filter/*: use std::span instead of ConstBuffer

src/filter/Filter.cxx

@@ -1,27 +0,0 @@
-/*
- * Copyright 2003-2021 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 "Filter.hxx"
-#include "util/ConstBuffer.hxx"
-
-ConstBuffer<void>
-Filter::Flush()
-{
-	return nullptr;
-}

src/filter/Filter.hxx

@@ -23,8 +23,8 @@
 #include "pcm/AudioFormat.hxx"
 
 #include <cassert>
-
+#include <cstddef>
-template<typename T> struct ConstBuffer;
+#include <span>
 
 class Filter {
 protected:
@@ -61,7 +61,7 @@ public:
 	 * invalidated by deleting this object or the next FilterPCM()
 	 * or Reset() call)
 	 */
-	virtual ConstBuffer<void> FilterPCM(ConstBuffer<void> src) = 0;
+	virtual std::span<const std::byte> FilterPCM(std::span<const std::byte> src) = 0;
 
 	/**
 	 * Flush pending data and return it.  This should be called
@@ -69,7 +69,9 @@ public:
 	 *
 	 * Throws on error.
 	 */
-	virtual ConstBuffer<void> Flush();
+	virtual std::span<const std::byte> Flush() {
+		return {};
+	}
 };
 
 #endif

src/filter/NullFilter.hxx

@@ -21,13 +21,12 @@
 #define MPD_NULL_FILTER_HXX
 
 #include "filter/Filter.hxx"
-#include "util/ConstBuffer.hxx"
 
 class NullFilter final : public Filter {
 public:
 	explicit NullFilter(const AudioFormat &af):Filter(af) {}
 
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override {
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override {
 		return src;
 	}
 };

src/filter/Observer.cxx

@@ -20,7 +20,6 @@
 #include "Observer.hxx"
 #include "Filter.hxx"
 #include "Prepared.hxx"
-#include "util/ConstBuffer.hxx"
 
 #include <cassert>
 
@@ -81,11 +80,11 @@ public:
 		filter->Reset();
 	}
 
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override {
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override {
 		return filter->FilterPCM(src);
 	}
 
-	ConstBuffer<void> Flush() override {
+	std::span<const std::byte> Flush() override {
 		return filter->Flush();
 	}
 };

src/filter/meson.build

@@ -1,7 +1,6 @@
 filter_api = static_library(
   'filter_api',
   'Observer.cxx',
-  'Filter.cxx',
   include_directories: inc,
 )
 

src/filter/plugins/ConvertFilterPlugin.cxx

@@ -22,7 +22,6 @@
 #include "filter/Prepared.hxx"
 #include "pcm/AudioFormat.hxx"
 #include "pcm/Convert.hxx"
-#include "util/ConstBuffer.hxx"
 
 #include <cassert>
 #include <memory>
@@ -50,9 +49,9 @@ public:
 			state->Reset();
 	}
 
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override;
 
-	ConstBuffer<void> Flush() override {
+	std::span<const std::byte> Flush() override {
 		return state
 			? state->Flush()
 			: std::span<const std::byte>{};
@@ -102,8 +101,8 @@ PreparedConvertFilter::Open(AudioFormat &audio_format)
 	return std::make_unique<ConvertFilter>(audio_format);
 }
 
-ConstBuffer<void>
+std::span<const std::byte>
-ConvertFilter::FilterPCM(ConstBuffer<void> src)
+ConvertFilter::FilterPCM(std::span<const std::byte> src)
 {
 	return state
 		? state->Convert(src)

src/filter/plugins/FfmpegFilter.cxx

@@ -20,7 +20,6 @@
 #include "FfmpegFilter.hxx"
 #include "lib/ffmpeg/Interleave.hxx"
 #include "lib/ffmpeg/SampleFormat.hxx"
-#include "util/ConstBuffer.hxx"
 
 extern "C" {
 #include <libavfilter/buffersrc.h>
@@ -46,8 +45,8 @@ FfmpegFilter::FfmpegFilter(const AudioFormat &in_audio_format,
 {
 }
 
-ConstBuffer<void>
+std::span<const std::byte>
-FfmpegFilter::FilterPCM(ConstBuffer<void> src)
+FfmpegFilter::FilterPCM(std::span<const std::byte> src)
 {
 	/* submit source data into the FFmpeg audio buffer source */
 
@@ -55,11 +54,11 @@ FfmpegFilter::FilterPCM(ConstBuffer<void> src)
 	frame->format = in_format;
 	frame->sample_rate = in_sample_rate;
 	frame->channels = in_channels;
-	frame->nb_samples = src.size / in_audio_frame_size;
+	frame->nb_samples = src.size() / in_audio_frame_size;
 
 	frame.GetBuffer();
 
