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path: root/src/math/floor.c
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 ```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 69 70 71 72 73 74 75 76 77 78 79 80 81 82 ``` ``````/* origin: FreeBSD /usr/src/lib/msun/src/s_floor.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. * ==================================================== */ /* * floor(x) * Return x rounded toward -inf to integral value * Method: * Bit twiddling. * Exception: * Inexact flag raised if x not equal to floor(x). */ #include "libm.h" static const double huge = 1.0e300; double floor(double x) { int32_t i0,i1,j0; uint32_t i,j; EXTRACT_WORDS(i0, i1, x); // FIXME: signed shift j0 = ((i0>>20)&0x7ff) - 0x3ff; if (j0 < 20) { if (j0 < 0) { /* |x| < 1 */ /* raise inexact if x != 0 */ if (huge+x > 0.0) { if (i0 >= 0) { /* x >= 0 */ i0 = i1 = 0; } else if (((i0&0x7fffffff)|i1) != 0) { i0 = 0xbff00000; i1 = 0; } } } else { i = 0x000fffff>>j0; if (((i0&i)|i1) == 0) return x; /* x is integral */ /* raise inexact flag */ if (huge+x > 0.0) { if (i0 < 0) i0 += 0x00100000>>j0; 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 = ((uint32_t)(0xffffffff))>>(j0-20); if ((i1&i) == 0) return x; /* x is integral */ /* raise inexact flag */ if (huge+x > 0.0) { if (i0 < 0) { if (j0 == 20) i0+=1; else { j = i1+(1<<(52-j0)); if (j < i1) i0 += 1; /* got a carry */ i1 = j; } } i1 &= ~i; } } INSERT_WORDS(x, i0, i1); return x; } ``````