Question

I am new in Queue (FIFO) and Qt. I want to create a Queue of unsigned char array in Qt. How to do it? Please help

unsigned char buffer[1024];

Answer 1

If you want to use the Qt API, then you can use the QQueue class –

 QQueue<unsigned char> queue;
 queue.enqueue(65);
 queue.enqueue(66);
 queue.enqueue(67);
 while (!queue.isEmpty())
     cout << queue.dequeue() << endl;

If you want to build the queue on your own, then I guess you can declare a Queue class like this –

class Queue
{
private:
    enum{SIZE=1024, EMPTY=0};
    unsigned char buffer[SIZE];
    int readHead, writeHead;

public:
    Queue()
    {
        readHead = writeHead = EMPTY;
    }

    void push(unsigned char data);
    unsigned char pop();
    unsigned char peek();
    bool isEmpty();
};

void Queue::push(unsigned char data)
{
    if((readHead - writeHead) >= SIZE)
    {
        // You should handle Queue overflow the way you want here.
        return;
    }

    buffer[writeHead++ % SIZE] = data;
}

unsigned char Queue::pop()
{
    unsigned char item = peek();
    readHead++;
    return item;
}

unsigned char Queue::peek()
{
    if(isEmpty())
    {
        // You should handle Queue underflow the way you want here.
        return;
    }

    return buffer[readHead % SIZE];
}

bool Queue::isEmpty()
{
    return (readHead == writeHead);
}    

If you want to maintain a Queue of unsigned char array, then you will have to maintain a queue of unsigned char pointers –

QQueue<unsigned char *> queue;
unsigned char *array1 = new unsigned char[10];    // array of 10 items
array1[0] = 65;
array1[1] = 66;
queue.enqueue(array1);
unsigned char *array2 = new unsigned char[20];    // an array of 20 items
queue.enqueue(array2);

unsigned char *arr = queue.dequeue();
qDebug() << arr[0] << ", " << arr[1];

Note: You should take care of the memory cleanup after you are done with this queue. IMHO, you better avoid this type of design though.