Thread: New to Programming: Need Help/Advice on Topic

I am having trouble starting this program, but I'm sure if I get a little hint on a direction to take, I'll be good to go.

I want to create a program that has multiple threads that takes lines from a simple text file and puts it into a circular array with a fixed size of 10 data lines.

While doing this, I'll have another thread that gets a line from the circular array and writes that line to another text file.


My question is, how to set up this circular array that takes lines from a text file and adds these full lines into the array.

A simple line would be, "Hello World" or anything like that. So the circular array will have ten lines from the input file, waits til the other thread takes from the array, then keeps adding the lines until end of file.

Where should I begin? How do I implement this circular array, and how should I set up the input/output streams?

Thanks in advance for all your help!

NOTE: I believe this is similar to the producer/consumer program, but I am not sure.

Was quite some time since i touched concurrency but I think you would want to read up on semaphores and/or monitors. For a container I would probably use something like the std::deque with the restriction of having max 10 objects in it at once.

Hope this will get you on your way.

I'm going to use a Queue because that's more like a circular array.. first in first out kind of deal.

But I have another question.. I want to have a thread that reads from a file, puts each "line" from the file into the queue, AND, while that is happening, have another thread that reads from the queue and puts these lines into an output file.

I know how to do threads, but I'm curious as to how to set it up so that while the "producer" thread is taking from the input file and putting in the queue, how do I make the "consumer" thread take from the queue and put it into an output file at the same time?

Thanks in advance!

Also,

how do I set the size of a queue? Is there a simple way to do this? I know of a way to set the size of an array in one line, is there a similar way of doing this?

I want to set the size of my queue to, say, 10.

Well, I want to make it a fixed size because I want to simulate the producer/consumer methodology. So that when the queue is "full," the producer thread will stop taking from the input file. It's just a restriction I want on the queue.

Is there a simple way of doing this?

Well, I want to make it a fixed size because I want to simulate the producer/consumer methodology. So that when the queue is "full," the producer thread will stop taking from the input file. It's just a restriction I want on the queue.

I don't think this needs to be concurrent, then.

There will be two threads... one picking from my input file and putting each line into the queue (up to 10 lines capacity)... then (and while the producer thread is doing that), the consumer thread will take from the queue and put them into an output file. It's a simple concept, I'm just having trouble getting started with the queue with a fixed size.

You say to make a check to see if it's full... like an if statement?

if(myQ.size() < 10)
//do work

else
//wait until consumer thread takes a line from the queue

something like that, or am I totally off?

What if I create an array of 10 integers... like x[10] for example.

I'd need two values to keep track of the input location (for the producer) and one for the output position for the consumer).

But then wouldn't I have to keep track of which positions are full and empty because the buffer wraps around (when you reach x[9], the next will be x[0])?

How would one do this ?

If you have the choice of using an array or a linked list, I would implement your circular array with a linked list; connect the head and tail. You'll know that you've gone around if you keep iterating in one direction to fill the list, you'll know you've gone around the list once you pass a sentinel (the head or tail) node.