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/* -*- mode: C -*- */
/*
IGraph library.
Copyright (C) 2003-2012 Gabor Csardi <csardi.gabor@gmail.com>
334 Harvard street, Cambridge, MA 02139 USA
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 Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#ifndef IGRAPH_INTERRUPT_H
#define IGRAPH_INTERRUPT_H
#include "igraph_decls.h"
#include "igraph_error.h"
__BEGIN_DECLS
/* This file contains the igraph interruption handling. */
/**
* \section interrupthandlers Interruption handlers
*
* <para>
* \a igraph is designed to be embeddable into several higher level
* languages (R and Python interfaces are included in the original
* package). Since most higher level languages consider internal \a igraph
* calls as atomic, interruption requests (like Ctrl-C in Python) must
* be handled differently depending on the environment \a igraph embeds
* into.</para>
* <para>
* An \emb interruption handler \eme is a function which is called regularly
* by \a igraph during long calculations. A typical usage of the interruption
* handler is to check whether the user tried to interrupt the calculation
* and return an appropriate value to signal this condition. For example,
* in R, one must call an internal R function regularly to check for
* interruption requests, and the \a igraph interruption handler is the
* perfect place to do that.</para>
* <para>
* If you are using the plain C interface of \a igraph or if you are
* allowed to replace the operating system's interruption handler (like
* SIGINT in Un*x systems), these calls are not of much use to you.</para>
* <para>
* The default interruption handler is empty.
* The \ref igraph_set_interruption_handler() function can be used to set a
* new interruption handler function of type
* \ref igraph_interruption_handler_t, see the
* documentation of this type for details.
* </para>
*/
/**
* \section writing_interruption_handlers Writing interruption handlers
*
* <para>
* You can write and install interruption handlers simply by defining a
* function of type \ref igraph_interruption_handler_t and calling
* \ref igraph_set_interruption_handler(). This feature is useful for
* interface writers, because usually this is the only way to allow handling
* of Ctrl-C and similar keypresses properly.
* </para>
* <para>
* Your interruption handler will be called regularly during long operations
* (so it is not guaranteed to be called during operations which tend to be
* short, like adding single edges). An interruption handler accepts no
* parameters and must return \c IGRAPH_SUCCESS if the calculation should go on. All
* other return values are considered to be a request for interruption,
* and the caller function would return a special error code, \c IGRAPH_INTERRUPTED.
* It is up to your error handler function to handle this error properly.
* </para>
*/
/**
* \section writing_functions_interruption_handling Writing \a igraph functions with
* proper interruption handling
*
* <para>
* There is practically a simple rule that should be obeyed when writing
* \a igraph functions. If the calculation is expected to take a long time
* in large graphs (a simple rule of thumb is to assume this for every
* function with a time complexity of at least O(n^2)), call
* \ref IGRAPH_ALLOW_INTERRUPTION in regular intervals like every 10th
* iteration or so.
* </para>
*/
/**
* \typedef igraph_interruption_handler_t
*
* This is the type of the interruption handler functions.
*
* \param data reserved for possible future use
* \return \c IGRAPH_SUCCESS if the calculation should go on, anything else otherwise.
*/
typedef igraph_error_t igraph_interruption_handler_t (void* data);
/**
* \function igraph_allow_interruption
*
* This is the function which is called (usually via the
* \ref IGRAPH_ALLOW_INTERRUPTION macro) if \a igraph is checking for interruption
* requests.
*
* \param data reserved for possible future use, now it is always \c NULL
* \return \c IGRAPH_SUCCESS if the calculation should go on, anything else otherwise.
*/
IGRAPH_EXPORT igraph_error_t igraph_allow_interruption(void* data);
IGRAPH_EXPORT igraph_interruption_handler_t * igraph_set_interruption_handler (igraph_interruption_handler_t * new_handler);
__END_DECLS
#endif
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