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sfcvt.c

/***********************************************************************
*                                                                      *
*               This software is part of the ast package               *
*                  Copyright (c) 1985-2005 AT&T Corp.                  *
*                      and is licensed under the                       *
*                  Common Public License, Version 1.0                  *
*                            by AT&T Corp.                             *
*                                                                      *
*                A copy of the License is available at                 *
*            http://www.opensource.org/licenses/cpl1.0.txt             *
*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
*                                                                      *
*              Information and Software Systems Research               *
*                            AT&T Research                             *
*                           Florham Park NJ                            *
*                                                                      *
*                 Glenn Fowler <gsf@research.att.com>                  *
*                  David Korn <dgk@research.att.com>                   *
*                   Phong Vo <kpv@research.att.com>                    *
*                                                                      *
***********************************************************************/
#include    "sfhdr.h"

/*    Convert a floating point value to ASCII.
**
**    Written by Kiem-Phong Vo and Glenn Fowler (SFFMT_AFORMAT)
*/

static char       *Inf = "Inf", *Zero = "0", *Nan = "NaN";
#define SF_INTPART      (SF_IDIGITS/2)
#define SF_INFINITE     ((_Sfi = 3), Inf)
#define SF_ZERO         ((_Sfi = 1), Zero)
#define SF_NAN          ((_Sfi = 3), Nan)

#if ! _lib_isnanl
#define isnanl(n) ((n)==_Sflnan)
#endif
#if ! _lib_isnan
#define isnan(n)  ((n)==_Sfdnan)
#endif

#if __STD_C
char* _sfcvt(Sfdouble_t dv, char* buf, size_t size, int n_digit,
            int* decpt, int* sign, int* len, int format)
#else
char* _sfcvt(dv,buf,size,n_digit,decpt,sign,len,format)
Sfdouble_t  dv;         /* value to convert           */
char*       buf;        /* conversion goes here       */
size_t            size;       /* size of buf                */
int         n_digit;    /* number of digits wanted    */
int*        decpt;            /* to return decimal point    */
int*        sign;       /* to return sign       */
int*        len;        /* return string length       */
int         format;           /* conversion format          */
#endif
{
      reg char          *sp;
      reg long          n, v;
      reg char          *ep, *b, *endsp;
      _ast_flt_unsigned_max_t m;

      static char       lx[] = "0123456789abcdef";
      static char       ux[] = "0123456789ABCDEF";

      *sign = *decpt = 0;

#if !_ast_fltmax_double
      if(format&SFFMT_LDOUBLE)
      {     Sfdouble_t  f = dv;

            if(isnanl(f))
                  return SF_NAN;
            else if(f == 0.)
                  return SF_ZERO;
            else if((*sign = (f < 0.)) )  /* assignment = */
                  f = -f;
            if(f < LDBL_MIN)
                  return SF_ZERO;
            else if(f > LDBL_MAX)
                  return SF_INFINITE;

            if(format & SFFMT_AFORMAT)
            {     Sfdouble_t  g;
                  int         x;
                  b = sp = buf;
                  ep = (format & SFFMT_UPPER) ? ux : lx;
                  if(n_digit <= 0 || n_digit >= (size - 9))
                        n_digit = size - 9;
                  endsp = sp + n_digit + 1;

                  g = frexpl(f, &x);
                  *decpt = x;
                  f = ldexpl(g, 8 * sizeof(m) - 3);

                  for (;;)
                  {     m = f;
                        x = 8 * sizeof(m);
                        while ((x -= 4) >= 0)
                        {     *sp++ = ep[(m >> x) & 0xf];
                              if (sp >= endsp)
                              {     ep = sp + 1;
                                    goto done;
                              }
                        }
                        f -= m;
                        f = ldexpl(f, 8 * sizeof(m));
                  }
            }

            n = 0;
            if(f >= (Sfdouble_t)SF_MAXLONG)
            {     /* scale to a small enough number to fit an int */
                  v = SF_MAXEXP10-1;
                  do
                  {     if(f < _Sfpos10[v])
                              v -= 1;
                        else
                        {
                              f *= _Sfneg10[v];
                              if((n += (1<<v)) >= SF_IDIGITS)
                                    return SF_INFINITE;
                        }
                  } while(f >= (Sfdouble_t)SF_MAXLONG);
            }
            *decpt = (int)n;

            b = sp = buf + SF_INTPART;
            if((v = (int)f) != 0)
            {     /* translate the integer part */
                  f -= (Sfdouble_t)v;

                  sfucvt(v,sp,n,ep,long,ulong);

                  n = b-sp;
                  if((*decpt += (int)n) >= SF_IDIGITS)
                        return SF_INFINITE;
                  b = sp;
                  sp = buf + SF_INTPART;
            }
            else  n = 0;

