exiv2/src/xmpsidecar.cpp

// SPDX-License-Identifier: GPL-2.0-or-later
#include "xmpsidecar.hpp"

#include "basicio.hpp"
#include "config.h"
#include "convert.hpp"
#include "error.hpp"
#include "futils.hpp"
#include "image.hpp"
#include "xmp_exiv2.hpp"

#include <iostream>

namespace {
    constexpr auto xmlHeader = "<?xpacket begin=\"\xef\xbb\xbf\" id=\"W5M0MpCehiHzreSzNTczkc9d\"?>\n";
    const auto xmlHdrCnt = static_cast<long>(std::strlen(xmlHeader));  // without the trailing 0-character
    constexpr auto xmlFooter = "<?xpacket end=\"w\"?>";
}  // namespace

// class member definitions
namespace Exiv2 {


    XmpSidecar::XmpSidecar(BasicIo::UniquePtr io, bool create)
        : Image(ImageType::xmp, mdXmp, std::move(io))
    {
        if (create) {
            if (io_->open() == 0) {
                IoCloser closer(*io_);
                io_->write(reinterpret_cast<const byte*>(xmlHeader), xmlHdrCnt);
            }
        }
    } // XmpSidecar::XmpSidecar

    std::string XmpSidecar::mimeType() const
    {
        return "application/rdf+xml";
    }

    void XmpSidecar::setComment(std::string_view /*comment*/)
    {
        // not supported
        throw(Error(ErrorCode::kerInvalidSettingForImage, "Image comment", "XMP"));
    }

    void XmpSidecar::readMetadata()
    {
#ifdef EXIV2_DEBUG_MESSAGES
        std::cerr << "Reading XMP file " << io_->path() << "\n";
#endif
        if (io_->open() != 0) {
            throw Error(ErrorCode::kerDataSourceOpenFailed, io_->path(), strError());
        }
        IoCloser closer(*io_);
        // Ensure that this is the correct image type
        if (!isXmpType(*io_, false)) {
            if (io_->error() || io_->eof())
                throw Error(ErrorCode::kerFailedToReadImageData);
            throw Error(ErrorCode::kerNotAnImage, "XMP");
        }
        // Read the XMP packet from the IO stream
        std::string xmpPacket;
        const long len = 64 * 1024;
        byte buf[len];
        size_t l;
        while ((l = io_->read(buf, len)) > 0) {
            xmpPacket.append(reinterpret_cast<char*>(buf), l);
        }
        if (io_->error())
            throw Error(ErrorCode::kerFailedToReadImageData);
        clearMetadata();
        xmpPacket_ = xmpPacket;
        if (!xmpPacket_.empty() && XmpParser::decode(xmpData_, xmpPacket_)) {
#ifndef SUPPRESS_WARNINGS
            EXV_WARNING << "Failed to decode XMP metadata.\n";
#endif
        }

        // #1112 - store dates to deal with loss of TZ information during conversions
        for (auto&& it : xmpData_) {
            std::string key(it.key());
            if ( key.find("Date") != std::string::npos ) {
                std::string value(it.value().toString());
                dates_[key] = value;
            }
        }

        copyXmpToIptc(xmpData_, iptcData_);
        copyXmpToExif(xmpData_, exifData_);
    } // XmpSidecar::readMetadata

    // lower case string
    /// \todo very similar function in pngimage (upper). We should move those things to a string utilities file
    static std::string toLowerCase(const std::string& a)
    {
        std::string b = a;
        std::transform(a.begin(), a.end(), b.begin(), ::tolower);
        return b;
    }

    static bool matchi(const std::string& key, const char* substr)
    {
        return toLowerCase(key).find(substr) != std::string::npos;
    }

    void XmpSidecar::writeMetadata()
    {
        if (io_->open() != 0) {
            throw Error(ErrorCode::kerDataSourceOpenFailed, io_->path(), strError());
        }
        IoCloser closer(*io_);

        if (!writeXmpFromPacket()) {
            // #589 copy XMP tags
            Exiv2::XmpData  copy   ;
            for (auto&& it : xmpData_) {
                if (!matchi(it.key(), "exif") && !matchi(it.key(), "iptc")) {
                    copy[it.key()] = it.value();
                }
            }

