nuttx/libs/libc/stdio/lib_libdtoa.c

/****************************************************************************
 * libs/libc/stdio/lib_libdtoa.c
 *
 * This file was ported to NuttX by Yolande Cates.
 *
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdbool.h>
#include <math.h>
#include <assert.h>

#include <nuttx/arch.h>

#include "libc.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#ifndef MIN
#  define MIN(a,b)          (a < b ? a : b)
#endif

#ifndef MAX
#  define MAX(a,b)          (a > b ? a : b)
#endif

/* Use the maximim precision with %g format if no precision is specified.
 * NOTE:  This may result in numbers with precision that exceeds the
 * precision of type double.
 */

#define DOUBLE_PRECISON_MAX 15

/* Use a default precision of 6 for the %f format if no precision is
 * specified.
 */

#define DEFAULT_PRECISON    6

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: zeroes
 *
 * Description:
 *   Print the specified number of zeres
 *
 ****************************************************************************/

static void zeroes(FAR struct lib_outstream_s *obj, int nzeroes)
{
  int i;

  for (i = nzeroes; i > 0; i--)
    {
      obj->put(obj, '0');
    }
}

/****************************************************************************
 * Name: truncate_zeroes
 *
 * Description:
 *   Adjust the string length to eliminate zeros in the fractional part of
 *   the string.
 *
 ****************************************************************************/

static inline int truncate_zeroes(FAR char *digits, int expt, int numlen)
{
  for (; numlen > expt && digits[numlen - 1] == '0'; numlen--)
    {
    }

  return numlen;
}

/****************************************************************************
 * Name: lib_dtoa_string
 *
 * Description:
 *   Print the specified string
 *
 ****************************************************************************/

static void lib_dtoa_string(FAR struct lib_outstream_s *obj, const char *str)
{
  while (*str)
    {
      obj->put(obj, *str++);
    }
}

/****************************************************************************
 * Name: lib_dtoa
 *
 * Description:
 *   This is part of lib_vsprintf().  It handles the floating point formats.
 *   This version supports only the %f (with precision).  If no precision
 *   was provided in the format, this will use precision == 0 which is
 *   probably not what you want.
 *
 * Input Parameters:
 *   obj   - The output stream object
 *   fmt   - The format character.  Not used 'f' is always assumed
 *   prec  - The number of digits to the right of the decimal point. If no
 *           precision is provided in the format, this will be zero.  And,
 *           unfortunately in this case, it will be treated literally as
 *           a precision of zero.
 *   flags - Only ALTFORM and SHOWPLUS flags are supported.  ALTFORM only
 *           applies if prec == 0 which is not supported anyway.
 *   value - The floating point value to convert.
 *
 ****************************************************************************/

static void lib_dtoa(FAR struct lib_outstream_s *obj, int fmt, int prec,
                     uint16_t flags, double value)
{
  FAR char *digits;     /* String returned by __dtoa */
  FAR char *rve;        /* Points to the end of the return value */
  bool notrailing;      /* True:  No trailing zeros */
  int  expt;            /* Integer value of exponent */
  int  numlen;          /* Actual number of digits returned by cvt */
  int  nchars;          /* Number of characters to print */
  int  dsgn;            /* Unused sign indicator */
  int  i;

  /* Set to default precision if none specified */

  notrailing = false;
  if (!IS_HASDOT(flags) && prec == 0)
    {
      if (IS_NOTRAILINGZERO(flags))
        {
          prec       = DOUBLE_PRECISON_MAX;
          notrailing = true;
        }
      else
        {
          prec       = DEFAULT_PRECISON;
        }
    }

  /* Special handling for NaN and Infinity */

  if (isnan(value))
    {
      lib_dtoa_string(obj, "NaN");
      return;
    }

  if (isinf(value))
    {
      if (value < 0.0)
        {
          obj->put(obj, '-');
        }

      lib_dtoa_string(obj, "Infinity");
      return;
    }

  /* Non-zero... positive or negative */

  if (value < 0)
    {
      value = -value;
      SET_NEGATE(flags);
    }

  /* Perform the conversion */

  digits = __dtoa(value, 3, prec, &expt, &dsgn, &rve);
  numlen = rve - digits;

