INI File - File Mapping

File Mapping

Initialization File Mapping creates a mapping between an INI file and the Registry. It was introduced with Windows NT and Windows 95 as a way to migrate from storing settings in classic .ini files to the new Windows Registry. File mapping traps the Profile API calls and, using settings from the IniFileMapping Registry section, directs reads and writes to appropriate places in the Registry.

Using the Example above, a string call could be made to fetch the name key from the owner section from a settings file called, say, dbsettings.ini. The returned value should be the string "John Doe":

GetPrivateProfileString("owner", "name", ..., "c:\\programs\\oldprogram\\dbsettings.ini");

INI mapping takes this Profile API call, ignores any path in the given filename and checks to see if there is a Registry key matching the filename under:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\
CurrentVersion\IniFileMapping

If this exists, it looks for an entry name matching the requested section. If an entry is found, INI mapping uses its value as a pointer to another part of the Registry. It then looks up the requested INI setting in that part of the Registry.

If no matching entry name is found and there is an entry under the (Default) entry name, INI mapping uses that instead. Thus each section name does not need its own entry.

HKEY_LOCAL_MACHINE\Software\...\IniFileMapping\dbsettings.ini
(Default)	@USR:Software\oldprogs\inisettings\all
database	USR:Software\oldprogs\inisettings\db

So, in this case the profile call for the section is mapped through to:

HKEY_CURRENT_USER\Software\oldprogs\inisettings\all
name	John Doe
organization	Acme Products

where the "name" Registry entry name is found to match the requested INI key. The value of "John Doe" is then returned to the Profile call. In this case, the @ prefix on the default prevents any reads from going to the dbsettings.ini file on disk. The result is that any settings not found in the Registry are not looked for in the INI file.

The "database" Registry entry does not have the @ prefix on the value; thus, for the section only, settings in the Registry are taken first followed by settings in the dbsettings.ini file on disk.