From 84e5da4bf021a0750152659d71fd85ee7b6b5471 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Fri, 20 May 2022 10:09:50 +0200
Subject: [PATCH] pcm/Silence: use std::span

---
 src/filter/plugins/RouteFilterPlugin.cxx |  3 +--
 src/lib/ffmpeg/DetectFilterFormat.cxx    |  3 +--
 src/pcm/Export.cxx                       |  3 +--
 src/pcm/PcmChannels.cxx                  |  3 +--
 src/pcm/Silence.cxx                      | 11 +++++------
 src/pcm/Silence.hxx                      |  5 +++--
 src/pcm/Volume.cxx                       |  4 ++--
 7 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/src/filter/plugins/RouteFilterPlugin.cxx b/src/filter/plugins/RouteFilterPlugin.cxx
index d8d98a08b..796af56a4 100644
--- a/src/filter/plugins/RouteFilterPlugin.cxx
+++ b/src/filter/plugins/RouteFilterPlugin.cxx
@@ -50,7 +50,6 @@
 #include "util/StringStrip.hxx"
 #include "util/RuntimeError.hxx"
 #include "util/ConstBuffer.hxx"
-#include "util/WritableBuffer.hxx"
 
 #include <array>
 #include <cstdint>
@@ -237,7 +236,7 @@ RouteFilter::FilterPCM(ConstBuffer<void> src)
 	void *const result = output_buffer.Get(result_size);
 
 	// A moving pointer that always refers to the currently filled channel of the currently handled frame, in the output
-	auto *chan_destination = (uint8_t *)result;
+	auto *chan_destination = (std::byte *)result;
 
 	// Perform our copy operations, with N input channels and M output channels
 	for (unsigned int s=0; s<number_of_frames; ++s) {
diff --git a/src/lib/ffmpeg/DetectFilterFormat.cxx b/src/lib/ffmpeg/DetectFilterFormat.cxx
index 7b44eabb4..036d8e70b 100644
--- a/src/lib/ffmpeg/DetectFilterFormat.cxx
+++ b/src/lib/ffmpeg/DetectFilterFormat.cxx
@@ -22,7 +22,6 @@
 #include "SampleFormat.hxx"
 #include "pcm/Silence.hxx"
 #include "pcm/CheckAudioFormat.hxx"
-#include "util/WritableBuffer.hxx"
 
 extern "C" {
 #include <libavfilter/buffersrc.h>
@@ -42,7 +41,7 @@ DetectFilterOutputFormat(const AudioFormat &in_audio_format,
 	const size_t silence_size = in_audio_format.GetFrameSize();
 	assert(sizeof(silence) >= silence_size);
 
-	PcmSilence(WritableBuffer<void>{&silence, silence_size},
+	PcmSilence(std::as_writable_bytes(std::span{silence}),
 		   in_audio_format.format);
 
 	Frame frame;
diff --git a/src/pcm/Export.cxx b/src/pcm/Export.cxx
index 40a00bdaa..5f5858ae8 100644
--- a/src/pcm/Export.cxx
+++ b/src/pcm/Export.cxx
@@ -23,7 +23,6 @@
 #include "Silence.hxx"
 #include "util/ByteReverse.hxx"
 #include "util/ConstBuffer.hxx"
-#include "util/WritableBuffer.hxx"
 
 #include <cassert>
 
@@ -94,7 +93,7 @@ PcmExport::Open(SampleFormat sample_format, unsigned _channels,
 	}
 
 	/* prepare a moment of silence for GetSilence() */
-	char buffer[sizeof(silence_buffer)];
+	std::byte buffer[sizeof(silence_buffer)];
 	const size_t buffer_size = GetInputBlockSize();
 	assert(buffer_size < sizeof(buffer));
 	PcmSilence({buffer, buffer_size}, src_sample_format);
diff --git a/src/pcm/PcmChannels.cxx b/src/pcm/PcmChannels.cxx
index b7108f564..91189ab60 100644
--- a/src/pcm/PcmChannels.cxx
+++ b/src/pcm/PcmChannels.cxx
@@ -23,7 +23,6 @@
 #include "Silence.hxx"
 #include "Traits.hxx"
 #include "util/ConstBuffer.hxx"
-#include "util/WritableBuffer.hxx"
 
 #include <array>
 #include <algorithm>
@@ -109,7 +108,7 @@ StereoToN(typename Traits::pointer dest,
 	assert((end - src) % 2 == 0);
 
 	std::array<typename Traits::value_type, MAX_CHANNELS - 2> silence;
-	PcmSilence({&silence.front(), sizeof(silence)}, F);
+	PcmSilence(std::as_writable_bytes(std::span{silence}), F);
 
 	while (src != end) {
 		/* copy left/right to front-left/front-right, which is
diff --git a/src/pcm/Silence.cxx b/src/pcm/Silence.cxx
index 7c7395bb6..de17f7dd0 100644
--- a/src/pcm/Silence.cxx
+++ b/src/pcm/Silence.cxx
@@ -20,16 +20,15 @@
 #include "Silence.hxx"
 #include "Traits.hxx"
 #include "SampleFormat.hxx"
-#include "util/WritableBuffer.hxx"
 
-#include <string.h>
+#include <algorithm>
 
 void
-PcmSilence(WritableBuffer<void> dest, SampleFormat format) noexcept
+PcmSilence(std::span<std::byte> dest, SampleFormat format) noexcept
 {
-	uint8_t pattern = 0;
+	std::byte pattern{0};
 	if (format == SampleFormat::DSD)
-		pattern = SampleTraits<SampleFormat::DSD>::SILENCE;
+		pattern = std::byte{SampleTraits<SampleFormat::DSD>::SILENCE};
 
-	memset(dest.data, pattern, dest.size);
+	std::fill(dest.begin(), dest.end(), pattern);
 }
diff --git a/src/pcm/Silence.hxx b/src/pcm/Silence.hxx
index 7e3ef6743..1e9f68bd0 100644
--- a/src/pcm/Silence.hxx
+++ b/src/pcm/Silence.hxx
@@ -20,15 +20,16 @@
 #ifndef MPD_PCM_SILENCE_HXX
 #define MPD_PCM_SILENCE_HXX
 
+#include <cstddef>
 #include <cstdint>
+#include <span>
 
-template<typename T> struct WritableBuffer;
 enum class SampleFormat : uint8_t;
 
 /**
  * Fill the given buffer with the format-specific silence pattern.
  */
 void
-PcmSilence(WritableBuffer<void> dest, SampleFormat format) noexcept;
+PcmSilence(std::span<std::byte> dest, SampleFormat format) noexcept;
 
 #endif
diff --git a/src/pcm/Volume.cxx b/src/pcm/Volume.cxx
index c0183cdc3..415ac3ec4 100644
--- a/src/pcm/Volume.cxx
+++ b/src/pcm/Volume.cxx
@@ -21,7 +21,6 @@
 #include "Silence.hxx"
 #include "Traits.hxx"
 #include "util/ConstBuffer.hxx"
-#include "util/WritableBuffer.hxx"
 #include "util/RuntimeError.hxx"
 #include "util/TransformN.hxx"
 
@@ -204,7 +203,8 @@ PcmVolume::Apply(ConstBuffer<void> src) noexcept
 
 	if (volume == 0) {
 		/* optimized special case: 0% volume = memset(0) */
-		PcmSilence({data, dest_size}, format);
+		PcmSilence(std::span{(std::byte *)data, dest_size},
+			   format);
 		return { data, dest_size };
 	}