libgfortran/runtime/select.c

   1 /* Implement the SELECT statement for character variables.
   2    Contributed by Andy Vaught
   3
   4 This file is part of the GNU Fortran 95 runtime library (libgfor).
   5
   6 Libgfor 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 2, or (at your option)
   9 any later version.
  10
  11 Libgfor 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 You should have received a copy of the GNU General Public License
  17 along with libgfor; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21 #include "libgfortran.h"
  22
  23 typedef struct
  24 {
  25   char *low;
  26   int low_len;
  27   char *high;
  28   int high_len;
  29   void *address;
  30 }
  31 select_struct;
  32
  33
  34 #define select_string prefix(select_string)
  35
  36
  37 /* select_string()-- Given a selector string and a table of
  38  * select_struct structures, return the address to jump to. */
  39
  40 void *select_string (select_struct *table, int table_len, void *default_jump,
  41                     const char *selector, int selector_len)
  42 {
  43   select_struct *t;
  44   int i, low, high, mid;
  45
  46   if (table_len == 0)
  47     return default_jump;
  48
  49   /* Record the default address if present */
  50
  51   if (table->low == NULL && table->high == NULL)
  52     {
  53       default_jump = table->address;
  54
  55       table++;
  56       table_len--;
  57       if (table_len == 0)
  58         return default_jump;
  59     }
  60
  61   /* Try the high and low bounds if present. */
  62
  63   if (table->low == NULL)
  64     {
  65       if (compare_string (table->high_len, table->high,
  66                                 selector_len, selector) >= 0)
  67         return table->address;
  68
  69       table++;
  70       table_len--;
  71       if (table_len == 0)
  72         return default_jump;
  73     }
  74
  75   t = table + table_len - 1;
  76
  77   if (t->high == NULL)
  78     {
  79       if (compare_string (t->low_len, t->low,
  80                                 selector_len, selector) <= 0)
  81         return t->address;
  82
  83       table_len--;
  84       if (table_len == 0)
  85         return default_jump;
  86     }
  87
  88   /* At this point, the only table entries are bounded entries.  Find
  89      the right entry with a binary chop. */
  90
  91   low = -1;
  92   high = table_len;
  93
  94   while (low + 1 < high)
  95     {
  96       mid = (low + high) / 2;
  97
  98       t = table + mid;
  99       i = compare_string (t->low_len, t->low, selector_len, selector);
 100
 101       if (i == 0)
 102         return t->address;
 103
 104       if (i < 0)
 105         low = mid;
 106       else
 107         high = mid;
 108     }
 109
 110   /* The string now lies between the low indeces of the now-adjacent
 111      high and low entries.  Because it is less than the low entry of
 112      'high', it can't be that one.  If low is still -1, then no
 113      entries match.  Otherwise, we have to check the high entry of
 114      'low'. */
 115
 116   if (low == -1)
 117     return default_jump;
 118
 119   t = table + low;
 120   if (compare_string (selector_len, selector,
 121                             t->high_len, t->high) <= 0)
 122     return t->address;
 123
 124   return default_jump;
 125 }