utils: add Mu::Error (runtime exception)

lib/utils/Makefile.am

@@ -38,6 +38,7 @@ noinst_LTLIBRARIES=							\
 libmu_utils_la_SOURCES=							\
 	mu-date.c							\
 	mu-date.h							\
+	mu-error.hh							\
 	mu-log.c							\
 	mu-log.h							\
 	mu-str.c							\

lib/utils/mu-error.hh

@@ -0,0 +1,82 @@
+/*
+** Copyright (C) 2019 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+**
+** This program 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 3, or (at your option) any
+** later version.
+**
+** This program 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.
+**
+*/
+
+
+#ifndef MU_ERROR_HH__
+#define MU_ERROR_HH__
+
+#include <stdexcept>
+#include "mu-utils.hh"
+
+namespace Mu {
+
+struct Error final: public std::runtime_error {
+        enum struct Code {
+                AccessDenied,
+                Internal,
+                InvalidArgument,
+                NotFound,
+                SchemaMismatch,
+        };
+
+        /**
+         * Construct an error
+         *
+         * @param codearg error-code
+         * #param msgarg the error diecription
+         */
+        Error(Code codearg, const std::string& msgarg):
+                std::runtime_error(msgarg), code_{codearg}
+                {}
+
+
+        /**
+         * Build an error from an error-code and a format string
+         *
+         * @param code error-code
+         * @param frm format string
+         * @param ... format parameters
+         *
+         * @return an Error object
+         */
+        __attribute__((format(printf, 2, 0)))
+        static Error make(Code codearg, const char *frm, ...) {
+                va_list args;
+                va_start(args, frm);
+                auto msg = format(frm, args);
+                va_end(args);
+                return Error(codearg, msg);
+        }
+
+        /**
+         * Get the error-code for this error
+         *
+         * @return the error-code
+         */
+        Code code() const { return code_; }
+
+private:
+        const Code   code_;
+};
+
+
+} // namespace Mu
+
+
+#endif /* MU_ERROR_HH__ */

lib/utils/mu-utils.cc

@@ -181,21 +181,29 @@ Mu::quote (const std::string& str)
 	 va_list args;
 
 	 va_start (args, frm);
-
-	 char *s = {};
-	 const auto res = g_vasprintf (&s, frm, args);
+         auto str = format(frm, args);
 	 va_end (args);
-	 if (res == -1) {
-		 std::cerr << "string format failed" << std::endl;
-		 return {};
-	 }
-
-	 std::string str = s;
-	 free (s);
 
 	 return str;
  }
 
+std::string
+Mu::format (const char *frm, va_list args)
+{
+        char *s{};
+        const auto res = g_vasprintf (&s, frm, args);
+        if (res == -1) {
+                std::cerr << "string format failed" << std::endl;
+                return {};
+        }
+
+	 std::string str{s};
+	 g_free (s);
+
+	 return str;
+}
+
+
 constexpr const auto InternalDateFormat = "%010" G_GINT64_FORMAT;
 constexpr const char InternalDateMin[] = "0000000000";
 constexpr const char InternalDateMax[] = "9999999999";