libgfortran/runtime/select_inc.c

   1 /* Implement the SELECT statement for character variables.
   2    Copyright 2008 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 2, or (at your option)
   9 any later version.
  10
  11 In addition to the permissions in the GNU General Public License, the
  12 Free Software Foundation gives you unlimited permission to link the
  13 compiled version of this file into combinations with other programs,
  14 and to distribute those combinations without any restriction coming
  15 from the use of this file.  (The General Public License restrictions
  16 do apply in other respects; for example, they cover modification of
  17 the file, and distribution when not linked into a combine
  18 executable.)
  19
  20 Libgfortran is distributed in the hope that it will be useful,
  21 but WITHOUT ANY WARRANTY; without even the implied warranty of
  22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23 GNU General Public License for more details.
  24
  25 You should have received a copy of the GNU General Public License
  26 along with libgfortran; see the file COPYING.  If not, write to
  27 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  28 Boston, MA 02110-1301, USA.  */
  29
  30
  31 #define select_string SUFFIX(select_string)
  32 #define select_struct SUFFIX(select_struct)
  33 #define compare_string SUFFIX(compare_string)
  34
  35 typedef struct
  36 {
  37   CHARTYPE *low;
  38   gfc_charlen_type low_len;
  39   CHARTYPE *high;
  40   gfc_charlen_type high_len;
  41   int address;
  42 }
  43 select_struct;
  44
  45 extern int select_string (select_struct *table, int table_len,
  46                           const CHARTYPE *selector,
  47                           gfc_charlen_type selector_len);
  48 export_proto(select_string);
  49
  50
  51 /* select_string()-- Given a selector string and a table of
  52  * select_struct structures, return the address to jump to. */
  53
  54 int
  55 select_string (select_struct *table, int table_len, const CHARTYPE *selector,
  56                gfc_charlen_type selector_len)
  57 {
  58   select_struct *t;
  59   int i, low, high, mid;
  60   int default_jump = -1;
  61
  62   if (table_len == 0)
  63     return -1;
  64
  65   /* Record the default address if present */
  66
  67   if (table->low == NULL && table->high == NULL)
  68     {
  69       default_jump = table->address;
  70
  71       table++;
  72       table_len--;
  73       if (table_len == 0)
  74         return default_jump;
  75     }
  76
  77   /* Try the high and low bounds if present. */
  78
  79   if (table->low == NULL)
  80     {
  81       if (compare_string (table->high_len, table->high,
  82                           selector_len, selector) >= 0)
  83         return table->address;
  84
  85       table++;
  86       table_len--;
  87       if (table_len == 0)
  88         return default_jump;
  89     }
  90
  91   t = table + table_len - 1;
  92
  93   if (t->high == NULL)
  94     {
  95       if (compare_string (t->low_len, t->low, selector_len, selector) <= 0)
  96         return t->address;
  97
  98       table_len--;
  99       if (table_len == 0)
 100         return default_jump;
 101     }
 102
 103   /* At this point, the only table entries are bounded entries.  Find
 104      the right entry with a binary chop. */
 105
 106   low = -1;
 107   high = table_len;
 108
 109   while (low + 1 < high)
 110     {
 111       mid = (low + high) / 2;
 112
 113       t = table + mid;
 114       i = compare_string (t->low_len, t->low, selector_len, selector);
 115
 116       if (i == 0)
 117         return t->address;
 118
 119       if (i < 0)
 120         low = mid;
 121       else
 122         high = mid;
 123     }
 124
 125   /* The string now lies between the low indeces of the now-adjacent
 126      high and low entries.  Because it is less than the low entry of
 127      'high', it can't be that one.  If low is still -1, then no
 128      entries match.  Otherwise, we have to check the high entry of
 129      'low'. */
 130
 131   if (low == -1)
 132     return default_jump;
 133
 134   t = table + low;
 135   if (compare_string (selector_len, selector, t->high_len, t->high) <= 0)
 136     return t->address;
 137
 138   return default_jump;
 139 }