mpd-dbcreate/src/encoder/plugins/WaveEncoderPlugin.cxx

// SPDX-License-Identifier: GPL-2.0-or-later
// Copyright The Music Player Daemon Project

#include "WaveEncoderPlugin.hxx"
#include "../EncoderAPI.hxx"
#include "tag/RiffFormat.hxx"
#include "util/ByteOrder.hxx"
#include "util/DynamicFifoBuffer.hxx"

#include <cassert>

#include <string.h>

class WaveEncoder final : public Encoder {
	unsigned bits;

	DynamicFifoBuffer<std::byte> buffer{8192};

public:
	explicit WaveEncoder(AudioFormat &audio_format) noexcept;

	/* virtual methods from class Encoder */
	void Write(std::span<const std::byte> src) override;

	std::span<const std::byte> Read(std::span<std::byte> b) noexcept override {
		return b.first(buffer.Read(b.data(), b.size()));
	}
};

class PreparedWaveEncoder final : public PreparedEncoder {
	/* virtual methods from class PreparedEncoder */
	Encoder *Open(AudioFormat &audio_format) override {
		return new WaveEncoder(audio_format);
	}

	[[nodiscard]] const char *GetMimeType() const noexcept override {
		return "audio/wav";
	}
};

struct WaveHeader {
	RiffFileHeader file_header;
	RiffChunkHeader fmt_header;
	RiffFmtChunk fmt;
	RiffChunkHeader data_header;
};

static_assert(sizeof(WaveHeader) == 44);

static WaveHeader
MakeWaveHeader(int channels, int bits,
	       int freq, int block_size) noexcept
{
	WaveHeader header{};

	int data_size = 0x0FFFFFFF;

	/* constants */
	memcpy(header.file_header.id, "RIFF", 4);
	memcpy(header.file_header.format, "WAVE", 4);
	memcpy(header.fmt_header.id, "fmt ", 4);
	memcpy(header.data_header.id, "data", 4);

	/* wave format */
	header.fmt.tag = ToLE16(RiffFmtChunk::TAG_PCM);
	header.fmt.channels = ToLE16(channels);
	header.fmt.bits_per_sample = ToLE16(bits);
	header.fmt.sample_rate = ToLE32(freq);
	header.fmt.block_align = ToLE16(block_size);
	header.fmt.byte_rate = ToLE32(freq * block_size);

	/* chunk sizes (fake data length) */
	header.fmt_header.size = ToLE32(sizeof(header.fmt));
	header.data_header.size = ToLE32(data_size);
	header.file_header.size = ToLE32(4 +
					 sizeof(header.fmt_header) + sizeof(header.fmt) +
					 sizeof(header.data_header) + data_size);

	return header;
}

static PreparedEncoder *
wave_encoder_init([[maybe_unused]] const ConfigBlock &block)
{
	return new PreparedWaveEncoder();
}

WaveEncoder::WaveEncoder(AudioFormat &audio_format) noexcept
	:Encoder(false)
{
	assert(audio_format.IsValid());

	switch (audio_format.format) {
	case SampleFormat::S8:
		bits = 8;
		break;

	case SampleFormat::S16:
		bits = 16;
		break;

	case SampleFormat::S24_P32:
		bits = 24;
		break;

	case SampleFormat::S32:
		bits = 32;
		break;

	default:
		audio_format.format = SampleFormat::S16;
		bits = 16;
		break;
	}

	auto range = buffer.Write();
	assert(range.size() >= sizeof(WaveHeader));
	auto *header = (WaveHeader *)(void *)range.data();

	/* create PCM wave header in initial buffer */
	*header = MakeWaveHeader(audio_format.channels,
				 bits,
				 audio_format.sample_rate,
				 (bits / 8) * audio_format.channels);

	buffer.Append(sizeof(*header));
}

static size_t
pcm16_to_wave(uint16_t *dst16, const uint16_t *src16, size_t length)
{
	size_t cnt = length >> 1;
	while (cnt > 0) {
		*dst16++ = ToLE16(*src16++);
		cnt--;
	}
	return length;
}

static size_t
pcm32_to_wave(uint32_t *dst32, const uint32_t *src32, size_t length) noexcept
{
	size_t cnt = length >> 2;
	while (cnt > 0){
		*dst32++ = ToLE32(*src32++);
		cnt--;
	}
	return length;
}

static size_t
pcm24_to_wave(uint8_t *dst8, const uint32_t *src32, size_t length) noexcept
{
	uint32_t value;
	uint8_t *dst_old = dst8;

	length = length >> 2;
	while (length > 0){
		value = *src32++;
		*dst8++ = (value) & 0xFF;
		*dst8++ = (value >> 8) & 0xFF;
		*dst8++ = (value >> 16) & 0xFF;
		length--;
	}
	//correct buffer length
	return (dst8 - dst_old);
}

void
WaveEncoder::Write(std::span<const std::byte> src)
{
	std::size_t length = src.size();
	std::byte *dst = buffer.Write(length);

	if (IsLittleEndian()) {
		switch (bits) {
		case 8:
		case 16:
		case 32:// optimized cases
			memcpy(dst, src.data(), length);
			break;
		case 24:
			length = pcm24_to_wave((uint8_t *)dst,
					       (const uint32_t *)(const void *)src.data(),
					       length);
			break;
		}
	} else {
		switch (bits) {
		case 8:
			memcpy(dst, src.data(), length);
			break;
		case 16:
			length = pcm16_to_wave((uint16_t *)dst,
					       (const uint16_t *)(const void *)src.data(),
					       length);
			break;
		case 24:
			length = pcm24_to_wave((uint8_t *)dst,
					       (const uint32_t *)(const void *)src.data(),
					       length);
			break;
		case 32:
			length = pcm32_to_wave((uint32_t *)dst,
					       (const uint32_t *)(const void *)src.data(),
					       length);
			break;
		}
	}

	buffer.Append(length);
}

const EncoderPlugin wave_encoder_plugin = {
	"wave",
	wave_encoder_init,
};