/*

Copyright (C) 1996-2017 John W. Eaton

This file is part of Octave.

Octave 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 of the License, or
(at your option) any later version.

Octave 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 Octave; see the file COPYING.  If not, see
<http://www.gnu.org/licenses/>.

*/

#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif

#include "f77-fcn.h"
#include "lo-error.h"
#include "mach-info.h"
#include "singleton-cleanup.h"

extern "C"
{
  double F77_FUNC (d1mach, D1MACH) (const octave_idx_type&);
}

namespace octave
{
  mach_info *mach_info::instance = 0;

  union equiv
  {
    double d;
    int i[2];
  };

  struct
  float_params
  {
    mach_info::float_format fp_fmt;
    equiv fp_par[4];
  };

#define INIT_FLT_PAR(fp, fmt, sm1, sm2, lrg1, lrg2, rt1, rt2, dv1, dv2) \
  do                                                                    \
    {                                                                   \
      fp.fp_fmt = (fmt);                                                \
      fp.fp_par[0].i[0] = (sm1);  fp.fp_par[0].i[1] = (sm2);            \
      fp.fp_par[1].i[0] = (lrg1); fp.fp_par[1].i[1] = (lrg2);           \
      fp.fp_par[2].i[0] = (rt1);  fp.fp_par[2].i[1] = (rt2);            \
      fp.fp_par[3].i[0] = (dv1);  fp.fp_par[3].i[1] = (dv2);            \
    }                                                                   \
  while (0)

  static int
  equiv_compare (const equiv *std, const equiv *v, int len)
  {
    int i;
    for (i = 0; i < len; i++)
      if (v[i].i[0] != std[i].i[0] || v[i].i[1] != std[i].i[1])
        return 0;
    return 1;
  }

  static mach_info::float_format
  get_float_format (void)
  {
    mach_info::float_format retval = mach_info::flt_fmt_unknown;

    float_params fp[5];

    INIT_FLT_PAR (fp[0], mach_info::flt_fmt_ieee_big_endian,
                     1048576,  0,
                  2146435071, -1,
                  1017118720,  0,
                  1018167296,  0);

    INIT_FLT_PAR (fp[1], mach_info::flt_fmt_ieee_little_endian,
                   0,    1048576,
                  -1, 2146435071,
                   0, 1017118720,
                   0, 1018167296);

    INIT_FLT_PAR (fp[4], mach_info::flt_fmt_unknown,
                  0, 0,
                  0, 0,
                  0, 0,
                  0, 0);

    equiv mach_fp_par[4];

    mach_fp_par[0].d = F77_FUNC (d1mach, D1MACH) (1);
    mach_fp_par[1].d = F77_FUNC (d1mach, D1MACH) (2);
    mach_fp_par[2].d = F77_FUNC (d1mach, D1MACH) (3);
    mach_fp_par[3].d = F77_FUNC (d1mach, D1MACH) (4);

    int i = 0;
    do
      {
        if (equiv_compare (fp[i].fp_par, mach_fp_par, 4))
          {
            retval = fp[i].fp_fmt;
            break;
          }
      }
    while (fp[++i].fp_fmt != mach_info::flt_fmt_unknown);

    return retval;
  }

  static bool
  ten_little_endians (void)
  {
    // Are we little or big endian?  From Harbison & Steele.

    union
    {
      long l;
      char c[sizeof (long)];
    } u;

    u.l = 1;

    return (u.c[sizeof (long) - 1] == 1);
  }

  mach_info::mach_info (void)
    : native_float_fmt (get_float_format ()),
      big_chief (ten_little_endians ()) { }

  bool
  mach_info::instance_ok (void)
  {
    bool retval = true;

    if (! instance)
      {
        instance = new mach_info ();

        if (instance)
          singleton_cleanup_list::add (cleanup_instance);
      }

    if (! instance)
      (*current_liboctave_error_handler)
        ("unable to create command history object!");

    return retval;
  }

  mach_info::float_format
  mach_info::native_float_format (void)
  {
    return (instance_ok ())
           ? instance->native_float_fmt : mach_info::flt_fmt_unknown;
  }

  bool
  mach_info::words_big_endian (void)
  {
    return (instance_ok ())
           ? instance->big_chief : false;
  }

  bool
  mach_info::words_little_endian (void)
  {
    return (instance_ok ())
           ? (! instance->big_chief) : false;
  }

  mach_info::float_format
  mach_info::string_to_float_format (const std::string& s)
  {
    mach_info::float_format retval = mach_info::flt_fmt_unknown;

    if (s == "native" || s == "n")
      retval = mach_info::native_float_format ();
    else if (s == "ieee-be" || s == "b")
      retval = mach_info::flt_fmt_ieee_big_endian;
    else if (s == "ieee-le" || s == "l")
      retval = mach_info::flt_fmt_ieee_little_endian;
    else if (s == "unknown")
      retval = mach_info::flt_fmt_unknown;
    else
      (*current_liboctave_error_handler) ("invalid architecture type specified");

    return retval;
  }

  std::string
  mach_info::float_format_as_string (float_format flt_fmt)
  {
    std::string retval = "unknown";

    switch (flt_fmt)
      {
      case flt_fmt_ieee_big_endian:
        retval = "ieee-be";
        break;

      case flt_fmt_ieee_little_endian:
        retval = "ieee-le";
        break;

      default:
        break;
      }

    return retval;
  }
}