christoph/lecture-operating-system-development
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update queue

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This commit is contained in:
churl
2022-06-15 21:30:48 +02:00
parent f7b6cb658d
commit 7870f2e247
2 changed files with 43 additions and 9 deletions
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50
c_os/lib/Queue.cc
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@ -10,7 +10,7 @@ void Queue::enqueue(Chain* item) {
} }
Chain* Queue::dequeue() { Chain* Queue::dequeue() {
if (*this->tail == this->head) { if (this->isEmpty()) {
// This should not ever happen as the idle thread exists always // This should not ever happen as the idle thread exists always
// std::cout << "Dequeue called on empty queue." << std::endl; // std::cout << "Dequeue called on empty queue." << std::endl;
return NULL; return NULL;
@ -20,7 +20,7 @@ Chain* Queue::dequeue() {
this->head = this->head->next; // If *item was the only item this->head->next this->head = this->head->next; // If *item was the only item this->head->next
// is equal to this->tail // is equal to this->tail
if (*this->tail == this->head) { if (this->isEmpty()) {
// Reset after last element was removed // Reset after last element was removed
this->head = 0; this->head = 0;
this->tail = &this->head; this->tail = &this->head;
@ -31,11 +31,46 @@ Chain* Queue::dequeue() {
return item; return item;
} }
void Queue::remove(Chain* item) {} void Queue::remove(Chain* item) {
if (this->isEmpty()) {
// std::cout << "Remove called on empty queue" << std::endl;
return;
}
Chain* current = this->head;
Chain* lastnext = NULL;
while (current != item) {
if (current->next == *this->tail) {
// std::cout << "Element not in queue." << std::endl;
return;
}
lastnext = current;
current = current->next;
}
// std::cout << "Remove " << item->val << std::endl;
if (current == this->head) {
// current is first element
this->head = current->next;
} else if (current->next == *this->tail) {
// current is last element
this->tail = &lastnext->next;
} else {
// current is in the middle
lastnext->next = current->next;
}
if (this->isEmpty()) {
// Reset after last element was removed
this->head = 0;
this->tail = &this->head;
}
}
/*
void Queue::print() const { void Queue::print() const {
if (*this->tail == this->head) { if (this->isEmpty()) {
// Queue is empty // Queue is empty
// std::cout << "List is empty!" << std::endl; // std::cout << "List is empty!" << std::endl;
return; return;
@ -44,9 +79,9 @@ void Queue::print() const {
// std::cout << "List: "; // std::cout << "List: ";
Chain* current = this->head; Chain* current = this->head;
// std::cout << current->val << " "; // At least one element in queue // std::cout << current->val << " "; // At least one element in queue
while (&current->next != this->tail) { while (current->next != *this->tail) {
// More than one element in queue // More than one element in queue
current = current->next; current = current->next;
// std::cout << current->val << " "; // std::cout << current->val << " ";
@ -54,7 +89,6 @@ void Queue::print() const {
// std::cout << std::endl; // std::cout << std::endl;
} }
*/
bool Queue::isEmpty() const { bool Queue::isEmpty() const {
return *this->tail == this->head; return *this->tail == this->head;

2
c_os/lib/Queue.h
View File

@ -36,7 +36,7 @@ public:
void enqueue(Chain* item); void enqueue(Chain* item);
Chain* dequeue(); Chain* dequeue();
void remove(Chain* item); void remove(Chain* item);
// void print() const; void print() const;
bool isEmpty() const; bool isEmpty() const;
}; };