libgfortran/runtime/select_inc.c

   1 /* Implement the SELECT statement for character variables.
   2    Copyright (C) 2008-2021 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 }