Protobuf：将 protobuf 消息从 Javascript 传递到 C++ WebAssembly 模块

Question

我想将 Javascript 的 protobuf 消息传递给 C++ WebAssembly 模块。

我确实收到并可以在 C++ 端成功解析更简单的 protobuf 消息，但是，protobuf 无法解析不太简单的 protobuf 消息。

这是我正在使用的代码：

goog.module('protobufMessageGenerator');
goog.require('proto.my_proto.MyMessage');

function generateMyMessage() {
    var msg = new proto.my_proto.MyMessage()
    var internal = new proto.my_proto.MyMessageInternal()
    internal.setAccentColor("#CC1D24")
    internal.setLogo("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")
    msg.setInternal(internal)
    return msg
}

使用 google-closure-compiler，我将此 protobuf 消息生成器编译为纯 Javascript。我使用此代码将消息传递给 C++ WebAssembly 模块：

function sendMessage() {
    Module.self().setMyMessage(module$contents$protobufMessageGenerator_generateMyMessage().serializeBinary())
}
sendMessage()

我使用以下代码在 C++ 端收到消息：

void JavascriptPublicInterface::setMyMessage(const QString &myMessage)
{
    if (_myMessage != myMessage)
    {
        _myMessage = myMessage;
        emit myMessageChanged();
    }
}

void JavascriptPublicInterface::setMyMessageEMS(const std::string &myMessage)
{
    setMyMessage(QString::fromStdString(myMessage));
}

//...

void startListeningToMyMessage(std::function<void(euf_proto::MyMessage myMessage)> listener)
{
    const auto changedListener = [listener]() {
        const auto newMyMessageString = JavascriptPublicInterface::self()->myMessage();
        my_proto::MyMessage myMessagePb;
        if (myMessagePb.ParseFromString(newMyMessageString.toStdString()))
        {
            qDebug() << "C++ : Successfully parsed new MyMessage: " << newMyMessageString;
        }
        else
        {
            qDebug() << "C++ : Failed to parse new MyMessage: " << newMyMessageString;
        }

        qDebug() << "MyMessage received: " << QString::fromStdString(myMessagePb.DebugString());

        listener(myMessagePb);
    };
    if (!QObject::connect(JavascriptPublicInterface::self(), &JavascriptPublicInterface::myMessageChanged, changedListener))
    {
        throw std::runtime_error("Failed to connect to JavascriptPublicInterface myMessageChanged");
    }
}

在 Javascript 控制台中，我看到：“C++：无法解析新的 MyMessage：...”

我猜这可能与Javascript使用UTF-16和C++使用UTF-8编码有关（因为UTF-8的消息只能被成功解析），所以我尝试这样修复发送和接收：

//For more info see : https://emscripten.org/docs/api_reference/emscripten.h.html?highlight=stringtoutf8
function convertUtf16ToUtf8(input) {
    var uint8Arr = input
    var jsString = String.fromCharCode.apply(null, uint8Arr)
    var lengthBytes = lengthBytesUTF8(jsString)+1
    var stringOnWasmHeap = _malloc(lengthBytes)
    stringToUTF8(jsString, stringOnWasmHeap, lengthBytes)
    return stringOnWasmHeap
}

function sendMessage() {
var myMessage = convertUtf16ToUtf8(module$contents$protobufMessageGenerator_generateMyMessage().serializeBinary())
    Module.self().setMyMessage(myMessage)
    _free(myMessage)
}
sendMessage()

我像这样修改了 C++ 端的解析：

void JavascriptPublicInterface::setMyMessageEMS(const int pointer)
{
    const char* msg = (char*)pointer;
    setMyMessage(QString::fromStdString(msg));
}

但我仍然收到此错误：“C++：无法解析新的 MyMessage：...”

我该如何解决这个问题？

（我使用的是 protobuf 3.19.1（Javascript 和 C++ 端的版本相同）。）

更新：如果我修改我的代码，它传递一个简单的字符串作为标志，那么我可以成功地解析 C++ 端的 protobuf 消息：

internal.setLogo("logo")

所以我想问题出在这个领域。 原始字符串是一个 base64 编码的图像。 我应该如何处理这个字符串来修复解析？

Answer 1

我找到了解决方案。

这个 stackoverflow 帖子描述了一个非常相似的问题，它也帮助我修复了我的解析： Protobuf: Serialize/DeSerialize C++ to Js

这是我更新的代码，效果很好：我必须更新 Javascript 端：

function sendMessage() {
    Module.self().setMyMessage(module$contents$protobufMessageGenerator_generateMyMessage().serializeBinary().toString())
}
sendMessage()

和 C++ 端：

namespace
{
QByteArray decryptProtobufMessage(const std::string &str)
{
    QStringList strList = QString::fromStdString(str).split(',');
    QByteArray bytedata;
    foreach (const QString &str, strList)
    {
        bytedata += (str.toUInt());
    }
    return bytedata;
}
} // namespace

void JavascriptPublicInterface::setMyMessage(const QByteArray &myMessage)
{
    if (_myMessage != myMessage)
    {
        _myMessage = myMessage;
        emit myMessageChanged();
    }
}

void JavascriptPublicInterface::setMyMessageEMS(const std::string &myMessage)
{
    setMyMessage(decryptProtobufMessage(myMessage));
}

//...

void startListeningToMyMessage(std::function<void(euf_proto::MyMessage myMessage)> listener)
{
    const auto changedListener = [listener]() {
        const auto newMyMessageByteArray = JavascriptPublicInterface::self()->myMessage();
        my_proto::MyMessage myMessagePb;
        if (myMessagePb.ParseFromArray(newMyMessageByteArray.data(), newMyMessageByteArray.size()))
        {
            qDebug() << "C++ : Successfully parsed new MyMessage: " << newMyMessageByteArray;
        }
        else
        {
            qDebug() << "C++ : Failed to parse new MyMessage: " << newMyMessageByteArray;
        }

        qDebug() << "MyMessage received: " << QString::fromStdString(myMessagePb.DebugString());

        listener(myMessagePb);
    };
    if (!QObject::connect(JavascriptPublicInterface::self(), &JavascriptPublicInterface::myMessageChanged, changedListener))
    {
        throw std::runtime_error("Failed to connect to JavascriptPublicInterface myMessageChanged");
    }
}