cpp: Add gpgme_data_rewind to cpp API

* lang/cpp/src/data.h, lang/cpp/src/data.cpp (Data::rewind): New.
* lang/qt/tests/t-various.cpp (testDataRewind): Test it.

--
The advantage of this convieniance function in GPGME is that
it avoids the messiness that are declarations with off_t.

GnuPG-Bug-Id: T3996

1 files changed, 19 insertions, 0 deletions

diff --git a/lang/qt/tests/t-various.cpp b/lang/qt/tests/t-various.cpp
index 75456281..76e68063 100644
--- a/lang/qt/tests/t-various.cpp
+++ b/lang/qt/tests/t-various.cpp
@@ -98,6 +98,25 @@ private Q_SLOTS:
         QVERIFY(key.primaryFingerprint() == QStringLiteral("7A0904B6950DA998020A1AD4BE41C0C3A5FF1F3C"));
     }
 
+    void testDataRewind()
+    {
+        if (GpgME::engineInfo(GpgME::GpgEngine).engineVersion() < "2.1.14") {
+            return;
+        }
+        QGpgME::QByteArrayDataProvider dp(aKey);
+        Data data(&dp);
+        char buf[20];
+        data.read(buf, 20);
+
+        auto keys = data.toKeys();
+        QVERIFY(keys.size() == 0);
+
+        data.rewind();
+
+        keys = data.toKeys();
+        QVERIFY(keys.size() == 1);
+    }
+
     void testQuickUid()
     {
         if (GpgME::engineInfo(GpgME::GpgEngine).engineVersion() < "2.1.13") {