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 extern void * select_string (select_struct *table, int table_len,
  34                              void *default_jump, const char *selector,
  35                              int selector_len);
  36 export_proto(select_string);
  37
  38
  39 /* select_string()-- Given a selector string and a table of
  40  * select_struct structures, return the address to jump to. */
  41
  42 void *
  43 select_string (select_struct *table, int table_len, void *default_jump,
  44                const char *selector, int selector_len)
  45 {
  46   select_struct *t;
  47   int i, low, high, mid;
  48
  49   if (table_len == 0)
  50     return default_jump;
  51
  52   /* Record the default address if present */
  53
  54   if (table->low == NULL && table->high == NULL)
  55     {
  56       default_jump = table->address;
  57
  58       table++;
  59       table_len--;
  60       if (table_len == 0)
  61         return default_jump;
  62     }
  63
  64   /* Try the high and low bounds if present. */
  65
  66   if (table->low == NULL)
  67     {
  68       if (compare_string (table->high_len, table->high,
  69                                 selector_len, selector) >= 0)
  70         return table->address;
  71
  72       table++;
  73       table_len--;
  74       if (table_len == 0)
  75         return default_jump;
  76     }
  77
  78   t = table + table_len - 1;
  79
  80   if (t->high == NULL)
  81     {
  82       if (compare_string (t->low_len, t->low,
  83                                 selector_len, selector) <= 0)
  84         return t->address;
  85
  86       table_len--;
  87       if (table_len == 0)
  88         return default_jump;
  89     }
  90
  91   /* At this point, the only table entries are bounded entries.  Find
  92      the right entry with a binary chop. */
  93
  94   low = -1;
  95   high = table_len;
  96
  97   while (low + 1 < high)
  98     {
  99       mid = (low + high) / 2;
 100
 101       t = table + mid;
 102       i = compare_string (t->low_len, t->low, selector_len, selector);
 103
 104       if (i == 0)
 105         return t->address;
 106
 107       if (i < 0)
 108         low = mid;
 109       else
 110         high = mid;
 111     }
 112
 113   /* The string now lies between the low indeces of the now-adjacent
 114      high and low entries.  Because it is less than the low entry of
 115      'high', it can't be that one.  If low is still -1, then no
 116      entries match.  Otherwise, we have to check the high entry of
 117      'low'. */
 118
 119   if (low == -1)
 120     return default_jump;
 121
 122   t = table + low;
 123   if (compare_string (selector_len, selector,
 124                             t->high_len, t->high) <= 0)
 125     return t->address;
 126
 127   return default_jump;
 128 }