encoder/Interface: move instance methods to abstract class

Rename struct Encoder to PreparedEncoder, and add a new (abstract)
class Encoder which represents one encoder instance.

src/output/plugins/RecorderOutputPlugin.cxx

@@ -47,7 +47,8 @@ class RecorderOutput {
 	/**
 	 * The configured encoder plugin.
 	 */
-	Encoder *encoder = nullptr;
+	PreparedEncoder *prepared_encoder = nullptr;
+	Encoder *encoder;
 
 	/**
 	 * The destination file name.
@@ -75,8 +76,8 @@ class RecorderOutput {
 		:base(recorder_output_plugin) {}
 
 	~RecorderOutput() {
-		if (encoder != nullptr)
-			encoder->Dispose();
+		if (prepared_encoder != nullptr)
+			prepared_encoder->Dispose();
 	}
 
 	bool Initialize(const ConfigBlock &block, Error &error_r) {
@@ -148,8 +149,8 @@ RecorderOutput::Configure(const ConfigBlock &block, Error &error)
 
 	/* initialize encoder */
 
-	encoder = encoder_init(*encoder_plugin, block, error);
-	if (encoder == nullptr)
+	prepared_encoder = encoder_init(*encoder_plugin, block, error);
+	if (prepared_encoder == nullptr)
 		return false;
 
 	return true;
@@ -205,7 +206,8 @@ RecorderOutput::Open(AudioFormat &audio_format, Error &error)
 
 	/* open the encoder */
 
-	if (!encoder->Open(audio_format, error)) {
+	encoder = prepared_encoder->Open(audio_format, error);
+	if (encoder == nullptr) {
 		delete file;
 		return false;
 	}
@@ -214,7 +216,7 @@ RecorderOutput::Open(AudioFormat &audio_format, Error &error)
 		try {
 			EncoderToFile();
 		} catch (const std::exception &e) {
-			encoder->Close();
+			delete encoder;
 			error.Set(recorder_domain, e.what());
 			return false;
 		}
@@ -224,7 +226,7 @@ RecorderOutput::Open(AudioFormat &audio_format, Error &error)
 
 		/* close the encoder for now; it will be opened as
 		   soon as we have received a tag */
-		encoder->Close();
+		delete encoder;
 	}
 
 	return true;
@@ -237,19 +239,19 @@ RecorderOutput::Commit(Error &error)
 
 	/* flush the encoder and write the rest to the file */
 
-	bool success = encoder_end(encoder, error);
+	bool success = encoder->End(error);
 	if (success) {
 		try {
 			EncoderToFile();
 		} catch (...) {
-			encoder->Close();
+			delete encoder;
 			throw;
 		}
 	}
 
 	/* now really close everything */
 
-	encoder->Close();
+	delete encoder;
 
 	if (success) {
 		try {
@@ -326,7 +328,8 @@ RecorderOutput::ReopenFormat(AllocatedPath &&new_path, Error &error)
 	}
 
 	AudioFormat new_audio_format = effective_audio_format;
-	if (!encoder->Open(new_audio_format, error)) {
+	encoder = prepared_encoder->Open(new_audio_format, error);
+	if (encoder == nullptr) {
 		delete new_file;
 		return false;
 	}
@@ -338,7 +341,7 @@ RecorderOutput::ReopenFormat(AllocatedPath &&new_path, Error &error)
 	try {
 		EncoderToOutputStream(*new_file, *encoder);
 	} catch (const std::exception &e) {
-		encoder->Close();
+		delete encoder;
 		delete new_file;
 		error.Set(recorder_domain, e.what());
 		return false;
@@ -386,7 +389,7 @@ RecorderOutput::SendTag(const Tag &tag)
 	}
 
 	Error error;
-	if (!encoder_pre_tag(encoder, error)) {
+	if (!encoder->PreTag(error)) {
 		LogError(error);
 		return;
 	}
@@ -398,7 +401,7 @@ RecorderOutput::SendTag(const Tag &tag)
 		return;
 	}
 
-	if (!encoder_tag(encoder, tag, error))
+	if (!encoder->SendTag(tag, error))
 		LogError(error);
 }
 
