priqueue

Thread Safe Priority Queue in C

The implementation is based on a max-heap derived from here.

Examples

• test.c

  Generic example with one producer and two consumer threads to showcase the functionality of the API.

• test_iterator.c

  Example with one consumer and one producer that prevents inserting items that are already present in the queue by using the queue iterator API.

API

WARNING: Do not use the priqueue_insert and priqueue_pop functions outside of a running thread!

Generic functions

Initialize Priority Queue with initial_length, choose if its functions should be blocking or not and set a limit_length (zero means no limit). On failure, priqueue_initialize returns NULL.

Priqueue *priqueue_initialize(unsigned int initial_length, unsigned int blocking, unsigned int limit_length);

Insert into Queue with specified priority. On success, priqueue_insert returns 0 or -1 if the queue is full (only possible if limit_length was set to a value greater than zero on priqueue_initialize).

int priqueue_insert(Priqueue *, Data *, uintptr_t);

Pop the node with maximum priority (head).

Node *priqueue_pop(Priqueue *);

Deallocate data node after poping.

void priqueue_node_free(Priqueue *, Node *);

Deallocate memory. Also deallocates remaining nodes from queue.

void priqueue_free(Priqueue *);

Create a new queue from all elements in current queue.

Priqueue *priqueue_popall(Priqueue *heap);

Check if queue is empty. If the queue is empty, priqueue_isempty returns 0 or -1 if the queue is not empty.

int priqueue_isempty(Priqueue *);

Get the node with maximum priority (head) without removing it from the queue. If the queue is empty, priqueue_peek returns NULL.

Node *priqueue_peek(Priqueue *);

Get the number of items in the queue.

int priqueue_getsize(Priqueue *);

Iterator functions

Initialize a Priority Queue Iterator for a given Priority Queue. On failure, priqueue_iterator_create returns NULL.

Priqueue_Iterator *priqueue_iterator_create(Priqueue *);

Returns the next node from the given Priority Queue Iterator. If the end of the queue is reached, priqueue_iterator_get_next returns NULL.

Beware: This function does not return the nodes in the correct order of the queue!

Node *priqueue_iterator_get_next(Priqueue_Iterator *);

Deallocate the memory of the given Priority Queue Iterator. On success, priqueue_iterator_free returns 0 or -1 if the operation failed.

int priqueue_iterator_free(Priqueue_Iterator *);

ToDos

1. Lightweight Mutex
2. API to shrink array size