-	memcpy(frame.GetData(0), src.data, src.size);
+	memcpy(frame.GetData(0), src.data(), src.size());
 
 	int err = av_buffersrc_add_frame(&buffer_src, frame.get());
 	if (err < 0)
@@ -72,7 +71,7 @@ FfmpegFilter::FilterPCM(ConstBuffer<void> src)
 	err = av_buffersink_get_frame(&buffer_sink, frame.get());
 	if (err < 0) {
 		if (err == AVERROR(EAGAIN) || err == AVERROR_EOF)
-			return nullptr;
+			return {};
 
 		throw MakeFfmpegError(err, "av_buffersink_get_frame() failed");
 	}

src/filter/plugins/FfmpegFilter.hxx

@@ -55,7 +55,7 @@ public:
 		     AVFilterContext &_buffer_sink) noexcept;
 
 	/* virtual methods from class Filter */
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override;
 };
 
 #endif

src/filter/plugins/NormalizeFilterPlugin.cxx

@@ -24,7 +24,6 @@
 #include "pcm/Buffer.hxx"
 #include "pcm/AudioFormat.hxx"
 #include "pcm/AudioCompress/compress.h"
-#include "util/ConstBuffer.hxx"
 
 #include <string.h>
 
@@ -47,7 +46,7 @@ public:
 	NormalizeFilter &operator=(const NormalizeFilter &) = delete;
 
 	/* virtual methods from class Filter */
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override;
 };
 
 class PreparedNormalizeFilter final : public PreparedFilter {
@@ -70,14 +69,14 @@ PreparedNormalizeFilter::Open(AudioFormat &audio_format)
 	return std::make_unique<NormalizeFilter>(audio_format);
 }
 
-ConstBuffer<void>
+std::span<const std::byte>
-NormalizeFilter::FilterPCM(ConstBuffer<void> src)
+NormalizeFilter::FilterPCM(std::span<const std::byte> src)
 {
-	auto *dest = (int16_t *)buffer.Get(src.size);
+	auto *dest = (int16_t *)buffer.Get(src.size());
-	memcpy(dest, src.data, src.size);
+	memcpy(dest, src.data(), src.size());
 
-	Compressor_Process_int16(compressor, dest, src.size / 2);
+	Compressor_Process_int16(compressor, dest, src.size() / 2);
-	return { (const void *)dest, src.size };
+	return { (const std::byte *)dest, src.size() };
 }
 
 const FilterPlugin normalize_filter_plugin = {

src/filter/plugins/ReplayGainFilterPlugin.cxx

@@ -25,7 +25,6 @@
 #include "mixer/MixerControl.hxx"
 #include "pcm/AudioFormat.hxx"
 #include "pcm/Volume.hxx"
-#include "util/ConstBuffer.hxx"
 #include "util/Domain.hxx"
 #include "Idle.hxx"
 #include "Log.hxx"
@@ -109,7 +108,7 @@ public:
 	void Update();
 
 	/* virtual methods from class Filter */
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override;
 };
 
 class PreparedReplayGainFilter final : public PreparedFilter {
@@ -197,8 +196,8 @@ PreparedReplayGainFilter::Open(AudioFormat &af)
 						  af, mixer, base);
 }
 
-ConstBuffer<void>
+std::span<const std::byte>
-ReplayGainFilter::FilterPCM(ConstBuffer<void> src)
+ReplayGainFilter::FilterPCM(std::span<const std::byte> src)
 {
 	return mixer != nullptr
 		? std::span<const std::byte>{src}

src/filter/plugins/RouteFilterPlugin.cxx

@@ -49,7 +49,6 @@
 #include "pcm/Silence.hxx"
 #include "util/StringStrip.hxx"
 #include "util/RuntimeError.hxx"
-#include "util/ConstBuffer.hxx"
 
 #include <array>
 #include <cstdint>
@@ -94,7 +93,7 @@ public:
 		    const std::array<int8_t, MAX_CHANNELS> &_sources);
 
 	/* virtual methods from class Filter */
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override;
 };
 
 class PreparedRouteFilter final : public PreparedFilter {
@@ -221,15 +220,15 @@ PreparedRouteFilter::Open(AudioFormat &audio_format)
 					     sources);
 }
 
-ConstBuffer<void>
+std::span<const std::byte>
-RouteFilter::FilterPCM(ConstBuffer<void> src)
+RouteFilter::FilterPCM(std::span<const std::byte> src)
 {
-	size_t number_of_frames = src.size / input_frame_size;
+	size_t number_of_frames = src.size() / input_frame_size;
 
 	const size_t bytes_per_frame_per_channel = input_format.GetSampleSize();
 
