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    1.1.0 • Public • Published


    Build Status License: MIT

    Javascript QDatastream (de)serializer.

    List of types handled for (de)serialization: QBool, QShort, QInt, QInt64, QUInt, QUInt64, QDouble, QMap, QList, QString, QVariant, QStringList, QByteArray, QUserType, QDateTime, QTime, QChar, QInvalid

    Getting Started

    Install the module with npm install node-qtdatastream --production, or npm install node-qtdatastream for development purpose.


    Technical documentation

    Type inference

    Javascript types can be automatically converted to Qt Types, and here is the default behavior

    javascript to QClass

    javascript QClass
    string QString
    number QUInt (this can be overloaded)
    boolean QBool
    Array QList<QVariant<?>>
    Date QDateTime
    Map QMap<QString, QVariant<?>>
    Object QMap<QString, QVariant<?>>

    You can always force any type to be coerced to any Qt type

    const { QByteArray } = require('qtdatastream').types;
    const s = "hello"; // If given to the writer, it will be coerced to QString
    const qbytearray = QByteArray.from(s); // This will write the same string but as a QByteArray

    NB: you can change default behavior for number

    const { QVariant, Types } = require('qtdatastream').types;
    const n = 1; // Would be written as QUInt
    QVariant.coerceNumbersTo(Types.DOUBLE); // Will now write any number as QDouble

    QClass to javascript

    Qt Types are also converted to native javascript type automatically upon reading

    QClass javascript
    QString string
    QUInt number
    QInt number
    QUInt64 number
    QInt64 number
    QDouble number
    QShort number
    QBool number
    QList Array
    QStringList Array<string>
    QByteArray Buffer
    QMap Object
    QUserType Object
    QDateTime Date
    QTime number
    QChar string
    QInvalid undefined

    QUserType special treatment

    QUserType are special types defined by user (QVariant::UserType).

    QUserType are defined like this <size:uint32><bytearray of size>. bytearray can be casted to string (but it is not a string as intended by Qt, because it is UTF8 and not UTF16) : bytearray.toString(). The resulting string is the QUserType key.


    The Reader use an internal mechanism to know which parser must be used for each QUserType. They are defined like this:

    const { QUserType } = require('qtdatastream').types;
    QUserType.register("NetworkId", qtdatastream.Types.INT); //NetworkId here is our key

    This tell the reader to decode NetworkId bytearray like and INT. But those structures can be much more complicated:

    const { QUserType } = require('qtdatastream').types;
    QUserType.register("BufferInfo", [
        {id: qtdatastream.Types.INT},
        {network: qtdatastream.Types.INT},
        {type: qtdatastream.Types.SHORT},
        {group: qtdatastream.Types.INT},
        {name: qtdatastream.Types.BYTEARRAY}

    The bytearray corresponding to this structure look like this :


    The whole new type will be put in a new Object, the id key will contain the first <int32>, the network key will contain the second <int32>, etc. The definition is contained into an array to force a parsing order (here, id will always be the first <int32> block).

    UserTypes can also be nested, by specifying the usertype name instead of Qt type :

    QUserType.register("BufferInfoContainer", [
        {id: qtdatastream.Types.INT},
        {bufferInfo: "BufferInfo"} // here we reference the BufferInfo QUserType

    Keep in mind that if a usertype X references usertype Y, Y should be declared before X.


    Custom usertypes can be defined as for Reader, with the help of QUserType.register method.

    Writing UserType is done as follow:

    const { Socket } = require('qtdatastream').socket;
    const { QUserType } = require('qtdatastream').types;
    const qtsocket = new Socket(myRealSocket);
    const data = {
        "BufferInfo": new QUserType("BufferInfo", {
            id: 2,
            network: 4,
            type: 5,
            group: 1,
            name: "BufferInfo name"

    Some more examples can be found in test folder.


    ES7 decorators can be used to simplify serializable data representation

    const { types: { QUserType, QString, QUInt, Types }, serialization: { Serializable, serialize } } = require('qtdatastream');
    // Register usertype
    QUserType.register('Network::Server', Types.MAP);
    export class Server {
        @serialize(QString, {in: 'HostIn', out: 'HostOut'))
        @serialize(QUInt, 'Port')
        port = 6667;
        sslVersion = 0;
        constructor(args) {
            this.blob = true; // will not be serialized at export
            Object.assign(this, args);
    const parsedUserType = {
        HostIn: 'myHost',
        Port: 1234
    }; // This usually comes from qtsocket
    const server = new Server(parsedUserType);
    // server == {
    //     host: 'myHost',
    //     port: 1234,
    //     sslVersion: 0
    // }
    // This will call server.export() method before sending to the server,
    // which exports the object as dictated by Server class and 'Network::Server' usertype

    Serializable parameter (usertype) is optionnal. If unspecified, it will be exported as a QMap.

    If Serializable class implements _export method, the return of this function will be used instead of object own attributes.

    export class Server {
      _export() {
        return {
          'a': 'b'


    const { Socket } = require('qtdatastream').socket;
    const { QUserType } = require('qtdatastream').types;
    const net = require('net');
    var client = net.Socket();
    // Connect to a Qt socket
    // and write something into the socket
    client.connect(65000, "domain.tld", function(){
        const qtsocket = new Socket(client);
        // Here data is the already parsed response
        qtsocket.on('data', function(data) {
        // Write something to the socket
            "AString": "BString",
            "CString": 42


    Debug mode can be activated by setting environment variable DEBUG in your shell before launching your program:

    export DEBUG="qtdatastream:*"


    Copyright (c) 2019 Joël Charles Licensed under the MIT license.


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