ComponentsThreadChannel::isEmpty()

ThreadChannel::isEmpty ​

(PHP 8.6+, True Async 1.0)

php
public ThreadChannel::isEmpty(): bool

Returns true if the channel buffer contains no values.

For an unbuffered channel (capacity = 0), this always returns true because data is transferred directly between threads without buffering.

isEmpty() is thread-safe. The result reflects the state at the moment of the call; another thread may place a value into the channel immediately afterward.

Return values ​

true — the buffer is empty (no values available). false — the buffer contains at least one value.

Examples ​

Example #1 Checking for buffered data before receiving ​

php
<?php

use Async\ThreadChannel;

$channel = new ThreadChannel(5);

echo $channel->isEmpty() ? "empty" : "has data"; // "empty"

$channel->send(42);

echo $channel->isEmpty() ? "empty" : "has data"; // "has data"

$channel->recv();

echo $channel->isEmpty() ? "empty" : "has data"; // "empty"

Example #2 Consumer that drains a closed channel ​

php
<?php

use Async\ThreadChannel;
use function Async\spawn;
use function Async\spawn_thread;
use function Async\await;

spawn(function() {
    $channel = new ThreadChannel(50);

    $producer = spawn_thread(function() use ($channel) {
        for ($i = 0; $i < 20; $i++) {
            $channel->send($i);
        }
        $channel->close();
    });

    $consumer = spawn_thread(function() use ($channel) {
        // Wait until there is something to read, or the channel closes
        while (!$channel->isClosed() || !$channel->isEmpty()) {
            if ($channel->isEmpty()) {
                // Buffer momentarily empty — yield and retry
                continue;
            }
            try {
                echo $channel->recv(), "\n";
            } catch (\Async\ThreadChannelException) {
                break;
            }
        }
    });

    await($producer);
    await($consumer);
});

See also ​