Add byte array API for extractor scripts

This enables converting QByteArrays to JS ArrayBuffers, and thus allows
custom binary barcode decoding also in extractor scripts.

The existing API related to byte arrays can be migrated from the barcode
API to the more appropriate place here, and more of that can be adapted
to use JS ArrayBuffers rather than opaque QByteArray variants.

First user is the MÁV barcode decoder.

src/lib/CMakeLists.txt

@@ -49,6 +49,7 @@ target_sources(KPimItinerary PRIVATE
 
     jsapi/barcode.cpp
     jsapi/bitarray.cpp
+    jsapi/bytearray.cpp
     jsapi/jsonld.cpp
 
     knowledgedb/alphaid.cpp
@@ -142,6 +143,7 @@ target_link_libraries(KPimItinerary
         KF5::Mime
     PRIVATE
         Qt::Qml
+        Qt::QmlPrivate
         KF5::Archive
         KF5::I18n
         KF5::Contacts

src/lib/engine/extractorscriptengine.cpp

@@ -12,6 +12,7 @@
 #include "logging.h"
 
 #include "jsapi/barcode.h"
+#include "jsapi/bytearray.h"
 #include "jsapi/jsonld.h"
 
 #include <QFile>
@@ -60,6 +61,7 @@ void ExtractorScriptEngine::ensureInitialized()
     d->m_engine.globalObject().setProperty(QStringLiteral("JsonLd"), d->m_engine.newQObject(d->m_jsonLdApi));
     d->m_barcodeApi = new JsApi::Barcode;
     d->m_engine.globalObject().setProperty(QStringLiteral("Barcode"), d->m_engine.newQObject(d->m_barcodeApi));
+    d->m_engine.globalObject().setProperty(QStringLiteral("ByteArray"), d->m_engine.newQObject(new JsApi::ByteArray));
 
     d->m_watchdogThread.start();
     d->m_watchdogTimer = new QTimer;

src/lib/jsapi/bytearray.cpp

+/*
+    SPDX-FileCopyrightText: 2021 Volker Krause <vkrause@kde.org>
+
+    SPDX-License-Identifier: LGPL-2.0-or-later
+*/
+
+#include "bytearray.h"
+#include "logging.h"
+
+#include <QQmlEngine>
+
+#include <private/qv4arraybuffer_p.h>
+#include <private/qv4engine_p.h>
+
+#include <zlib.h>
+
+using namespace KItinerary;
+
+QJSValue JsApi::ByteArray::inflate(const QByteArray &input) const
+{
+    QByteArray output;
+    output.resize(4096);
+    z_stream stream;
+    stream.zalloc = nullptr;
+    stream.zfree = nullptr;
+    stream.opaque = nullptr;
+    stream.avail_in = input.size();
+    stream.next_in = reinterpret_cast<unsigned char*>(const_cast<char*>(input.data()));
+    stream.avail_out = output.size();
+    stream.next_out = reinterpret_cast<unsigned char*>(output.data());
+
+    inflateInit2(&stream, MAX_WBITS + 32);
+    const auto res = ::inflate(&stream, Z_NO_FLUSH);
+    switch (res) {
+        case Z_OK:
+        case Z_STREAM_END:
+            break; // all good
+        default:
+            qCWarning(Log) << "zlib decompression failed " << stream.msg << stream.avail_in;
+            return {};
+    }
+    inflateEnd(&stream);
+    output.truncate(output.size() - stream.avail_out);
+    return toArrayBuffer(output);
+}
+
+QString JsApi::ByteArray::decodeUtf8(const QByteArray &input) const
+{
+    return QString::fromUtf8(input);
+}
+
+QJSValue JsApi::ByteArray::toArrayBuffer(const QByteArray &input) const
+{
+    const auto engine = qjsEngine(this);
+    return QJSValue(engine->handle(), engine->handle()->newArrayBuffer(input)->asReturnedValue());
+}

src/lib/jsapi/bytearray.h

+/*
+    SPDX-FileCopyrightText: 2021 Volker Krause <vkrause@kde.org>
+
+    SPDX-License-Identifier: LGPL-2.0-or-later
+*/
+
+#ifndef KITINERARY_JSAPI_BYTEARRAY_H
+#define KITINERARY_JSAPI_BYTEARRAY_H
+
+#include <QObject>
+#include <QJSValue>
+
+class QByteArray;
+
+namespace KItinerary {
+namespace JsApi {
+
+/** API for dealing with QByteArray and/or JS ArrayBuffer objects. */
+class ByteArray : public QObject
+{
+    Q_OBJECT
+public:
+    /** Perform zlib decompression on the given byte array.
+     *  @returns a JS ArrayBuffer with the decompressed result.
+     */
+    Q_INVOKABLE QJSValue inflate(const QByteArray &input) const;
+
+    /** Convert a QByteArray/ArrayBuffer to a string, assuming UTF-8 encoding. */
+    Q_INVOKABLE QString decodeUtf8(const QByteArray &input) const;
+
+    /** Convert a QByteArray to a JS ArrayBuffer.
+     *  This is mainly a migration aid until we return ArrayBuffers everywhere.
+     */
+    Q_INVOKABLE QJSValue toArrayBuffer(const QByteArray &input) const;
+};
+
+}}
+
+#endif // KITINERARY_JSAPI_BYTEARRAY_H

src/lib/scripts/mav.js

@@ -21,6 +21,19 @@ function parseTicket(pdf, node, triggerNode) {
         res.reservationFor.trainNumber = trip[6];
         res.reservedTicket.ticketedSeat.seatingType = trip[7];
         res.reservedTicket.ticketToken = "pdf417bin:" + Barcode.toBase64(triggerNode.content);
+
+        // see https://community.kde.org/KDE_PIM/KItinerary/MAV_Barcode
+        const outer = ByteArray.toArrayBuffer(triggerNode.content);
+        const inner = ByteArray.inflate(outer.slice(2));
+        if (inner.byteLength >=  217) {
+            const view = new DataView(inner);
+            res.reservationFor.departureStation.identifier = "uic:" + (view.getUint32(106, false) & 0xffffff);
+            res.reservationFor.arrivalStation.identifier = "uic:" + (view.getUint32(109, false) & 0xffffff);
+            res.reservationFor.provider.identifier = "uic:" + view.getUint16(18, false);
+            res.reservationNumber = ByteArray.decodeUtf8(inner.slice(0, 17));
+            res.underName.name = ByteArray.decodeUtf8(inner.slice(39, 39 + 45));
+        }
+
         reservations.push(res);
     }
     return reservations;