Check out the latest version of Routino: svn co http://routino.org/svn/trunk routino
Use SlimMapFile() and SlimUnmapFile() [see previous log message] and also use SlimFetch() instead of SeekReadFileUnbuffered() and SlimReplace() instead of SeekWriteFileUnbuffered() to hide the internals of the slim mode.
trunk/src/cache.h