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#include <stdio.h>
#define QUEUE_SIZE 10
/*
* Simple queue algorithm implementation
*
* tail will always point to the next available slot
*/
struct queue {
int data[QUEUE_SIZE];
int head;
int tail;
};
int queue_empty(struct queue *Q)
{
return Q->head == Q->tail;
}
/*
* Queue is full when:
* tail + 1 == HEAD or
* TAIL == QUEUE_SIZE - 1 and HEAD == 0
*/
int queue_full(struct queue *Q)
{
if (((Q->tail + 1) == Q->head) ||
((Q->tail == (QUEUE_SIZE - 1)) && (Q->head == 0)))
return 1;
else
return 0;
}
int queue_push(struct queue *Q, int value)
{
if (queue_full(Q)) {
printf("Queue is full, avoiding overflow\n");
return 0;
}
Q->data[Q->tail] = value;
if (Q->tail == (QUEUE_SIZE - 1))
Q->tail = 0;
else
Q->tail++;
return value;
}
/* FIXME: function return 0 in case of failure, should return something
* else, once 0 is a valid value to the queue
*/
int queue_pop(struct queue *Q)
{
int value = 0;
if (queue_empty(Q)) {
printf("Queue is empty, avoiding underflow\n");
return value;
}
value = Q->data[Q->head];
if (Q->head == (QUEUE_SIZE - 1))
Q->head = 0;
else
Q->head++;
return value;
}
void print_queue(struct queue *Q)
{
int i = Q->head;
int pos = 1;
if (queue_empty(Q)) {
printf("Nothing to print, queue is empty\n");
return;
}
printf(" Pos | Tail \n");
for (;;) {
printf(" %d | %d \n", pos, Q->data[i]);
if (i == (QUEUE_SIZE - 1))
i = 0;
else
i++;
pos++;
if (i == Q->tail)
break;
}
}
void debug_queue(struct queue *Q)
{
int i;
for (i = 0; i < QUEUE_SIZE; i++) {
printf("| %d | ", Q->data[i]);
if (i == Q->head)
printf("<-- HEAD ");
if (i == Q->tail)
printf("<-- TAIL");
printf("\n");
}
}
int main(void)
{
struct queue my_queue;
int i, val;
char cmd;
/* Init queue */
my_queue.head = 0;
my_queue.tail = 0;
for (i = 0; i < QUEUE_SIZE; i++)
my_queue.data[i] = 0;
while (1) {
printf("Select an option: ");
scanf(" %c", &cmd);
switch (cmd) {
case 'a':
printf("Value to add: ");
scanf(" %d", &val);
queue_push(&my_queue, val);
break;
case 'p':
queue_pop(&my_queue);
break;
case 'd':
debug_queue(&my_queue);
break;
case 'l':
print_queue(&my_queue);
break;
default:
printf("Invalid option\n");
printf("a = add, p = pop, d = debug, l = print\n");
}
}
return 0;
}
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