 	// A moving pointer that always refers to channel 0 in the input, at the currently handled frame
-	const auto *base_source = (const uint8_t *)src.data;
+	const auto *base_source = (const uint8_t *)src.data();
 
 	// Grow our reusable buffer, if needed, and set the moving pointer
 	const size_t result_size = number_of_frames * output_frame_size;
@@ -268,7 +267,7 @@ RouteFilter::FilterPCM(ConstBuffer<void> src)
 	}
 
 	// Here it is, ladies and gentlemen! Rerouted data!
-	return { result, result_size };
+	return { (const std::byte *)result, result_size };
 }
 
 const FilterPlugin route_filter_plugin = {

src/filter/plugins/TwoFilters.cxx

@@ -19,21 +19,20 @@
 
 #include "TwoFilters.hxx"
 #include "pcm/AudioFormat.hxx"
-#include "util/ConstBuffer.hxx"
 #include "util/RuntimeError.hxx"
 #include "util/StringBuffer.hxx"
 
-ConstBuffer<void>
+std::span<const std::byte>
-TwoFilters::FilterPCM(ConstBuffer<void> src)
+TwoFilters::FilterPCM(std::span<const std::byte> src)
 {
 	return second->FilterPCM(first->FilterPCM(src));
 }
 
-ConstBuffer<void>
+std::span<const std::byte>
 TwoFilters::Flush()
 {
 	auto result = first->Flush();
-	if (!result.IsNull())
+	if (result.data() != nullptr)
 		/* Flush() output from the first Filter must be
 		   filtered by the second Filter */
 		return second->FilterPCM(result);

src/filter/plugins/TwoFilters.hxx

@@ -44,8 +44,8 @@ public:
 		second->Reset();
 	}
 
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override;
-	ConstBuffer<void> Flush() override;
+	std::span<const std::byte> Flush() override;
 };
 
 /**

src/filter/plugins/VolumeFilterPlugin.cxx

@@ -22,7 +22,6 @@
 #include "filter/Prepared.hxx"
 #include "pcm/Volume.hxx"
 #include "pcm/AudioFormat.hxx"
-#include "util/ConstBuffer.hxx"
 
 class VolumeFilter final : public Filter {
 	PcmVolume pv;
@@ -43,7 +42,7 @@ public:
 	}
 
 	/* virtual methods from class Filter */
-	ConstBuffer<void> FilterPCM(ConstBuffer<void> src) override;
+	std::span<const std::byte> FilterPCM(std::span<const std::byte> src) override;
 };
 
 class PreparedVolumeFilter final : public PreparedFilter {
@@ -58,8 +57,8 @@ PreparedVolumeFilter::Open(AudioFormat &audio_format)
 	return std::make_unique<VolumeFilter>(audio_format);
 }
 
-ConstBuffer<void>
+std::span<const std::byte>
-VolumeFilter::FilterPCM(ConstBuffer<void> src)
+VolumeFilter::FilterPCM(std::span<const std::byte> src)
 {
 	return pv.Apply(src);
 }

src/output/Source.cxx

@@ -255,5 +255,5 @@ AudioOutputSource::Flush()
 {
 	return filter
 		? filter->Flush()
-		: nullptr;
+		: std::span<const std::byte>{};
 }

test/run_filter.cxx

@@ -30,7 +30,6 @@
 #include "mixer/MixerControl.hxx"
 #include "system/Error.hxx"
 #include "io/FileDescriptor.hxx"
-#include "util/ConstBuffer.hxx"
 #include "util/StringBuffer.hxx"
 #include "util/RuntimeError.hxx"
 #include "util/PrintException.hxx"
@@ -102,22 +101,22 @@ try {
 	FileDescriptor output_fd(STDOUT_FILENO);
 
 	while (true) {
-		char buffer[4096];
+		std::byte buffer[4096];
 
 		ssize_t nbytes = ReadFrames(input_fd, buffer, sizeof(buffer),
 					    in_frame_size);
 		if (nbytes == 0)
 			break;
 
-		auto dest = filter->FilterPCM({(const void *)buffer, (size_t)nbytes});
+		auto dest = filter->FilterPCM(std::span{buffer}.first(nbytes));
-		output_fd.FullWrite(dest.data, dest.size);
+		output_fd.FullWrite(dest.data(), dest.size());
 	}
 
 	while (true) {
 		auto dest = filter->Flush();
-		if (dest.IsNull())
+		if (dest.data() == nullptr)
 			break;
-		output_fd.FullWrite(dest.data, dest.size);
+		output_fd.FullWrite(dest.data(), dest.size());
 	}
 
 	/* cleanup and exit */