/* Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   Contributed by Andy Vaught
   Write float code factoring to this file by Jerry DeLisle   
   F2003 I/O support contributed by Jerry DeLisle

This file is part of the GNU Fortran runtime library (libgfortran).

Libgfortran is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

Libgfortran is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#include "config.h"

typedef enum
{ S_NONE, S_MINUS, S_PLUS }
sign_t;

/* Given a flag that indicates if a value is negative or not, return a
   sign_t that gives the sign that we need to produce.  */

static sign_t
calculate_sign (st_parameter_dt *dtp, int negative_flag)
{
  sign_t s = S_NONE;

  if (negative_flag)
    s = S_MINUS;
  else
    switch (dtp->u.p.sign_status)
      {
      case SIGN_SP:	/* Show sign. */
	s = S_PLUS;
	break;
      case SIGN_SS:	/* Suppress sign. */
	s = S_NONE;
	break;
      case SIGN_S:	/* Processor defined. */
      case SIGN_UNSPECIFIED:
	s = options.optional_plus ? S_PLUS : S_NONE;
	break;
      }

  return s;
}


/* Output a real number according to its format which is FMT_G free.  */

static void
output_float (st_parameter_dt *dtp, const fnode *f, char *buffer, size_t size, 
	      int sign_bit, bool zero_flag, int ndigits, int edigits)
{
  char *out;
  char *digits;
  int e;
  char expchar, rchar;
  format_token ft;
  int w;
  int d;
  /* Number of digits before the decimal point.  */
  int nbefore;
  /* Number of zeros after the decimal point.  */
  int nzero;
  /* Number of digits after the decimal point.  */
  int nafter;
  /* Number of zeros after the decimal point, whatever the precision.  */
  int nzero_real;
  int leadzero;
  int nblanks;
  int i;
  sign_t sign;

  ft = f->format;
  w = f->u.real.w;
  d = f->u.real.d;

  rchar = '5';
  nzero_real = -1;

  /* We should always know the field width and precision.  */
  if (d < 0)
    internal_error (&dtp->common, "Unspecified precision");

  sign = calculate_sign (dtp, sign_bit);
  
  /* The following code checks the given string has punctuation in the correct
     places.  Uncomment if needed for debugging.
     if (d != 0 && ((buffer[2] != '.' && buffer[2] != ',')
		    || buffer[ndigits + 2] != 'e'))
       internal_error (&dtp->common, "printf is broken");  */

  /* Read the exponent back in.  */
  e = atoi (&buffer[ndigits + 3]) + 1;

  /* Make sure zero comes out as 0.0e0.   */
  if (zero_flag)
    {
      e = 0;
      if (compile_options.sign_zero == 1)
	sign = calculate_sign (dtp, sign_bit);
      else
	sign = calculate_sign (dtp, 0);

      /* Handle special cases.  */
      if (w == 0)
	w = d + 2;

      /* For this one we choose to not output a decimal point.
	 F95 10.5.1.2.1  */
      if (w == 1 && ft == FMT_F)
	{
	  out = write_block (dtp, w);
	  if (out == NULL)
	    return;

	  if (unlikely (is_char4_unit (dtp)))
	    {
	      gfc_char4_t *out4 = (gfc_char4_t *) out;
	      *out4 = '0';
	      return;
	    }

	  *out = '0';
	  return;
	}
	      
    }

  /* Normalize the fractional component.  */
  buffer[2] = buffer[1];
  digits = &buffer[2];

  /* Figure out where to place the decimal point.  */
  switch (ft)
    {
    case FMT_F:
      if (d == 0 && e <= 0 && dtp->u.p.scale_factor == 0)
	{
	  memmove (digits + 1, digits, ndigits - 1);
	  digits[0] = '0';
	  e++;
	}

      nbefore = e + dtp->u.p.scale_factor;
      if (nbefore < 0)
	{
	  nzero = -nbefore;
          nzero_real = nzero;
	  if (nzero > d)
	    nzero = d;
	  nafter = d - nzero;
	  nbefore = 0;
	}
      else
	{
	  nzero = 0;
	  nafter = d;
	}
      expchar = 0;
      break;

