text: #include "config.h"
  #include "../ntdb.h"
  #include "../private.h"
  #include "tap-interface.h"
  #include "external-agent.h"
  #include "logging.h"
  #include "helpapi-external-agent.h"
  
  #define KEY_STR "key"
  
  static enum NTDB_ERROR clear_if_first(int fd, void *arg)
  {
  /* We hold a lock offset 4 always, so we can tell if anyone is holding it.
   * (This is compatible with tdb's TDB_CLEAR_IF_FIRST flag).  */
  	struct flock fl;
  
  	if (arg != clear_if_first)
  		return NTDB_ERR_CORRUPT;
  
  	fl.l_type = F_WRLCK;
  	fl.l_whence = SEEK_SET;
  	fl.l_start = 4;
  	fl.l_len = 1;
  
  	if (fcntl(fd, F_SETLK, &fl) == 0) {
  		/* We must be first ones to open it! */
  		diag("truncating file!");
  		if (ftruncate(fd, 0) != 0) {
  			return NTDB_ERR_IO;
  		}
  	}
  	fl.l_type = F_RDLCK;
  	if (fcntl(fd, F_SETLKW, &fl) != 0) {
  		return NTDB_ERR_IO;
  	}
  	return NTDB_SUCCESS;
  }
  
  int main(int argc, char *argv[])
  {
  	unsigned int i;
  	struct ntdb_context *ntdb, *ntdb2;
  	struct agent *agent;
  	union ntdb_attribute cif;
  	NTDB_DATA key = ntdb_mkdata(KEY_STR, strlen(KEY_STR));
  	int flags[] = { NTDB_DEFAULT, NTDB_NOMMAP,
  			NTDB_CONVERT, NTDB_NOMMAP|NTDB_CONVERT };
  
  	cif.openhook.base.attr = NTDB_ATTRIBUTE_OPENHOOK;
  	cif.openhook.base.next = &tap_log_attr;
  	cif.openhook.fn = clear_if_first;
  	cif.openhook.data = clear_if_first;
  
  	agent = prepare_external_agent();
  	plan_tests(sizeof(flags) / sizeof(flags[0]) * 16);
  	for (i = 0; i < sizeof(flags) / sizeof(flags[0]); i++) {
  		/* Create it */
  		ntdb = ntdb_open("run-83-openhook.ntdb", flags[i]|MAYBE_NOSYNC,
  				 O_RDWR|O_CREAT|O_TRUNC, 0600, NULL);
  		ok1(ntdb);
  		ok1(ntdb_store(ntdb, key, key, NTDB_REPLACE) == 0);
  		ntdb_close(ntdb);
  
  		/* Now, open with CIF, should clear it. */
  		ntdb = ntdb_open("run-83-openhook.ntdb", flags[i]|MAYBE_NOSYNC,
  				 O_RDWR, 0, &cif);
  		ok1(ntdb);
  		ok1(!ntdb_exists(ntdb, key));
  		ok1(ntdb_store(ntdb, key, key, NTDB_REPLACE) == 0);
  
  		/* Agent should not clear it, since it's still open. */
  		ok1(external_agent_operation(agent, OPEN_WITH_HOOK,
  					     "run-83-openhook.ntdb") == SUCCESS);
  		ok1(external_agent_operation(agent, FETCH, KEY_STR "=" KEY_STR)
  		    == SUCCESS);
  		ok1(external_agent_operation(agent, CLOSE, "") == SUCCESS);
  
  		/* Still exists for us too. */
  		ok1(ntdb_exists(ntdb, key));
  
  		/* Nested open should not erase db. */
  		ntdb2 = ntdb_open("run-83-openhook.ntdb", flags[i]|MAYBE_NOSYNC,
  				  O_RDWR, 0, &cif);
  		ok1(ntdb_exists(ntdb2, key));
  		ok1(ntdb_exists(ntdb, key));
  		ntdb_close(ntdb2);
  
  		ok1(ntdb_exists(ntdb, key));
  
  		/* Close it, now agent should clear it. */
  		ntdb_close(ntdb);
  
  		ok1(external_agent_operation(agent, OPEN_WITH_HOOK,
  					     "run-83-openhook.ntdb") == SUCCESS);
  		ok1(external_agent_operation(agent, FETCH, KEY_STR "=" KEY_STR)
  		    == FAILED);
  		ok1(external_agent_operation(agent, CLOSE, "") == SUCCESS);
  
  		ok1(tap_log_messages == 0);
  	}
  
  	free_external_agent(agent);
  	return exit_status();
  }
  