/* Numeric types for XEmacs using the GNU MP library.
   Copyright (C) 2004 Jerry James.

This file is part of XEmacs.

XEmacs 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 2, or (at your option) any
later version.

XEmacs 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.

You should have received a copy of the GNU General Public License
along with XEmacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 51 Franklin St - Fifth Floor,
Boston, MA 02111-1301, USA.  */

/* Synched up with: Not in FSF. */

#include <config.h>
#include <limits.h>
#include <math.h>
#include "lisp.h"
#include "sysproc.h"    /* For qxe_getpid */

static mp_exp_t float_print_min, float_print_max;
gmp_randstate_t random_state;

CIbyte *
bigfloat_to_string(mpf_t f, int base)
{
  mp_exp_t expt;
  CIbyte *str = mpf_get_str (NULL, &expt, base, 0, f);
  const int sign = mpf_sgn (f);
  const int neg = (sign < 0) ? 1 : 0;
  int len = strlen (str) + 1;  /* Count the null terminator */

  if (sign == 0)
    {
      XREALLOC_ARRAY (str, CIbyte, 4);
      strncpy (str, "0.0", 4);
    }
  else if (float_print_min <= expt && expt <= float_print_max)
    {
      if (expt < 0)
	{
	  /* We need room for a radix point and leading zeroes */
	  const int space = -expt + 2;
	  XREALLOC_ARRAY (str, CIbyte, len + space);
	  memmove (&str[space + neg], &str[neg], len - neg);
	  memset (&str[neg], '0', space);
	  str[neg + 1] = '.';
	}
      else if (len <= expt + neg + 1)
	{
	  /* We need room for a radix point and trailing zeroes */
	  XREALLOC_ARRAY (str, CIbyte, expt + neg + 3);
	  memset (&str[len - 1], '0', expt + neg + 3 - len);
	  str[expt + neg] = '.';
	  str[expt + neg + 2] = '\0';
	}
      else
	{
	  /* We just need room for a radix point */
	  XREALLOC_ARRAY (str, CIbyte, len + 1);
	  memmove (&str[expt + neg + 1], &str[expt + neg], len - (expt + neg));
	  str[expt + neg] = '.';
	}
    }
  else
    {
      /* Computerized scientific notation: We need room for a possible radix
	 point, format identifier, and exponent */
      /* GMP's idea of the exponent is 1 greater than scientific notation's */
      expt--;
      const int point = (len == neg + 2) ? 0 : 1;
      const int exponent = (expt < 0)
	? (int)(log ((double) (-expt)) / log ((double) base)) + 3
	: (int)(log ((double) expt) / log ((double) base)) + 2;
      const int space = point + exponent;
      XREALLOC_ARRAY (str, CIbyte, len + space);
      if (point > 0)
	{
	  memmove (&str[neg + 2], &str[neg + 1], len - neg);
	  str[neg + 1] = '.';
	}
      sprintf (&str[len + point - 1], "E%ld", expt);
    }
  return str;
}

/* We need the next two functions since GNU MP insists on giving us an extra
   parameter. */
static void *gmp_realloc (void *ptr, size_t UNUSED (old_size), size_t new_size)
{
  return xrealloc (ptr, new_size);
}

static void gmp_free (void *ptr, size_t UNUSED (size))
{
  xfree (ptr);
}

void
init_number_gmp ()
{
  mp_set_memory_functions ((void *(*) (size_t)) xmalloc, gmp_realloc,
			   gmp_free);

  /* Numbers with smaller exponents than this are printed in scientific
     notation. */
  float_print_min = -4;

  /* Numbers with larger exponents than this are printed in scientific
     notation. */
  float_print_max = 8;

  /* Prepare the bignum/bigfloat random number generator */
  gmp_randinit_default (random_state);
  gmp_randseed_ui (random_state, qxe_getpid () + time (NULL));
}