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118 lines
3.0 KiB
118 lines
3.0 KiB
/*
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* JACK Rack
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*
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* Original:
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* Copyright (C) Robert Ham 2002, 2003 (node@users.sourceforge.net)
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*
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* Modification for MLT:
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* Copyright (C) 2004 Ushodaya Enterprises Limited
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* Author: Dan Dennedy <dan@dennedy.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <glib.h>
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#include "lock_free_fifo.h"
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/** initialise a lock free fifo */
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void
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lff_init (lff_t * lff, unsigned int size, size_t object_size)
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{
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lff->size = size;
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lff->object_size = object_size;
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lff->read_index = 0;
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lff->write_index = 0;
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lff->data = g_malloc (object_size * size);
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}
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lff_t *
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lff_new (unsigned int size, size_t object_size)
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{
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lff_t * lff;
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lff = g_malloc (sizeof (lff_t));
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lff_init (lff, size, object_size);
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return lff;
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}
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void
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lff_free (lff_t * lff)
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{
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g_free (lff->data);
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}
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void
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lff_destroy (lff_t * lff)
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{
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lff_free (lff);
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g_free (lff);
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}
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/** read an element from the fifo into data.
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returns 0 on success, non-zero if there were no elements to read */
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int lff_read (lff_t * lff, void * data) {
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if (lff->read_index == lff->write_index) {
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return -1;
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} else {
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memcpy (data, ((char *)lff->data) + (lff->read_index * lff->object_size),
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lff->object_size);
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lff->read_index++;
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if (lff->read_index >= lff->size) {
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lff->read_index = 0;
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}
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return 0;
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}
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}
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/** write an element from data to the fifo.
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returns 0 on success, non-zero if there was no space */
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int lff_write (lff_t * lff, void * data) {
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static unsigned int ri;
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/* got to read read_index only once for safety */
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ri = lff->read_index;
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/* lots of logic for when we're allowed to write to the fifo which basically
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boils down to "don't write if we're one element behind the read index" */
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if ((ri > lff->write_index && ri - lff->write_index > 1) ||
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(lff->write_index >= ri && lff->write_index != lff->size - 1) ||
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(lff->write_index >= ri && lff->write_index == lff->size - 1 && ri != 0)) {
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/* if ((ri > lff->write_index && ri - lff->write_index > 1) ||
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(lff->write_index >= ri && (lff->write_index != lff->size - 1 || ri != 0))) { */
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memcpy (((char *)lff->data) + (lff->write_index * lff->object_size),
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data, lff->object_size);
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/* FIXME: is this safe? */
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lff->write_index++;
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if (lff->write_index >= lff->size) {
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lff->write_index = 0;
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}
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return 0;
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} else {
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return -1;
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}
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}
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