float.h

/*
 * PSPLINK
 * -----------------------------------------------------------------------
 * Licensed under the BSD license, see LICENSE in PSPLINK root for details.
 *
 * util.c - util functions for psplink
 *
 * Copyright (c) 2005 James F <tyranid@gmail.com>
 * Copyright (c) 2005 Julian T <lovely@crm114.net>
 *
 * $HeadURL: svn://svn.ps2dev.org/psp/trunk/psplink/psplink/util.c $
 * $Id: util.c 1981 2006-07-24 21:51:41Z tyranid $
 */
 
#define MODE_GENERIC 0
#define MODE_EXP 1
#define MODE_FLOAT_ONLY 2

static int is_nan(unsigned int val)
{
  unsigned int conv;
  int sign;
  int exp;
  int mantissa;

  conv = *((unsigned int *) val);
  sign = (conv >> 31) & 1;

  exp = (conv >> 23) & 0xff;
  mantissa = conv & 0x7fffff;

  if(exp == 255)
  {
    return 1;
  }
  return 0;
}

static int is_inf(unsigned int val)
{
  unsigned int conv;
  int sign;
  int exp;
  int mantissa;

  conv = *((unsigned int *) val);
  sign = (conv >> 31) & 1;

  exp = (conv >> 23) & 0xff;
  mantissa = conv & 0x7fffff;

  if((exp == 255) && (mantissa == 0))
  {
    if(sign)
    {
      return -1;
    }
    else
    {
      return 1;
    }
  }

  return 0;
}

static char get_num(float *val, int *exp)
{
  int digit;
  float tmp;
  char ret = '0';

  if((*exp)++ < 16)
  {
    digit = (int) *val;
    if((digit >= 0) && (digit < 10))
    {
      ret = digit + '0';
      tmp = (float) digit;
      *val = (*val - digit)*10.0f;
    }
  }

  return ret;
}

void f_cvt(unsigned int addr, char *buf, int bufsize, int precision, int mode)
{
  if(addr % 4) 
  {
    strncpy(buf, "ERR", bufsize);
    buf[bufsize-1] = 0;
    return;
  }
  char conv_buf[128];
  char *conv_p = conv_buf;
  float normval;
  int digits = 0;
  int exp = 0;
  int exp_pos = 0;
  int inf;
  int sign = 0;
  float round;
  int rndpos = 0;
  float val=*((float*)(addr));

  /* check for nan and +/- infinity */  
  inf = is_inf(addr);
  if(inf != 0)
  {
    if(inf < 0)
    {
      strncpy(buf, "-INF", bufsize);
      buf[bufsize-1] = 0;
    }
    else
    {
      strncpy(buf, "INF", bufsize);
      buf[bufsize-1] = 0;
    }

    return;
  }
  if(is_nan(addr))
  {
    strncpy(buf, "NAN", bufsize);
    buf[bufsize-1] = 0;
    return;
  }

  if(val < 0.0f)
  {
    sign = 1;
    normval -= val;
  }
  else
  {
    sign = 0;
    normval = val;
  }

  if(precision < 0)
  {
    precision = 6;
  }

  /* normalise value */
  if(normval > 0.0f)
  {
    while((normval >= 1e8f) && (digits++ < 100))
    {
      normval *= 1e-8f;
      exp += 8;
    }
    while((normval >= 10.0f) && (digits++ < 100))
    {
      normval *= 0.1f;
      exp++;
    }
    while((normval < 1e-8f) && (digits++ < 100))
    {
      normval *= 1e8f;
      exp -= 8;
    }
    while((normval < 1.0f) && (digits++ < 100))
    {
      normval *= 10.0f;
      exp--;
    }
  }

  for(rndpos = precision, round = 0.4999f; rndpos > 0; rndpos--, round *= 0.1f);

  if(sign)
  {
    *conv_p++ = '-';
  }

  if((mode != MODE_EXP) && (mode != MODE_FLOAT_ONLY))
  {
    if((exp < -4) || (exp > precision))
    {
      mode = MODE_EXP;
    }
  }

  normval += round;

  if(mode == MODE_EXP)
  {
    *conv_p++ = get_num(&normval, &exp_pos);
    *conv_p++ = '.';

    while(precision > 0)
    {
      *conv_p++ = get_num(&normval, &exp_pos);
      precision--;
    }

    while((conv_p[-1] == '0') || (conv_p[-1] == '.'))
    {
      conv_p--;
    }

    *conv_p++ = 'e';
    if(exp < 0)
    {
      exp = -exp;
      *conv_p++ = '-';
    }
    else
    {
      *conv_p++ = '+';
    }

    if(exp / 100)
    {
      *conv_p++ = (exp / 100) + '0';
      exp %= 100;
    }

    if(exp / 10)
    {
      *conv_p++ = (exp / 10) + '0';
      exp %= 10;
    }
    *conv_p++ = exp + '0';
  }
  else
  {
    if(exp >= 0)
    {
      for(; (exp >= 0); exp--)
      {
        *conv_p++ = get_num(&normval, &exp_pos);
      }
    }
    else
    {
      *conv_p++ = '0';
    }

    exp++;
    if(precision > 0)
    {
      *conv_p++ = '.';
    }

    for( ; (exp < 0) && (precision > 0); exp++, precision--)
    {
      *conv_p++ = '0';
    }

    while(precision > 0)
    {
      *conv_p++ = get_num(&normval, &exp_pos);
      precision--;
    }
  }

  *conv_p = 0;

  strncpy(buf, conv_buf, bufsize);
  buf[bufsize-1] = 0;

  return;
}