@@ -413,7 +416,7 @@ RecorderOutput::Play(const void *chunk, size_t size, Error &error)
 		return size;
 	}
 
-	if (!encoder_write(encoder, chunk, size, error))
+	if (!encoder->Write(chunk, size, error))
 		return 0;
 
 	try {

src/output/plugins/ShoutOutputPlugin.cxx

@@ -45,7 +45,8 @@ struct ShoutOutput final {
 	shout_t *shout_conn;
 	shout_metadata_t *shout_meta;
 
-	Encoder *encoder = nullptr;
+	PreparedEncoder *prepared_encoder = nullptr;
+	Encoder *encoder;
 
 	float quality = -2.0;
 	int bitrate = -1;
@@ -93,8 +94,7 @@ ShoutOutput::~ShoutOutput()
 	if (shout_init_count == 0)
 		shout_shutdown();
 
-	if (encoder != nullptr)
-		encoder->Dispose();
+	delete prepared_encoder;
 }
 
 static const EncoderPlugin *
@@ -192,8 +192,8 @@ ShoutOutput::Configure(const ConfigBlock &block, Error &error)
 		return false;
 	}
 
-	encoder = encoder_init(*encoder_plugin, block, error);
-	if (encoder == nullptr)
+	prepared_encoder = encoder_init(*encoder_plugin, block, error);
+	if (prepared_encoder == nullptr)
 		return false;
 
 	unsigned shout_format;
@@ -345,8 +345,8 @@ write_page(ShoutOutput *sd, Error &error)
 	assert(sd->encoder != nullptr);
 
 	while (true) {
-		size_t nbytes = encoder_read(sd->encoder,
-					     sd->buffer, sizeof(sd->buffer));
+		size_t nbytes = sd->encoder->Read(sd->buffer,
+						  sizeof(sd->buffer));
 		if (nbytes == 0)
 			return true;
 
@@ -362,10 +362,10 @@ void
 ShoutOutput::Close()
 {
 	if (encoder != nullptr) {
-		if (encoder_end(encoder, IgnoreError()))
+		if (encoder->End(IgnoreError()))
 			write_page(this, IgnoreError());
 
-		encoder->Close();
+		delete encoder;
 	}
 
 	if (shout_get_connected(shout_conn) != SHOUTERR_UNCONNECTED &&
@@ -406,13 +406,14 @@ ShoutOutput::Open(AudioFormat &audio_format, Error &error)
 	if (!shout_connect(this, error))
 		return false;
 
-	if (!encoder->Open(audio_format, error)) {
+	encoder = prepared_encoder->Open(audio_format, error);
+	if (encoder == nullptr) {
 		shout_close(shout_conn);
 		return false;
 	}
 
 	if (!write_page(this, error)) {
-		encoder->Close();
+		delete encoder;
 		shout_close(shout_conn);
 		return false;
 	}
@@ -433,7 +434,7 @@ ShoutOutput::Delay() const
 size_t
 ShoutOutput::Play(const void *chunk, size_t size, Error &error)
 {
-	return encoder_write(encoder, chunk, size, error) &&
+	return encoder->Write(chunk, size, error) &&
 		write_page(this, error)
 		? size
 		: 0;
@@ -476,13 +477,13 @@ shout_tag_to_metadata(const Tag &tag, char *dest, size_t size)
 void
 ShoutOutput::SendTag(const Tag &tag)
 {
-	if (encoder->plugin.tag != nullptr) {
+	if (encoder->ImplementsTag()) {
 		/* encoder plugin supports stream tags */
 
 		Error error;
-		if (!encoder_pre_tag(encoder, error) ||
+		if (!encoder->PreTag(error) ||
 		    !write_page(this, error) ||
-		    !encoder_tag(encoder, tag, error)) {
+		    !encoder->SendTag(tag, error)) {
 			LogError(error);
 			return;
 		}

src/output/plugins/httpd/HttpdInternal.hxx

@@ -45,7 +45,8 @@ class EventLoop;
 class ServerSocket;
 class HttpdClient;
 class Page;
-struct Encoder;
+struct PreparedEncoder;
+class Encoder;
 struct Tag;
 
 class HttpdOutput final : ServerSocket, DeferredMonitor {
@@ -60,6 +61,7 @@ class HttpdOutput final : ServerSocket, DeferredMonitor {
 	/**
 	 * The configured encoder plugin.
 	 */
+	PreparedEncoder *prepared_encoder = nullptr;
 	Encoder *encoder;
 
