pcm/Volume: convert to class

Prepare for adding state.

8 files changed, 233 insertions, 273 deletions

diff --git a/Makefile.am b/Makefile.am
index 767b4dcf2..0448cf416 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1397,7 +1397,7 @@ endif
 
 test_software_volume_SOURCES = test/software_volume.cxx \
 	test/stdbin.h \
-	src/CheckAudioFormat.cxx \
+	src/AudioFormat.cxx src/CheckAudioFormat.cxx \
 	src/AudioParser.cxx
 test_software_volume_LDADD = \
 	$(PCM_LIBS) \
@@ -1484,6 +1484,7 @@ test_read_mixer_SOURCES = test/read_mixer.cxx \
 	src/Log.cxx src/LogBackend.cxx \
 	src/MixerControl.cxx \
 	src/FilterPlugin.cxx \
+	src/AudioFormat.cxx \
 	src/filter/VolumeFilterPlugin.cxx
 
 if ENABLE_BZIP2_TEST
@@ -1538,6 +1539,7 @@ test_test_mixramp_LDADD = \
 	$(CPPUNIT_LIBS)
 
 test_test_pcm_SOURCES = \
+	src/AudioFormat.cxx \
 	test/test_pcm_util.hxx \
 	test/test_pcm_dither.cxx \
 	test/test_pcm_pack.cxx \
diff --git a/src/filter/ReplayGainFilterPlugin.cxx b/src/filter/ReplayGainFilterPlugin.cxx
index c6c3cc2aa..998fda6f7 100644
--- a/src/filter/ReplayGainFilterPlugin.cxx
+++ b/src/filter/ReplayGainFilterPlugin.cxx
@@ -28,6 +28,7 @@
 #include "MixerControl.hxx"
 #include "pcm/Volume.hxx"
 #include "pcm/PcmBuffer.hxx"
+#include "util/ConstBuffer.hxx"
 #include "util/Error.hxx"
 #include "util/Domain.hxx"
 #include "Log.hxx"
@@ -55,8 +56,8 @@ class ReplayGainFilter final : public Filter {
 	ReplayGainInfo info;
 
 	/**
-	 * The current volume, between 0 and a value that may or may not exceed
-	 * #PCM_VOLUME_1.
+	 * About the current volume: it is between 0 and a value that
+	 * may or may not exceed #PCM_VOLUME_1.
 	 *
 	 * If the default value of true is used for replaygain_limit, the
 	 * application of the volume to the signal will never cause clipping.
@@ -66,16 +67,11 @@ class ReplayGainFilter final : public Filter {
 	 * maintain a consistent audio level. Whether clipping will actually
 	 * occur depends on what value the user is using for replaygain_preamp.
 	 */
-	unsigned volume;
-
-	AudioFormat format;
-
-	PcmBuffer buffer;
+	PcmVolume pv;
 
 public:
 	ReplayGainFilter()
-		:mixer(nullptr), mode(REPLAY_GAIN_OFF),
-		volume(PCM_VOLUME_1) {
+		:mixer(nullptr), mode(REPLAY_GAIN_OFF) {
 		info.Clear();
 	}
 
@@ -125,6 +121,7 @@ public:
 void
 ReplayGainFilter::Update()
 {
+	unsigned volume = PCM_VOLUME_1;
 	if (mode != REPLAY_GAIN_OFF) {
 		const auto &tuple = info.tuples[mode];
 		float scale = tuple.CalculateScale(replay_gain_preamp,
@@ -134,8 +131,9 @@ ReplayGainFilter::Update()
 			    "scale=%f\n", (double)scale);
 
 		volume = pcm_float_to_volume(scale);
-	} else
-		volume = PCM_VOLUME_1;
+	}
+
+	pv.SetVolume(volume);
 
 	if (mixer != nullptr) {
 		/* update the hardware mixer volume */
@@ -160,48 +158,25 @@ replay_gain_filter_init(gcc_unused const config_param &param,
 AudioFormat
 ReplayGainFilter::Open(AudioFormat &af, gcc_unused Error &error)
 {
-	format = af;
+	if (!pv.Open(af.format, error))
+		return AudioFormat::Undefined();
 