            /* remaining number of digits to compute; add 1 for later rounding */
            n = (((format&SFFMT_EFORMAT) || *decpt <= 0) ? 1 : *decpt+1) - n;
            if(n_digit > 0)
            {     if(n_digit > LDBL_DIG)
                        n_digit = LDBL_DIG;
                  n += n_digit;
            }

            if((ep = (sp+n)) > (endsp = buf+(size-2)))
                  ep = endsp; 
            if(sp > ep)
                  sp = ep;
            else
            {
                  if((format&SFFMT_EFORMAT) && *decpt == 0 && f > 0.)
                  {     Sfdouble_t  d;
                        while((int)(d = f*10.) == 0)
                        {     f = d;
                              *decpt -= 1;
                        }
                  }

                  while(sp < ep)
                  {     /* generate fractional digits */
                        if(f <= 0.)
                        {     /* fill with 0's */
                              do { *sp++ = '0'; } while(sp < ep);
                              goto done;
                        }
                        else if((n = (long)(f *= 10.)) < 10)
                        {     *sp++ = '0' + n;
                              f -= n;
                        }
                        else /* n == 10 */
                        {     do { *sp++ = '9'; } while(sp < ep);
                        }
                  }
            }
      } else
#endif
      {     double      f = (double)dv;

            if(isnan(f))
                  return SF_NAN;
            else if(f == 0.)
                  return SF_ZERO;
            else if((*sign = (f < 0.)) )  /* assignment = */
                  f = -f;
            if(f < DBL_MIN)
                  return SF_ZERO;
            else if(f > DBL_MAX)
                  return SF_INFINITE;

            if(format & SFFMT_AFORMAT)
            {     double      g;
                  int   x;
                  b = sp = buf;
                  ep = (format & SFFMT_UPPER) ? ux : lx;
                  if(n_digit <= 0 || n_digit >= (size - 9))
                        n_digit = size - 9;
                  endsp = sp + n_digit;

                  g = frexp(f, &x);
                  *decpt = x;
                  f = ldexp(g, 8 * sizeof(m) - 3);

                  for (;;)
                  {     m = f;
                        x = 8 * sizeof(m);
                        while ((x -= 4) >= 0)
                        {     *sp++ = ep[(m >> x) & 0xf];
                              if (sp >= endsp)
                              {     ep = sp + 1;
                                    goto done;
                              }
                        }
                        f -= m;
                        f = ldexp(f, 8 * sizeof(m));
                  }
            }
            n = 0;
            if(f >= (double)SF_MAXLONG)
            {     /* scale to a small enough number to fit an int */
                  v = SF_MAXEXP10-1;
                  do
                  {     if(f < _Sfpos10[v])
                              v -= 1;
                        else
                        {     f *= _Sfneg10[v];
                              if((n += (1<<v)) >= SF_IDIGITS)
                                    return SF_INFINITE;
                        }
                  } while(f >= (double)SF_MAXLONG);
            }
            *decpt = (int)n;

            b = sp = buf + SF_INTPART;
            if((v = (int)f) != 0)
            {     /* translate the integer part */
                  f -= (double)v;

                  sfucvt(v,sp,n,ep,long,ulong);

                  n = b-sp;
                  if((*decpt += (int)n) >= SF_IDIGITS)
                        return SF_INFINITE;
                  b = sp;
                  sp = buf + SF_INTPART;
            }
            else  n = 0;

            /* remaining number of digits to compute; add 1 for later rounding */
            n = (((format&SFFMT_EFORMAT) || *decpt <= 0) ? 1 : *decpt+1) - n;
            if(n_digit > 0)
            {     if(n_digit > DBL_DIG)
                        n_digit = DBL_DIG;
                  n += n_digit;
            }

            if((ep = (sp+n)) > (endsp = buf+(size-2)))
                  ep = endsp; 
            if(sp > ep)
                  sp = ep;
            else
            {
                  if((format&SFFMT_EFORMAT) && *decpt == 0 && f > 0.)
                  {     reg double  d;
                        while((int)(d = f*10.) == 0)
                        {     f = d;
                              *decpt -= 1;
                        }
                  }

                  while(sp < ep)
                  {     /* generate fractional digits */
                        if(f <= 0.)
                        {     /* fill with 0's */
                              do { *sp++ = '0'; } while(sp < ep);
                              goto done;
                        }
                        else if((n = (int)(f *= 10.)) < 10)
                        {     *sp++ = (char)('0' + n);
                              f -= n;
                        }
                        else /* n == 10 */
                        {     do { *sp++ = '9'; } while(sp < ep);
                        }
                  }
            }
      }

      if(ep <= b)
            ep = b+1;
      else if(ep < endsp)
      {     /* round the last digit */
            *--sp += 5;
            while(*sp > '9')
            {     *sp = '0';
                  if(sp > b)
                        *--sp += 1;
                  else
                  {     /* next power of 10 */
                        *sp = '1';
                        *decpt += 1;
                        if(!(format&SFFMT_EFORMAT))
                        {     /* add one more 0 for %f precision */
                              ep[-1] = '0';
                              ep += 1;
                        }
                  }
            }
      }

done:
      *--ep = '\0';
      if(len)
            *len = ep-b;
      return b;
}

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