input/Stream: remove attribute "cond", replace with handler interface

This adds a bit of overhead, but also adds flexibility to the API,
because arbitrary triggers may be invoked from that virtual method
implementation, not just Cond::signal().

The motivation for this is to make the handlers more dynamic, for the
upcoming buffering class utilizing ProxyInputStream.

src/decoder/Bridge.cxx

@@ -370,7 +370,8 @@ DecoderBridge::OpenUri(const char *uri)
 	Mutex &mutex = dc.mutex;
 	Cond &cond = dc.cond;
 
-	auto is = InputStream::Open(uri, mutex, cond);
+	auto is = InputStream::Open(uri, mutex);
+	is->SetHandler(&dc);
 
 	const std::lock_guard<Mutex> lock(mutex);
 	while (true) {
@@ -404,7 +405,7 @@ try {
 		if (is.IsAvailable())
 			break;
 
-		is.cond.wait(is.mutex);
+		dc.cond.wait(is.mutex);
 	}
 
 	size_t nbytes = is.Read(buffer, length);

src/decoder/DecoderControl.hxx

@@ -23,6 +23,7 @@
 #include "DecoderCommand.hxx"
 #include "AudioFormat.hxx"
 #include "MixRampInfo.hxx"
+#include "input/Handler.hxx"
 #include "thread/Mutex.hxx"
 #include "thread/Cond.hxx"
 #include "thread/Thread.hxx"
@@ -60,7 +61,7 @@ enum class DecoderState : uint8_t {
 	ERROR,
 };
 
-struct DecoderControl {
+struct DecoderControl final : InputStreamHandler {
 	/**
 	 * The handle of the decoder thread.
 	 */
@@ -422,6 +423,15 @@ public:
 
 private:
 	void RunThread() noexcept;
+
+	/* virtual methods from class InputStreamHandler */
+	void OnInputStreamReady() noexcept override {
+		cond.signal();
+	}
+
+	void OnInputStreamAvailable() noexcept override {
+		cond.signal();
+	}
 };
 
 #endif

src/decoder/DecoderThread.cxx

@@ -56,7 +56,8 @@ static constexpr Domain decoder_thread_domain("decoder_thread");
 static InputStreamPtr
 decoder_input_stream_open(DecoderControl &dc, const char *uri)
 {
-	auto is = InputStream::Open(uri, dc.mutex, dc.cond);
+	auto is = InputStream::Open(uri, dc.mutex);
+	is->SetHandler(&dc);
 
 	/* wait for the input stream to become ready; its metadata
 	   will be available then */
@@ -81,7 +82,7 @@ decoder_input_stream_open(DecoderControl &dc, const char *uri)
 static InputStreamPtr
 decoder_input_stream_open(DecoderControl &dc, Path path)
 {
-	auto is = OpenLocalInputStream(path, dc.mutex, dc.cond);
+	auto is = OpenLocalInputStream(path, dc.mutex);
 
 	assert(is->IsReady());