input/Plugin: migrate open() from class Error to C++ exceptions

src/decoder/DecoderAPI.cxx

@@ -258,7 +258,7 @@ void decoder_seek_error(Decoder & decoder)
 }
 
 InputStreamPtr
-decoder_open_uri(Decoder &decoder, const char *uri, Error &error)
+decoder_open_uri(Decoder &decoder, const char *uri)
 {
 	assert(decoder.dc.state == DecoderState::START ||
 	       decoder.dc.state == DecoderState::DECODE);
@@ -267,9 +267,7 @@ decoder_open_uri(Decoder &decoder, const char *uri, Error &error)
 	Mutex &mutex = dc.mutex;
 	Cond &cond = dc.cond;
 
-	auto is = InputStream::Open(uri, mutex, cond, error);
-	if (!is)
-		return nullptr;
+	auto is = InputStream::Open(uri, mutex, cond);
 
 	const ScopeLock lock(mutex);
 	while (true) {

src/decoder/DecoderAPI.hxx

@@ -121,11 +121,12 @@ decoder_seek_error(Decoder &decoder);
 
 /**
  * Open a new #InputStream and wait until it's ready.  Can get
- * cancelled by DecoderCommand::STOP (returns nullptr without setting
- * #Error).
+ * cancelled by DecoderCommand::STOP (returns nullptr).
+ *
+ * Throws std::runtime_error on error.
  */
 InputStreamPtr
-decoder_open_uri(Decoder &decoder, const char *uri, Error &error);
+decoder_open_uri(Decoder &decoder, const char *uri);
 
 /**
  * Blocking read from the input stream.

src/decoder/DecoderThread.cxx

@@ -56,10 +56,7 @@ static constexpr Domain decoder_thread_domain("decoder_thread");
 static InputStreamPtr
 decoder_input_stream_open(DecoderControl &dc, const char *uri)
 {
-	Error error;
-	auto is = InputStream::Open(uri, dc.mutex, dc.cond, error);
-	if (is == nullptr)
-		throw error;
+	auto is = InputStream::Open(uri, dc.mutex, dc.cond);
 
 	/* wait for the input stream to become ready; its metadata
 	   will be available then */
@@ -76,6 +73,7 @@ decoder_input_stream_open(DecoderControl &dc, const char *uri)
 		is->Update();
 	}
 
+	Error error;
 	if (!is->Check(error))
 		throw error;
 
@@ -85,10 +83,7 @@ decoder_input_stream_open(DecoderControl &dc, const char *uri)
 static InputStreamPtr
 decoder_input_stream_open(DecoderControl &dc, Path path)
 {
-	Error error;
-	auto is = OpenLocalInputStream(path, dc.mutex, dc.cond, error);
-	if (is == nullptr)
-		throw error;
+	auto is = OpenLocalInputStream(path, dc.mutex, dc.cond);
 
 	assert(is->IsReady());
 

src/decoder/plugins/WavpackDecoderPlugin.cxx

@@ -34,6 +34,8 @@
 
 #include <wavpack/wavpack.h>
 
+#include <stdexcept>
+
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -490,7 +492,11 @@ wavpack_open_wvc(Decoder &decoder, const char *uri)
 		free(wvc_url);
 	};
 
-	return decoder_open_uri(decoder, uri, IgnoreError());
+	try {
+		return decoder_open_uri(decoder, uri);
+	} catch (const std::runtime_error &) {
+		return nullptr;
+	}
 }
 
 /*