Extract repeated code into trim_trailing_new_line() (!105)

Create function to replace repeated code which optionally removes
trailing new line character from a string.

Closes !105 - Update used btrfs file system commands, new minimum is
              btrfs-progs 4.5

include/Utils.h

@@ -170,6 +170,7 @@ public:
 	                                 , const Glib::ustring & pattern
 	                                 ) ;
 	static Glib::ustring trim( const Glib::ustring & src, const Glib::ustring & c = " \t\r\n" ) ;
+	static Glib::ustring trim_trailing_new_line(const Glib::ustring& src);
 	static Glib::ustring last_line( const Glib::ustring & src );
 	static Glib::ustring get_lang() ;
 	static void tokenize( const Glib::ustring& str,

src/DMRaid.cc

@@ -572,11 +572,8 @@ std::vector<Glib::ustring> DMRaid::lookup_dmraid_members(const Glib::ustring& ar
 	Glib::ustring error;
 	Utils::execute_command("udevadm info --query=name " + Glib::shell_quote(array),
 	                       output, error, true);
-
 	// Strip terminating new line from output.
-	size_t len = output.length();
-	if (len > 0 && output[len-1] == '\n')
-		output.resize(len-1);
+	output = Utils::trim_trailing_new_line(output);
 
 	if (output.empty())
 		return members;  // Empty vector

src/Dialog_Partition_Info.cc

@@ -105,13 +105,7 @@ Dialog_Partition_Info::Dialog_Partition_Info( const Partition & partition ) : pa
 			if ( concatenated_messages.size() > 0 )
 				concatenated_messages += "\n\n";
 
-			Glib::ustring::size_type take = messages[i].size();
-			if ( take > 0 )
-			{
-				if ( messages[i][take-1] == '\n' )
-					take -- ;  //Skip optional trailing new line
-				concatenated_messages += "<i>" + messages[i].substr( 0, take ) + "</i>";
-			}
+			concatenated_messages += "<i>" + Utils::trim_trailing_new_line(messages[i]) + "</i>";
 		}
 		Gtk::Box *vbox = manage(new Gtk::Box(Gtk::ORIENTATION_VERTICAL));
 		vbox ->set_border_width( 5 ) ;

src/FS_Info.cc

@@ -289,17 +289,12 @@ bool FS_Info::run_blkid_update_cache_one_label( FS_Entry & fs_entry )
 	if ( ! success )
 		return false;
 
-	size_t len = output.length();
-	if ( len > 0 && output[len-1] == '\n' )
-	{
-		// Output is either the label with a terminating new line or zero bytes
-		// when the file system has no label.  Strip optional trailing new line
-		// from blkid output.
-		output.resize( len-1 );
-	}
-	// Update cache entry with the read label.
+	// Output from blkid is either the label with a trailing new line character or
+	// zero bytes when the file system has no label.  Update the cache entry in both
+	// cases as the label was successfully read even if it didn't exist so is zero
+	// characters long.
 	fs_entry.have_label = true;
-	fs_entry.label = output;
+	fs_entry.label = Utils::trim_trailing_new_line(output);
 	return true;
 }
 

src/Utils.cc

@@ -809,6 +809,17 @@ Glib::ustring Utils::trim( const Glib::ustring & src, const Glib::ustring & c /*
 	return src.substr(p1, (p2-p1)+1);
 }
 
+
+// Return string with optional trailing new line character removed.
+Glib::ustring Utils::trim_trailing_new_line(const Glib::ustring& src)
+{
+	Glib::ustring::size_type len = src.length();
+	if (len > 0 && src[len-1] == '\n')
+		len --;
+	return src.substr(0, len);
+}
+
+
 // Return portion of string after the last carriage return character or
 // the whole string when there is no carriage return character.
 Glib::ustring Utils::last_line( const Glib::ustring & src )

src/btrfs.cc

@@ -357,12 +357,7 @@ void btrfs::read_label(Partition& partition)
 		return;
 	}
 
-	// Strip terminating new line from output.
-	size_t len = output.length();
-	if (len > 0 && output[len-1] == '\n')
-		output.resize(len-1);
-
-	partition.set_filesystem_label(output);
+	partition.set_filesystem_label(Utils::trim_trailing_new_line(output));
 }