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path: root/src/math/modf.c
blob: cca3b652182c5e363fbd20a798db6c6a0becb9d9 (plain) (blame)
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 ``` ``````/* origin: FreeBSD /usr/src/lib/msun/src/s_modf.c */ /* * ==================================================== * 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. * ==================================================== */ /* * modf(double x, double *iptr) * return fraction part of x, and return x's integral part in *iptr. * Method: * Bit twiddling. * * Exception: * No exception. */ #include "libm.h" double modf(double x, double *iptr) { int32_t i0,i1,j0; uint32_t i; EXTRACT_WORDS(i0, i1, x); j0 = ((i0>>20) & 0x7ff) - 0x3ff; /* exponent of x */ if (j0 < 20) { /* integer part in high x */ if (j0 < 0) { /* |x| < 1 */ INSERT_WORDS(*iptr, i0 & 0x80000000, 0); /* *iptr = +-0 */ return x; } i = 0x000fffff >> j0; if (((i0&i)|i1) == 0) { /* x is integral */ uint32_t high; *iptr = x; GET_HIGH_WORD(high, x); INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */ return x; } INSERT_WORDS(*iptr, i0&~i, 0); return x - *iptr; } else if (j0 > 51) { /* no fraction part */ uint32_t high; if (j0 == 0x400) { /* inf/NaN */ *iptr = x; return 0.0 / x; } *iptr = x; GET_HIGH_WORD(high, x); INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */ return x; } else { /* fraction part in low x */ i = (uint32_t)0xffffffff >> (j0 - 20); if ((i1&i) == 0) { /* x is integral */ uint32_t high; *iptr = x; GET_HIGH_WORD(high, x); INSERT_WORDS(x, high & 0x80000000, 0); /* return +-0 */ return x; } INSERT_WORDS(*iptr, i0, i1&~i); return x - *iptr; } } ``````