Mercurial > sdl-ios-xcode
view src/libm/s_scalbn.c @ 2845:1cc5d5b164e2
Added official support for GL_APPLE_ycbcr_422 and GL_MESA_ycbcr_texture
author | Sam Lantinga <slouken@libsdl.org> |
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date | Sun, 07 Dec 2008 04:02:23 +0000 |
parents | a98604b691c8 |
children | dc1eb82ffdaa |
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/* @(#)s_scalbn.c 5.1 93/09/24 */ /* * ==================================================== * 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. * ==================================================== */ #if defined(LIBM_SCCS) && !defined(lint) static char rcsid[] = "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $"; #endif /* * scalbn (double x, int n) * scalbn(x,n) returns x* 2**n computed by exponent * manipulation rather than by actually performing an * exponentiation or a multiplication. */ #include "math.h" #include "math_private.h" libm_hidden_proto(copysign) #ifdef __STDC__ static const double #else static double #endif two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ huge = 1.0e+300, tiny = 1.0e-300; libm_hidden_proto(scalbn) #ifdef __STDC__ double scalbn(double x, int n) #else double scalbn(x, n) double x; int n; #endif { 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 (n < -50000) return tiny * x; /*underflow */ } if (k == 0x7ff) return x + x; /* NaN or Inf */ k = k + n; if (k > 0x7fe) return huge * copysign(huge, x); /* overflow */ 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 */ else return tiny * copysign(tiny, x); /*underflow */ } k += 54; /* subnormal result */ SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20)); return x * twom54; } libm_hidden_def(scalbn)