input/Icy: manage the parser in a std::shared_ptr

This resolves the circular dependency between IcyInputStream and
CurlInputStream.

src/input/IcyInputStream.cxx

@@ -19,15 +19,25 @@
 
 #include "config.h"
 #include "IcyInputStream.hxx"
+#include "IcyMetaDataParser.hxx"
 #include "tag/Tag.hxx"
 
-IcyInputStream::IcyInputStream(InputStream *_input) noexcept
-	:ProxyInputStream(_input)
+IcyInputStream::IcyInputStream(InputStream *_input,
+			       std::shared_ptr<IcyMetaDataParser> _parser) noexcept
+	:ProxyInputStream(_input), parser(std::move(_parser))
 {
 }
 
 IcyInputStream::~IcyInputStream() noexcept = default;
 
+inline bool
+IcyInputStream::IsEnabled() const noexcept
+{
+	assert(parser);
+
+	return parser->IsDefined();
+}
+
 void
 IcyInputStream::Update() noexcept
 {
@@ -48,7 +58,7 @@ IcyInputStream::ReadTag()
 	if (new_input_tag != nullptr)
 		input_tag = std::move(new_input_tag);
 
-	auto new_icy_tag = parser.ReadTag();
+	auto new_icy_tag = parser->ReadTag();
 	const bool had_new_icy_tag = !!new_icy_tag;
 	if (new_icy_tag != nullptr)
 		icy_tag = std::move(new_icy_tag);
@@ -81,7 +91,7 @@ IcyInputStream::Read(void *ptr, size_t read_size)
 		if (nbytes == 0)
 			return 0;
 
-		size_t result = parser.ParseInPlace(ptr, nbytes);
+		size_t result = parser->ParseInPlace(ptr, nbytes);
 		if (result > 0) {
 			override_offset += result;
 			offset = override_offset;

src/input/IcyInputStream.hxx

@@ -21,18 +21,18 @@
 #define MPD_ICY_INPUT_STREAM_HXX
 
 #include "ProxyInputStream.hxx"
-#include "IcyMetaDataParser.hxx"
 #include "Compiler.h"
 
 #include <memory>
 
 struct Tag;
+class IcyMetaDataParser;
 
 /**
  * An #InputStream filter that parses Icy metadata.
  */
 class IcyInputStream final : public ProxyInputStream {
-	IcyMetaDataParser parser;
+	std::shared_ptr<IcyMetaDataParser> parser;
 
 	/**
 	 * The #Tag object ready to be requested via ReadTag().
@@ -47,19 +47,21 @@ class IcyInputStream final : public ProxyInputStream {
 	offset_type override_offset = 0;
 
 public:
-	IcyInputStream(InputStream *_input) noexcept;
+	/**
+	 * @param _parser a IcyMetaDataParser instance which is shared
+	 * with our input; it needs to be shared because our input
+	 * needs to feed parameters (e.g. from the "icy-metaint"
+	 * header) into it
+	 */
+	IcyInputStream(InputStream *_input,
+		       std::shared_ptr<IcyMetaDataParser> _parser) noexcept;
 	virtual ~IcyInputStream() noexcept;
 
 	IcyInputStream(const IcyInputStream &) = delete;
 	IcyInputStream &operator=(const IcyInputStream &) = delete;
 
-	void Enable(size_t _data_size) noexcept {
-		parser.Start(_data_size);
-	}
-
-	bool IsEnabled() const noexcept {
-		return parser.IsDefined();
-	}
+	gcc_pure
+	bool IsEnabled() const noexcept;
 
 	/* virtual methods from InputStream */
 	void Update() noexcept override;

src/input/plugins/CurlInputPlugin.cxx

@@ -27,6 +27,7 @@
 #include "lib/curl/Slist.hxx"
 #include "../AsyncInputStream.hxx"
 #include "../IcyInputStream.hxx"
+#include "IcyMetaDataParser.hxx"
 #include "../InputPlugin.hxx"
 #include "config/ConfigGlobal.hxx"
 #include "config/Block.hxx"
@@ -72,14 +73,14 @@ struct CurlInputStream final : public AsyncInputStream, CurlResponseHandler {
 	CurlRequest *request = nullptr;
 
 	/** parser for icy-metadata */
-	IcyInputStream *icy;
+	std::shared_ptr<IcyMetaDataParser> icy;
 
 	CurlInputStream(EventLoop &event_loop, const char *_url,
 			Mutex &_mutex, Cond &_cond)
 		:AsyncInputStream(event_loop, _url, _mutex, _cond,
 				  CURL_MAX_BUFFERED,
 				  CURL_RESUME_AT),
-		 icy(new IcyInputStream(this)) {
+		 icy(new IcyMetaDataParser()) {
 	}
 
 	~CurlInputStream();
@@ -199,7 +200,7 @@ CurlInputStream::OnHeaders(unsigned status,
 		return;
 	}
 
-	if (!icy->IsEnabled() &&
+	if (!icy->IsDefined() &&
 	    headers.find("accept-ranges") != headers.end())
 		/* a stream with icy-metadata is not seekable */
 		seekable = true;
@@ -226,7 +227,7 @@ CurlInputStream::OnHeaders(unsigned status,
 		SetTag(tag_builder.CommitNew());
 	}
 
-	if (!icy->IsEnabled()) {
+	if (!icy->IsDefined()) {
 		i = headers.find("icy-metaint");
 
 		if (i != headers.end()) {
@@ -237,7 +238,7 @@ CurlInputStream::OnHeaders(unsigned status,
 #endif
 
 			if (icy_metaint > 0) {
-				icy->Enable(icy_metaint);
+				icy->Start(icy_metaint);
 
 				/* a stream with icy-metadata is not
 				   seekable */
@@ -450,7 +451,8 @@ CurlInputStream::Open(const char *url, Mutex &mutex, Cond &cond)
 		throw;
 	}
 
-	return c->icy;
+	auto icy = c->icy;
+	return new IcyInputStream(c, std::move(icy));
 }
 
 static InputStream *