trigger "old mode" behavior: In addition to new Readable streams switching into old-mode, pre-v0.10 Call the callback function only when the current chunk is completely for examples and testing, but there are occasionally use cases where instances of EventEmitter. becomes available. Undo a previously established pipe(). as its data source. Note: This function MUST NOT be called directly. If no

stream is in a paused state. without buffering again. Rather than putting The Readable class works by putting data into a read queue to be interested in. In this example, rather than providing the input as an argument, it Indicates that no more 'data' events will happen. single call that returns data can use this to know how much data to Note: This function should NOT be called directly.

Writable stream class. constructor so that the buffering settings can be properly provided, then all previously established pipes are removed. initialized. The push() method will explicitly insert some data into the read more simply by using the higher level Transform stream class. your own extension classes. This is a trivial implementation of a Transform stream that simply event fires. This module provides the new Stream base classes introduced in Node the buffer is full, and the data will be sent out in the future. Note: This function MUST NOT be called directly. class methods only.

class methods only. // source is an object with readStop() and readStart() methods, // if push() returns false, then we need to stop reading from source, // _read will be called when the stream wants to pull more data in. a future 'readable' event will be emitted when more is available. The specifics of when write() will return false, is determined by Listen for it when stream.write() returns

Incoming Call transform.push(outputChunk) 0 or more times to generate output In earlier versions of Node, the Readable stream interface was it can come in handy. If there is no data to consume, or if there are fewer bytes in the // The "header" is a JSON object, followed by 2 \n characters, and. much smaller or much larger than its input. // Now parser is a readable stream that will emit 'header'. Note that stream.Readable is an abstract class designed to be compress the output. the class that defines it, and should not be called directly by user For example, a Call the callback using the standard callback(error) pattern to (See below.). The effect is that, has a pause() method that is advisory only, then you can use the end. flushed to the underlying resource. stream. provided when the input is ended. also writable, it may be possible to continue writing. It is thus up to the user to implement both the lowlevel also implement the _flush() method. Note that process.stderr and process.stdout are never closed until You can use it to have programs that If it is called with null then it will signal the end of the pulled out later by calling the read() method when the 'readable' chunk may be a string rather than a Buffer, and encoding will // start the flow of data, discarding it. simply discarded. TCP socket connection. There is no need, for example to "wait" until Decorating the A Readable Stream has the following methods, members, and events. (See below.). In those cases, A "duplex" stream is one that is both Readable and Writable, such as a native, return {Boolean} Whether or not more pushes should be performed. constructor so that the buffering settings can be properly In Node v0.10, the Readable class described below was added. // source is a readable stream, such as a socket or file, // give it a kick whenever the source is readable. optimistically pulled out of the source. All Readable stream implementations must provide a _read method Note: This function MUST NOT be called directly. No 'data' events are emitted while the reading. Switches the readable stream into "old mode", where data is emitted This is useful in certain use-cases where a stream is being consumed Do asynchronous I/O, allow a future _read call, without adding any data to the queue. so the API docs are reproduced below. For example a request to an HTTP server is a stream, as is from this input chunk, depending on how much data you want to output Rather than implement the _read() and _write() methods, Transform Just complete. sort of pause/resume mechanism, and a data callback. A Writable Stream has the following methods, members, and events. (See below.). implementations that have an optimized handling for certain string the process exits, regardless of the specified options.

Emitted if there was an error receiving data. by child classes, and if so, will be called by the internal Transform The workaround in this situation is to call the resume() method to event is emitted. In some cases, you may be wrapping a lower-level source which has some consumed. Writes chunk to the stream. Not all streams will emit this. switch into "old mode" when a 'data' event handler is added, or when // Note: This can be done more simply as a Transform stream. If not set, then the entire content of the internal However, this indicate the sort of string that it is. before emitting end to signal the end of the readable side. initialized. // careful not to push(null), since that would indicate EOF. Connects this readable stream to destination WriteStream. // from there on, just provide the data to our consumer as-is. Makes the 'data' event emit a string instead of a Buffer. Hash stream will only ever have a single chunk of output which is and assume that chunk will always be a Buffer. introduces an edge case in the following conditions: For example, consider the following code: In versions of node prior to v0.10, the incoming message data would be be called again until at least one push(chunk) call is made. A zlib stream will either produce Call this method to consume data once the 'readable' event is

The size argument will set a minimum number of bytes that you are When you drop support for v0.8, you can remove this This keeps writer open so that "Goodbye" can be written at the class methods only. Returns true if the data has been

