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.Dd May 6, 2018
.Dt cryb_memset_s 3
.Os
.Sh NAME
.Nm cryb_memset_s
.Nd safely fill a buffer
.Sh LIBRARY
.Lb libcryb-core
.Sh SYNOPSIS
.In cryb/memset_s.h
.Ft errno_t
.Fn cryb_memset_s "void *d" "rsize_t dsz" "int ch" "rsize_t n"
.Sh DESCRIPTION
The
.Nm cryb_memset_s
function overwrites the first
.Va n
bytes of the buffer pointed to by
.Va d ,
of size
.Va dsz ,
with copies of the least-significant byte of
.Va ch .
If
.Va n
is greater than
.Va dsz ,
only
.Va dsz
bytes are overwritten, and an error is returned.
.Sh RETURN VALUES
The
.Nm
function returns zero if successful and a non-zero error code if an
error occurred.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Va d
argument was
.Dv NULL .
.It Bq Er ERANGE
Either or both of the
.Va dsz
and
.Va n
arguments were greater than
.Dv RSIZE_MAX .
.It Bq Er EOVERFLOW
The
.Va n
argument was greater than the
.Va dsz
argument.
.El
.Sh IMPLEMENTATION NOTES
If the
.Dv HAVE_MEMSET_S
preprocessor macro is defined to 0 or undefined, the
.In cryb/memset_s.h
header provides a
.Fn memset_s
macro as an alias to
.Fn cryb_memset_s .
.Pp
Software that includes
.In cryb/memset_s.h
should ensure that the
.Dv HAVE_ERRNO_T ,
.Dv HAVE_RSIZE_T ,
.Dv HAVE_RSIZE_MAX
and
.Dv HAVE_MEMSET_S
macros correctly reflect the availability of these features at compile
time.
For projects that use the GNU autotools, this can be achieved by
including the following code in
.Pa configure.ac :
.Bd -literal -offset indent
AC_CHECK_TYPES([errno_t], [], [], [[#include <errno.h>]])
AC_CHECK_TYPES([rsize_t], [], [], [[#include <stdint.h>]])
AC_CHECK_DECL([RSIZE_MAX], [], [], [[#include <stdint.h>]])
AC_CHECK_FUNCS([memset_s])
.Ed
.Sh SEE ALSO
.Xr cryb_memcpy_s 3 ,
.Xr memset 3
.Sh STANDARDS
The
.Fn cryb_memset_s
function is equivalent to the
.Fn memset_s
function described in ISO/IEC 9899:2011
.Pq Dq C11
section K.3.7.4.1.
.Sh AUTHORS
The
.Fn cryb_memset_s
function and this manual page were written for the University of Oslo
by
.An Dag-Erling Sm\(/orgrav Aq Mt d.e.smorgrav@usit.uio.no .