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/*
* File : lf_fifo.c
* Author : Jérémy Zurcher <jeremy@asynk.ch>
* Date : 2009/11/01
* License :
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#include "lf_fifo.h"
#include <stdlib.h>
void lf_fifo_init( lf_fifo_t *fifo )
{
lf_pointer_set(fifo->head,NULL);
lf_pointer_set(fifo->tail,NULL);
lf_counter_set(fifo->head,0);
lf_counter_set(fifo->tail,0);
}
void lf_fifo_push( lf_fifo_t *fifo, lf_pointer_t *node )
{
lf_pointer_t tail;
lf_pointer_t last;
lf_pointer_t new_node;
lf_pointer_set(*node,NULL);
lf_counter_set(*node,0);
lf_pointer_set(new_node,node);
lf_counter_set(new_node,1);
for(;;)
{
tail = fifo->tail;
if (lf_pointer_null(tail))
{
/* link new_node as first node */
if (lf_cas(&fifo->tail, tail, new_node))
{
lf_cas(&fifo->head, tail, new_node);
break;
}
}
else
{
last = *((lf_pointer_t*)tail.pointer);
if (lf_pointer_null(last))
{
/* link new_node as last node */
if (lf_cas((lf_pointer_t*)(fifo->tail.pointer), last, new_node))
{
break;
}
}
else
{
/* try to swing tail to the next node */
lf_counter_set(last,tail.counter+1);
lf_cas(&fifo->tail, tail, last);
}
}
}
/* try to swing tail to the new node */
lf_counter_set(new_node,tail.counter+1);
lf_cas(&fifo->tail, tail, new_node);
}
/* pop a node from the head of q */
lf_pointer_t* lf_fifo_pop( lf_fifo_t *fifo )
{
lf_pointer_t head;
lf_pointer_t tail;
lf_pointer_t tmp;
lf_pointer_t *node;
for(;;)
{
if (lf_pointer_null(fifo->head))
{
return NULL;
}
head = fifo->head;
tail = fifo->tail;
if (lf_eq(tail,head))
{
/* try to swing tail to the next node */
tmp = *((lf_pointer_t*)tail.pointer);
lf_counter_set(tmp,tail.counter+1);
lf_cas(&fifo->tail, tail, tmp);
}
node = (lf_pointer_t*)head.pointer;
tmp = *node;
/* try to swing head to the next node */
lf_counter_set(tmp,head.counter+1);
if ( lf_cas(&fifo->head, head, tmp) ) break;
}
return node;
}
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