| 1 | /* @(#)s_modf.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_modf.c,v 1.7 2002/05/28 18:15:04 alfred Exp $";
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| 15 | #endif
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| 16 |
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| 17 | /*
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| 18 | * modf(double x, double *iptr)
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| 19 | * return fraction part of x, and return x's integral part in *iptr.
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| 20 | * Method:
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| 21 | * Bit twiddling.
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| 22 | *
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| 23 | * Exception:
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| 24 | * No exception.
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| 25 | */
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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 | static const double one = 1.0;
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| 31 |
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| 32 | double
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| 33 | modf(double x, double *iptr)
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| 34 | {
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| 35 | int32_t i0,i1,j0;
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| 36 | u_int32_t i;
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| 37 | EXTRACT_WORDS(i0,i1,x);
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| 38 | j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
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| 39 | if(j0<20) { /* integer part in high x */
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| 40 | if(j0<0) { /* |x|<1 */
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| 41 | INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
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| 42 | return x;
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| 43 | } else {
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| 44 | i = (0x000fffff)>>j0;
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| 45 | if(((i0&i)|i1)==0) { /* x is integral */
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| 46 | u_int32_t high;
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| 47 | *iptr = x;
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| 48 | GET_HIGH_WORD(high,x);
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| 49 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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| 50 | return x;
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| 51 | } else {
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| 52 | INSERT_WORDS(*iptr,i0&(~i),0);
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| 53 | return x - *iptr;
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| 54 | }
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| 55 | }
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| 56 | } else if (j0>51) { /* no fraction part */
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| 57 | u_int32_t high;
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| 58 | *iptr = x*one;
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| 59 | GET_HIGH_WORD(high,x);
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| 60 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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| 61 | return x;
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| 62 | } else { /* fraction part in low x */
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| 63 | i = ((u_int32_t)(0xffffffff))>>(j0-20);
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| 64 | if((i1&i)==0) { /* x is integral */
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| 65 | u_int32_t high;
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| 66 | *iptr = x;
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| 67 | GET_HIGH_WORD(high,x);
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| 68 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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| 69 | return x;
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| 70 | } else {
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| 71 | INSERT_WORDS(*iptr,i0,i1&(~i));
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| 72 | return x - *iptr;
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| 73 | }
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| 74 | }
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| 75 | }
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