qt: Add data provider for list of file names

* lang/qt/src/Makefile.am: Add new files and corresponding camel-case
header.
* lang/qt/src/dataprovider.h: Include interface from gpgme++ when
not building.
* lang/qt/src/filelistdataprovider.cpp,
lang/qt/src/filelistdataprovider.h: New.
--

The new data provider simplifies providing a nul-separated list of
UTF-8-encoded filenames, e.g. for creating signed or encrypted
archives. It is a simple read-only proxy for QByteArrayDataProvider.

GnuPG-bug-id: 6342

NEWS

@@ -49,6 +49,7 @@ Noteworthy changes in version 1.18.1 (unreleased)
  qt: ListAllKeysJob::options                NEW.
  qt: Job::startNow                          NEW.
  qt: ImportJob::startLater                  NEW.
+ qt: FileListDataProvider                   NEW.
 
 
 Noteworthy changes in version 1.18.0 (2022-08-10)

lang/qt/src/Makefile.am

@@ -34,6 +34,7 @@ EXTRA_DIST = QGpgmeConfig.cmake.in.in QGpgmeConfigVersion.cmake.in \
 qgpgme_sources = \
     dataprovider.cpp \
     debug.cpp \
+    filelistdataprovider.cpp \
     job.cpp multideletejob.cpp qgpgmeadduseridjob.cpp \
     qgpgmeaddexistingsubkeyjob.cpp \
     qgpgmebackend.cpp qgpgmechangeexpiryjob.cpp qgpgmechangeownertrustjob.cpp \
@@ -72,6 +73,7 @@ qgpgme_headers= \
     downloadjob.h \
     encryptjob.h \
     exportjob.h \
+    filelistdataprovider.h \
     hierarchicalkeylistjob.h \
     job.h \
     keyformailboxjob.h \
@@ -120,6 +122,7 @@ camelcase_headers= \
     DownloadJob \
     EncryptJob \
     ExportJob \
+    FileListDataProvider \
     HierarchicalKeyKistJob \
     Job \
     MultiDeleteJob \

lang/qt/src/dataprovider.h

@@ -25,7 +25,13 @@
 #define __QGPGME_DATAPROVIDER_H__
 
 #include "qgpgme_export.h"
+
+#ifdef BUILDING_QGPGME
 #include <interfaces/dataprovider.h>
+#else
+#include <gpgme++/interfaces/dataprovider.h>
+#endif
+
 #include <memory>
 
