MdePkg UefiLib: Use comparison logic to check UINTN parameter

[mirror_edk2.git] / StdLib / LibC / Math / e_log2.c

\r
/* @(#)e_log.c 1.3 95/01/18 */\r
/*\r
 * ====================================================\r
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\r
 *\r
 * Developed at SunSoft, 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_log2.c,v 1.1 2005/07/21 12:55:58 christos Exp $");\r
#endif\r
\r
#include "math.h"\r
#include "math_private.h"\r
\r
#if defined(_MSC_VER)           /* Handle Microsoft VC++ compiler specifics. */\r
  // potential divide by 0 -- near line 53, (x-x)/zero is on purpose\r
  #pragma warning ( disable : 4723 )\r
#endif\r
\r
static const double\r
ln2 = 0.6931471805599452862268,\r
two54   =  1.80143985094819840000e+16,  /* 43500000 00000000 */\r
Lg1 = 6.666666666666735130e-01,  /* 3FE55555 55555593 */\r
Lg2 = 3.999999999940941908e-01,  /* 3FD99999 9997FA04 */\r
Lg3 = 2.857142874366239149e-01,  /* 3FD24924 94229359 */\r
Lg4 = 2.222219843214978396e-01,  /* 3FCC71C5 1D8E78AF */\r
Lg5 = 1.818357216161805012e-01,  /* 3FC74664 96CB03DE */\r
Lg6 = 1.531383769920937332e-01,  /* 3FC39A09 D078C69F */\r
Lg7 = 1.479819860511658591e-01;  /* 3FC2F112 DF3E5244 */\r
\r
static const double zero   =  0.0;\r
\r
double\r
__ieee754_log2(double x)\r
{\r
  double hfsq,f,s,z,R,w,t1,t2,dk;\r
  int32_t k,hx,i,j;\r
  u_int32_t lx;\r
\r
  EXTRACT_WORDS(hx,lx,x);\r
\r
  k=0;\r
  if (hx < 0x00100000) {      /* x < 2**-1022  */\r
      if (((hx&0x7fffffff)|lx)==0)\r
    return -two54/zero;   /* log(+-0)=-inf */\r
      if (hx<0) return (x-x)/zero;  /* log(-#) = NaN */\r
      k -= 54; x *= two54; /* subnormal number, scale up x */\r
      GET_HIGH_WORD(hx,x);\r
  }\r
  if (hx >= 0x7ff00000) return x+x;\r
  k += (hx>>20)-1023;\r
  hx &= 0x000fffff;\r
  i = (hx+0x95f64)&0x100000;\r
  SET_HIGH_WORD(x,hx|(i^0x3ff00000)); /* normalize x or x/2 */\r
  k += (i>>20);\r
  f = x-1.0;\r
  dk = (double)k;\r
  if((0x000fffff&(2+hx))<3) { /* |f| < 2**-20 */\r
      if (f==zero)\r
        return (dk);\r
      R = f*f*(0.5-0.33333333333333333*f);\r
      return (dk-(R-f)/ln2);\r
  }\r
  s = f/(2.0+f);\r
  z = s*s;\r
  i = hx-0x6147a;\r
  w = z*z;\r
  j = 0x6b851-hx;\r
  t1= w*(Lg2+w*(Lg4+w*Lg6));\r
  t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));\r
  i |= j;\r
  R = t2+t1;\r
  if(i>0) {\r
      hfsq=0.5*f*f;\r
      return (dk-(hfsq-s*(hfsq+R)-f)/ln2);\r
  } else\r
    return (dk-((s*(f-R))-f)/ln2);\r
}\r