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.\" Copyright (c) 1993 Andrew Moore, Talke Studio
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)fpgetround.3 1.0 (Berkeley) 9/23/93
.\" $FreeBSD$
.\"
.Dd August 23, 1993
.Dt FPGETROUND 3
.Os
.Sh NAME
.Nm fpgetround ,
.Nm fpsetround ,
.Nm fpsetprec ,
.Nm fpgetprec ,
.Nm fpgetmask ,
.Nm fpsetmask ,
.Nm fpgetsticky ,
.Nm fpresetsticky
.Nd IEEE floating point interface
.Sh SYNOPSIS
.In ieeefp.h
.Pp
.Bd -literal
typedef enum {
FP_RN, /* round to nearest */
FP_RM, /* round down to minus infinity */
FP_RP, /* round up to plus infinity */
FP_RZ /* truncate */
} fp_rnd_t;
.Ed
.Ft fp_rnd_t
.Fn fpgetround void
.Ft fp_rnd_t
.Fn fpsetround "fp_rnd_t direction"
.Pp
.Bd -literal
typedef enum {
FP_PS, /* 24 bit (single-precision) */
FP_PRS, /* reserved */
FP_PD, /* 53 bit (double-precision) */
FP_PE /* 64 bit (extended-precision) */
} fp_prec_t;
.Ed
.Ft fp_prec_t
.Fn fpgetprec void
.Ft fp_prec_t
.Fn fpsetprec "fp_prec_t precision"
.Pp
.Bd -literal
#define fp_except_t int
#define FP_X_INV 0x01 /* invalid operation */
#define FP_X_DNML 0x02 /* denormal */
#define FP_X_DZ 0x04 /* zero divide */
#define FP_X_OFL 0x08 /* overflow */
#define FP_X_UFL 0x10 /* underflow */
#define FP_X_IMP 0x20 /* (im)precision */
#define FP_X_STK 0x40 /* stack fault */
.Ed
.Ft fp_except_t
.Fn fpgetmask void
.Ft fp_except_t
.Fn fpsetmask "fp_except_t mask"
.Ft fp_except_t
.Fn fpgetsticky void
.Ft fp_except_t
.Fn fpresetsticky "fp_except_t sticky"
.Sh DESCRIPTION
When a floating point exception is detected, the exception sticky flag is
set and the exception mask is tested.
If the mask is set, then a trap
occurs. These routines allow both setting the floating point exception
masks, and resetting the exception sticky flags after an exception is
detected. In addition, they allow setting the floating point rounding mode
and precision.
.Pp
The
.Fn fpgetround
function
returns the current floating point rounding mode.
.Pp
The
.Fn fpsetround
function
sets the floating point rounding mode and returns
the previous mode.
.Pp
The
.Fn fpgetprec
function
returns the current floating point precision.
.Pp
The
.Fn fpsetprec
function
sets the floating point precision and returns
the previous precision.
.Pp
The
.Fn fpgetmask
function
returns the current floating point exception masks.
.Pp
The
.Fn fpsetmask
function
sets the floating point exception masks and returns the
previous masks.
.Pp
The
.Fn fpgetsticky
function
returns the current floating point sticky flags.
.Pp
The
.Fn fpresetsticky
function
clears the floating point sticky flags and returns
the previous flags.
.Pp
Sample code which prevents a trap on divide-by-zero:
.Bd -literal -offset indent
fpsetmask(~FP_X_DZ);
a = 1.0;
b = 0;
c = a / b;
fpresetsticky(FP_X_DZ);
fpsetmask(FP_X_DZ);
.Ed
.Sh SEE ALSO
.Xr isnan 3
.Sh CAVEAT
After a floating point exception and before a mask is set, the sticky
flags must be reset. If another exception occurs before the sticky
flags are reset, then a wrong exception type may be signaled.
.Sh HISTORY
These routines are based on SysV/386 routines of the same name.
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