add a pure virtual FileSource::close() method so that FileSource::set_path() can ensure we no longer have a handle open

libs/ardour/ardour/coreaudiosource.h

@@ -48,6 +48,7 @@ class LIBARDOUR_API CoreAudioSource : public AudioFileSource {
 	static int get_soundfile_info (string path, SoundFileInfo& _info, string& error_msg);
 
   protected:
+	void close ();
 	framecnt_t read_unlocked (Sample *dst, framepos_t start, framecnt_t cnt) const;
 	framecnt_t write_unlocked (Sample *, framecnt_t) { return 0; }
 

libs/ardour/ardour/file_source.h

@@ -89,9 +89,9 @@ public:
 	 */
 	int rename (const std::string& name);
 
-	virtual void release_descriptor () {}
+	virtual void close () = 0;
 
-protected:
+  protected:
 	FileSource (Session& session, DataType type,
 	            const std::string& path,
 	            const std::string& origin,

libs/ardour/ardour/silentfilesource.h

@@ -40,6 +40,7 @@ public:
 	bool clamped_at_unity() const { return false; }
 
 protected:
+	void close() {}
 	friend class SourceFactory;
 
 	SilentFileSource (Session& s, const XMLNode& x, framecnt_t len, float srate)

libs/ardour/ardour/smf_source.h

@@ -72,6 +72,7 @@ public:
 	void prevent_deletion ();
 
   protected:
+	void close ();
 	void set_path (const std::string& newpath);
 	void flush_midi (const Lock& lock);
 

libs/ardour/ardour/sndfilesource.h

@@ -75,6 +75,8 @@ class LIBARDOUR_API SndFileSource : public AudioFileSource {
 	static int get_soundfile_info (const std::string& path, SoundFileInfo& _info, std::string& error_msg);
 
   protected:
+	void close ();
+
 	void set_path (const std::string& p);
 	void set_header_timeline_position ();
 

libs/ardour/ardour/srcfilesource.h

@@ -52,6 +52,7 @@ public:
 	bool clamped_at_unity() const { return false; }
 
 protected:
+	void close ();
 	framecnt_t read_unlocked (Sample *dst, framepos_t start, framecnt_t cnt) const;
 	framecnt_t write_unlocked (Sample */*dst*/, framecnt_t /*cnt*/) { return 0; }
 

libs/ardour/coreaudiosource.cc

@@ -104,6 +104,12 @@ CoreAudioSource::~CoreAudioSource ()
 {
 }
 
+void
+CoreAudioSource::close ()
+{
+	af.Close ();
+}
+
 int
 CoreAudioSource::safe_read (Sample* dst, framepos_t start, framecnt_t cnt, AudioBufferList& abl) const
 {

libs/ardour/file_source.cc

@@ -544,6 +544,7 @@ FileSource::set_within_session_from_path (const std::string& path)
 void
 FileSource::set_path (const std::string& newpath)
 {
+	close ();
         _path = newpath;
 	set_within_session_from_path (newpath);
 	if (_within_session) {

libs/ardour/smf_source.cc

@@ -202,6 +202,12 @@ SMFSource::open_for_write ()
 	return 0;
 }
 
+void
+SMFSource::close ()
+{
+	/* nothing to do: file descriptor is never kept open */
+}
+
 /** All stamps in audio frames */
 framecnt_t
 SMFSource::read_unlocked (const Lock&                    lock,

libs/ardour/sndfilesource.cc

@@ -180,7 +180,7 @@ SndFileSource::SndFileSource (Session& s, const string& path, const string& orig
 			throw failed_constructor();
 		}
 	} else {
-		/* normal mode: do not open the file here - do that in write_unlocked() as needed
+		/* normal mode: do not open the file here - do that in {read,write}_unlocked() as needed
 		 */
 	}
 }
@@ -230,6 +230,15 @@ SndFileSource::init_sndfile ()
 	AudioFileSource::HeaderPositionOffsetChanged.connect_same_thread (header_position_connection, boost::bind (&SndFileSource::handle_header_position_change, this));
 }
 
+void
+SndFileSource::close ()
+{
+	if (_sndfile) {
+		sf_close (_sndfile);
+		_sndfile = 0;
+	}
+}
+
 int
 SndFileSource::open ()
 {
@@ -334,10 +343,7 @@ SndFileSource::open ()
 
 SndFileSource::~SndFileSource ()
 {
-	if (_sndfile) {
-		sf_close (_sndfile);
-		_sndfile = 0;
-	}
+	close ();
 	delete _broadcast_info;
 	delete [] xfade_buf;
 }
@@ -364,10 +370,10 @@ SndFileSource::read_unlocked (Sample *dst, framepos_t start, framecnt_t cnt) con
                 return cnt;
         }
 
-	if (_sndfile == 0) {
-		error << string_compose (_("could not allocate file %1 for reading."), _path) << endmsg;
+        if (const_cast<SndFileSource*>(this)->open()) {
+		error << string_compose (_("could not open file %1 for reading."), _path) << endmsg;
 		return 0;
-	}
+        }
 
 	if (start > _length) {
 

libs/ardour/srcfilesource.cc

@@ -84,6 +84,15 @@ SrcFileSource::~SrcFileSource ()
 	delete [] _src_buffer;
 }
 
+void
+SrcFileSource::close ()
+{
+	boost::shared_ptr<FileSource> fs = boost::dynamic_pointer_cast<FileSource> (_source);
+	if (fs) {
+		fs->close ();
+	}
+}
+
 framecnt_t
 SrcFileSource::read_unlocked (Sample *dst, framepos_t start, framecnt_t cnt) const
 {