qtbase/examples/corelib/serialization/convert/cborconverter.cpp

// Copyright (C) 2018 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

#include "cborconverter.h"
#include "variantorderedmap.h"

#include <QCborArray>
#include <QCborMap>
#include <QCborStreamReader>
#include <QCborStreamWriter>
#include <QCborValue>
#include <QDataStream>
#include <QDebug>
#include <QFile>
#include <QFloat16>
#include <QMetaType>
#include <QTextStream>

#include <stdio.h>

using namespace Qt::StringLiterals;

static CborConverter cborConverter;
static CborDiagnosticDumper cborDiagnosticDumper;

static const char cborOptionHelp[] =
        "convert-float-to-int=yes|no    Write integers instead of floating point, if no\n"
        "                               loss of precision occurs on conversion.\n"
        "float16=yes|always|no          Write using half-precision floating point.\n"
        "                               If 'always', won't check for loss of precision.\n"
        "float32=yes|always|no          Write using single-precision floating point.\n"
        "                               If 'always', won't check for loss of precision.\n"
        "signature=yes|no               Prepend the CBOR signature to the file output.\n"
        ;

static const char diagnosticHelp[] =
        "extended=no|yes                Use extended CBOR diagnostic format.\n"
        "line-wrap=yes|no               Split output into multiple lines.\n"
        ;

QT_BEGIN_NAMESPACE

QDataStream &operator<<(QDataStream &ds, QCborTag tag)
{
    return ds << quint64(tag);
}

QDataStream &operator>>(QDataStream &ds, QCborTag &tag)
{
    quint64 v;
    ds >> v;
    tag = QCborTag(v);
    return ds;
}

QT_END_NAMESPACE

// We can't use QCborValue::toVariant directly because that would destroy
// non-string keys in CBOR maps (QVariantMap can't handle those). Instead, we
// have our own set of converter functions so we can keep the keys properly.

//! [0]
static QVariant convertCborValue(const QCborValue &value);

static QVariant convertCborMap(const QCborMap &map)
{
    VariantOrderedMap result;
    result.reserve(map.size());
    for (auto pair : map)
        result.append({ convertCborValue(pair.first), convertCborValue(pair.second) });
    return QVariant::fromValue(result);
}

static QVariant convertCborArray(const QCborArray &array)
{
    QVariantList result;
    result.reserve(array.size());
    for (auto value : array)
        result.append(convertCborValue(value));
    return result;
}

static QVariant convertCborValue(const QCborValue &value)
{
    if (value.isArray())
        return convertCborArray(value.toArray());
    if (value.isMap())
        return convertCborMap(value.toMap());
    return value.toVariant();
}
//! [0]

//! [1]
enum TrimFloatingPoint { Double, Float, Float16 };
static QCborValue convertFromVariant(const QVariant &v, TrimFloatingPoint fpTrimming)
{
    if (v.userType() == QMetaType::QVariantList) {
        const QVariantList list = v.toList();
        QCborArray array;
        for (const QVariant &v : list)
            array.append(convertFromVariant(v, fpTrimming));

        return array;
    }

    if (v.userType() == qMetaTypeId<VariantOrderedMap>()) {
        const auto m = qvariant_cast<VariantOrderedMap>(v);
        QCborMap map;
        for (const auto &pair : m)
            map.insert(convertFromVariant(pair.first, fpTrimming),
                       convertFromVariant(pair.second, fpTrimming));
        return map;
    }

    if (v.userType() == QMetaType::Double && fpTrimming != Double) {
        float f = float(v.toDouble());
        if (fpTrimming == Float16)
            return float(qfloat16(f));
        return f;
    }

    return QCborValue::fromVariant(v);
}
//! [1]

QString CborDiagnosticDumper::name() const
{
    return "cbor-dump"_L1;
}

Converter::Directions CborDiagnosticDumper::directions() const
{
    return Direction::Out;
}

Converter::Options CborDiagnosticDumper::outputOptions() const
{
    return SupportsArbitraryMapKeys;
}

const char *CborDiagnosticDumper::optionsHelp() const
{
    return diagnosticHelp;
}

void CborDiagnosticDumper::saveFile(QIODevice *f, const QVariant &contents,
                                    const QStringList &options) const
{
    QCborValue::DiagnosticNotationOptions opts = QCborValue::LineWrapped;
    for (const QString &s : options) {
        QStringList pair = s.split('=');
        if (pair.size() == 2) {
            if (pair.first() == "line-wrap") {
                opts &= ~QCborValue::LineWrapped;
                if (pair.last() == "yes") {
                    opts |= QCborValue::LineWrapped;
                    continue;
                } else if (pair.last() == "no") {
                    continue;
                }
            }
            if (pair.first() == "extended") {
                opts &= ~QCborValue::ExtendedFormat;
                if (pair.last() == "yes")
                    opts |= QCborValue::ExtendedFormat;
                continue;
            }
        }

        qFatal("Unknown CBOR diagnostic option '%s'. Available options are:\n%s",
               qPrintable(s), diagnosticHelp);
    }

