glibc/misc/efgcvt_r.c

/* Compatibility functions for floating point formatting, reentrant versions.
   Copyright (C) 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
#include <stdlib.h>
#include <sys/param.h>

#ifndef FLOAT_TYPE
#define FLOAT_TYPE double
#define FUNC_PREFIX
#define FLOAT_FMT_FLAG
#define FLOAT_NAME_EXT
#endif

#define APPEND(a, b) APPEND2 (a, b)
#define APPEND2(a, b) a##b

#define FLOOR APPEND(floor, FLOAT_NAME_EXT)
#define FABS APPEND(fabs, FLOAT_NAME_EXT)
#define LOG10 APPEND(log10, FLOAT_NAME_EXT)
#define EXP APPEND(exp, FLOAT_NAME_EXT)


int
APPEND (FUNC_PREFIX, fcvt_r) (value, ndigit, decpt, sign, buf, len)
     FLOAT_TYPE value;
     int ndigit, *decpt, *sign;
     char *buf;
     size_t len;
{
  int n, i;
  int left;

  if (buf == NULL)
    {
      __set_errno (EINVAL);
      return -1;
    }

  left = 0;
  if (isfinite (value))
    {
      *sign = signbit (value) != 0;
      if (*sign)
	value = -value;

      if (ndigit < 0)
	{
	  /* Rounding to the left of the decimal point.  */
	  while (ndigit < 0)
	    {
	      FLOAT_TYPE new_value = value * 0.1;

	      if (new_value < 1.0)
		{
		  ndigit = 0;
		  break;
		}

	      value = new_value;
	      ++left;
	      ++ndigit;
	    }
	}
    }
  else
    /* Value is Inf or NaN.  */
    *sign = 0;

  n = __snprintf (buf, len, "%.*" FLOAT_FMT_FLAG "f", ndigit, value);
  if (n < 0)
    return -1;

  i = 0;
  while (i < n && isdigit (buf[i]))
    ++i;
  *decpt = i;

  if (i == 0)
    /* Value is Inf or NaN.  */
    return 0;

  if (i < n)
    {
      do
	++i;
      while (i < n && !isdigit (buf[i]));

      if (*decpt == 1 && buf[0] == '0' && value != 0.0)
	{
	  /* We must not have leading zeroes.  Strip them all out and
	     adjust *DECPT if necessary.  */
	  --*decpt;
	  while (i < n && buf[i] == '0')
	    {
	      --*decpt;
	      ++i;
	    }
	}

      memmove (&buf[MAX (*decpt, 0)], &buf[i], n - i);
      buf[n - (i - MAX (*decpt, 0))] = '\0';
    }

  if (left)
    {
      *decpt += left;
      if (--len > n)
	{
	  while (left-- > 0 && n < len)
	    buf[n++] = '0';
	  buf[n] = '\0';
	}
    }

  return 0;
}

#define weak_extern2(name) weak_extern (name)
weak_extern2 (FLOOR) weak_extern2 (LOG10) weak_extern2 (FABS)
weak_extern2 (EXP)

int
APPEND (FUNC_PREFIX, ecvt_r) (value, ndigit, decpt, sign, buf, len)
     FLOAT_TYPE value;
     int ndigit, *decpt, *sign;
     char *buf;
     size_t len;
{
  int exponent = 0;

  if (isfinite (value) && value != 0.0)
    {
      FLOAT_TYPE (*log10_function) (FLOAT_TYPE) = &LOG10;

      if (log10_function)
	{
	  /* Use the reasonable code if -lm is included.  */
	  FLOAT_TYPE dexponent;
	  dexponent = FLOOR (LOG10 (FABS (value)));
	  value *= EXP (dexponent * -M_LN10);
	  exponent = (int) dexponent;
	}
      else
	{
	  /* Slow code that doesn't require -lm functions.  */
	  FLOAT_TYPE d;
	  if (value < 0.0)
	    d = -value;
	  else
	    d = value;
	  if (d < 1.0)
	    {
	      do
		{
		  d *= 10.0;
		  --exponent;
		}
	      while (d < 1.0);
	    }
	  else if (d >= 10.0)
	    {
	      do
		{
		  d *= 0.1;
		  ++exponent;
		}
	      while (d >= 10.0);
	    }
	  if (value < 0.0)
	    value = -d;
	  else
	    value = d;
	}
    }
  else if (value == 0.0)
    /* SUSv2 leaves it unspecified whether *DECPT is 0 or 1 for 0.0.
       This could be changed to -1 if we want to return 0.  */
    exponent = 0;

  if (ndigit <= 0 && len > 0)
    {
      buf[0] = '\0';
      *decpt = 1;
      *sign = isfinite (value) ? signbit (value) != 0 : 0;
    }
  else
    if (APPEND (FUNC_PREFIX, fcvt_r) (value, ndigit - 1, decpt, sign,
				      buf, len))
      return -1;

  *decpt += exponent;
  return 0;
}