    case FMT_E:
    case FMT_D:
      i = dtp->u.p.scale_factor;
      if (d <= 0 && i == 0)
	{
	  generate_error (&dtp->common, LIBERROR_FORMAT, "Precision not "
			  "greater than zero in format specifier 'E' or 'D'");
	  return;
	}
      if (i <= -d || i >= d + 2)
	{
	  generate_error (&dtp->common, LIBERROR_FORMAT, "Scale factor "
			  "out of range in format specifier 'E' or 'D'");
	  return;
	}

      if (!zero_flag)
	e -= i;
      if (i < 0)
	{
	  nbefore = 0;
	  nzero = -i;
	  nafter = d + i;
	}
      else if (i > 0)
	{
	  nbefore = i;
	  nzero = 0;
	  nafter = (d - i) + 1;
	}
      else /* i == 0 */
	{
	  nbefore = 0;
	  nzero = 0;
	  nafter = d;
	}

      if (ft == FMT_E)
	expchar = 'E';
      else
	expchar = 'D';
      break;

    case FMT_EN:
      /* The exponent must be a multiple of three, with 1-3 digits before
	 the decimal point.  */
      if (!zero_flag)
        e--;
      if (e >= 0)
	nbefore = e % 3;
      else
	{
	  nbefore = (-e) % 3;
	  if (nbefore != 0)
	    nbefore = 3 - nbefore;
	}
      e -= nbefore;
      nbefore++;
      nzero = 0;
      nafter = d;
      expchar = 'E';
      break;

    case FMT_ES:
      if (!zero_flag)
        e--;
      nbefore = 1;
      nzero = 0;
      nafter = d;
      expchar = 'E';
      break;

    default:
      /* Should never happen.  */
      internal_error (&dtp->common, "Unexpected format token");
    }

  /* Round the value.  The value being rounded is an unsigned magnitude.
     The ROUND_COMPATIBLE is rounding away from zero when there is a tie.  */
  switch (dtp->u.p.current_unit->round_status)
    {
      case ROUND_ZERO: /* Do nothing and truncation occurs.  */
	goto skip;
      case ROUND_UP:
	if (sign_bit)
	  goto skip;
	rchar = '0';
	break;
      case ROUND_DOWN:
	if (!sign_bit)
	  goto skip;
	rchar = '0';
	break;
      case ROUND_NEAREST:
	/* Round compatible unless there is a tie. A tie is a 5 with
	   all trailing zero's.  */
	i = nafter + nbefore;
	if (digits[i] == '5')
	  {
	    for(i++ ; i < ndigits; i++)
	      {
		if (digits[i] != '0')
		  goto do_rnd;
	      }
	    /* It is a  tie so round to even.  */
	    switch (digits[nafter + nbefore - 1])
	      {
		case '1':
		case '3':
		case '5':
		case '7':
		case '9':
		  /* If odd, round away from zero to even.  */
		  break;
		default:
		  /* If even, skip rounding, truncate to even.  */
		  goto skip;
	      }
	  }
	 /* Fall through.  */ 
      case ROUND_PROCDEFINED:
      case ROUND_UNSPECIFIED:
      case ROUND_COMPATIBLE:
	rchar = '5';
	/* Just fall through and do the actual rounding.  */
    }
    
  do_rnd:
 
  if (nbefore + nafter == 0)
    {
      ndigits = 0;
      if (nzero_real == d && digits[0] >= rchar)
	{
	  /* We rounded to zero but shouldn't have */
	  nzero--;
	  nafter = 1;
	  digits[0] = '1';
	  ndigits = 1;
	}
    }
  else if (nbefore + nafter < ndigits)
    {
      ndigits = nbefore + nafter;
      i = ndigits;
      if (digits[i] >= rchar)
	{
	  /* Propagate the carry.  */
	  for (i--; i >= 0; i--)
	    {
	      if (digits[i] != '9')
		{
		  digits[i]++;
		  break;
		}
	      digits[i] = '0';
	    }

	  if (i < 0)
	    {
	      /* The carry overflowed.  Fortunately we have some spare
	         space at the start of the buffer.  We may discard some
	         digits, but this is ok because we already know they are
	         zero.  */
	      digits--;
	      digits[0] = '1';
	      if (ft == FMT_F)
		{
		  if (nzero > 0)
		    {
		      nzero--;
		      nafter++;
		    }
		  else
		    nbefore++;
		}
	      else if (ft == FMT_EN)
		{
		  nbefore++;
		  if (nbefore == 4)
		    {
		      nbefore = 1;
		      e += 3;
		    }
		}
	      else
		e++;
	    }
	}
    }

  skip:

  /* Calculate the format of the exponent field.  */
  if (expchar)
    {
      edigits = 1;
      for (i = abs (e); i >= 10; i /= 10)
	edigits++;

      if (f->u.real.e < 0)
	{
	  /* Width not specified.  Must be no more than 3 digits.  */
	  if (e > 999 || e < -999)
	    edigits = -1;
	  else
	    {
	      edigits = 4;
	      if (e > 99 || e < -99)
		expchar = ' ';
	    }
	}
      else
	{
	  /* Exponent width specified, check it is wide enough.  */
	  if (edigits > f->u.real.e)
	    edigits = -1;
	  else
	    edigits = f->u.real.e + 2;
	}
    }
  else
    edigits = 0;

  /* Zero values always output as positive, even if the value was negative
     before rounding.  */
  for (i = 0; i < ndigits; i++)
    {
      if (digits[i] != '0')
	break;
    }
  if (i == ndigits)
    {
      /* The output is zero, so set the sign according to the sign bit unless
	 -fno-sign-zero was specified.  */
      if (compile_options.sign_zero == 1)
        sign = calculate_sign (dtp, sign_bit);
      else
	sign = calculate_sign (dtp, 0);
    }

  /* Pick a field size if none was specified.  */
  if (w <= 0)
    w = nbefore + nzero + nafter + (sign != S_NONE ? 2 : 1);
  
  /* Work out how much padding is needed.  */
  nblanks = w - (nbefore + nzero + nafter + edigits + 1);
  if (sign != S_NONE)
    nblanks--;

  if (dtp->u.p.g0_no_blanks)
    {
      w -= nblanks;
      nblanks = 0;
    }

  /* Create the ouput buffer.  */
  out = write_block (dtp, w);
  if (out == NULL)
    return;

  /* Check the value fits in the specified field width.  */
  if (nblanks < 0 || edigits == -1)
    {
      if (unlikely (is_char4_unit (dtp)))
	{
	  gfc_char4_t *out4 = (gfc_char4_t *) out;
	  memset4 (out4, '*', w);
	  return;
	}
      star_fill (out, w);
      return;
    }

  /* See if we have space for a zero before the decimal point.  */
  if (nbefore == 0 && nblanks > 0)
    {
      leadzero = 1;
      nblanks--;
    }
  else
    leadzero = 0;

  /* For internal character(kind=4) units, we duplicate the code used for
     regular output slightly modified.  This needs to be maintained
     consistent with the regular code that follows this block.  */
  if (unlikely (is_char4_unit (dtp)))
    {
      gfc_char4_t *out4 = (gfc_char4_t *) out;
      /* Pad to full field width.  */

      if ( ( nblanks > 0 ) && !dtp->u.p.no_leading_blank)
	{
	  memset4 (out4, ' ', nblanks);
	  out4 += nblanks;
	}

      /* Output the initial sign (if any).  */
      if (sign == S_PLUS)
	*(out4++) = '+';
      else if (sign == S_MINUS)
	*(out4++) = '-';

      /* Output an optional leading zero.  */
      if (leadzero)
	*(out4++) = '0';

      /* Output the part before the decimal point, padding with zeros.  */
      if (nbefore > 0)
	{
	  if (nbefore > ndigits)
	    {
	      i = ndigits;
	      memcpy4 (out4, digits, i);
	      ndigits = 0;
	      while (i < nbefore)
		out4[i++] = '0';
	    }
	  else
	    {
	      i = nbefore;
	      memcpy4 (out4, digits, i);
	      ndigits -= i;
	    }

	  digits += i;
	  out4 += nbefore;
	}

      /* Output the decimal point.  */
      *(out4++) = dtp->u.p.current_unit->decimal_status
		    == DECIMAL_POINT ? '.' : ',';

