CODEWITHSUNDEEP
carraysqueuefifo
user2953190
user2953190

Reputation: 41

Creating a FIFO queue in c

I am trying to code a FIFO queue which takes data in and once full releases the oldest piece of data to make room for the new data.

I am new at programming but have managed to come up with the following code:

int Q[size], f=0, r=-1;

int Qfull()
{
    if (r==size) return 1;
    return 0;
}

int Qinsert()
{
    if(Qfull())
    {
        elem=Q[f];
        f=f+1;
        return elem;
        r++;
        Q[r]=SPI1BUF;

    }
    else
    {
        r++;
        Q[r]=SPI1BUF;
    }
}

The problem i am having is that this does not shift data and will fail once the array is full due to r increasing past the array size. Is there any way to solve this?

Upvotes: 4

Views: 6207

Answers (2)

ThorMJ
ThorMJ

Reputation: 89

What Dan said, and you really can't put statements after a return; they don't get executed.

Upvotes: 1

Dillon Welch
Dillon Welch

Reputation: 482

You are trying to make a cyclic queue without doing the extra steps to make that work. You either need to do that (as mentioned by cHao) or look into using a linked list. I would recommend working towards the cyclic queue as it should not require much modification.

Also, you have the same two lines in both of your if/else clauses. You should be able to move those two lines out and save yourself that if clause. I'm not 100% on your logic, so make sure that it can go before the if statement.

int Qinsert()
{
    r++;
    Q[r]=SPI1BUF;
    if(Qfull())
    {
    //...
    }
}

Upvotes: 0

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