            // run the convertors
            copyExifToXmp(exifData_, xmpData_);
            copyIptcToXmp(iptcData_, xmpData_);

            // #1112 - restore dates if they lost their TZ info
            for (auto&& date : dates_) {
                std::string sKey = date.first;
                Exiv2::XmpKey key(sKey);
                if ( xmpData_.findKey(key) != xmpData_.end() ) {
                    std::string value_orig(date.second);
                    std::string value_now(xmpData_[sKey].value().toString());
                    // std::cout << key << " -> " << value_now << " => " << value_orig << std::endl;
                    if ( value_orig.find(value_now.substr(0,10)) != std::string::npos ) {
                        xmpData_[sKey] = value_orig ;
                    }
                }
            }

            // #589 - restore tags which were modified by the convertors
            for (auto&& it : copy) {
                xmpData_[it.key()] = it.value();
            }

            if (XmpParser::encode(xmpPacket_, xmpData_,
                                  XmpParser::omitPacketWrapper|XmpParser::useCompactFormat) > 1) {
#ifndef SUPPRESS_WARNINGS
                EXV_ERROR << "Failed to encode XMP metadata.\n";
#endif
            }
        }
        if (!xmpPacket_.empty()) {
            if (xmpPacket_.substr(0, 5)  != "<?xml") {
                xmpPacket_ = xmlHeader + xmpPacket_ + xmlFooter;
            }
            auto tempIo = std::make_unique<MemIo>();

            // Write XMP packet
            if (tempIo->write(reinterpret_cast<const byte*>(xmpPacket_.data()), xmpPacket_.size()) != xmpPacket_.size())
                throw Error(ErrorCode::kerImageWriteFailed);
            if (tempIo->error()) throw Error(ErrorCode::kerImageWriteFailed);
            io_->close();
            io_->transfer(*tempIo); // may throw
        }
    } // XmpSidecar::writeMetadata

    // *************************************************************************
    // free functions
    Image::UniquePtr newXmpInstance(BasicIo::UniquePtr io, bool create)
    {
        auto image = std::make_unique<XmpSidecar>(std::move(io), create);
        if (!image->good()) {
            image.reset();
        }
        return image;
    }

    bool isXmpType(BasicIo& iIo, bool advance)
    {
        /*
          Check if the file starts with an optional XML declaration followed by
          either an XMP header (<?xpacket ... ?>) or an <x:xmpmeta> element.

          In addition, in order for empty XmpSidecar objects as created by
          Exiv2 to pass the test, just an XML header is also considered ok.
         */
        const int32_t len = 80;
        byte buf[len];
        iIo.read(buf, xmlHdrCnt + 1);
        if (   iIo.eof()
            && 0 == strncmp(reinterpret_cast<const char*>(buf), xmlHeader, xmlHdrCnt)) {
            return true;
        }
        if (iIo.error() || iIo.eof()) {
            return false;
        }
        iIo.read(buf + xmlHdrCnt + 1, len - xmlHdrCnt - 1);
        if (iIo.error() || iIo.eof()) {
            return false;
        }
        // Skip leading BOM
        int32_t start = 0;
        if (0 == strncmp(reinterpret_cast<const char*>(buf), "\xef\xbb\xbf", 3)) {
            start = 3;
        }
        bool rc = false;
        std::string head(reinterpret_cast<const char*>(buf + start), len - start);
        if (head.substr(0, 5)  == "<?xml") {
            // Forward to the next tag
            for (size_t i = 5; i < head.size(); ++i) {
                if (head[i] == '<') {
                    head = head.substr(i);
                    break;
                }
            }
        }
        if (   head.size() > 9
            && (   head.substr(0, 9)  == "<?xpacket"
                || head.substr(0, 10) == "<x:xmpmeta")) {
            rc = true;
        }
        if (!advance || !rc) {
            iIo.seek(-(len - start), BasicIo::cur); // Swallow the BOM
        }
        return rc;

    }

}                                       // namespace Exiv2