      /* Output leading zeros after the decimal point.  */
      if (nzero > 0)
	{
	  for (i = 0; i < nzero; i++)
	    *(out4++) = '0';
	}

      /* Output digits after the decimal point, padding with zeros.  */
      if (nafter > 0)
	{
	  if (nafter > ndigits)
	    i = ndigits;
	  else
	    i = nafter;

	  memcpy4 (out4, digits, i);
	  while (i < nafter)
	    out4[i++] = '0';

	  digits += i;
	  ndigits -= i;
	  out4 += nafter;
	}

      /* Output the exponent.  */
      if (expchar)
	{
	  if (expchar != ' ')
	    {
	      *(out4++) = expchar;
	      edigits--;
	    }
#if HAVE_SNPRINTF
	  snprintf (buffer, size, "%+0*d", edigits, e);
#else
	  sprintf (buffer, "%+0*d", edigits, e);
#endif
	  memcpy4 (out4, buffer, edigits);
	}

      if (dtp->u.p.no_leading_blank)
	{
	  out4 += edigits;
	  memset4 (out4, ' ' , nblanks);
	  dtp->u.p.no_leading_blank = 0;
	}
      return;
    } /* End of character(kind=4) internal unit code.  */

  /* Pad to full field width.  */

  if ( ( nblanks > 0 ) && !dtp->u.p.no_leading_blank)
    {
      memset (out, ' ', nblanks);
      out += nblanks;
    }

  /* Output the initial sign (if any).  */
  if (sign == S_PLUS)
    *(out++) = '+';
  else if (sign == S_MINUS)
    *(out++) = '-';

  /* Output an optional leading zero.  */
  if (leadzero)
    *(out++) = '0';

  /* Output the part before the decimal point, padding with zeros.  */
  if (nbefore > 0)
    {
      if (nbefore > ndigits)
	{
	  i = ndigits;
	  memcpy (out, digits, i);
	  ndigits = 0;
	  while (i < nbefore)
	    out[i++] = '0';
	}
      else
	{
	  i = nbefore;
	  memcpy (out, digits, i);
	  ndigits -= i;
	}

      digits += i;
      out += nbefore;
    }

  /* Output the decimal point.  */
  *(out++) = dtp->u.p.current_unit->decimal_status == DECIMAL_POINT ? '.' : ',';

  /* Output leading zeros after the decimal point.  */
  if (nzero > 0)
    {
      for (i = 0; i < nzero; i++)
	*(out++) = '0';
    }

  /* Output digits after the decimal point, padding with zeros.  */
  if (nafter > 0)
    {
      if (nafter > ndigits)
	i = ndigits;
      else
	i = nafter;

      memcpy (out, digits, i);
      while (i < nafter)
	out[i++] = '0';

      digits += i;
      ndigits -= i;
      out += nafter;
    }

  /* Output the exponent.  */
  if (expchar)
    {
      if (expchar != ' ')
	{
	  *(out++) = expchar;
	  edigits--;
	}
#if HAVE_SNPRINTF
      snprintf (buffer, size, "%+0*d", edigits, e);
#else
      sprintf (buffer, "%+0*d", edigits, e);
#endif
      memcpy (out, buffer, edigits);
    }

  if (dtp->u.p.no_leading_blank)
    {
      out += edigits;
      memset( out , ' ' , nblanks );
      dtp->u.p.no_leading_blank = 0;
    }

#undef STR
#undef STR1
#undef MIN_FIELD_WIDTH
}


/* Write "Infinite" or "Nan" as appropriate for the given format.  */

static void
write_infnan (st_parameter_dt *dtp, const fnode *f, int isnan_flag, int sign_bit)
{
  char * p, fin;
  int nb = 0;

  if (f->format != FMT_B && f->format != FMT_O && f->format != FMT_Z)
    {
      nb =  f->u.real.w;
  