-	return format;
+	return af;
 }
 
 void
 ReplayGainFilter::Close()
 {
-	buffer.Clear();
+	pv.Close();
 }
 
 const void *
 ReplayGainFilter::FilterPCM(const void *src, size_t src_size,
-			    size_t *dest_size_r, Error &error)
+			    size_t *dest_size_r, gcc_unused Error &error)
 {
-
-	*dest_size_r = src_size;
-
-	if (volume == PCM_VOLUME_1)
-		/* optimized special case: 100% volume = no-op */
-		return src;
-
-	void *dest = buffer.Get(src_size);
-	if (volume <= 0) {
-		/* optimized special case: 0% volume = memset(0) */
-		/* XXX is this valid for all sample formats? What
-		   about floating point? */
-		memset(dest, 0, src_size);
-		return dest;
-	}
-
-	memcpy(dest, src, src_size);
-
-	bool success = pcm_volume(dest, src_size,
-				  format.format,
-				  volume);
-	if (!success) {
-		error.Set(replay_gain_domain, "pcm_volume() has failed");
-		return nullptr;
-	}
-
-	return dest;
+	const auto dest = pv.Apply({src, src_size});
+	*dest_size_r = dest.size;
+	return dest.data;
 }
 
 const struct filter_plugin replay_gain_filter_plugin = {
diff --git a/src/filter/VolumeFilterPlugin.cxx b/src/filter/VolumeFilterPlugin.cxx
index 2438e0336..8b9c6f8e9 100644
--- a/src/filter/VolumeFilterPlugin.cxx
+++ b/src/filter/VolumeFilterPlugin.cxx
@@ -23,8 +23,8 @@
 #include "FilterInternal.hxx"
 #include "FilterRegistry.hxx"
 #include "pcm/Volume.hxx"
-#include "pcm/PcmBuffer.hxx"
 #include "AudioFormat.hxx"
+#include "util/ConstBuffer.hxx"
 #include "util/Error.hxx"
 #include "util/Domain.hxx"
 
@@ -32,29 +32,15 @@
 #include <string.h>
 
 class VolumeFilter final : public Filter {
-	/**
-	 * The current volume, from 0 to #PCM_VOLUME_1.
-	 */
-	unsigned volume;
-
-	AudioFormat format;
-
-	PcmBuffer buffer;
+	PcmVolume pv;
 
 public:
-	VolumeFilter()
-		:volume(PCM_VOLUME_1) {}
-
 	unsigned GetVolume() const {
-		assert(volume <= PCM_VOLUME_1);
-
-		return volume;
+		return pv.GetVolume();
 	}
 
 	void SetVolume(unsigned _volume) {
-		assert(_volume <= PCM_VOLUME_1);
-
-		volume = _volume;
+		pv.SetVolume(_volume);
 	}
 
 	virtual AudioFormat Open(AudioFormat &af, Error &error) override;
@@ -73,50 +59,27 @@ volume_filter_init(gcc_unused const config_param &param,
 }
 
 AudioFormat
-VolumeFilter::Open(AudioFormat &audio_format, gcc_unused Error &error)
+VolumeFilter::Open(AudioFormat &audio_format, Error &error)
 {
-	format = audio_format;
+	if (!pv.Open(audio_format.format, error))
+		return AudioFormat::Undefined();
 
-	return format;
+	return audio_format;
 }
 
 void
 VolumeFilter::Close()
 {
-	buffer.Clear();
+	pv.Close();
 }
 
 const void *
 VolumeFilter::FilterPCM(const void *src, size_t src_size,
-			size_t *dest_size_r, Error &error)
+			size_t *dest_size_r, gcc_unused Error &error)
 {
-	*dest_size_r = src_size;
-
-	if (volume >= PCM_VOLUME_1)
-		/* optimized special case: 100% volume = no-op */
-		return src;
-
-	void *dest = buffer.Get(src_size);
-
-	if (volume <= 0) {
-		/* optimized special case: 0% volume = memset(0) */
-		/* XXX is this valid for all sample formats? What
-		   about floating point? */
-		memset(dest, 0, src_size);
-		return dest;
-	}
-
-	memcpy(dest, src, src_size);
-
-	bool success = pcm_volume(dest, src_size,
-				  format.format,
-				  volume);
-	if (!success) {
-		error.Set(volume_domain, "pcm_volume() has failed");
-		return NULL;
-	}
-
-	return dest;
+	const auto dest = pv.Apply({src, src_size});
+	*dest_size_r = dest.size;
+	return dest.data;
 }
 
