Bobby L. Craig

delayed-stream

# delayed-stream Buffers events from a stream until you are ready to handle them. ## Installation ``` bash npm install delayed-stream ``` ## Usage The following example shows how to write a http echo server that delays its response by 1000 ms. ``` javascript var DelayedStream = require('delayed-stream'); var http = require('http'); http.createServer(function(req, res) { var delayed = DelayedStream.create(req); setTimeout(function() { res.writeHead(200); delayed.pipe(res); }, 1000); }); ``` If you are not using `Stream#pipe`, you can also manually release the buffered events by calling `delayedStream.resume()`: ``` javascript var delayed = DelayedStream.create(req); setTimeout(function() { // Emit all buffered events and resume underlaying source delayed.resume(); }, 1000); ``` ## Implementation In order to use this meta stream properly, here are a few things you should know about the implementation. ### Event Buffering / Proxying All events of the `source` stream are hijacked by overwriting the `source.emit` method. Until node implements a catch-all event listener, this is the only way. However, delayed-stream still continues to emit all events it captures on the `source`, regardless of whether you have released the delayed stream yet or not. Upon creation, delayed-stream captures all `source` events and stores them in an internal event buffer. Once `delayedStream.release()` is called, all buffered events are emitted on the `delayedStream`, and the event buffer is cleared. After that, delayed-stream merely acts as a proxy for the underlaying source. ### Error handling Error events on `source` are buffered / proxied just like any other events. However, `delayedStream.create` attaches a no-op `'error'` listener to the `source`. This way you only have to handle errors on the `delayedStream` object, rather than in two places. ### Buffer limits delayed-stream provides a `maxDataSize` property that can be used to limit the amount of data being buffered. In order to protect you from bad `source` streams that don't react to `source.pause()`, this feature is enabled by default. ## API ### DelayedStream.create(source, [options]) Returns a new `delayedStream`. Available options are: * `pauseStream` * `maxDataSize` The description for those properties can be found below. ### delayedStream.source The `source` stream managed by this object. This is useful if you are passing your `delayedStream` around, and you still want to access properties on the `source` object. ### delayedStream.pauseStream = true Whether to pause the underlaying `source` when calling `DelayedStream.create()`. Modifying this property afterwards has no effect. ### delayedStream.maxDataSize = 1024 * 1024 The amount of data to buffer before emitting an `error`. If the underlaying source is emitting `Buffer` objects, the `maxDataSize` refers to bytes. If the underlaying source is emitting JavaScript strings, the size refers to characters. If you know what you are doing, you can set this property to `Infinity` to disable this feature. You can also modify this property during runtime. ### delayedStream.maxDataSize = 1024 * 1024 The amount of data to buffer before emitting an `error`. If the underlaying source is emitting `Buffer` objects, the `maxDataSize` refers to bytes. If the underlaying source is emitting JavaScript strings, the size refers to characters. If you know what you are doing, you can set this property to `Infinity` to disable this feature. ### delayedStream.dataSize = 0 The amount of data buffered so far. ### delayedStream.readable An ECMA5 getter that returns the value of `source.readable`. ### delayedStream.resume() If the `delayedStream` has not been released so far, `delayedStream.release()` is called. In either case, `source.resume()` is called. ### delayedStream.pause() Calls `source.pause()`. ### delayedStream.pipe(dest) Calls `delayedStream.resume()` and then proxies the arguments to `source.pipe`. ### delayedStream.release() Emits and clears all events that have been buffered up so far. This does not resume the underlaying source, use `delayedStream.resume()` instead. ## License delayed-stream is licensed under the MIT license.