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/*
* This file is part of ltrace.
* Copyright (C) 2011,2012,2013 Petr Machata, Red Hat Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
*/
#ifndef CALLBACK_H
#define CALLBACK_H
/* Notes on the iteration interface used across ltrace. Typically the
* iteration function looks something like this:
*
* foo *each_foo(foo *start_after,
* enum callback_status (*cb)(foo *f, void *data),
* void *data);
*
* The iteration starts after the element designated by START_AFTER,
* or at the first element if START_AFTER is NULL. CB is then called
* for each element of the collection. DATA is passed verbatim to CB.
* If CB returns CBS_STOP, the iteration stops and the current element
* is returned. That element can then be passed as START_AFTER to
* restart the iteration. NULL is returned when iteration ends.
*
* CBS_FAIL is not currently handled, and essentially means the same
* thing as CBS_STOP. There's no provision for returning error
* states. Errors need to be signaled to the caller via DATA,
* together with any other data that the callback needs.
*
* A richer iteration interface looks like this:
*
* struct each_foo_t {
* foo *restart;
* int status;
* } each_foo(foo *start_after,
* enum callback_status (*cb)(foo *f, void *data),
* void *data);
*
* These provide error handling. The two-part structure encodes both
* the restart cookie and status. Status of 0 means success, negative
* values signify failures. Status of -1 is dedicated to failures in
* user callback (such that the callback returns CBS_FAIL). Other
* negative values signal failures in the iteration mechanism itself.
*/
enum callback_status {
CBS_STOP, /* The iteration should stop. */
CBS_CONT, /* The iteration should continue. */
CBS_FAIL, /* There was an error. The iteration should stop
* and return error. */
};
#define CBS_STOP_IF(X) ((X) ? CBS_STOP : CBS_CONT)
#define CBS_CONT_IF(X) ((X) ? CBS_CONT : CBS_STOP)
#endif /* CALLBACK_H */
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