newlib/libm/mathfp/sf_frexp.c

   1
   2 /* @(#)z_frexpf.c 1.0 98/08/13 */
   3 /******************************************************************
   4  * frexp
   5  *
   6  * Input:
   7  *   d   - floating point value
   8  *   exp - exponent value
   9  *
  10  * Output:
  11  *   A floating point value in the range [0.5, 1).
  12  *
  13  * Description:
  14  *   This routine breaks a floating point value into a number f and
  15  *   an exponent exp such that d = f * 2 ^ exp.
  16  *
  17  *****************************************************************/
  18
  19 #include "fdlibm.h"
  20 #include "zmath.h"
  21
  22 float frexpf (float d, int *exp)
  23 {
  24   float f;
  25   __int32_t wf, wd;
  26
  27   /* Check for special values. */
  28   switch (numtestf (d))
  29     {
  30       case NAN:
  31       case INF:
  32         errno = EDOM;
  33       case 0:
  34         *exp = 0;
  35         return (d);
  36     }
  37
  38   GET_FLOAT_WORD (wd, d);
  39
  40   /* Get the exponent. */
  41   *exp = ((wd & 0x7f800000) >> 23) - 126;
  42
  43   /* Get the mantissa. */
  44   wf = wd & 0x7fffff;
  45   wf |= 0x3f000000;
  46
  47   SET_FLOAT_WORD (f, wf);
  48
  49   return (f);
  50 }
  51
  52 #ifdef _DOUBLE_IS_32BITS
  53
  54 double frexp (double x, int *exp)
  55 {
  56   return (double) frexpf ((float) x, exp);
  57 }
  58
  59 #endif /* defined(_DOUBLE_IS_32BITS) */