pcm/PcmFormat: eliminate more duplicate code with templates

Refactor the conversion functions to classes and pass an instance to
the new function AllocateConvert().

1 files changed, 69 insertions, 0 deletions

diff --git a/src/pcm/ShiftConvert.hxx b/src/pcm/ShiftConvert.hxx
new file mode 100644
index 000000000..92f96b7ba
--- /dev/null
+++ b/src/pcm/ShiftConvert.hxx
@@ -0,0 +1,69 @@
+/*
+ * 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_PCM_SHIFT_CONVERT_HXX
+#define MPD_PCM_SHIFT_CONVERT_HXX
+
+#include "Traits.hxx"
+
+/**
+ * Convert from one integer sample format to another by shifting bits
+ * to the left.
+ */
+template<SampleFormat SF, SampleFormat DF,
+	 class ST=SampleTraits<SF>,
+	 class DT=SampleTraits<DF>>
+struct LeftShiftSampleConvert {
+	typedef ST SrcTraits;
+	typedef DT DstTraits;
+
+	typedef typename SrcTraits::value_type SV;
+	typedef typename DstTraits::value_type DV;
+
+	static_assert(SrcTraits::BITS < DstTraits::BITS,
+		      "Source format must be smaller than destination format");
+
+	constexpr static DV Convert(SV src) {
+		return DV(src) << (DstTraits::BITS - SrcTraits::BITS);
+	}
+};
+
+/**
+ * Convert from one integer sample format to another by shifting bits
+ * to the right.
+ */
+template<SampleFormat SF, SampleFormat DF,
+	 class ST=SampleTraits<SF>,
+	 class DT=SampleTraits<DF>>
+struct RightShiftSampleConvert {
+	typedef ST SrcTraits;
+	typedef DT DstTraits;
+
+	typedef typename SrcTraits::value_type SV;
+	typedef typename DstTraits::value_type DV;
+
+	static_assert(SrcTraits::BITS > DstTraits::BITS,
+		      "Source format must be smaller than destination format");
+
+	constexpr static DV Convert(SV src) {
+		return src >> (SrcTraits::BITS - DstTraits::BITS);
+	}
+};
+
+#endif