 const struct filter_plugin volume_filter_plugin = {
diff --git a/src/pcm/Volume.cxx b/src/pcm/Volume.cxx
index 410df7695..539ef1238 100644
--- a/src/pcm/Volume.cxx
+++ b/src/pcm/Volume.cxx
@@ -19,9 +19,11 @@
 
 #include "config.h"
 #include "Volume.hxx"
+#include "Domain.hxx"
 #include "PcmUtils.hxx"
 #include "Traits.hxx"
-#include "AudioFormat.hxx"
+#include "util/ConstBuffer.hxx"
+#include "util/Error.hxx"
 
 #include <stdint.h>
 #include <string.h>
@@ -143,61 +145,88 @@ pcm_volume_change_float(float *dest, const float *src, const float *end,
 }
 
 bool
-pcm_volume(void *buffer, size_t length,
-	   SampleFormat format,
-	   int volume)
+PcmVolume::Open(SampleFormat _format, Error &error)
 {
-	if (volume == PCM_VOLUME_1S)
-		return true;
+	assert(format == SampleFormat::UNDEFINED);
 
-	if (volume <= 0) {
-		memset(buffer, 0, length);
-		return true;
+	switch (_format) {
+	case SampleFormat::UNDEFINED:
+	case SampleFormat::DSD:
+		error.Format(pcm_domain,
+			     "Software volume for %s is not implemented",
+			     sample_format_to_string(_format));
+		return false;
+
+	case SampleFormat::S8:
+	case SampleFormat::S16:
+	case SampleFormat::S24_P32:
+	case SampleFormat::S32:
+	case SampleFormat::FLOAT:
+		break;
 	}
 
-	const void *end = pcm_end_pointer(buffer, length);
+	format = _format;
+	return true;
+}
+
+ConstBuffer<void>
+PcmVolume::Apply(ConstBuffer<void> src)
+{
+	if (volume == PCM_VOLUME_1)
+		return src;
+
+	void *data = buffer.Get(src.size);
+
+	if (volume == 0) {
+		/* optimized special case: 0% volume = memset(0) */
+		/* TODO: is this valid for all sample formats? What
+		   about floating point? */
+		memset(data, 0, src.size);
+		return { data, src.size };
+	}
+
+	const void *end = pcm_end_pointer(src.data, src.size);
 	switch (format) {
 	case SampleFormat::UNDEFINED:
 	case SampleFormat::DSD:
-		/* not implemented */
-		return false;
+		assert(false);
+		gcc_unreachable();
 
 	case SampleFormat::S8:
-		pcm_volume_change_8((int8_t *)buffer,
-				    (const int8_t *)buffer,
+		pcm_volume_change_8((int8_t *)data,
+				    (const int8_t *)src.data,
 				    (const int8_t *)end,
 				    volume);
-		return true;
+		break;
 
 	case SampleFormat::S16:
-		pcm_volume_change_16((int16_t *)buffer,
-				     (const int16_t *)buffer,
+		pcm_volume_change_16((int16_t *)data,
+				     (const int16_t *)src.data,
 				     (const int16_t *)end,
 				     volume);
-		return true;
+		break;
 
 	case SampleFormat::S24_P32:
-		pcm_volume_change_24((int32_t *)buffer,
-				     (const int32_t *)buffer,
+		pcm_volume_change_24((int32_t *)data,
+				     (const int32_t *)src.data,
 				     (const int32_t *)end,
 				     volume);
-		return true;
+		break;
 
 	case SampleFormat::S32:
-		pcm_volume_change_32((int32_t *)buffer,
-				     (const int32_t *)buffer,
+		pcm_volume_change_32((int32_t *)data,
+				     (const int32_t *)src.data,
 				     (const int32_t *)end,
 				     volume);
-		return true;
+		break;
 
 	case SampleFormat::FLOAT:
-		pcm_volume_change_float((float *)buffer,
-					(const float *)buffer,
+		pcm_volume_change_float((float *)data,
+					(const float *)src.data,
 					(const float *)end,
 					pcm_volume_to_float(volume));
-		return true;
+		break;
 	}
 
