1 /* S_FLOOR.C

     2  * 

     3  * Portions Copyright (c) 1993-2005 Nokia Corporation and/or its subsidiary(-ies).

     4  * All rights reserved.

     5  */

     6 

     7 

     8 /* @(#)s_floor.c 5.1 93/09/24 */

     9 /*

    10  * ====================================================

    11  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

    12  *

    13  * Developed at SunPro, a Sun Microsystems, Inc. business.

    14  * Permission to use, copy, modify, and distribute this

    15  * software is freely granted, provided that this notice 

    16  * is preserved.

    17  * ====================================================

    18  */

    19 

    20 /*

    21 FUNCTION

    22 <<floor>>, <<floorf>>, <<ceil>>, <<ceilf>>---floor and ceiling

    23 INDEX

    24 	floor

    25 INDEX

    26 	floorf

    27 INDEX

    28 	ceil

    29 INDEX

    30 	ceilf

    31 

    32 ANSI_SYNOPSIS

    33 	#include <math.h>

    34 	double floor(double <[x]>);

    35         float floorf(float <[x]>);

    36         double ceil(double <[x]>);

    37         float ceilf(float <[x]>);

    38 

    39 TRAD_SYNOPSIS

    40 	#include <math.h>

    41         double floor(<[x]>)

    42 	double <[x]>;

    43         float floorf(<[x]>) 

    44 	float <[x]>;

    45         double ceil(<[x]>) 

    46 	double <[x]>;

    47         float ceilf(<[x]>) 

    48 	float <[x]>;

    49 

    50 DESCRIPTION

    51 <<floor>> and <<floorf>> find 

    52 @tex

    53 $\lfloor x \rfloor$, 

    54 @end tex

    55 the nearest integer less than or equal to <[x]>.

    56 <<ceil>> and <<ceilf>> find 

    57 @tex

    58 $\lceil x\rceil$,

    59 @end tex

    60 the nearest integer greater than or equal to <[x]>.

    61 

    62 RETURNS

    63 <<floor>> and <<ceil>> return the integer result as a double.

    64 <<floorf>> and <<ceilf>> return the integer result as a float.

    65 

    66 PORTABILITY

    67 <<floor>> and <<ceil>> are ANSI.

    68 <<floorf>> and <<ceilf>> are extensions.

    69 

    70 

    71 */

    72 

    73 /*

    74  * floor(x)

    75  * Return x rounded toward -inf to integral value

    76  * Method:

    77  *	Bit twiddling.

    78  * Exception:

    79  *	Inexact flag raised if x not equal to floor(x).

    80  */

    81 

    82 #include "FDLIBM.H"

    83 

    84 static const double huge = 1.0e300;

    85 

    86 /**

    87 Round down value.

    88 Returns the largest integer that is less than or equal to x 

    89 @return   Floor of x.

    90 @param x Floating point value

    91 */	

    92 EXPORT_C double floor(double x) __SOFTFP

    93 {

    94 	__int32_t i0,i1,j0;

    95 	__uint32_t i,j;

    96 	EXTRACT_WORDS(i0,i1,x);

    97 	j0 = ((i0>>20)&0x7ff)-0x3ff;

    98 	if(j0<20) {

    99 	    if(j0<0) { 	/* raise inexact if x != 0 */

   100 		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */

   101 		    if(i0>=0) {i0=i1=0;} 

   102 		    else if(((i0&0x7fffffff)|i1)!=0)

   103 			{ i0=0xbff00000;i1=0;}

   104 		}

   105 	    } else {

   106 		i = (0x000fffff)>>j0;

   107 		if(((i0&i)|i1)==0) return x; /* x is integral */

   108 		if(huge+x>0.0) {	/* raise inexact flag */

   109 		    if(i0<0) i0 += (0x00100000)>>j0;

   110 		    i0 &= (~i); i1=0;

   111 		}

   112 	    }

   113 	} else if (j0>51) {

   114 	    if(j0==0x400) return x+x;	/* inf or NaN */

   115 	    else return x;		/* x is integral */

   116 	} else {

   117 	    i = ((__uint32_t)(0xffffffff))>>(j0-20);

   118 	    if((i1&i)==0) return x;	/* x is integral */

   119 	    if(huge+x>0.0) { 		/* raise inexact flag */

   120 		if(i0<0) {

   121 		    if(j0==20) i0+=1; 

   122 		    else {

   123 			j = i1+(1<<(52-j0));

   124 			if(j<i1) i0 +=1 ; 	/* got a carry */

   125 			i1=j;

   126 		    }

   127 		}

   128 		i1 &= (~i);

   129 	    }

   130 	}

   131 	INSERT_WORDS(x,i0,i1);

   132 	return x;

   133 }