Hi Zhenyu,
>
> My suggestion is to introduce a new version of current messaging interface
> instead of a whole new interface.
>
> struct XW_MessagingInterface_2 {
>
> void (*Register)(XW_Extension extension, XW_HandleMessageCallback
> handle_message);
> void (*PostMessage)(XW_Instance instance, const char* message);
>
> void (*RegisterBinaryMessageCallback)(XW_Extension extension,
> XW_HandleBinaryMessageCallback handle_message);
> void (*PostBinaryMessage)(XW_Instance instance, const char* message,
> const size_t size); };
>
Thanks for your suggestion.
XW_MessagingInterface_2 looks better than XW_BinaryMessagingInterface_1, as the
binary messaging API is an enhancement to the async messaging interface. And it
looks consistent to Java API proposal.
I will integrate this change into my design.
With this change, does it look good you?
Thanks,
-ningxin
> Thanks,
>
> Zhenyu
>
> On 7/16/15 15:25 , "Hu, Ningxin" <[email protected]> wrote:
>
> >Intent to Implement: Binary Messaging Interface for Crosswalk External
> >Extension
> >
> >Description:
> >Today's Crosswalk external extension API only provides text based
> >messaging interface. However, coming use cases require the external
> >extension native code to exchange binary data with JavaScript code. For
> >example, an external extension wants to transfer the images stream from
> >native to JavaScript in real-time (30FPS at least). With today's
> >external extension messaging API, the extension has to encode the
> >binary image data into text in native first, posts to JavaScript and
> >then decodes from the text to binary data in JavaScript. The encoding,
> >decoding (in
> >JavaScript!) and increased message size leads to low performance.
> >Experiment shows by using base64 to transfer VGA (640x480) images, this
> >approach can only deliver less 10 FPS on mainstream PC.
> >The binary messaging interface is proposed to added into Crosswalk
> >external extension API. It allows native code to exchange binary data
> >(a byte array) to JavaScript without unnecessary encoding/decoding.
> >JavaScript receives an ArrayBuffer object and can access the binary
> >data via different Typed Array View. Vice versa, JavaScript can send
> >the binary data in an ArrayBuffer object to native, native code
> >receives a byte array.
> >Prototype shows 3X-8X (binary messaging vs. text messaging) performance
> >speedup when transferring different size of data on both PC and mobile
> >device. Initial data shows with binary messaging interface, an external
> >extension is able to transfer VGA images at 60FPS on PC.
> >
> >Affected component: Crosswalk External Extension
> >
> >Related feature: https://crosswalk-project.org/jira/browse/XWALK-4615
> >
> >Target release: Crosswalk-17
> >
> >Implementation details:
> >1. Interface change:
> >For Crosswalk External Extension C API, a new interface
> >XW_BinaryMessagingInterface_1 will be added. To keep API and ABI
> >compatibility with existing external extension, a new file
> >(extensions/public/XW_Extension_BinaryMessage.h) will be added to
> >contain the XW_BinaryMessagingInterface_1 interface. The
> >XW_BinaryMessagingInterface_1 looks like:
> >
> >///////////////////////////////////////////////////////////////////////
> >///
> >/////////////////
> >#ifdef __cplusplus
> >extern "C" {
> >#endif
> >
> >#define XW_BINARY_MESSAGING_INTERFACE_1 "XW_BinaryMessagingInterface_1"
> >#define XW_BINARY_MESSAGING_INTERFACE XW_BINARY_MESSAGING_INTERFACE_1
> >
> >typedef void (*XW_HandleBinaryMessageCallback)(XW_Instance instance,
> >
> > const char* message,
> >
> > const size_t size);
> >
> >struct XW_BinaryMessagingInterface_1 {
> > void (*Register)(XW_Extension extension,
> > XW_HandleBinaryMessageCallback
> >handle_message);
> >
> > void (*PostMessage)(XW_Instance instance, const char* message, const
> >size_t size); };
> >
> >typedef struct XW_BinaryMessagingInterface_1
> >XW_BinaryMessagingInterface;
> >
> >#ifdef __cplusplus
> >} // extern "C"
> >#endif
> >///////////////////////////////////////////////////////////////////////
> >///
> >////////////////
> >
> >If the C extension wants to use binary messaging, it needs to query the
> >"XW_BinaryMessagingInterface_1" interface and use the PostMessage
> >method to post binary data to JavaScript. On other hand, it needs to
> >register a XW_HandleBinaryMessageCallback to receive binary data from
> JavaScript.
