select.c   [plain text]

/* Implement the SELECT statement for character variables.
   Contributed by Andy Vaught

This file is part of the GNU Fortran 95 runtime library (libgfor).

Libgfor 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.

Libgfor 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 libgfor; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include "libgfortran.h"

typedef struct
{
  char *low;
  int low_len;
  char *high;
  int high_len;
  void *address;
}
select_struct;


#define select_string prefix(select_string)


/* select_string()-- Given a selector string and a table of
 * select_struct structures, return the address to jump to. */

void *select_string (select_struct *table, int table_len, void *default_jump,
                    const char *selector, int selector_len)
{
  select_struct *t;
  int i, low, high, mid;

  if (table_len == 0)
    return default_jump;

  /* Record the default address if present */

  if (table->low == NULL && table->high == NULL)
    {
      default_jump = table->address;

      table++;
      table_len--;
      if (table_len == 0)
        return default_jump;
    }

  /* Try the high and low bounds if present. */

  if (table->low == NULL)
    {
      if (compare_string (table->high_len, table->high,
			        selector_len, selector) >= 0)
        return table->address;

      table++;
      table_len--;
      if (table_len == 0)
        return default_jump;
    }

  t = table + table_len - 1;

  if (t->high == NULL)
    {
      if (compare_string (t->low_len, t->low,
			        selector_len, selector) <= 0)
        return t->address;

      table_len--;
      if (table_len == 0)
        return default_jump;
    }

  /* At this point, the only table entries are bounded entries.  Find
     the right entry with a binary chop. */

  low = -1;
  high = table_len;

  while (low + 1 < high)
    {
      mid = (low + high) / 2;

      t = table + mid;
      i = compare_string (t->low_len, t->low, selector_len, selector);

      if (i == 0)
        return t->address;

      if (i < 0)
        low = mid;
      else
        high = mid;
    }

  /* The string now lies between the low indeces of the now-adjacent
     high and low entries.  Because it is less than the low entry of
     'high', it can't be that one.  If low is still -1, then no
     entries match.  Otherwise, we have to check the high entry of
     'low'. */

  if (low == -1)
    return default_jump;

  t = table + low;
  if (compare_string (selector_len, selector,
			    t->high_len, t->high) <= 0)
    return t->address;

  return default_jump;
}