 	/**

src/output/plugins/httpd/HttpdOutputPlugin.cxx

@@ -63,8 +63,8 @@ HttpdOutput::~HttpdOutput()
 	if (metadata != nullptr)
 		metadata->Unref();
 
-	if (encoder != nullptr)
-		encoder->Dispose();
+	if (prepared_encoder != nullptr)
+		prepared_encoder->Dispose();
 
 }
 
@@ -123,12 +123,12 @@ HttpdOutput::Configure(const ConfigBlock &block, Error &error)
 
 	/* initialize encoder */
 
-	encoder = encoder_init(*encoder_plugin, block, error);
-	if (encoder == nullptr)
+	prepared_encoder = encoder_init(*encoder_plugin, block, error);
+	if (prepared_encoder == nullptr)
 		return false;
 
 	/* determine content type */
-	content_type = encoder_get_mime_type(encoder);
+	content_type = encoder_get_mime_type(prepared_encoder);
 	if (content_type == nullptr)
 		content_type = "application/octet-stream";
 
@@ -169,7 +169,7 @@ inline void
 HttpdOutput::AddClient(int fd)
 {
 	auto *client = new HttpdClient(*this, fd, GetEventLoop(),
-				       encoder->plugin.tag == nullptr);
+				       !encoder->ImplementsTag());
 	clients.push_front(*client);
 
 	/* pass metadata to client */
@@ -250,15 +250,14 @@ HttpdOutput::ReadPage()
 		/* we have fed a lot of input into the encoder, but it
 		   didn't give anything back yet - flush now to avoid
 		   buffer underruns */
-		encoder_flush(encoder, IgnoreError());
+		encoder->Flush(IgnoreError());
 		unflushed_input = 0;
 	}
 
 	size_t size = 0;
 	do {
-		size_t nbytes = encoder_read(encoder,
-					     buffer + size,
-					     sizeof(buffer) - size);
+		size_t nbytes = encoder->Read(buffer + size,
+					      sizeof(buffer) - size);
 		if (nbytes == 0)
 			break;
 
@@ -292,7 +291,8 @@ httpd_output_disable(AudioOutput *ao)
 inline bool
 HttpdOutput::OpenEncoder(AudioFormat &audio_format, Error &error)
 {
-	if (!encoder->Open(audio_format, error))
+	encoder = prepared_encoder->Open(audio_format, error);
+	if (encoder == nullptr)
 		return false;
 
 	/* we have to remember the encoder header, i.e. the first
@@ -351,7 +351,7 @@ HttpdOutput::Close()
 	if (header != nullptr)
 		header->Unref();
 
-	encoder->Close();
+	delete encoder;
 }
 
 static void
@@ -441,7 +441,7 @@ HttpdOutput::BroadcastFromEncoder()
 inline bool
 HttpdOutput::EncodeAndPlay(const void *chunk, size_t size, Error &error)
 {
-	if (!encoder_write(encoder, chunk, size, error))
+	if (!encoder->Write(chunk, size, error))
 		return false;
 
 	unflushed_input += size;
@@ -491,18 +491,18 @@ httpd_output_pause(AudioOutput *ao)
 inline void
 HttpdOutput::SendTag(const Tag &tag)
 {
-	if (encoder->plugin.tag != nullptr) {
+	if (encoder->ImplementsTag()) {
 		/* embed encoder tags */
 
 		/* flush the current stream, and end it */
 
-		encoder_pre_tag(encoder, IgnoreError());
+		encoder->PreTag(IgnoreError());
 		BroadcastFromEncoder();
 
 		/* send the tag to the encoder - which starts a new
 		   stream now */
 
-		encoder_tag(encoder, tag, IgnoreError());
+		encoder->SendTag(tag, IgnoreError());
 
 		/* the first page generated by the encoder will now be
 		   used as the new "header" page, which is sent to all