/*
 * This file shows how an interface can be built to cache regexp patterns
 * and ultimately provide a more streamlined interface to the regexp kfuns.
 *
 * Note that since regexp_match() severely depends on the return result from
 * regexp_compile() being unaltered, it is a good idea to provide an
 * interface like this, and also to mask the regexp_match() kfun from the
 * auto object.
 */

# define CACHE_SIZE  10

private	mapping	cache;
private	string *list;
private	string	last_pattern;

static
void create(void)
{
  cache = ([ ]);
  list  = ({ });
}

int *match(string subject, string pattern)
{
  string *buffer;

  if ((buffer = cache[pattern]) == 0)
    {
      buffer = regexp_compile(pattern);

      if (sizeof(list) >= CACHE_SIZE)
	{
	  cache[list[0]] = 0;
	  list = list[1 ..] + ({ pattern });
	}
      else
	list += ({ pattern });

      cache[pattern] = buffer;
    }
  else if (pattern != last_pattern)
    {
      list = list - ({ pattern }) + ({ pattern });
      last_pattern = pattern;
    }

  return regexp_match(buffer, subject);
}