Sfio, or Safe/Fast String/File I/O, is a C programming language I/O library developed by David Korn and Kiem-Phong Vo AT&T Labs Research, intended as a replacement for the standard C standard I/O library.
Sfio offers several improvements over stdio: names and calling conventions are more regular (all exported names start with sf, the file handle on which operations are performed is always the first argument), callback functions can be used to preprocess data, and greatly improved performance.
Sfio is available under the terms of the Common Public License.