New library for files

libraries/lib-files/FileException.h

@@ -0,0 +1,67 @@
+/*!
+  @file FileException.h
+  @brief MessageBoxException for failures of file operations
+  
+
+  Created by Paul Licameli on 11/22/16.
+
+*/
+
+#ifndef __AUDACITY_FILE_EXCEPTION__
+#define __AUDACITY_FILE_EXCEPTION__
+
+#include "AudacityException.h" // to inherit
+#include <wx/filename.h> // wxFileName member variable
+
+//! Thrown for failure of file or database operations in deeply nested places
+class FILES_API FileException /* not final */
+   : public MessageBoxException
+{
+public:
+   //! Identifies file operation that failed
+   enum class Cause {
+      Open,
+      Read,
+      Write, //!< most important to detect when storage space is exhausted
+      Rename //!< involves two filenames
+   };
+
+   explicit FileException(
+      Cause cause_, //!< What kind of file operation failed
+      const wxFileName &fileName_, //!< Which file suffered a failure
+      const TranslatableString &caption = XO("File Error"), //!< Shown in message box frame, not the main message
+      const wxFileName &renameTarget_ = {} //!< A second file name, only for renaming failure
+   )
+   // DV: We consider a FileException to be internal for now.
+   // We used to have some odd cases related to the read-only folder in 3.0.0,
+   // so it is good to have a full picture here.
+   // In case we see too many - we will tweak this behavior in the next release.
+   : MessageBoxException{ ExceptionType::Internal, caption }
+   , cause{ cause_ }, fileName{ fileName_ }, renameTarget{ renameTarget_ }
+   {}
+
+   FileException( const FileException &that )
+      : MessageBoxException( that )
+      , cause{ that.cause }
+      , fileName{ that.fileName }
+      , renameTarget{ that.renameTarget }
+   {}
+
+   FileException& operator= (FileException&&) = delete;
+
+   ~FileException() override;
+
+   static TranslatableString WriteFailureMessage(const wxFileName &fileName);
+
+protected:
+   //! %Format an error message appropriate for the @ref Cause.
+   TranslatableString ErrorMessage() const override;
+   wxString ErrorHelpUrl() const override;
+
+public:
+   Cause cause;
+   wxFileName fileName;
+   wxFileName renameTarget;
+};
+
+#endif