/* 
Copyright (C) 1990 Free Software Foundation
    written by Doug Lea (dl@rocky.oswego.edu)

This file is part of GNU CC.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY.  No author or distributor
accepts responsibility to anyone for the consequences of using it
or for whether it serves any particular purpose or works at all,
unless he says so in writing.  Refer to the GNU CC General Public
License for full details.

Everyone is granted permission to copy, modify and redistribute
GNU CC, but only under the conditions described in the
GNU CC General Public License.   A copy of this license is
supposed to have been given to you along with GNU CC so you
can know your rights and responsibilities.  It should be in a
file named COPYING.  Among other things, the copyright notice
and this notice must be preserved on all copies.  
*/

#ifdef __GNUG__
#pragma implementation
#endif
#include <builtin.h>
#include <math.h>
#include <values.h>
#include <AllocRing.h>

extern AllocRing _libgxx_fmtq;

char* dtoa(double fpnum,  char cvt, int width, int prec)
{
  // set up workspace

  // max possible digits <= those need to show all of prec + exp
  // <= ceil(log10(HUGE)) plus space for null, etc.

  const int worksiz = int((M_LN2 / M_LN10) * DMAXEXP) + 8; 

  // for fractional part
  char  fwork[worksiz];
  char* fw = fwork;

  // for integer part
  char  iwork[worksiz];
  char* iworkend = &iwork[sizeof(iwork) - 1];
  char* iw = iworkend;
  *iw = 0;

  // for exponent part

  const int eworksiz = int(M_LN2 * _DEXPLEN) + 8;
  char  ework[eworksiz];
  char* eworkend = &ework[sizeof(ework) - 1];
  char* ew = eworkend;
  *ew = 0;

#if (_IEEE != 0)
  if (isinf(fpnum))
  {
    char* inffmt = (char *) _libgxx_fmtq.alloc(5);
    char* inffmtp = inffmt;
    if (fpnum < 0)
      *inffmtp++ = '-';
    strcpy(inffmtp, "Inf");
    return inffmt;
  }

  if (isnan(fpnum))
  {
    char* nanfmt = (char *) _libgxx_fmtq.alloc(4);
    strcpy(nanfmt, "NaN");
    return nanfmt;
  }
#endif

  // grab sign & make non-negative
  int is_neg = fpnum < 0;
  if (is_neg) fpnum = -fpnum;

  // precision matters

  if (prec > worksiz - 2) // can't have more prec than supported
    prec = worksiz - 2;
  
  double powprec;
  if (prec == 6)
    powprec = 1.0e6;
  else
    powprec = pow(10.0, (long) prec);

  double rounder = 0.5 / powprec;

  int f_fmt = cvt == 'f' ||
    ((cvt == 'g') && (fpnum == 0.0 || (fpnum >= 1e-4 && fpnum < powprec)));

  int iwidth = 0;
  int fwidth = 0;
  int ewidth = 0;

  if (f_fmt)  // fixed format
  {
    double ipart;
    double fpart = modf(fpnum, &ipart);

    // convert fractional part

    if (fpart >= rounder || cvt != 'g')
    {
      fpart += rounder;
      if (fpart >= 1.0)
      {
        ipart += 1.0;
        fpart -= 1.0;
      }
      double ffpart = fpart;
      double ifpart;
      for (int i = 0; i < prec; ++i)
      {
        ffpart = modf(ffpart * 10.0, &ifpart);
        *fw++ = '0' + int(ifpart);
        ++fwidth;
      }
      if (cvt == 'g')  // inhibit trailing zeroes if g-fmt
      {
        for (char* p = fw - 1; p >= fwork && *p == '0'; --p)
        {
          *p = 0;
          --fwidth;
        }
      }
    }

    // convert integer part
    if (ipart == 0.0)
    {
      if (cvt != 'g' || fwidth < prec || fwidth < width)
      {
        *--iw = '0'; ++iwidth;
      }
    }
    else if (ipart <= double(MAXLONG)) // a useful speedup
    {
      long li = long(ipart);
      while (li != 0)
      {
        *--iw = '0' + (li % 10);
        li = li / 10;
        ++iwidth;
      }
    }
    else // the slow way
    {
      while (ipart > 0.5)
      {
        double ff = modf(ipart / 10.0, &ipart);
        ff = (ff + 0.05) * 10.0;
        *--iw = '0' + int(ff);
        ++iwidth;
      }
    }

