SDL_mmap is a cross-platform memory abstraction library. Memory mapping is an elegant way to "load" files into memory without needing to allocate buffers.
The magic of virtual memory makes the mapped memory act like the file it is mapped from without having to physically hold the whole file in memory -- the parts you're using automatically are read in right as you use them, and discarded from memory when they expire from the OS' cache. Most modern operating systems, read, ones with virtual memory, support this; probably because it reduces memory and swap waste, and makes it makes it a hell of a lot easier to do basic things like loading programs and libraries.
So far SDL_mmap works under Microsoft Windows 95® through Microsoft Windows XP®, Microsoft Windows CE®, Linux®, Macintosh OSX©, and Sun SunOS/Solaris©.
It is licensed under the GNU Lesser General Public License.