php-ipc/README.md

noccylabs/ipc
=============

This is a one-size-fits-all IPC library to facilitate communication between
threads and processes. 

For complete examples, see the `examples` directory in the source tree.

## Signals

Asynchronous signals are automatically enabled if supported. Otherwise, the
`pcntl_signal_dispatch()` method must be frequently called from your main loop.
You can test for this using the `SIGNALS_ASYNC` constant:

    if (!SIGNALS_ASYNC) {
        pcntl_signal_dispatch();
    }

### Signal handlers

Signal handlers allow for multiple listeners, with any one of them being able to
prevent the signal from bubbling up.

    $handler = new SignalHandler(SIGUSR1);

    $handler->addHandler(function () {
        // Handle SIGUSR1, return true to stop bubbling
        return true;
    });

You can also handle as well as fire signals using the `Signal` class:

    $signal = new Signal(SIGUSR1);
    $signal->setHandler(function () {
        // Handle SIGUSR1
    });

    // Dispatch the signal to ourselves
    (new Signal(SIGUSR1))->dispatch($pid);


### Signal traps

Traps are used in the main loop to break on signals

    $trap = new SignalTrap(SIGINT);

    while (!$trap->isTrapped()) {
        // ...
    }

### Timers

Timers fire asynchronously at fixed 1 second intervals. It requires signals to be
processed; see above.

    // Once every second...
    $timer = new Timer(function () {
        echo ".";
    });

## File locks

File locks uses a shared file as a resource for locking.

    // Creating the lock will not acquire it
    $lock = new FileLock(__FILE__);

    if (!$lock->acquire()) {
        echo "fail!\n";
    } else {
        $lock->release();
    }

## SysV wrappers

All these wrappers depend on a `KeyInterface` being passed to the constructor.
This is usually an instance of a `FileKey`, created as such:

    $key = new FileKey(__FILE__);

The key has a project identifier that starts at `chr(0)`, or `"\0"`. To increase
this identifier, and thus point to another segment, just clone it.

    $key2 = clone $key1;

### Semaphores

Semaphores are created with a key and a max count.

    $key = new FileKey(__FILE__);
    $sem = new Semaphore($key, 2);

    $sem->allocate(); // -> true
    $sem->allocate(); // -> true
    $sem->allocate(); // -> false
    $sem->release();

    $mutex->destroy();

### Mutexes

A mutex is a semaphore with a max count of 1.

    $key = new FileKey(__FILE__);
    $mutex = new Mutex($key);

    $mutex->allocate(); // -> true
    $mutex->allocate(); // -> false
    $mutex->release();

    $mutex->destroy();

### Message Queues

    $key = new FileKey(__FILE__);
    $msgq = new Queue($key);

    $msgq->send(1, [ "Some data", [ "format"=>"foo" ]]);

    $data = $msgq->receive(1, $type);

    $msgq->destroy();

### Shared Memory

Shared memory using `SharedData` supports integrity checking when setting, using
the third parameter to `set()`.

    $key = new FileKey(__FILE__);
    $shm = new SharedData($key);

    do {
        $counter = $shm->get("counter") + 1;
    } while (!$shm->set("counter", $counter, true));

    $shm->destroy();

The `SharedMemory` class is a simple integer-indexed array

    $key = new FileKey(__FILE__);
    $shm = new SharedMemory($key);

    $shm[0] = 42;    

    $shm->destroy();

## Communication

### Channels

Channels are essentially connected pipes. A channel can be created with a stream resource,
or through the `createPair()` factory method.

    [ $ch1, $ch2 ] = StreamChannel::createPair();
    $ch1->send($data);
    $rcvd = $ch2->receive();