  /* If we are going to truncate trailing zeros, then make sure we have not
   * exceeded the precision of type double.
   */

  if (notrailing && numlen > DOUBLE_PRECISON_MAX)
    {
      /* Make sure there are fractional digits to truncate */

      if (expt <= DOUBLE_PRECISON_MAX)
        {
          numlen = DOUBLE_PRECISON_MAX;
        }
      else
        {
          numlen = expt;
        }

      /* Shortening the string probably now exposes some trailing zeroes */

      numlen =  truncate_zeroes(digits, expt, numlen);
    }

  /* Avoid precision error from missing trailing zeroes */

  numlen = MAX(expt, numlen);

  if (IS_NEGATE(flags))
    {
      obj->put(obj, '-');
    }
  else if (IS_SHOWPLUS(flags))
    {
      obj->put(obj, '+');
    }

  /* Special case exact zero or the case where the number is smaller than
   * the print precision.
   */

  if (value == 0.0 || (expt < (notrailing ? 0 : -prec)))
    {
      /* kludge for __dtoa irregularity */

      obj->put(obj, '0');

      /* A decimal point is printed only in the alternate form or if a
       * particular precision is requested.
       */

      if ((prec > 0 && !notrailing) || IS_ALTFORM(flags))
        {
          obj->put(obj, '.');

          /* Always print at least one digit to the right of the decimal
           * point.
           */

          if (notrailing)
            {
              prec = MAX(1, numlen);
            }
          else
            {
              prec = MAX(1, prec);
            }
        }
    }

  /* A non-zero value will be printed */

  else
    {
      /* Handle the case where the value is less than 1.0 (in magnitude) and
       * will need a leading zero.
       */

      if (expt <= 0)
        {
          /* Print a single zero to the left of the decimal point */

          obj->put(obj, '0');

          /* Print the decimal point */

          obj->put(obj, '.');

          /* Print any leading zeros to the right of the decimal point */

          if (expt < 0 || !notrailing)
            {
              nchars = MIN(-expt, prec);
              zeroes(obj, nchars);
              prec -= nchars;
            }
        }

      /* Handle the general case where the value is greater than 1.0 (in
       * magnitude).
       */

      else
        {
          /* Print the integer part to the left of the decimal point */

          for (i = expt; i > 0; i--)
            {
              if (*digits != '\0')
                {
                  obj->put(obj, *digits);
                  digits++;
                }
              else
                {
                  obj->put(obj, '0');
                }
            }

          /* Get the length of the fractional part */

          numlen -= expt;

          /* If there is no fractional part, then a decimal point is printed
           * only in the alternate form or if a particular precision is
           * requested.
           */

          if (numlen > 0 || (prec > 0 && !notrailing) ||
              IS_ALTFORM(flags))
            {
              /* Print the decimal point */

              obj->put(obj, '.');

              /* Always print at least one digit to the right of the decimal
               * point.
               */

              if (notrailing)
                {
                  prec = MAX(1, numlen);
                }
              else
                {
                  prec = MAX(1, prec);
                }
            }
        }

      /* If a precision was specified, then limit the number digits to the
       * right of the decimal point.
       */

      if (prec > 0)
        {
          nchars = MIN(numlen, prec);
        }
      else
        {
          nchars = numlen;
        }

      /* Print the fractional part to the right of the decimal point */

      for (i = nchars; i > 0; i--)
        {
          obj->put(obj, *digits);
          digits++;
        }

      /* Decrement to get the number of trailing zeroes to print */

      prec -= nchars;
    }

  /* Finally, print any trailing zeroes */

  if (!notrailing)
    {
      zeroes(obj, prec);
    }
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/