-	assert(false);
-	gcc_unreachable();
+	return { data, src.size };
 }
diff --git a/src/pcm/Volume.hxx b/src/pcm/Volume.hxx
index 52102a294..c31aafb6e 100644
--- a/src/pcm/Volume.hxx
+++ b/src/pcm/Volume.hxx
@@ -22,10 +22,18 @@
 
 #include "PcmPrng.hxx"
 #include "AudioFormat.hxx"
+#include "PcmBuffer.hxx"
 
 #include <stdint.h>
 #include <stddef.h>
 
+#ifndef NDEBUG
+#include <assert.h>
+#endif
+
+class Error;
+template<typename T> struct ConstBuffer;
+
 /**
  * Number of fractional bits for a fixed-point volume value.
  */
@@ -71,17 +79,66 @@ pcm_volume_dither(void)
 }
 
 /**
- * Adjust the volume of the specified PCM buffer.
- *
- * @param buffer the PCM buffer
- * @param length the length of the PCM buffer
- * @param format the sample format of the PCM buffer
- * @param volume the volume between 0 and #PCM_VOLUME_1
- * @return true on success, false if the audio format is not supported
+ * A class that converts samples from one format to another.
  */
-bool
-pcm_volume(void *buffer, size_t length,
-	   SampleFormat format,
-	   int volume);
+class PcmVolume {
+	SampleFormat format;
+
+	unsigned volume;
+
+	PcmBuffer buffer;
+
+public:
+	PcmVolume()
+		:volume(PCM_VOLUME_1) {
+#ifndef NDEBUG
+		format = SampleFormat::UNDEFINED;
+#endif
+	}
+
+#ifndef NDEBUG
+	~PcmVolume() {
+		assert(format == SampleFormat::UNDEFINED);
+	}
+#endif
+
+	unsigned GetVolume() const {
+		return volume;
+	}
+
+	/**
+	 * @param _volume the volume level in the range
+	 * [0..#PCM_VOLUME_1]; may be bigger than #PCM_VOLUME_1, but
+	 * then it will most likely clip a lot
+	 */
+	void SetVolume(unsigned _volume) {
+		volume = _volume;
+	}
+
+	/**
+	 * Opens the object, prepare for Apply().
+	 *
+	 * @param format the sample format
+	 * @param error location to store the error
+	 * @return true on success
+	 */
+	bool Open(SampleFormat format, Error &error);
+
+	/**
+	 * Closes the object.  After that, you may call Open() again.
+	 */
+	void Close() {
+#ifndef NDEBUG
+		assert(format != SampleFormat::UNDEFINED);
+		format = SampleFormat::UNDEFINED;
+#endif
+	}
+
+	/**
+	 * Apply the volume level.
+	 */
+	gcc_pure
+	ConstBuffer<void> Apply(ConstBuffer<void> src);
+};
 
 #endif
diff --git a/test/read_mixer.cxx b/test/read_mixer.cxx
index 07ff931c8..5decc5798 100644
--- a/test/read_mixer.cxx
+++ b/test/read_mixer.cxx
@@ -101,15 +101,6 @@ filter_plugin_by_name(gcc_unused const char *name)
 	return NULL;
 }
 
-bool
-pcm_volume(gcc_unused void *buffer, gcc_unused size_t length,
-	   gcc_unused SampleFormat format,
-	   gcc_unused int volume)
-{
-	assert(false);
-	return false;
-}
-
 int main(int argc, gcc_unused char **argv)
 {
 	int volume;
diff --git a/test/software_volume.cxx b/test/software_volume.cxx
index b850217df..ae2d53a08 100644
--- a/test/software_volume.cxx
+++ b/test/software_volume.cxx
@@ -27,12 +27,14 @@
 #include "pcm/Volume.hxx"
 #include "AudioParser.hxx"
 #include "AudioFormat.hxx"
+#include "util/ConstBuffer.hxx"
 #include "util/Error.hxx"
 #include "stdbin.h"
 