      /* If the field width is zero, the processor must select a width 
	 not zero.  4 is chosen to allow output of '-Inf' or '+Inf' */
     
      if (nb == 0) nb = 4;
      p = write_block (dtp, nb);
      if (p == NULL)
	return;
      if (nb < 3)
	{
	  if (unlikely (is_char4_unit (dtp)))
	    {
	      gfc_char4_t *p4 = (gfc_char4_t *) p;
	      memset4 (p4, '*', nb);
	    }
	  else
	    memset (p, '*', nb);
	  return;
	}

      if (unlikely (is_char4_unit (dtp)))
	{
	  gfc_char4_t *p4 = (gfc_char4_t *) p;
	  memset4 (p4, ' ', nb);
	}
      else
	memset(p, ' ', nb);

      if (!isnan_flag)
	{
	  if (sign_bit)
	    {
	      /* If the sign is negative and the width is 3, there is
		 insufficient room to output '-Inf', so output asterisks */
	      if (nb == 3)
		{
		  if (unlikely (is_char4_unit (dtp)))
		    {
		      gfc_char4_t *p4 = (gfc_char4_t *) p;
		      memset4 (p4, '*', nb);
		    }
		  else
		    memset (p, '*', nb);
		  return;
		}
	      /* The negative sign is mandatory */
	      fin = '-';
	    }    
	  else
	    /* The positive sign is optional, but we output it for
	       consistency */
	    fin = '+';
	    
	  if (unlikely (is_char4_unit (dtp)))
	    {
	      gfc_char4_t *p4 = (gfc_char4_t *) p;
	      if (nb > 8)
		/* We have room, so output 'Infinity' */
		memcpy4 (p4 + nb - 8, "Infinity", 8);
	      else
		/* For the case of width equals 8, there is not enough room
		   for the sign and 'Infinity' so we go with 'Inf' */
		memcpy4 (p4 + nb - 3, "Inf", 3);

	      if (nb < 9 && nb > 3)
	        /* Put the sign in front of Inf */
		p4[nb - 4] = (gfc_char4_t) fin;
	      else if (nb > 8)
	        /* Put the sign in front of Infinity */
		p4[nb - 9] = (gfc_char4_t) fin;
	      return;
	    }

	  if (nb > 8)
	    /* We have room, so output 'Infinity' */
	    memcpy(p + nb - 8, "Infinity", 8);
	  else
	    /* For the case of width equals 8, there is not enough room
	       for the sign and 'Infinity' so we go with 'Inf' */
	    memcpy(p + nb - 3, "Inf", 3);

	  if (nb < 9 && nb > 3)
	    p[nb - 4] = fin;  /* Put the sign in front of Inf */
	  else if (nb > 8)
	    p[nb - 9] = fin;  /* Put the sign in front of Infinity */
	}
      else
        {
	  if (unlikely (is_char4_unit (dtp)))
	    {
	      gfc_char4_t *p4 = (gfc_char4_t *) p;
	      memcpy4 (p4 + nb - 3, "NaN", 3);
	    }
	  else
	    memcpy(p + nb - 3, "NaN", 3);
	}
      return;
    }
}


/* Returns the value of 10**d.  */

#define CALCULATE_EXP(x) \
inline static GFC_REAL_ ## x \
calculate_exp_ ## x  (int d)\
{\
  int i;\
  GFC_REAL_ ## x r = 1.0;\
  for (i = 0; i< (d >= 0 ? d : -d); i++)\
    r *= 10;\
  r = (d >= 0) ? r : 1.0 / r;\
  return r;\
}

CALCULATE_EXP(4)

CALCULATE_EXP(8)

#ifdef HAVE_GFC_REAL_10
CALCULATE_EXP(10)
#endif

#ifdef HAVE_GFC_REAL_16
CALCULATE_EXP(16)
#endif
#undef CALCULATE_EXP

/* Generate corresponding I/O format for FMT_G and output.
   The rules to translate FMT_G to FMT_E or FMT_F from DEC fortran
   LRM (table 11-2, Chapter 11, "I/O Formatting", P11-25) is:

   Data Magnitude                              Equivalent Conversion
   0< m < 0.1-0.5*10**(-d-1)                   Ew.d[Ee]
   m = 0                                       F(w-n).(d-1), n' '
   0.1-0.5*10**(-d-1)<= m < 1-0.5*10**(-d)     F(w-n).d, n' '
   1-0.5*10**(-d)<= m < 10-0.5*10**(-d+1)      F(w-n).(d-1), n' '
   10-0.5*10**(-d+1)<= m < 100-0.5*10**(-d+2)  F(w-n).(d-2), n' '
   ................                           ..........
   10**(d-1)-0.5*10**(-1)<= m <10**d-0.5       F(w-n).0,n(' ')
   m >= 10**d-0.5                              Ew.d[Ee]

   notes: for Gw.d ,  n' ' means 4 blanks
          for Gw.dEe, n' ' means e+2 blanks  */

#define OUTPUT_FLOAT_FMT_G(x) \
static void \
output_float_FMT_G_ ## x (st_parameter_dt *dtp, const fnode *f, \
		      GFC_REAL_ ## x m, char *buffer, size_t size, \
		      int sign_bit, bool zero_flag, int ndigits, int edigits) \
{ \
  int e = f->u.real.e;\
  int d = f->u.real.d;\
  int w = f->u.real.w;\
  fnode *newf;\
  GFC_REAL_ ## x rexp_d;\
  int low, high, mid;\
  int ubound, lbound;\
  char *p;\
  int save_scale_factor, nb = 0;\
\
  save_scale_factor = dtp->u.p.scale_factor;\
  newf = (fnode *) get_mem (sizeof (fnode));\
\
  rexp_d = calculate_exp_ ## x (-d);\
  if ((m > 0.0 && m < 0.1 - 0.05 * rexp_d) || (rexp_d * (m + 0.5) >= 1.0) ||\
      ((m == 0.0) && !(compile_options.allow_std & GFC_STD_F2003)))\
    { \
      newf->format = FMT_E;\
      newf->u.real.w = w;\
      newf->u.real.d = d;\
      newf->u.real.e = e;\
      nb = 0;\
      goto finish;\
    }\
\
  mid = 0;\
  low = 0;\
  high = d + 1;\
  lbound = 0;\
  ubound = d + 1;\
\
  while (low <= high)\
    { \
      GFC_REAL_ ## x temp;\
      mid = (low + high) / 2;\
\
      temp = (calculate_exp_ ## x (mid - 1) * (1 - 0.5 * rexp_d));\
\
      if (m < temp)\
        { \
          ubound = mid;\
          if (ubound == lbound + 1)\
            break;\
          high = mid - 1;\
        }\
      else if (m > temp)\
        { \
          lbound = mid;\
          if (ubound == lbound + 1)\
            { \
              mid ++;\
              break;\
            }\
          low = mid + 1;\
        }\
      else\
	{\
	  mid++;\
	  break;\
	}\
    }\
\
  if (e < 0)\
    nb = 4;\
  else\
    nb = e + 2;\
\
  newf->format = FMT_F;\
  newf->u.real.w = f->u.real.w - nb;\
\
  if (m == 0.0)\
    newf->u.real.d = d - 1;\
  else\
    newf->u.real.d = - (mid - d - 1);\
\
  dtp->u.p.scale_factor = 0;\
\
 finish:\
  output_float (dtp, newf, buffer, size, sign_bit, zero_flag, ndigits, \
		edigits);\
  dtp->u.p.scale_factor = save_scale_factor;\
\
  free (newf);\
\
  if (nb > 0 && !dtp->u.p.g0_no_blanks)\
    {\
      p = write_block (dtp, nb);\
      if (p == NULL)\
	return;\
      if (unlikely (is_char4_unit (dtp)))\
	{\
	  gfc_char4_t *p4 = (gfc_char4_t *) p;\
	  memset4 (p4, ' ', nb);\
	}\
      else\
	memset (p, ' ', nb);\
    }\
}\

OUTPUT_FLOAT_FMT_G(4)

OUTPUT_FLOAT_FMT_G(8)

#ifdef HAVE_GFC_REAL_10
OUTPUT_FLOAT_FMT_G(10)
#endif

#ifdef HAVE_GFC_REAL_16
OUTPUT_FLOAT_FMT_G(16)
#endif

#undef OUTPUT_FLOAT_FMT_G


/* Define a macro to build code for write_float.  */

  /* Note: Before output_float is called, sprintf is used to print to buffer the
     number in the format +D.DDDDe+ddd. For an N digit exponent, this gives us
     (MIN_FIELD_WIDTH-5)-N digits after the decimal point, plus another one
     before the decimal point.

