Fix a bug about the iSCSI DHCP dependency issue.

[mirror_edk2.git] / StdLib / LibC / Math / e_cosh.c

/* @(#)e_cosh.c 5.1 93/09/24 */\r
/*\r
 * ====================================================\r
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\r
 *\r
 * Developed at SunPro, a Sun Microsystems, Inc. business.\r
 * Permission to use, copy, modify, and distribute this\r
 * software is freely granted, provided that this notice\r
 * is preserved.\r
 * ====================================================\r
 */\r
#include  <LibConfig.h>\r
#include  <sys/EfiCdefs.h>\r
#if defined(LIBM_SCCS) && !defined(lint)\r
__RCSID("$NetBSD: e_cosh.c,v 1.11 2002/05/26 22:01:49 wiz Exp $");\r
#endif\r
\r
#if defined(_MSC_VER)           /* Handle Microsoft VC++ compiler specifics. */\r
  // C4756: overflow in constant arithmetic\r
  #pragma warning ( disable : 4756 )\r
#endif\r
\r
/* __ieee754_cosh(x)\r
 * Method :\r
 * mathematically cosh(x) if defined to be (exp(x)+exp(-x))/2\r
 *  1. Replace x by |x| (cosh(x) = cosh(-x)).\r
 *  2.\r
 *                                            [ exp(x) - 1 ]^2\r
 *      0        <= x <= ln2/2  :  cosh(x) := 1 + -------------------\r
 *                             2*exp(x)\r
 *\r
 *                                      exp(x) +  1/exp(x)\r
 *      ln2/2    <= x <= 22     :  cosh(x) := -------------------\r
 *                            2\r
 *      22       <= x <= lnovft :  cosh(x) := exp(x)/2\r
 *      lnovft   <= x <= ln2ovft:  cosh(x) := exp(x/2)/2 * exp(x/2)\r
 *      ln2ovft  <  x     :  cosh(x) := huge*huge (overflow)\r
 *\r
 * Special cases:\r
 *  cosh(x) is |x| if x is +INF, -INF, or NaN.\r
 *  only cosh(0)=1 is exact for finite x.\r
 */\r
\r
#include "math.h"\r
#include "math_private.h"\r
\r
static const double one = 1.0, half=0.5, huge = 1.0e300;\r
\r
double\r
__ieee754_cosh(double x)\r
{\r
  double t,w;\r
  int32_t ix;\r
  u_int32_t lx;\r
\r
    /* High word of |x|. */\r
  GET_HIGH_WORD(ix,x);\r
  ix &= 0x7fffffff;\r
\r
    /* x is INF or NaN */\r
  if(ix>=0x7ff00000) return x*x;\r
\r
    /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */\r
  if(ix<0x3fd62e43) {\r
      t = expm1(fabs(x));\r
      w = one+t;\r
      if (ix<0x3c800000) return w;  /* cosh(tiny) = 1 */\r
      return one+(t*t)/(w+w);\r
  }\r
\r
    /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */\r
  if (ix < 0x40360000) {\r
    t = __ieee754_exp(fabs(x));\r
    return half*t+half/t;\r
  }\r
\r
    /* |x| in [22, log(maxdouble)] return half*exp(|x|) */\r
  if (ix < 0x40862E42)  return half*__ieee754_exp(fabs(x));\r
\r
    /* |x| in [log(maxdouble), overflowthresold] */\r
  GET_LOW_WORD(lx,x);\r
  if (ix<0x408633CE ||\r
        ((ix==0x408633ce)&&(lx<=(u_int32_t)0x8fb9f87d))) {\r
      w = __ieee754_exp(half*fabs(x));\r
      t = half*w;\r
      return t*w;\r
  }\r
\r
    /* |x| > overflowthresold, cosh(x) overflow */\r
  return huge*huge;\r
}\r