 #include <glib.h>
 
 #include <stddef.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 int main(int argc, char **argv)
@@ -55,14 +57,16 @@ int main(int argc, char **argv)
 		}
 	}
 
-	while ((nbytes = read(0, buffer, sizeof(buffer))) > 0) {
-		if (!pcm_volume(buffer, nbytes,
-				audio_format.format,
-				PCM_VOLUME_1 / 2)) {
-			g_printerr("pcm_volume() has failed\n");
-			return 2;
-		}
+	PcmVolume pv;
+	if (!pv.Open(audio_format.format, error)) {
+		fprintf(stderr, "%s\n", error.GetMessage());
+		return EXIT_FAILURE;
+	}
 
-		gcc_unused ssize_t ignored = write(1, buffer, nbytes);
+	while ((nbytes = read(0, buffer, sizeof(buffer))) > 0) {
+		auto dest = pv.Apply({buffer, size_t(nbytes)});
+		gcc_unused ssize_t ignored = write(1, dest.data, dest.size);
 	}
+
+	pv.Close();
 }
diff --git a/test/test_pcm_volume.cxx b/test/test_pcm_volume.cxx
index fae937c30..bba5d3bbf 100644
--- a/test/test_pcm_volume.cxx
+++ b/test/test_pcm_volume.cxx
@@ -17,169 +17,108 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "config.h"
 #include "test_pcm_all.hxx"
 #include "pcm/Volume.hxx"
+#include "pcm/Traits.hxx"
+#include "util/ConstBuffer.hxx"
+#include "util/Error.hxx"
 #include "test_pcm_util.hxx"
 
 #include <algorithm>
 
 #include <string.h>
 
-void
-PcmVolumeTest::TestVolume8()
+template<SampleFormat F, class Traits=SampleTraits<F>,
+	 typename G=RandomInt<typename Traits::value_type>>
+static void
+TestVolume(G g=G())
 {
-	constexpr unsigned N = 256;
-	static int8_t zero[N];
-	const auto src = TestDataBuffer<int8_t, N>();
+	typedef typename Traits::value_type value_type;
+
+	PcmVolume pv;
+	CPPUNIT_ASSERT(pv.Open(F, IgnoreError()));
 
-	int8_t dest[N];
+	constexpr size_t N = 256;
+	static value_type zero[N];
+	const auto _src = TestDataBuffer<value_type, N>(g);
+	const ConstBuffer<void> src(_src, sizeof(_src));
 
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S8, 0));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, zero, sizeof(zero)));
+	pv.SetVolume(0);
+	auto dest = pv.Apply(src);
+	CPPUNIT_ASSERT_EQUAL(src.size, dest.size);
+	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest.data, zero, sizeof(zero)));
 
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S8, PCM_VOLUME_1));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, src, sizeof(src)));
+	pv.SetVolume(PCM_VOLUME_1);
+	dest = pv.Apply(src);
+	CPPUNIT_ASSERT_EQUAL(src.size, dest.size);
+	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest.data, src.data, src.size));
 
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S8, PCM_VOLUME_1 / 2));
+	pv.SetVolume(PCM_VOLUME_1 / 2);
+	dest = pv.Apply(src);
+	CPPUNIT_ASSERT_EQUAL(src.size, dest.size);
 
+	const auto _dest = ConstBuffer<value_type>::FromVoid(dest);
 	for (unsigned i = 0; i < N; ++i) {
-		CPPUNIT_ASSERT(dest[i] >= (src[i] - 1) / 2);
-		CPPUNIT_ASSERT(dest[i] <= src[i] / 2 + 1);
+		CPPUNIT_ASSERT(_dest.data[i] >= (_src[i] - 1) / 2);
+		CPPUNIT_ASSERT(_dest.data[i] <= _src[i] / 2 + 1);
 	}
+
+	pv.Close();
 }
 
 void
-PcmVolumeTest::TestVolume16()
+PcmVolumeTest::TestVolume8()
 {
-	constexpr unsigned N = 256;
-	static int16_t zero[N];
-	const auto src = TestDataBuffer<int16_t, N>();
-
-	int16_t dest[N];
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S16, 0));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, zero, sizeof(zero)));
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S16, PCM_VOLUME_1));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, src, sizeof(src)));
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S16, PCM_VOLUME_1 / 2));
+	TestVolume<SampleFormat::S8>();
+}
 
