1  /* Implement the SELECT statement for character variables.
       2     Copyright (C) 2008-2023 Free Software Foundation, Inc.
       3  
       4  This file is part of the GNU Fortran runtime library (libgfortran).
       5  
       6  Libgfortran is free software; you can redistribute it and/or modify
       7  it under the terms of the GNU General Public License as published by
       8  the Free Software Foundation; either version 3, or (at your option)
       9  any later version.
      10  
      11  Libgfortran is distributed in the hope that it will be useful,
      12  but WITHOUT ANY WARRANTY; without even the implied warranty of
      13  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14  GNU General Public License for more details.
      15  
      16  Under Section 7 of GPL version 3, you are granted additional
      17  permissions described in the GCC Runtime Library Exception, version
      18  3.1, as published by the Free Software Foundation.
      19  
      20  You should have received a copy of the GNU General Public License and
      21  a copy of the GCC Runtime Library Exception along with this program;
      22  see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23  <http://www.gnu.org/licenses/>.  */
      24  
      25  #define select_string SUFFIX(select_string)
      26  #define select_struct SUFFIX(select_struct)
      27  #define compare_string SUFFIX(compare_string)
      28  
      29  typedef struct
      30  {
      31    CHARTYPE *low;
      32    gfc_charlen_type low_len;
      33    CHARTYPE *high;
      34    gfc_charlen_type high_len;
      35    int address;
      36  }
      37  select_struct;
      38  
      39  extern int select_string (select_struct *table, int table_len,
      40  			  const CHARTYPE *selector,
      41  			  gfc_charlen_type selector_len);
      42  export_proto(select_string);
      43  
      44  
      45  /* select_string()-- Given a selector string and a table of
      46   * select_struct structures, return the address to jump to. */
      47  
      48  int
      49  select_string (select_struct *table, int table_len, const CHARTYPE *selector,
      50  	       gfc_charlen_type selector_len)
      51  {
      52    select_struct *t;
      53    int i, low, high, mid;
      54    int default_jump = -1;
      55  
      56    if (table_len == 0)
      57      return -1;
      58  
      59    /* Record the default address if present */
      60  
      61    if (table->low == NULL && table->high == NULL)
      62      {
      63        default_jump = table->address;
      64  
      65        table++;
      66        table_len--;
      67        if (table_len == 0)
      68          return default_jump;
      69      }
      70  
      71    /* Try the high and low bounds if present. */
      72  
      73    if (table->low == NULL)
      74      {
      75        if (compare_string (table->high_len, table->high,
      76  			  selector_len, selector) >= 0)
      77          return table->address;
      78  
      79        table++;
      80        table_len--;
      81        if (table_len == 0)
      82          return default_jump;
      83      }
      84  
      85    t = table + table_len - 1;
      86  
      87    if (t->high == NULL)
      88      {
      89        if (compare_string (t->low_len, t->low, selector_len, selector) <= 0)
      90          return t->address;
      91  
      92        table_len--;
      93        if (table_len == 0)
      94          return default_jump;
      95      }
      96  
      97    /* At this point, the only table entries are bounded entries.  Find
      98       the right entry with a binary chop. */
      99  
     100    low = -1;
     101    high = table_len;
     102  
     103    while (low + 1 < high)
     104      {
     105        mid = (low + high) / 2;
     106  
     107        t = table + mid;
     108        i = compare_string (t->low_len, t->low, selector_len, selector);
     109  
     110        if (i == 0)
     111          return t->address;
     112  
     113        if (i < 0)
     114          low = mid;
     115        else
     116          high = mid;
     117      }
     118  
     119    /* The string now lies between the low indeces of the now-adjacent
     120       high and low entries.  Because it is less than the low entry of
     121       'high', it can't be that one.  If low is still -1, then no
     122       entries match.  Otherwise, we have to check the high entry of
     123       'low'. */
     124  
     125    if (low == -1)
     126      return default_jump;
     127  
     128    t = table + low;
     129    if (compare_string (selector_len, selector, t->high_len, t->high) <= 0)
     130      return t->address;
     131  
     132    return default_jump;
     133  }