pcm/PcmResampler: convert to abstract interface

The PcmResampler interface is implemented by the two classes
FallbackPcmResampler and LibsampleratePcmResampler.  This prepares for
adding more resampler libraries.

src/pcm/FallbackResampler.cxx

@@ -0,0 +1,147 @@
+/*
+ * Copyright (C) 2003-2013 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 "config.h"
+#include "FallbackResampler.hxx"
+
+#include <assert.h>
+
+AudioFormat
+FallbackPcmResampler::Open(AudioFormat &af, unsigned new_sample_rate,
+			   gcc_unused Error &error)
+{
+	assert(af.IsValid());
+	assert(audio_valid_sample_rate(new_sample_rate));
+
+	switch (af.format) {
+	case SampleFormat::UNDEFINED:
+		assert(false);
+		gcc_unreachable();
+
+	case SampleFormat::S8:
+		af.format = SampleFormat::S16;
+		break;
+
+	case SampleFormat::S16:
+	case SampleFormat::FLOAT:
+	case SampleFormat::S24_P32:
+	case SampleFormat::S32:
+		break;
+
+	case SampleFormat::DSD:
+		af.format = SampleFormat::FLOAT;
+		break;
+	}
+
+	format = af;
+	out_rate = new_sample_rate;
+
+	AudioFormat result = af;
+	result.sample_rate = new_sample_rate;
+	return result;
+}
+
+void
+FallbackPcmResampler::Close()
+{
+}
+
+template<typename T>
+static ConstBuffer<T>
+pcm_resample_fallback(PcmBuffer &buffer,
+		      unsigned channels,
+		      unsigned src_rate,
+		      ConstBuffer<T> src,
+		      unsigned dest_rate)
+{
+	unsigned dest_pos = 0;
+	unsigned src_frames = src.size / channels;
+	unsigned dest_frames =
+		(src_frames * dest_rate + src_rate - 1) / src_rate;
+	unsigned dest_samples = dest_frames * channels;
+	size_t dest_size = dest_samples * sizeof(*src.data);
+	T *dest_buffer = (T *)buffer.Get(dest_size);
+
+	assert((src.size % channels) == 0);
+
+	switch (channels) {
+	case 1:
+		while (dest_pos < dest_samples) {
+			unsigned src_pos = dest_pos * src_rate / dest_rate;
+
+			dest_buffer[dest_pos++] = src.data[src_pos];
+		}
+		break;
+	case 2:
+		while (dest_pos < dest_samples) {
+			unsigned src_pos = dest_pos * src_rate / dest_rate;
+			src_pos &= ~1;
+
+			dest_buffer[dest_pos++] = src.data[src_pos];
+			dest_buffer[dest_pos++] = src.data[src_pos + 1];
+		}
+		break;
+	}
+
+	return { dest_buffer, dest_samples };
+}
+
+template<typename T>
+static ConstBuffer<void>
+pcm_resample_fallback_void(PcmBuffer &buffer,
+			   unsigned channels,
+			   unsigned src_rate,
+			   ConstBuffer<void> src,
+			   unsigned dest_rate)
+{
+	const auto typed_src = ConstBuffer<T>::FromVoid(src);
+	return pcm_resample_fallback(buffer, channels, src_rate, typed_src,
+				     dest_rate);
+}
+
+ConstBuffer<void>
+FallbackPcmResampler::Resample(ConstBuffer<void> src, gcc_unused Error &error)
+{
+	switch (format.format) {
+	case SampleFormat::UNDEFINED:
+	case SampleFormat::S8:
+	case SampleFormat::DSD:
+		assert(false);
+		gcc_unreachable();
+
+	case SampleFormat::S16:
+		return pcm_resample_fallback_void<int16_t>(buffer,
+							   format.channels,
+							   format.sample_rate,
+							   src,
+							   out_rate);
+
+	case SampleFormat::FLOAT:
+	case SampleFormat::S24_P32:
+	case SampleFormat::S32:
+		return pcm_resample_fallback_void<int32_t>(buffer,
+							   format.channels,
+							   format.sample_rate,
+							   src,
+							   out_rate);
+	}
+
+	assert(false);
+	gcc_unreachable();
+}