cpp: Add internal adapter for passing a vector of strings to gpgme

* lang/cpp/src/util.h (class StringsToCStrings): New.
* lang/cpp/src/util.cpp: New.
* lang/cpp/src/Makefile.am: Add new file.
--

This adapter simplifies passing a vector of strings as NULL-terminated
array of const char* to the C-interface of gpgme.

GnuPG-bug-id: 5808

1 files changed, 24 insertions, 1 deletions

diff --git a/lang/cpp/src/util.h b/lang/cpp/src/util.h
index e04115bf..b6f9ca50 100644
--- a/lang/cpp/src/util.h
+++ b/lang/cpp/src/util.h
@@ -1,8 +1,10 @@
 /*
-  util.h - some inline helper functions
+  util.h - some internal helpers
   Copyright (C) 2004 Klarälvdalens Datakonsult AB
   2016 Bundesamt für Sicherheit in der Informationstechnik
   Software engineering by Intevation GmbH
+  Copyright (c) 2022 g10 Code GmbH
+  Software engineering by Ingo Klöcker <[email protected]>
 
   This file is part of GPGME++.
 
@@ -175,4 +177,25 @@ static inline gpgme_sig_notation_flags_t  add_to_gpgme_sig_notation_flags_t(unsi
     return static_cast<gpgme_sig_notation_flags_t>(result);
 }
 
+/**
+ * Adapter for passing a vector of strings as NULL-terminated array of
+ * const char* to the C-interface of gpgme.
+ */
+class StringsToCStrings
+{
+public:
+    explicit StringsToCStrings(const std::vector<std::string> &v);
+    ~StringsToCStrings() = default;
+
+    StringsToCStrings(const StringsToCStrings &) = delete;
+    StringsToCStrings &operator=(const StringsToCStrings &) = delete;
+    StringsToCStrings(StringsToCStrings &&) = delete;
+    StringsToCStrings &operator=(StringsToCStrings &&) = delete;
+
+    const char **c_strs() const;
+private:
+    const std::vector<std::string> m_strings;
+    mutable std::vector<const char *> m_cstrings;
+};
+
 #endif // __GPGMEPP_UTIL_H__