 #include <QtCore/QByteArray>

lang/qt/src/filelistdataprovider.cpp

@@ -0,0 +1,98 @@
+/*
+    filelistdataprovider.cpp
+
+    This file is part of qgpgme, the Qt API binding for gpgme
+    Copyright (c) 2023 g10 Code GmbH
+    Software engineering by Ingo Klöcker <dev@ingo-kloecker.de>
+
+    QGpgME is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License as
+    published by the Free Software Foundation; either version 2 of the
+    License, or (at your option) any later version.
+
+    QGpgME is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+    In addition, as a special exception, the copyright holders give
+    permission to link the code of this program with any edition of
+    the Qt library by Trolltech AS, Norway (or with modified versions
+    of Qt that use the same license as Qt), and distribute linked
+    combinations including the two.  You must obey the GNU General
+    Public License in all respects for all of the code used other than
+    Qt.  If you modify this file, you may extend this exception to
+    your version of the file, but you are not obligated to do so.  If
+    you do not wish to do so, delete this exception statement from
+    your version.
+*/
+
+#ifdef HAVE_CONFIG_H
+ #include "config.h"
+#endif
+
+#include "filelistdataprovider.h"
+
+#include "dataprovider.h"
+
+#include <QString>
+
+#include <gpgme++/error.h>
+
+#include <numeric>
+
+using namespace QGpgME;
+using namespace GpgME;
+
+static QByteArray encodeFilenames(const std::vector<QString> &filenames)
+{
+    QByteArray ret;
+    if (filenames.empty()) {
+        return ret;
+    }
+    // calculate and reserve the needed minimum size of the result
+    const auto addSize = [](unsigned int n, const QString &s) { return n + s.size(); };
+    const unsigned int minSize = filenames.size()
+        + std::accumulate(filenames.cbegin(), filenames.cend(), 0u, addSize);
+    ret.reserve(minSize);
+    // pack the filenames into the byte array
+    for (const auto &f : filenames) {
+        if (!f.isEmpty()) {
+            ret += f.toUtf8() + '\0';
+        }
+    }
+    ret.chop(1); // remove the trailing nul
+    return ret;
+}
+
+FileListDataProvider::FileListDataProvider(const std::vector<QString> &filenames)
+    : mProvider{new QByteArrayDataProvider{encodeFilenames(filenames)}}
+{
+}
+
+FileListDataProvider::~FileListDataProvider() = default;
+
+ssize_t FileListDataProvider::read(void* buffer, size_t bufSize)
+{
+    return mProvider->read(buffer, bufSize);
+}
+
+ssize_t FileListDataProvider::write(const void *, size_t)
+{
+    Error::setSystemError(GPG_ERR_EBADF);
+    return -1;
+}
+
+off_t FileListDataProvider::seek(off_t offset, int whence)
+{
+    return mProvider->seek(offset, whence);
+}
+
+void FileListDataProvider::release()
+{
+    mProvider->release();
+}

lang/qt/src/filelistdataprovider.h

@@ -0,0 +1,79 @@
+/*
+    filelistdataprovider.h
+
+    This file is part of qgpgme, the Qt API binding for gpgme
+    Copyright (c) 2023 g10 Code GmbH
+    Software engineering by Ingo Klöcker <dev@ingo-kloecker.de>
+
+    QGpgME is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License as
+    published by the Free Software Foundation; either version 2 of the
+    License, or (at your option) any later version.
+
+    QGpgME is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+    In addition, as a special exception, the copyright holders give
+    permission to link the code of this program with any edition of
+    the Qt library by Trolltech AS, Norway (or with modified versions
+    of Qt that use the same license as Qt), and distribute linked
+    combinations including the two.  You must obey the GNU General
+    Public License in all respects for all of the code used other than
+    Qt.  If you modify this file, you may extend this exception to
+    your version of the file, but you are not obligated to do so.  If
+    you do not wish to do so, delete this exception statement from
+    your version.
+*/
+
+#ifndef __QGPGME_FILELISTDATAPROVIDER_H__
+#define __QGPGME_FILELISTDATAPROVIDER_H__
+
+#include "qgpgme_export.h"
+
+#ifdef BUILDING_QGPGME
+#include <interfaces/dataprovider.h>
+#else
+#include <gpgme++/interfaces/dataprovider.h>
+#endif
+
+#include <memory>
+#include <vector>
+
+class QString;
+
+namespace QGpgME
+{
+
+/**
+ * This read-only data provider simplifies providing a nul-separated list of
+ * UTF-8-encoded filenames, e.g. for creating signed or encrypted archives.
+ */
+class QGPGME_EXPORT FileListDataProvider : public GpgME::DataProvider
+{
+public:
+    explicit FileListDataProvider(const std::vector<QString> &filenames);
+    ~FileListDataProvider() override;
+
+private:
+    bool isSupported(Operation op) const override
+    {
+        return op != Operation::Write;
+    }
+    ssize_t read(void *buffer, size_t bufSize) override;
+    ssize_t write(const void *buffer, size_t bufSize) override;
+    off_t seek(off_t offset, int whence) override;
+    void release() override;
+
+private:
+    std::unique_ptr<GpgME::DataProvider> mProvider;
+};
+
+}
+
+#endif // __QGPGME_FILELISTDATAPROVIDER_H__