96 lines
2.4 KiB
C++
96 lines
2.4 KiB
C++
#include "Queue.h"
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#include "kernel/Globals.h"
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#include <cstddef>
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void Queue::enqueue(Chain* item) {
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// kout << "Enqueue " << (unsigned int)item << endl;
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*this->tail = item; // If queue is empty tail points to head pointer,
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this->tail = &item->next; // otherwise to last next pointer
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}
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Chain* Queue::dequeue() {
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if (this->isEmpty()) {
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// This should not ever happen as the idle thread exists always
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// kout << "Dequeue called on empty queue." << endl;
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return NULL;
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}
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Chain* item = this->head;
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this->head = this->head->next; // If *item was the only item this->head->next
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// is equal to this->tail
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if (this->isEmpty()) {
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// Reset after last element was removed
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this->head = 0;
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this->tail = &this->head;
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}
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// kout << "Dequeue " << (unsigned int)item << endl;
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return item;
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}
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void Queue::remove(Chain* item) {
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if (this->isEmpty()) {
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// kout << "Remove called on empty queue" << endl;
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return;
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}
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Chain* current = this->head;
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Chain* lastnext = NULL;
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while (current != item) {
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if (current->next == *this->tail) {
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// kout << "Element not in queue." << endl;
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return;
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}
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lastnext = current;
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current = current->next;
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}
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// std::cout << "Remove " << item->val << std::endl;
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if (current == this->head) {
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// current is first element
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this->head = current->next;
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} else if (current->next == *this->tail) {
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// current is last element
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this->tail = &lastnext->next;
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} else {
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// current is in the middle
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lastnext->next = current->next;
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}
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if (this->isEmpty()) {
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// Reset after last element was removed
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this->head = 0;
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this->tail = &this->head;
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}
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}
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void Queue::print() const {
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if (this->isEmpty()) {
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// Queue is empty
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kout << "List is empty!" << endl;
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return;
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}
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kout << "List: ";
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Chain* current = this->head;
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kout << (unsigned int)current << " "; // At least one element in queue
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while (current->next != *this->tail) {
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// More than one element in queue
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current = current->next;
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kout << (unsigned int)current << " ";
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}
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kout << endl;
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}
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bool Queue::isEmpty() const {
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return *this->tail == this->head;
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}
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