playlist/Queue: add one-shot to single mode

src/SingleMode.cxx

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2003-2017 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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 2 of the License, 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.
+ */
+
+#include "SingleMode.hxx"
+
+#include <stdexcept>
+
+#include <assert.h>
+#include <string.h>
+
+const char *
+SingleToString(SingleMode mode) noexcept
+{
+	switch (mode) {
+	case SingleMode::OFF:
+		return "0";
+
+	case SingleMode::ON:
+		return "1";
+
+	case SingleMode::ONE_SHOT:
+		return "oneshot";
+	}
+
+	assert(false);
+	gcc_unreachable();
+}
+
+SingleMode
+SingleFromString(const char *s)
+{
+	assert(s != nullptr);
+
+	if (strcmp(s, "0") == 0)
+		return SingleMode::OFF;
+	else if (strcmp(s, "1") == 0)
+		return SingleMode::ON;
+	else if (strcmp(s, "oneshot") == 0)
+		return SingleMode::ONE_SHOT;
+	else
+		throw std::invalid_argument("Unrecognized single mode, expected 0, 1, or oneshot");
+}