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import queue from './internal/queue';
/**
* A cargo of tasks for the worker function to complete. Cargo inherits all of
* the same methods and event callbacks as {@link async.queue}.
* @typedef {Object} cargo
* @property {Function} length - A function returning the number of items
* waiting to be processed. Invoke with ().
* @property {number} payload - An `integer` for determining how many tasks
* should be process per round. This property can be changed after a `cargo` is
* created to alter the payload on-the-fly.
* @property {Function} push - Adds `task` to the `queue`. The callback is
* called once the `worker` has finished processing the task. Instead of a
* single task, an array of `tasks` can be submitted. The respective callback is
* used for every task in the list. Invoke with (task, [callback]).
* @property {Function} saturated - A callback that is called when the
* `queue.length()` hits the concurrency and further tasks will be queued.
* @property {Function} empty - A callback that is called when the last item
* from the `queue` is given to a `worker`.
* @property {Function} drain - A callback that is called when the last item
* from the `queue` has returned from the `worker`.
* @property {Function} idle - a function returning false if there are items
* waiting or being processed, or true if not. Invoke with ().
* @property {Function} pause - a function that pauses the processing of tasks
* until `resume()` is called. Invoke with ().
* @property {Function} resume - a function that resumes the processing of
* queued tasks when the queue is paused. Invoke with ().
* @property {Function} kill - a function that removes the `drain` callback and
* empties remaining tasks from the queue forcing it to go idle. Invoke with ().
*/
/**
* Creates a `cargo` object with the specified payload. Tasks added to the
* cargo will be processed altogether (up to the `payload` limit). If the
* `worker` is in progress, the task is queued until it becomes available. Once
* the `worker` has completed some tasks, each callback of those tasks is
* called. Check out [these](https://camo.githubusercontent.com/6bbd36f4cf5b35a0f11a96dcd2e97711ffc2fb37/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f313637363837312f36383130382f62626330636662302d356632392d313165322d393734662d3333393763363464633835382e676966) [animations](https://camo.githubusercontent.com/f4810e00e1c5f5f8addbe3e9f49064fd5d102699/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f313637363837312f36383130312f38346339323036362d356632392d313165322d383134662d3964336430323431336266642e676966)
* for how `cargo` and `queue` work.
*
* While [queue](#queue) passes only one task to one of a group of workers
* at a time, cargo passes an array of tasks to a single worker, repeating
* when the worker is finished.
*
* @name cargo
* @static
* @memberOf async
* @see async.queue
* @category Control Flow
* @param {Function} worker - An asynchronous function for processing an array
* of queued tasks, which must call its `callback(err)` argument when finished,
* with an optional `err` argument. Invoked with (tasks, callback).
* @param {number} [payload=Infinity] - An optional `integer` for determining
* how many tasks should be processed per round; if omitted, the default is
* unlimited.
* @returns {cargo} A cargo object to manage the tasks. Callbacks can
* attached as certain properties to listen for specific events during the
* lifecycle of the cargo and inner queue.
* @example
*
* // create a cargo object with payload 2
* var cargo = async.cargo(function(tasks, callback) {
* for (var i=0; i<tasks.length; i++) {
* console.log('hello ' + tasks[i].name);
* }
* callback();
* }, 2);
*
* // add some items
* cargo.push({name: 'foo'}, function(err) {
* console.log('finished processing foo');
* });
* cargo.push({name: 'bar'}, function(err) {
* console.log('finished processing bar');
* });
* cargo.push({name: 'baz'}, function(err) {
* console.log('finished processing baz');
* });
*/
export default function cargo(worker, payload) {
return queue(worker, 1, payload);
}
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