Sfio is a portable library for managing I/O streams.  It provides
similar functionality to the ANSI C Standard I/O functions known
collectively as Stdio.  However, it has a distinct interface and is
generally faster and more robust than most Stdio implementations. 
Sfio also introduces a number of new features and concepts beyond
Stdio stream I/O processing: 

+ Automatic locking to avoid concurrent stream accesses, 
+ I/O disciplines to pre/post-process read/write data from/to streams,
+ Stream stacking for recursive processing of nested streams, 
+ Stream pooling for automatic stream synchronization when I/O
       operations are performed on different streams,
+ Buffer reservation for safe access to the internal buffers of streams,
+ Robust handling of variable-sized records, and 
+ Extensible printf/scanf-like formatting I/O operations. 

For backward compatibility, Sfio provides two Stdio emulation
packages.  An application with source code can include the header file
stdio.h provided by Sfio instead of the native one to translate Stdio
calls to Sfio calls.  An application already compiled with the native
header file stdio.h can make use of Sfio functionality by linking with
the library libstdio.a which emulates Stdio functions.  In fact, it is
safe to mix and match modules that are compiled with either
Sfio-provided or native stdio.h. 

The current distribution of Sfio is Sfio1998.  This version of the
library is portable to all known UNIX platforms including various
flavors of IRIX, SUNOS, Solaris, Ultrix, MVS/OpenEdition, Linux and
BSDI.  The library handles 64-bit streams on platforms that support
64-bit files.  The formatting family of functions (e.g., sfprintf()
and sfscanf()) have been extended so that applications can redefine
the meanings of predefined patterns as well as define new patterns. 
The manual page has more details on recent changes. 

Below are papers related to Sfio: 

David G. Korn and Kiem-Phong Vo, ``Sfio: Safe/Fast String/File IO'',
Proceedings of the Summer '91 Usenix Conference, pp. 235-256, 1991. 

Glenn S. Fowler, David G. Korn and Kiem-Phong Vo,
``Feature-Based Portability'', Proceedings of the Usenix VHLL
Conference, pp. 197-207, 1994.

Kiem-Phong Vo, ``An Architecture for Reusable Libraries'',
Proc. of the IEEE Fifth Int. Conf. on Software Reuse, 1998.