     #   The result will always contain a decimal point, even if no
	 digits follow it

     -   The converted value is to be left adjusted on the field boundary

     +   A sign (+ or -) always be placed before a number

     MIN_FIELD_WIDTH  minimum field width

     *   (ndigits-1) is used as the precision

     e format: [-]d.ddde±dd where there is one digit before the
       decimal-point character and the number of digits after it is
       equal to the precision. The exponent always contains at least two
       digits; if the value is zero, the exponent is 00.  */

#ifdef HAVE_SNPRINTF

#define DTOA \
snprintf (buffer, size, "%+-#" STR(MIN_FIELD_WIDTH) ".*" \
	  "e", ndigits - 1, tmp);

#define DTOAL \
snprintf (buffer, size, "%+-#" STR(MIN_FIELD_WIDTH) ".*" \
	  "Le", ndigits - 1, tmp);

#else

#define DTOA \
sprintf (buffer, "%+-#" STR(MIN_FIELD_WIDTH) ".*" \
	 "e", ndigits - 1, tmp);

#define DTOAL \
sprintf (buffer, "%+-#" STR(MIN_FIELD_WIDTH) ".*" \
	 "Le", ndigits - 1, tmp);

#endif

#define WRITE_FLOAT(x,y)\
{\
	GFC_REAL_ ## x tmp;\
	tmp = * (GFC_REAL_ ## x *)source;\
	sign_bit = __builtin_signbit (tmp);\
	if (!isfinite (tmp))\
	  { \
	    write_infnan (dtp, f, isnan (tmp), sign_bit);\
	    return;\
	  }\
	tmp = sign_bit ? -tmp : tmp;\
	zero_flag = (tmp == 0.0);\
\
	DTOA ## y\
\
	if (f->format != FMT_G)\
	  output_float (dtp, f, buffer, size, sign_bit, zero_flag, ndigits, \
			edigits);\
	else \
	  output_float_FMT_G_ ## x (dtp, f, tmp, buffer, size, sign_bit, \
				    zero_flag, ndigits, edigits);\
}\

/* Output a real number according to its format.  */

static void
write_float (st_parameter_dt *dtp, const fnode *f, const char *source, int len)
{

#if defined(HAVE_GFC_REAL_16) && __LDBL_DIG__ > 18
# define MIN_FIELD_WIDTH 46
#else
# define MIN_FIELD_WIDTH 31
#endif
#define STR(x) STR1(x)
#define STR1(x) #x

  /* This must be large enough to accurately hold any value.  */
  char buffer[MIN_FIELD_WIDTH+1];
  int sign_bit, ndigits, edigits;
  bool zero_flag;
  size_t size;

  size = MIN_FIELD_WIDTH+1;

  /* printf pads blanks for us on the exponent so we just need it big enough
     to handle the largest number of exponent digits expected.  */
  edigits=4;

  if (f->format == FMT_F || f->format == FMT_EN || f->format == FMT_G 
      || ((f->format == FMT_D || f->format == FMT_E)
      && dtp->u.p.scale_factor != 0))
    {
      /* Always convert at full precision to avoid double rounding.  */
      ndigits = MIN_FIELD_WIDTH - 4 - edigits;
    }
  else
    {
      /* The number of digits is known, so let printf do the rounding.  */
      if (f->format == FMT_ES)
	ndigits = f->u.real.d + 1;
      else
	ndigits = f->u.real.d;
      if (ndigits > MIN_FIELD_WIDTH - 4 - edigits)
	ndigits = MIN_FIELD_WIDTH - 4 - edigits;
    }

  switch (len)
    {
    case 4:
      WRITE_FLOAT(4,)
      break;

    case 8:
      WRITE_FLOAT(8,)
      break;

#ifdef HAVE_GFC_REAL_10
    case 10:
      WRITE_FLOAT(10,L)
      break;
#endif
#ifdef HAVE_GFC_REAL_16
    case 16:
      WRITE_FLOAT(16,L)
      break;
#endif
    default:
      internal_error (NULL, "bad real kind");
    }
}