Implement trunc() and truncf().

svn path=/head/; revision=130767

lib/msun/man/trunc.3

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+.\" Copyright (c) 2004 David Schultz <das@FreeBSD.org>
+.\" 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.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd June 20, 2004
+.Dt TRUNC 3
+.Os
+.Sh NAME
+.Nm trunc ,
+.Nm truncf
+.Nd nearest integral value with magnitude less than or equal to |x|
+.Sh LIBRARY
+.Lb libm
+.Sh SYNOPSIS
+.In math.h
+.Ft double
+.Fn trunc "double x"
+.Ft float
+.Fn truncf "float x"
+.Sh DESCRIPTION
+The
+.Fn trunc
+and
+.Fn truncf
+functions return the nearest integral value with magnitude less than
+or equal to
+.Pf | Fa x Ns | .
+They are equivalent to
+.Fn rint
+and
+.Fn rintf ,
+respectively, in the
+.Dv FE_TOWARDZERO
+rounding mode.
+.Sh SEE ALSO
+.Xr ceil 3 ,
+.Xr fesetround 3 ,
+.Xr floor 3 ,
+.Xr math 3 ,
+.Xr nextafter 3 ,
+.Xr rint 3 ,
+.Xr round 3
+.Sh STANDARDS
+The
+.Fn trunc
+and
+.Fn truncf
+functions conform to
+.St -isoC-99 .
+.Sh HISTORY
+These routines first appeared in
+.Fx 5.3 .

lib/msun/src/s_trunc.c

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+/* @(#)s_floor.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/*
+ * trunc(x)
+ * Return x rounded toward 0 to integral value
+ * Method:
+ *	Bit twiddling.
+ * Exception:
+ *	Inexact flag raised if x not equal to trunc(x).
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+static const double huge = 1.0e300;
+
+double
+trunc(double x)
+{
+	int32_t i0,i1,j0;
+	u_int32_t i,j;
+	EXTRACT_WORDS(i0,i1,x);
+	j0 = ((i0>>20)&0x7ff)-0x3ff;
+	if(j0<20) {
+	    if(j0<0) { 	/* raise inexact if x != 0 */
+		if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
+		    i0 &= 0x80000000U;
+		    i1 = 0;
+		}
+	    } else {
+		i = (0x000fffff)>>j0;
+		if(((i0&i)|i1)==0) return x; /* x is integral */
+		if(huge+x>0.0) {	/* raise inexact flag */
+		    i0 &= (~i); i1=0;
+		}
+	    }
+	} else if (j0>51) {
+	    if(j0==0x400) return x+x;	/* inf or NaN */
+	    else return x;		/* x is integral */
+	} else {
+	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
+	    if((i1&i)==0) return x;	/* x is integral */
+	    if(huge+x>0.0)		/* raise inexact flag */
+		i1 &= (~i);
+	}
+	INSERT_WORDS(x,i0,i1);
+	return x;
+}

lib/msun/src/s_truncf.c

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+/* @(#)s_floor.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/*
+ * truncf(x)
+ * Return x rounded toward 0 to integral value
+ * Method:
+ *	Bit twiddling.
+ * Exception:
+ *	Inexact flag raised if x not equal to truncf(x).
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+static const float huge = 1.0e30F;
+
+float
+truncf(float x)
+{
+	int32_t i0,j0;
+	u_int32_t i;
+	GET_FLOAT_WORD(i0,x);
+	j0 = ((i0>>23)&0xff)-0x7f;
+	if(j0<23) {
+	    if(j0<0) { 	/* raise inexact if x != 0 */
+		if(huge+x>0.0F)		/* |x|<1, so return 0*sign(x) */
+		    i0 &= 0x80000000;
+	    } else {
+		i = (0x007fffff)>>j0;
+		if((i0&i)==0) return x; /* x is integral */
+		if(huge+x>0.0F)		/* raise inexact flag */
+		    i0 &= (~i);
+	    }
+	} else {
+	    if(j0==0x80) return x+x;	/* inf or NaN */
+	    else return x;		/* x is integral */
+	}
+	SET_FLOAT_WORD(x,i0);
+	return x;
+}