pcm/PcmConvert: eliminate Open() and Close()

Let the constructor and destructor do this.  This means that all users
have to be converted to allocate PcmConvert dynamically.

src/lib/chromaprint/DecoderClient.cxx

@@ -18,17 +18,21 @@
  */
 
 #include "DecoderClient.hxx"
+#include "pcm/PcmConvert.hxx"
 #include "input/InputStream.hxx"
 #include "util/ConstBuffer.hxx"
 
+ChromaprintDecoderClient::ChromaprintDecoderClient() = default;
+ChromaprintDecoderClient::~ChromaprintDecoderClient() noexcept = default;
+
 void
 ChromaprintDecoderClient::PrintResult()
 {
 	if (!ready)
 		throw std::runtime_error("Decoding failed");
 
-	if (need_convert) {
-		auto flushed = convert.Flush();
+	if (convert) {
+		auto flushed = convert->Flush();
 		auto data = ConstBuffer<int16_t>::FromVoid(flushed);
 		chromaprint.Feed(data.data, data.size);
 	}
@@ -48,8 +52,8 @@ ChromaprintDecoderClient::Ready(AudioFormat audio_format, bool, SignedSongTime)
 		const AudioFormat src_audio_format = audio_format;
 		audio_format.format = SampleFormat::S16;
 
-		convert.Open(src_audio_format, audio_format);
-		need_convert = true;
+		convert = std::make_unique<PcmConvert>(src_audio_format,
+						       audio_format);
 	}
 
 	chromaprint.Start(audio_format.sample_rate, audio_format.channels);
@@ -70,8 +74,8 @@ ChromaprintDecoderClient::SubmitData(InputStream *,
 	ConstBuffer<void> src{_data, length};
 	ConstBuffer<int16_t> data;
 
-	if (need_convert) {
-		auto result = convert.Convert(src);
+	if (convert) {
+		auto result = convert->Convert(src);
 		data = ConstBuffer<int16_t>::FromVoid(result);
 	} else
 		data = ConstBuffer<int16_t>::FromVoid(src);

src/lib/chromaprint/DecoderClient.hxx

@@ -22,17 +22,18 @@
 
 #include "Context.hxx"
 #include "decoder/Client.hxx"
-#include "pcm/PcmConvert.hxx"
 #include "thread/Mutex.hxx"
 
+#include <memory>
+
 #include <stdint.h>
 
+class PcmConvert;
+
 class ChromaprintDecoderClient : public DecoderClient {
 	bool ready = false;
 
-	bool need_convert = false;
-
-	PcmConvert convert;
+	std::unique_ptr<PcmConvert> convert;
 
 	Chromaprint::Context chromaprint;
 
@@ -41,10 +42,8 @@ class ChromaprintDecoderClient : public DecoderClient {
 public:
 	Mutex mutex;
 
-	~ChromaprintDecoderClient() noexcept {
-		if (need_convert)
-			convert.Close();
-	}
+	ChromaprintDecoderClient();
+	~ChromaprintDecoderClient() noexcept;
 
 	void PrintResult();