> >
> >For Crosswalk external extension Android Java API, two methods will be
> >added into XWalkExtensionClient interface:
> >
> >///////////////////////////////////////////////////////////////////////
> >///
> >///////////////
> >
> >public void onBinaryMessage(int extensionInstanceID, byte[] message);
> >
> >public final void postBinaryMessage(int instanceID, byte[] message);
> >
> >///////////////////////////////////////////////////////////////////////
> >///
> >//////////////
> >
> >Java extension which inherits XWalkExtensionClient can use
> >postBinaryMesssage to post binary data to JavaScript and implements
> >onBinaryMessage to receive binary data from JavaScript.
> >
> >No new APIs will be added into Crosswalk extension JavaScript API. When
> >native external extension posts binary message, the JavaScript message
> >listener receives an ArrayBuffer object.
> >When JavaScript invokes extension.postMessage with an ArrayBuffer
> >object as argument, the native binary message listener is invoked.
> >
> >This proposal doesn't cover binary messaging support in SyncMessage, as
> >there is no obvious use case.
> >
> >Sample code:
> >An external extension wants to transfer image data to JavaScript. To
> >transfer structured data, the extension can use simple custom binary
> >message format as this sample shows. Or it can leverage more
> >sophisticated binary format, e.g. Google's Protocol Buffer
> >(https://developers.google.com/protocol-buffers/).
> >C++:
> >///////////////////////////////////////////////////////////////////////
> >///
> >/////////////
> >// image binary format
> >// uint32_t width;
> >// uint32_t height;
> >// char data[width * height * 4];
> >
> >static const XW_BinaryMessagingInterface* g_binary_messaging =
> > get_interface(XW_BINARY_MESSAGING_INTERFACE);
> >.....
> >size_t buffer_size = sizeof(uint32_t) + sizeof(uint32_t) +
> >width*height*4*sizeof(char);
> >char* buffer = new char[buffer_size ];
> >uint32_t* uint32_array = reinterpret_cast<uint32_t*>(buffer);
> >uint32_array[0] = image.width();
> >uint32_array[1] = image.height();
> >char* data = buffer + 2 * sizeof(uint32_t); image.CopyImageData(data);
> >g_binary_messaging->postMessage(instance, buffer, buffer_size);
> >delete[] buffer;
> >///////////////////////////////////////////////////////////////////////
> >///
> >/////////////
> >
> >JavaScript:
> >///////////////////////////////////////////////////////////////////////
> >///
> >/////////////
> >extension.setMessageListener(function(msg) {
> > if (msg instaceof ArrayBuffer) {
> > var uint32_view = new Uint32Array(msg);
> > var width = uint32_view[0];
> > var height = uint32_view[1];
> > var data = new Uint8Array(msg, 8, width*height*4);
> > ....
> > }
> >}
> >///////////////////////////////////////////////////////////////////////
> >///
> >////////////
> >
> >Details:
> >It doesn't require to modify Crosswalk Core Extension code
> >(XWalkExtensionModule), as V8ValueConverter already supports to convert
> >a base::BinaryValue object to V8 ArrayBuffer object and vice versa.
> >
> >It mainly requires to modify the external extension components, to
> >expose the binary interface and convert the binary data to
> >base::BinaryValue and vice versa.
> >
> >For C external extension, files to be modified:
> >extensions/common/xwalk_external_adapter.cc
> >extensions/common/xwalk_external_adapter.h
> >extensions/common/xwalk_external_extension.cc
> >extensions/common/xwalk_external_extension.h
> >extensions/common/xwalk_external_instance.cc
> >extensions/common/xwalk_external_instance.h
> >extensions/extensions.gyp
> >
> >new file:
> >extensions/public/XW_Extension_BinaryMessage.h
> >
> >For Java external extension, files to be modified:
> >app/android/runtime_client/src/org/xwalk/app/runtime/extension/XWalkCor
> >eEx
> >tensionBridge.java
> >app/android/runtime_client/src/org/xwalk/app/runtime/extension/XWalkExt
> >ens
> >ionClient.java
> >app/android/runtime_client/src/org/xwalk/app/runtime/extension/XWalkExt
> >ens
> >ionContextClient.java
> >app/android/runtime_client/src/org/xwalk/app/runtime/extension/XWalkRun
> >tim
> >eExtensionBridge.java
> >app/android/runtime_client/src/org/xwalk/app/runtime/extension/XWalkRun
> >tim
> >eExtensionManager.java
> >extensions/android/java/src/org/xwalk/core/internal/extensions/XWalkExt
> >ens
> >ionAndroid.java
> >extensions/common/android/xwalk_extension_android.cc
> >extensions/common/android/xwalk_extension_android.h
> >runtime/android/core_internal/src/org/xwalk/core/internal/XWalkExtensio
> >nIn
> >ternal.java
> >
> >
> >Thanks,
> >-ningxin
> >
> >_______________________________________________
> >Crosswalk-dev mailing list
> >[email protected]
> >https://lists.crosswalk-project.org/mailman/listinfo/crosswalk-dev
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