summaryrefslogtreecommitdiff log msg author committer range
path: root/src/math/fmod.c
 ```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 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 ``` ``````/* origin: FreeBSD /usr/src/lib/msun/src/e_fmod.c */ /* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunSoft, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ /* * fmod(x,y) * Return x mod y in exact arithmetic * Method: shift and subtract */ #include "libm.h" static const double one = 1.0, Zero[] = {0.0, -0.0,}; double fmod(double x, double y) { int32_t n,hx,hy,hz,ix,iy,sx,i; uint32_t lx,ly,lz; EXTRACT_WORDS(hx, lx, x); EXTRACT_WORDS(hy, ly, y); sx = hx & 0x80000000; /* sign of x */ hx ^= sx; /* |x| */ hy &= 0x7fffffff; /* |y| */ /* purge off exception values */ if ((hy|ly) == 0 || hx >= 0x7ff00000 || /* y=0,or x not finite */ (hy|((ly|-ly)>>31)) > 0x7ff00000) /* or y is NaN */ return (x*y)/(x*y); if (hx <= hy) { if (hx < hy || lx < ly) /* |x| < |y| */ return x; if (lx == ly) /* |x| = |y|, return x*0 */ return Zero[(uint32_t)sx>>31]; } /* determine ix = ilogb(x) */ if (hx < 0x00100000) { /* subnormal x */ if (hx == 0) { for (ix = -1043, i = lx; i > 0; i <<= 1) ix -= 1; } else { for (ix = -1022, i = hx<<11; i > 0; i <<= 1) ix -= 1; } } else ix = (hx>>20) - 1023; /* determine iy = ilogb(y) */ if (hy < 0x00100000) { /* subnormal y */ if (hy == 0) { for (iy = -1043, i = ly; i > 0; i <<= 1) iy -= 1; } else { for (iy = -1022, i = hy<<11; i > 0; i <<= 1) iy -= 1; } } else iy = (hy>>20) - 1023; /* set up {hx,lx}, {hy,ly} and align y to x */ if (ix >= -1022) hx = 0x00100000|(0x000fffff&hx); else { /* subnormal x, shift x to normal */ n = -1022-ix; if (n <= 31) { hx = (hx<>(32-n)); lx <<= n; } else { hx = lx<<(n-32); lx = 0; } } if(iy >= -1022) hy = 0x00100000|(0x000fffff&hy); else { /* subnormal y, shift y to normal */ n = -1022-iy; if (n <= 31) { hy = (hy<>(32-n)); ly <<= n; } else { hy = ly<<(n-32); ly = 0; } } /* fix point fmod */ n = ix - iy; while (n--) { hz = hx-hy; lz = lx-ly; if (lx < ly) hz -= 1; if (hz < 0) { hx = hx+hx+(lx>>31); lx = lx+lx; } else { if ((hz|lz) == 0) /* return sign(x)*0 */ return Zero[(uint32_t)sx>>31]; hx = hz+hz+(lz>>31); lx = lz+lz; } } hz = hx-hy; lz = lx-ly; if (lx < ly) hz -= 1; if (hz >= 0) { hx = hz; lx = lz; } /* convert back to floating value and restore the sign */ if ((hx|lx) == 0) /* return sign(x)*0 */ return Zero[(uint32_t)sx>>31]; while (hx < 0x00100000) { /* normalize x */ hx = hx+hx+(lx>>31); lx = lx+lx; iy -= 1; } if (iy >= -1022) { /* normalize output */ hx = ((hx-0x00100000)|((iy+1023)<<20)); INSERT_WORDS(x, hx|sx, lx); } else { /* subnormal output */ n = -1022 - iy; if (n <= 20) { lx = (lx>>n)|((uint32_t)hx<<(32-n)); hx >>= n; } else if (n <= 31) { lx = (hx<<(32-n))|(lx>>n); hx = sx; } else { lx = hx>>(n-32); hx = sx; } INSERT_WORDS(x, hx|sx, lx); x *= one; /* create necessary signal */ } return x; /* exact output */ } ``````