q.cpp

#include "include/internal/q.h"

void InitQ(TCB_t **head) {
    *head = 0;
}

void AddQ(TCB_t **head, TCB_t *item) {
    if (*head == 0) {
        //When the head pointer is null
        *head = item;
        (*head)->next = *head;
        (*head)->prev = *head;
    } else {
        //When there is one or more nodes
        (*head)->prev->next = item;
        item->prev = (*head)->prev;
        (*head)->prev = item;
        item->next = *head;
    }
}

TCB_t * DelQ(TCB_t **head) {
    if ((*head) == 0)
        return 0;
    TCB_t *temp = *head;
    if ((*head)->next == *head) {
        //When there is one node
        *head = 0;
    } else {
        //When there are two or more nodes
        *head = (*head)->next;
        temp->prev->next = *head;
        (*head)->prev = temp->prev;
    }
    return temp;
}

void RotateQ(TCB_t **head) {
    if (*head != 0)
        (*head) = (*head)->next;
}