-	for (unsigned i = 0; i < N; ++i) {
-		CPPUNIT_ASSERT(dest[i] >= (src[i] - 1) / 2);
-		CPPUNIT_ASSERT(dest[i] <= src[i] / 2 + 1);
-	}
+void
+PcmVolumeTest::TestVolume16()
+{
+	TestVolume<SampleFormat::S16>();
 }
 
 void
 PcmVolumeTest::TestVolume24()
 {
-	constexpr unsigned N = 256;
-	static int32_t zero[N];
-	const auto src = TestDataBuffer<int32_t, N>(RandomInt24());
-
-	int32_t dest[N];
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S24_P32, 0));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, zero, sizeof(zero)));
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S24_P32, PCM_VOLUME_1));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, src, sizeof(src)));
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S24_P32, PCM_VOLUME_1 / 2));
-
-	for (unsigned i = 0; i < N; ++i) {
-		CPPUNIT_ASSERT(dest[i] >= (src[i] - 1) / 2);
-		CPPUNIT_ASSERT(dest[i] <= src[i] / 2 + 1);
-	}
+	TestVolume<SampleFormat::S24_P32>(RandomInt24());
 }
 
 void
 PcmVolumeTest::TestVolume32()
 {
-	constexpr unsigned N = 256;
-	static int32_t zero[N];
-	const auto src = TestDataBuffer<int32_t, N>();
-
-	int32_t dest[N];
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S32, 0));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, zero, sizeof(zero)));
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S32, PCM_VOLUME_1));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, src, sizeof(src)));
-
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::S32, PCM_VOLUME_1 / 2));
-
-	for (unsigned i = 0; i < N; ++i) {
-		CPPUNIT_ASSERT(dest[i] >= (src[i] - 1) / 2);
-		CPPUNIT_ASSERT(dest[i] <= src[i] / 2 + 1);
-	}
+	TestVolume<SampleFormat::S32>();
 }
 
 void
 PcmVolumeTest::TestVolumeFloat()
 {
-	constexpr unsigned N = 256;
-	static float zero[N];
-	const auto src = TestDataBuffer<float, N>(RandomFloat());
+	PcmVolume pv;
+	CPPUNIT_ASSERT(pv.Open(SampleFormat::FLOAT, IgnoreError()));
 
-	float dest[N];
+	constexpr size_t N = 256;
+	static float zero[N];
+	const auto _src = TestDataBuffer<float, N>(RandomFloat());
+	const ConstBuffer<void> src(_src, sizeof(_src));
 
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::FLOAT, 0));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, zero, sizeof(zero)));
+	pv.SetVolume(0);
+	auto dest = pv.Apply(src);
+	CPPUNIT_ASSERT_EQUAL(src.size, dest.size);
+	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest.data, zero, sizeof(zero)));
 
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::FLOAT, PCM_VOLUME_1));
-	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest, src, sizeof(src)));
+	pv.SetVolume(PCM_VOLUME_1);
+	dest = pv.Apply(src);
+	CPPUNIT_ASSERT_EQUAL(src.size, dest.size);
+	CPPUNIT_ASSERT_EQUAL(0, memcmp(dest.data, src.data, src.size));
 
-	std::copy(src.begin(), src.end(), dest);
-	CPPUNIT_ASSERT_EQUAL(true,
-			     pcm_volume(dest, sizeof(dest),
-					SampleFormat::FLOAT,
-					PCM_VOLUME_1 / 2));
+	pv.SetVolume(PCM_VOLUME_1 / 2);
+	dest = pv.Apply(src);
+	CPPUNIT_ASSERT_EQUAL(src.size, dest.size);
 
+	const auto _dest = ConstBuffer<float>::FromVoid(dest);
 	for (unsigned i = 0; i < N; ++i)
-		CPPUNIT_ASSERT_DOUBLES_EQUAL(src[i] / 2, dest[i], 1);
+		CPPUNIT_ASSERT_DOUBLES_EQUAL(_src[i] / 2, _dest.data[i], 1);
+
+	pv.Close();
 }