    // g-fmt: kill part of frac if prec/width exceeded
    if (cvt == 'g')
    {
      int m = prec;
      if (m < width)
        m = width;
      int adj = iwidth + fwidth - m;
      if (adj > fwidth)
        adj = fwidth;
      if (adj > 0)
      {
        for (char* f = &fwork[fwidth-1]; f >= fwork && adj > 0; --adj, --f)
        {
          --fwidth;
          char ch = *f;
          *f = 0;
          if (ch > '5') // properly round: unavoidable propagation
          {
            int carry = 1;
            for (char* p = f - 1; p >= fwork && carry; --p)
            {
              ++*p;
              if (*p > '9')
                *p = '0';
              else
                carry = 0;
            }
            if (carry)
            {
              for (p = iworkend - 1; p >= iw && carry; --p)
              {
                ++*p;
                if (*p > '9')
                  *p = '0';
                else
                  carry = 0;
              }
              if (carry)
              {
                *--iw = '1';
                ++iwidth;
                --adj;
              }
            }
          }
        }
      }
    }
              
  }
  else  // e-fmt
  {
    
    // normalize
    int exp = 0;
    while (fpnum >= 10.0)
    {
      fpnum *= 0.1;
      ++exp;
    }
    while (fpnum > 0.0 && fpnum < 1.0)
    {
      fpnum *= 10.0;
      --exp;
    }
    
    double ipart;
    double fpart = modf(fpnum, &ipart);


    if (cvt == 'g')     // used up one digit for int part...
    {
      --prec;
      powprec /= 10.0;
      rounder = 0.5 / powprec;
    }

    // convert fractional part -- almost same as above
    if (fpart >= rounder || cvt != 'g')
    {
      fpart += rounder;
      if (fpart >= 1.0)
      {
        fpart -= 1.0;
        ipart += 1.0;
        if (ipart >= 10.0)
        {
          ++exp;
          ipart /= 10.0;
          fpart /= 10.0;
        }
      }
      double ffpart = fpart;
      double ifpart;
      for (int i = 0; i < prec; ++i)
      {
        ffpart = modf(ffpart * 10.0, &ifpart);
        *fw++ = '0' + int(ifpart);
        ++fwidth;
      }
      if (cvt == 'g')  // inhibit trailing zeroes if g-fmt
      {
        for (char* p = fw - 1; p >= fwork && *p == '0'; --p)
        {
          *p = 0;
          --fwidth;
        }
      }
    }

    
    // convert exponent

    char eneg = exp < 0;
    if (eneg) exp = - exp;

    while (exp > 0)
    {
      *--ew = '0' + (exp % 10);
      exp /= 10;
      ++ewidth;
    }

    while (ewidth < 2)  // ensure at least 2 zeroes
    {
      *--ew = '0';
      ++ewidth;
    }

    *--ew = eneg ? '-' : '+';
    *--ew = 'e';

    ewidth += 2;

    // convert the one-digit integer part
    *--iw = '0' + int(ipart);
    ++iwidth;
    
  }

  // arrange everything in returned string

  int showdot = cvt != 'g' || fwidth > 0;

  int fmtwidth = is_neg + iwidth + showdot + fwidth + ewidth;
  
  int pad = width - fmtwidth;
  if (pad < 0) pad = 0;
  
  char* fmtbase = (char *) _libgxx_fmtq.alloc(fmtwidth + pad + 1);
  char* fmt = fmtbase;
  
  for (int i = 0; i < pad; ++i) *fmt++ = ' ';
  
  if (is_neg) *fmt++ = '-';
  
  for (i = 0; i < iwidth; ++i) *fmt++ = *iw++;
  
  if (showdot)
  {
    *fmt++ = '.';
    fw = fwork;
    for (i = 0; i < fwidth; ++i) *fmt++ = *fw++;
  }
  
  for (i = 0; i < ewidth; ++i) *fmt++ = *ew++;
  
  *fmt = 0;
  
  return fmtbase;
}