| 1 | /* @(#)s_nextafter.c 5.1 93/09/24 */
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| 2 | /*
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| 3 | * ====================================================
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| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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| 5 | *
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| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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| 7 | * Permission to use, copy, modify, and distribute this
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| 8 | * software is freely granted, provided that this notice
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| 9 | * is preserved.
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| 10 | * ====================================================
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| 11 | */
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| 12 |
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| 13 | #ifndef lint
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| 14 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_nextafter.c,v 1.11 2005/03/07 21:27:37 das Exp $";
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| 15 | #endif
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| 16 |
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| 17 | /* IEEE functions
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| 18 | * nextafter(x,y)
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| 19 | * return the next machine floating-point number of x in the
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| 20 | * direction toward y.
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| 21 | * Special cases:
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| 22 | */
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| 23 |
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| 24 | #include <sys/cdefs.h>
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| 25 | #include <float.h>
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| 26 |
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| 27 | #include "math.h"
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| 28 | #include "math_private.h"
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| 29 |
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| 30 | double
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| 31 | nextafter(double x, double y)
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| 32 | {
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| 33 | volatile double t;
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| 34 | int32_t hx,hy,ix,iy;
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| 35 | u_int32_t lx,ly;
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| 36 |
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| 37 | EXTRACT_WORDS(hx,lx,x);
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| 38 | EXTRACT_WORDS(hy,ly,y);
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| 39 | ix = hx&0x7fffffff; /* |x| */
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| 40 | iy = hy&0x7fffffff; /* |y| */
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| 41 |
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| 42 | if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) || /* x is nan */
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| 43 | ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0)) /* y is nan */
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| 44 | return x+y;
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| 45 | if(x==y) return y; /* x=y, return y */
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| 46 | if((ix|lx)==0) { /* x == 0 */
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| 47 | INSERT_WORDS(x,hy&0x80000000,1); /* return +-minsubnormal */
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| 48 | t = x*x;
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| 49 | if(t==x) return t; else return x; /* raise underflow flag */
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| 50 | }
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| 51 | if(hx>=0) { /* x > 0 */
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| 52 | if(hx>hy||((hx==hy)&&(lx>ly))) { /* x > y, x -= ulp */
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| 53 | if(lx==0) hx -= 1;
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| 54 | lx -= 1;
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| 55 | } else { /* x < y, x += ulp */
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| 56 | lx += 1;
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| 57 | if(lx==0) hx += 1;
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| 58 | }
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| 59 | } else { /* x < 0 */
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| 60 | if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
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| 61 | if(lx==0) hx -= 1;
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| 62 | lx -= 1;
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| 63 | } else { /* x > y, x += ulp */
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| 64 | lx += 1;
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| 65 | if(lx==0) hx += 1;
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| 66 | }
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| 67 | }
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| 68 | hy = hx&0x7ff00000;
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| 69 | if(hy>=0x7ff00000) return x+x; /* overflow */
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| 70 | if(hy<0x00100000) { /* underflow */
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| 71 | t = x*x;
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| 72 | if(t!=x) { /* raise underflow flag */
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| 73 | INSERT_WORDS(y,hx,lx);
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| 74 | return y;
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| 75 | }
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| 76 | }
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| 77 | INSERT_WORDS(x,hx,lx);
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| 78 | return x;
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| 79 | }
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| 80 |
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| 81 | #if (LDBL_MANT_DIG == 53)
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| 82 | __weak_reference(nextafter, nexttoward);
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| 83 | __weak_reference(nextafter, nexttowardl);
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| 84 | __weak_reference(nextafter, nextafterl);
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| 85 | #endif
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