s_fpclassify.c

来自「Newlib 嵌入式 C库 标准实现代码」· C语言 代码 · 共 32 行

/* Copyright (C) 2002, 2007 by  Red Hat, Incorporated. All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * is freely granted, provided that this notice is preserved.
 */

#include "fdlibm.h"

int
__fpclassifyd (double x)
{
  __uint32_t msw, lsw;

  EXTRACT_WORDS(msw,lsw,x);

  if ((msw == 0x00000000 && lsw == 0x00000000) ||
      (msw == 0x80000000 && lsw == 0x00000000))
    return FP_ZERO;
  else if ((msw >= 0x00100000 && msw <= 0x7fefffff) ||
           (msw >= 0x80100000 && msw <= 0xffefffff))
    return FP_NORMAL;
  else if ((msw >= 0x00000000 && msw <= 0x000fffff) ||
           (msw >= 0x80000000 && msw <= 0x800fffff))
    /* zero is already handled above */
    return FP_SUBNORMAL;
  else if ((msw == 0x7ff00000 && lsw == 0x00000000) ||
           (msw == 0xfff00000 && lsw == 0x00000000))
    return FP_INFINITE;
  else
    return FP_NAN;
}