DecoderAPI: use std::chrono::duration for decoder_seek*()

For type safety and code readability.

src/Chrono.hxx

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2003-2014 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.
+ */
+
+#ifndef MPD_CHRONO_HXX
+#define MPD_CHRONO_HXX
+
+#include <chrono>
+#include <cstdint>
+
+/**
+ * A time stamp within a song.  Granularity is 1 millisecond and the
+ * maximum value is about 49 days.
+ */
+class SongTime : public std::chrono::duration<std::uint32_t, std::milli> {
+	typedef std::chrono::duration<std::uint32_t, std::milli> Base;
+	typedef Base::rep rep;
+
+public:
+	SongTime() = default;
+
+	template<typename T>
+	explicit constexpr SongTime(T t):Base(t) {}
+
+	static constexpr SongTime FromS(unsigned s) {
+		return SongTime(rep(s) * 1000);
+	}
+
+	static constexpr SongTime FromS(float s) {
+		return SongTime(rep(s * 1000));
+	}
+
+	static constexpr SongTime FromS(double s) {
+		return SongTime(rep(s * 1000));
+	}
+
+	static constexpr SongTime FromMS(rep ms) {
+		return SongTime(ms);
+	}
+
+	constexpr rep ToMS() const {
+		return count();
+	}
+
+	constexpr unsigned ToScale(unsigned base) const {
+		// TODO: case to 64 bit to avoid integer overflow?
+		return count() * base / 1000;
+	}
+};
+
+#endif