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 /* * ==================================================== * 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. * ==================================================== */ /* * scalbln(double x, long n) * scalbln(x,n) returns x * 2**n computed by exponent * manipulation rather than by actually performing an * exponentiation or a multiplication. */ #include "math_libm.h" #include "math_private.h" #include #ifdef __WATCOMC__ /* Watcom defines huge=__huge */ #undef huge #endif static const double two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ huge = 1.0e+300, tiny = 1.0e-300; double scalbln(double x, long n) { int32_t k, hx, lx; EXTRACT_WORDS(hx, lx, x); k = (hx & 0x7ff00000) >> 20; /* extract exponent */ if (k == 0) { /* 0 or subnormal x */ if ((lx | (hx & 0x7fffffff)) == 0) return x; /* +-0 */ x *= two54; GET_HIGH_WORD(hx, x); k = ((hx & 0x7ff00000) >> 20) - 54; } if (k == 0x7ff) return x + x; /* NaN or Inf */ k = k + n; if (k > 0x7fe) return huge * copysign(huge, x); /* overflow */ if (n < -50000) return tiny * copysign(tiny, x); /* underflow */ if (k > 0) { /* normal result */ SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20)); return x; } if (k <= -54) { if (n > 50000) /* in case integer overflow in n+k */ return huge * copysign(huge, x); /* overflow */ return tiny * copysign(tiny, x); /* underflow */ } k += 54; /* subnormal result */ SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20)); return x * twom54; } libm_hidden_def(scalbln) double scalbn(double x, int n) { return scalbln(x, n); } libm_hidden_def(scalbn)