    QTextStream out(f);
    out << convertFromVariant(contents, Double).toDiagnosticNotation(opts) << Qt::endl;
}

CborConverter::CborConverter()
{
    qRegisterMetaType<QCborTag>();
}

QString CborConverter::name() const
{
    return "cbor";
}

Converter::Directions CborConverter::directions() const
{
    return Direction::InOut;
}

Converter::Options CborConverter::outputOptions() const
{
    return SupportsArbitraryMapKeys;
}

const char *CborConverter::optionsHelp() const
{
    return cborOptionHelp;
}

bool CborConverter::probeFile(QIODevice *f) const
{
    if (QFile *file = qobject_cast<QFile *>(f)) {
        if (file->fileName().endsWith(".cbor"_L1))
            return true;
    }
    return f->isReadable() && f->peek(3) == QByteArray("\xd9\xd9\xf7", 3);
}

QVariant CborConverter::loadFile(QIODevice *f, const Converter *&outputConverter) const
{
    const char *ptr = nullptr;
    if (auto file = qobject_cast<QFile *>(f))
        ptr = reinterpret_cast<char *>(file->map(0, file->size()));

    QByteArray mapped = QByteArray::fromRawData(ptr, ptr ? f->size() : 0);
    QCborStreamReader reader(mapped);
    if (!ptr)
        reader.setDevice(f);

    if (reader.isTag() && reader.toTag() == QCborKnownTags::Signature)
        reader.next();

    QCborValue contents = QCborValue::fromCbor(reader);
    qint64 offset = reader.currentOffset();
    if (reader.lastError()) {
        qFatal().nospace()
            << "Error loading CBOR contents (byte " << offset
            << "): " << reader.lastError().toString()
            << "\n bytes: " << (ptr ? mapped.mid(offset, 9) : f->read(9));
    } else if (offset < mapped.size() || (!ptr && f->bytesAvailable())) {
        qWarning("Warning: bytes remaining at the end of the CBOR stream");
    }

    if (outputConverter == nullptr)
        outputConverter = &cborDiagnosticDumper;
    else if (isNull(outputConverter))
        return QVariant();
    else if (!outputConverter->outputOptions().testFlag(SupportsArbitraryMapKeys))
        return contents.toVariant();
    return convertCborValue(contents);
}

void CborConverter::saveFile(QIODevice *f, const QVariant &contents, const QStringList &options) const
{
    bool useSignature = true;
    bool useIntegers = true;
    enum { Yes, No, Always } useFloat16 = Yes, useFloat = Yes;

    for (const QString &s : options) {
        QStringList pair = s.split('=');
        if (pair.size() == 2) {
            if (pair.first() == "convert-float-to-int") {
                if (pair.last() == "yes") {
                    useIntegers = true;
                    continue;
                } else if (pair.last() == "no") {
                    useIntegers = false;
                    continue;
                }
            }

            if (pair.first() == "float16") {
                if (pair.last() == "no") {
                    useFloat16 = No;
                    continue;
                } else if (pair.last() == "yes") {
                    useFloat16 = Yes;
                    continue;
                } else if (pair.last() == "always") {
                    useFloat16 = Always;
                    continue;
                }
            }

            if (pair.first() == "float32") {
                if (pair.last() == "no") {
                    useFloat = No;
                    continue;
                } else if (pair.last() == "yes") {
                    useFloat = Yes;
                    continue;
                } else if (pair.last() == "always") {
                    useFloat = Always;
                    continue;
                }
            }

            if (pair.first() == "signature") {
                if (pair.last() == "yes") {
                    useSignature = true;
                    continue;
                } else if (pair.last() == "no") {
                    useSignature = false;
                    continue;
                }
            }
        }

        qFatal("Unknown CBOR format option '%s'. Valid options are:\n%s",
               qPrintable(s), cborOptionHelp);
    }

    QCborValue v =
        convertFromVariant(contents,
                           useFloat16 == Always ? Float16 : useFloat == Always ? Float : Double);
    QCborStreamWriter writer(f);
    if (useSignature)
        writer.append(QCborKnownTags::Signature);

    QCborValue::EncodingOptions opts;
    if (useIntegers)
        opts |= QCborValue::UseIntegers;
    if (useFloat != No)
        opts |= QCborValue::UseFloat;
    if (useFloat16 != No)
        opts |= QCborValue::UseFloat16;
    v.toCbor(writer, opts);
}