+      "                                   false,"  // canBubble
+      "                                   false,"  // cancelable
+      "                                   message_data,"  // data
+      "                                   '',"  // origin
+      "                                   '',"  // lastEventId
+      "                                   module_instance,"  // source
+      "                                   []);"  // ports
+      "    module_instance.onmessage(message_event);"
+      "  }"
+      "})";
+  NPString function_string = { invoke_onmessage_js,
+                               sizeof(invoke_onmessage_js)-1 };
+  // Get the current frame to pass to the evaluate function.
+  WebKit::WebFrame* frame =
+      instance_->container()->element().document().frame();
+  // Evaluate the function and obtain an NPVariant pointing to it.
+  if (!WebBindings::evaluate(NULL, frame->windowObject(), &function_string,
+                             &onmessage_invoker_)) {
+    // If it fails, do nothing.
+    return false;
+  }
+  DCHECK(NPVARIANT_IS_OBJECT(onmessage_invoker_));
+  return true;
+}
+
+void MessageChannel::PostMessageToJavaScript(PP_Var message_data) {
+  // Make sure we have our function for invoking a JavaScript onmessage
+  // function.
+  bool success = EvaluateOnMessageInvoker();
+  DCHECK(success);
+  if (!success)
+    return;
+
+  DCHECK(instance_);
+
+  NPVariant result_var;
+  VOID_TO_NPVARIANT(result_var);
+  NPVariant npvariant_args[2];
+  OBJECT_TO_NPVARIANT(instance_->container()->scriptableObjectForElement(),
+                      npvariant_args[0]);
+  // Convert message to an NPVariant without copying.  Note this means that
+  // in-process plugins will not copy the data, so isn't really following the
+  // postMessage spec in spirit.  Copying is handled in the proxy, and we don't
+  // want to re-copy unnecessarily.
+  //
+  // TODO(dmichael):  We need to do structured clone eventually to copy a object
+  // structure.  The details and PPAPI changes for this are TBD.
+  if (!PPVarToNPVariantNoCopy(message_data, &npvariant_args[1]))
+    return;
+
+  WebBindings::invokeDefault(NULL,
+                             NPVARIANT_TO_OBJECT(onmessage_invoker_),
+                             npvariant_args,
+                             sizeof(npvariant_args)/sizeof(*npvariant_args),
+                             &result_var);
+}
+
+void MessageChannel::PostMessageToNative(PP_Var message_data) {
+  instance_->HandleMessage(message_data);
+}
+
+MessageChannel::~MessageChannel() {
+  WebBindings::releaseVariantValue(&onmessage_invoker_);
+}
+
+}  // namespace ppapi
+}  // namespace webkit
+