newlib/libm/mathfp/sf_ldexp.c

   1
   2 /* @(#)z_ldexpf.c 1.0 98/08/13 */
   3 /******************************************************************
   4  * ldexp
   5  *
   6  * Input:
   7  *   d - a floating point value
   8  *   e - an exponent value
   9  *
  10  * Output:
  11  *   A floating point value f such that f = d * 2 ^ e.
  12  *
  13  * Description:
  14  *   This function creates a floating point number f such that
  15  *   f = d * 2 ^ e.
  16  *
  17  *****************************************************************/
  18
  19 #include <float.h>
  20 #include "fdlibm.h"
  21 #include "zmath.h"
  22
  23 #define FLOAT_EXP_OFFS 127
  24
  25 float
  26 ldexpf (float d,
  27         int e)
  28 {
  29   int exp;
  30   __int32_t wd;
  31
  32   GET_FLOAT_WORD (wd, d);
  33
  34   /* Check for special values and then scale d by e. */
  35   switch (numtestf (wd))
  36     {
  37       case NAN:
  38         errno = EDOM;
  39         break;
  40
  41       case INF:
  42         errno = ERANGE;
  43         break;
  44
  45       case 0:
  46         break;
  47
  48       default:
  49         exp = (wd & 0x7f800000) >> 23;
  50         exp += e;
  51
  52         if (exp > FLT_MAX_EXP + FLOAT_EXP_OFFS)
  53          {
  54            errno = ERANGE;
  55            d = z_infinity_f.f;
  56          }
  57         else if (exp < FLT_MIN_EXP + FLOAT_EXP_OFFS)
  58          {
  59            errno = ERANGE;
  60            d = -z_infinity_f.f;
  61          }
  62         else
  63          {
  64            wd &= 0x807fffff;
  65            wd |= exp << 23;
  66            SET_FLOAT_WORD (d, wd);
  67          }
  68     }
  69
  70     return (d);
  71 }
  72
  73 #ifdef _DOUBLE_IS_32BITS
  74
  75 double ldexp (double x, int e)
  76 {
  77   return (double) ldexpf ((float) x, e);
  78 }
  79
  80 #endif /* defined(_DOUBLE_IS_32BITS) */