gp_threads.h

// SPDX-License-Identifier: LGPL-2.1-or-later
/*
 * Copyright (C) 2009-2012 Cyril Hrubis <metan@ucw.cz>
 */
 
 /*
 
   A code to ease multithreaded filters and more.
 
  */
 
#ifndef CORE_GP_THREADS_H
#define CORE_GP_THREADS_H
 
#include <pthread.h>
 
#include <core/gp_progress_callback.h>
#include <core/gp_types.h>
 
/*
 * Sets default number of threads the library uses
 * (changes the behavior of gp_nr_threads()).
 *
 * 0 == auto
 *      Most of the time, if the image is not too small, this makes
 *      the filter run number of processors (as seen by the operating system)
 *      threads.
 *
 * 1 == one thread
 *      Everything runs in exactly one thread. This is default value.
 *
 *   >= 2
 *      Runs exactly n threads unless the image is too small.
 *
 * This value may also be overriden by the GP_THREADS enviroment variable.
 *
 * Moreover the value may be changed for a single call by settings in progres
 * callback structure.
 */
void gp_nr_threads_set(unsigned int nr);
 
/*
 * Returns a number of threads to use.
 */
unsigned int gp_nr_threads(gp_size w, gp_size h, gp_progress_cb *callback);
 
/*
 * Multithreaded progress callback priv data guarded by a mutex.
 */
struct gp_progress_cb_mp_priv {
        float max;
        int abort;
        pthread_mutex_t mutex;
        gp_progress_cb *orig_callback;
};
 
/*
 * Creates and initalizes a on-the-stack progress callback
 *
 * The intended usage is:
 *
 * GP_PROGRESS_CALLBACK_MP(callback_mp, orig_callback);
 *
 * ...
 *
 * for n threads:
 *      run_filter(..., callback ? &callback_mp : NULL);
 */
#define GP_PROGRESS_CALLBACK_MP(name, callback)                        \
        struct gp_progress_cb_mp_priv name_priv = {                 \
                .max = 0,                                              \
                .abort = 0,                                            \
                .mutex = PTHREAD_MUTEX_INITIALIZER,                    \
                .orig_callback = callback,                             \
        };                                                             \
        GP_PROGRESS_CALLBACK(name, gp_progress_cb_mp, &name_priv);
 
/*
 * Multithreaded callback function itself.
 */
int gp_progress_cb_mp(gp_progress_cb *self);
 
#endif /* CORE_GP_THREADS_H */