project for a (works on my devices) demo

sources/glut_timers.c

@@ -0,0 +1,170 @@
+#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 */
+}