queue.h

// Define the Node struct for the queue
typedef struct Node
{
    struct PCB data;
    struct Node *next;
} Node;

// Define the Queue struct
typedef struct Queue
{
    Node *front;
    Node *rear;
} Queue;

// Initialize the queue
void init_queue(Queue *q)
{
    q->front = NULL;
    q->rear = NULL;
}

// Check if the queue is empty
int is_empty(Queue *q)
{
    return (q->front == NULL);
}

// Add an element to the queue
void enqueue(Queue *q, struct PCB data)
{
    Node *new_node = (Node *)malloc(sizeof(Node));
    new_node->data = data;
    new_node->next = NULL;

    if (is_empty(q))
    {
        q->front = new_node;
        q->rear = new_node;
    }
    else
    {
        q->rear->next = new_node;
        q->rear = new_node;
    }
}

// Remove an element from the queue
struct PCB dequeue(Queue *q)
{
    if (is_empty(q))
    {
        printf("Queue is empty.\n");
        struct PCB empty_pcb = {0};
        return empty_pcb;
    }

    struct PCB data = q->front->data;
    Node *temp = q->front;

    if (q->front == q->rear)
    {
        q->front = NULL;
        q->rear = NULL;
    }
    else
    {
        q->front = q->front->next;
    }

    free(temp);
    return data;
}

// Get the front element of the queue
struct PCB front(Queue *q)
{
    if (is_empty(q))
    {
        printf("Queue is empty.\n");
        struct PCB empty_pcb = {0};
        return empty_pcb;
    }

    return q->front->data;
}

// Get the size of the queue
int queue_size(Queue *q)
{
    int count = 0;
    Node *current = q->front;

    while (current != NULL)
    {
        count++;
        current = current->next;
    }

    return count;
}

// Delete the queue
void delete_queue(Queue *q)
{
    Node *current = q->front;

    while (current != NULL)
    {
        Node *temp = current;
        current = current->next;
        free(temp);
    }

    q->front = NULL;
    q->rear = NULL;
}

// Find the required id
void dequeueid(struct Queue *q, int id)
{
    // Check if the queue is empty
    if (q->front == NULL)
    {
        return;
    }

    // Traverse the queue to find the node with the given ID
    struct Node *prev = NULL;
    struct Node *curr = q->front;
    while (curr != NULL && curr->data.fileInfo.id != id)
    {
        prev = curr;
        curr = curr->next;
    }

    // If the ID is not found, return NULL
    if (curr == NULL)
    {
        return;
    }

    // Remove the node from the queue
    if (prev == NULL)
    {
        q->front = curr->next;
    }
    else
    {
        prev->next = curr->next;
    }
    if (curr == q->rear)
    {
        q->rear = prev;
    }

    // free the node
    free(curr);
}