add RageSoundReader::RetriedRead

stepmania/src/RageSoundReader.cpp

@@ -1,9 +1,39 @@
 #include "global.h"
 #include "RageSoundReader.h"
+#include "RageLog.h"
 #include "RageUtil_AutoPtr.h"
 
 REGISTER_CLASS_TRAITS( RageSoundReader, pCopy->Copy() );
 
+/* Read(), handling the empty return case. */
+int RageSoundReader::RetriedRead( char *pBuffer, int iFrames, int *iSourceFrame, float *fRate )
+{
+	if( iFrames == 0 )
+		return 0;
+
+	/* pReader may return 0, which means "try again immediately".  As a failsafe,
+	 * only try this a finite number of times.  Use a high number, because in
+	 * principle each filter in the stack may cause this. */
+	int iTries = 100;
+	while( --iTries )
+	{
+		if( fRate )
+			*fRate = this->GetStreamToSourceRatio();
+		if( iSourceFrame )
+			*iSourceFrame = this->GetNextSourceFrame();
+
+		int iGotFrames = this->Read( pBuffer, iFrames );
+
+		if( iGotFrames != 0 )
+			return iGotFrames;
+	}
+
+	LOG->Warn( "Read() busy looping" );
+
+	/* Pretend we got EOF. */
+	return RageSoundReader::END_OF_FILE;
+}
+
 /*
  * Copyright (c) 2006 Glenn Maynard
  * All rights reserved.

stepmania/src/RageSoundReader.h

@@ -32,6 +32,7 @@ public:
 	virtual float GetStreamToSourceRatio() const = 0;
 
 	RString GetError() const { return m_sError; }
+	int RetriedRead( char *pBuffer, int iFrames, int *iSourceFrame = NULL, float *fRate = NULL );
 
 protected:
 	void SetError( RString sError ) const { m_sError = sError; }