my_glut/sources/glut_timers.c

#include <stdlib.h>
#include "../headers/glut_timers.h"

#include <stdio.h>

static int is_updating_time=0;

static timer_list_entry *timers_first = NULL;
static timer_list_entry *timers_last = NULL;

static timer_list_entry *unissued_timers_first = NULL;
static timer_list_entry *unissued_timers_last = NULL;

/*CODE duplication*/
void timers_add_to_unissued(timer_list_entry *toAdd){
	//printf("timers add to unissued begin\n");
	if(unissued_timers_last != NULL){
		unissued_timers_last->next = toAdd;
	}
	else{
		if(NULL == unissued_timers_first){
			unissued_timers_first=toAdd;
		}
	}
	unissued_timers_last = toAdd;
	//printf("timers add to unissued end\n");
}

void timers_add(timer_list_entry *toAdd){
	//printf("timers add begin\n");
	if(is_updating_time){
		timers_add_to_unissued( toAdd);
		return;
	}

	if(timers_last != NULL){
		timers_last->next = toAdd;
	}
	else{
		if(NULL == timers_first){
			timers_first=toAdd;
		}
	}
	timers_last = toAdd;
	//printf("timers add end\n");
}

/**
	FULL OF PRINT STATEMENTS DUE TO A BUG MYSTERIOUSLY FIXED, see decrease_timers()
*/
/* unsafe, not checking the validity of the previous, toRemove precondition */
void timers_remove( 
	timer_list_entry *previous, 
	timer_list_entry *toRemove
){
	/*
	printf("timers remove\n");
	printf("timers remove previous is %p\n", (void*) previous);
	printf("timers remove toRemove is %p\n", (void*) toRemove);	
	
	if(NULL != previous){
		printf("timers remove previous->next is %p\n", (void*) previous->next);
		if(previous->next != toRemove){
			printf("timers remove previous->next is not the same as toRemove\n");
		}
	}
	else{
		printf("previous counts as NULL\n");
	}
	if(toRemove->next == NULL){
		printf("timers remove toRemove->next is NULL\n");	
	}
	else{
		printf("timers remove toRemove->next is %p\n", (void*) toRemove->next);	
	}
	*/
	if( toRemove == timers_first){
		// printf("timers remove toremove is the first\n");
		timers_first = timers_first->next;
		if(NULL == timers_first){
			timers_last = NULL;
		}
	}
	else{
		// printf("timers remove toremove is not the first\n");
		previous->next = toRemove->next;	
		/* could move elsewhere, timer_last is an auxiliary variable */
		if( NULL == previous->next){
			timers_last = previous;
		}
		// printf("timers remove previous->next is now %p\n", (void*) previous->next);
	}
	/* i added this and now works. should not need it, smells like bigger bug */
	toRemove->next = NULL;
	// printf("timers remove end\n");
}

void append_unissued_timers(){
	if( NULL == unissued_timers_first){
		return;
	}
	timers_add(unissued_timers_first);
	timers_last=unissued_timers_last;
	unissued_timers_first = NULL;
	unissued_timers_last = NULL;
}


/**
	FULL OF PRINT STATEMENTS DUE TO A BUG MYSTERIOUSLY FIXED
*/
void decrease_timers(){
	timer_list_entry *current, *previous;
	previous = NULL;
	
	int count = 0;		/*DEBUG ONLY*/
	current = timers_first;

	is_updating_time=1;
	
	//printf("decrease timers begin\n");

	while( current != NULL){
		/*
		printf("decreasing timer\n");
		printf("timer addr would be %p\n", (void*) current);
		*/
		current->remaining_ms--;
		//printf("decreased timer\n");
		if( 0 >= current->remaining_ms){
			//printf("will crash on removal?\n");
			timers_remove( previous, current);
			//printf("removed timer\nbreak on callback?\n");
			current->callback(0);				/*should receive an int (i guess the runover time)*/
			//printf("callback done\nbreak on free?\n");
			free( current);
			//printf("was not the free\n");
			/* would make a removal from head inconsistent */
			if(previous != NULL){
				//printf("previous is not null during the looping, sliding\n");
				current=previous;
			}
		}
		/*
		printf("updating cursors\n");
		printf("previous is %p\n", (void*) previous);
		printf("current is %p\n", (void*) current);
		*/
		previous = current;
		current = current->next;
		/*
		printf("updated cursors\n");
		printf("previous is %p\n", (void*) previous);
		printf("current is %p\n", (void*) current);		
		*/
		count++;
		// printf("wasn't even the counter\n");
	}
	// printf("out of the timers loop\n");
	/*
	printf("processed %d timers\n", count);
	*/
	is_updating_time=0;
	append_unissued_timers();
	// printf("reached the end of decrease timers\n");
}

int timers_isEmpty(){
	return ( NULL == timers_first);	/*could also check timer_last but it is an auxiliary variable */
}