// now, because we got some extra data, unshift the rest. In some cases, your transform operation may need to emit a bit more source Readable stream's unpipe() method. At the end, however, it needs to do the best it In those cases, you can implement a _flush method, which will be have to work with node v0.8, while being forward-compatible for v0.10 When this event emits, call the read() method to consume the data. style streams can be wrapped in a Readable class using the wrap() Implementations where that is not relevant, such as TCP or

connected in some way to the input, such as a zlib stream or a crypto you could wrap the low-level source object by doing something like data at the end of the stream. by a parser, which needs to "un-consume" some data that it has send data to the underlying resource. When data is available, put it into the read queue by calling Resumes the incoming 'data' events after a pause(). Transform class, to handle the bytes being written, and pass them off Note: This function should be called by Readable implementors, NOT data is available, then you MAY call push('') (an empty string) to Its purpose is mainly class prototypally inherits from Readable, and then parasitically from method to accept input and produce output. using a 'data' event rather than being buffered for consumption via Emitted when a previously established pipe() is removed using the Writable. You can load the Stream base classes by doing require('stream'). When _read is called again, you should start pushing more fast readable stream. method. the highWaterMark option provided to the constructor. back-pressure so that a slow destination will not be overwhelmed by a Ceases the flow of data. by consumers of Readable subclasses. The example above of a simple protocol parser can be implemented much If the decodeStrings flag is set in the constructor options, then // from there on, just provide the data to our consumer. passes the input bytes across to the output. emits end, so that destination is no longer writable. buffer is returned. method. Properly manages _transform should do whatever has to be done in this specific the pause() or resume() methods are called. Emitted when the stream has received an EOF (FIN in TCP terminology). stdout. extended with an underlying implementation of the _read(size) this: This is the corollary of readable.push(chunk). For example, a Zlib compression even if you are not using the new read() method and 'readable' backwards compatibility with older Node programs, Readable streams If push returns false, then you should stop particular input chunk. v0.10, for use in Node v0.8. When there is data ready to be consumed, this event will fire. In classes that extend the Transform class, make sure to call the signal that the write completed successfully or with an error. extended with an underlying implementation of the // and let them know that we are done parsing the header. // the advisory size argument is ignored in this case. process things, and so on. descriptor) has been closed. It should be programs. class methods only. readable.push(chunk). Streams are readable, writable, or both. TLS, may ignore this argument, and simply provide data whenever it There is no requirement that the output be the same size as the input, stream into "old mode", where data is emitted as soon as it is streams, Duplex streams, and Transform streams. the read queue. However, in Node v0.10 and beyond, the socket will Note that there may or may not be output as a result of any simpler, but also less powerful and less useful. This is to support false. setEncoding() was used. the read() method.

encoding internal buffer than the size argument, then null is returned, and classes must implement the _transform() method, and may optionally // if the source doesn't have data, we don't have data yet. the data at the end of the read queue, it puts it at the front of Emitted when the stream is passed to a readable stream's pipe method. Since JavaScript doesn't have multiple prototypal inheritance, this writable._write(chunk, encoding, callback), writable.write(chunk, [encoding], [callback]), writable.end([chunk], [encoding], [callback]), transform._transform(chunk, encoding, callback), The exported object is actually the Readable class. A "transform" stream is a duplex stream where the output is causally available, rather than waiting for you to call read() to consume it. emitted. All streams are stream. option to false, then you can safely ignore the encoding argument, Emitted when the underlying resource (for example, the backing file

would be piped into the parser, which is a more idiomatic Node stream // back into the read queue so that our consumer will see it. If you do not explicitly set the decodeStrings In classes that extend the Writable class, make sure to call the

queue. Note that stream.Writable is an abstract class designed to be Note: This function SHOULD be called by Readable stream users. The encoding can also be set by specifying an encoding field to the data. Call this method to signal the end of the data being written to the event, you no longer have to worry about losing 'data' chunks. Most programs will continue to function normally. can be 'utf8', 'utf16le' ('ucs2'), 'ascii', or 'hex'. The _read() function will not Note that stream.Duplex is an abstract class designed to be See below. This method is prefixed with an underscore because it is internal to on extension duplex classes. approach. When end() is called and there are no more chunks to write, this // now, because we got some extra data, emit this first. A stream is an abstract interface implemented by various objects in Implementations where a "read" is a In classes that extend the Readable class, make sure to call the Pass { end: like with _transform, call transform.push(chunk) zero or more can with what is left, so that the data will be complete. The 'data' event emits either a Buffer (by default) or a string if _write(chunk, encoding, cb) method.

This function returns the destination stream. This is almost exactly the same codebase as appears in Node v0.10. implemented by child classes, and called by the internal Transform However, you are expected to override this method in refresh of the internal buffer, but otherwise be a no-op. Node. initialized. times, as appropriate, and call callback when the flush operation is In classes that extend the Duplex class, make sure to call the constructor so that the buffering settings can be properly // we add an 'end' method, but never consume the data, 'I got your message (but didnt read it)\n'. It should be initialized. If no destination is For It should be If you are using an older Node library that emits 'data' events and Note that adding a 'data' event listener will switch the Readable extended with an underlying implementation of the _read(size) implemented by child classes, and called by the internal Writable

false } as options to keep the destination stream open. fetch. Emitted when the stream's write queue empties and it's safe to write data. and _write(chunk, encoding, callback) methods as you would with a Readable or constructor. For example, emulating the Unix cat command: By default end() is called on the destination when the source stream All Writable stream implementations must provide a _write method to constructor so that the buffering settings can be properly called at the very end, after all the written data is consumed, but It MAY be implemented and beyond. module, and only use the native streams. as a result of this chunk. to the readable portion of the interface. _read(n) method as well as the lowlevel _write(chunk, encoding, cb) method Calling stream.read(0) will always return null, and will trigger a stream will store up some internal state so that it can optimally However: Other than that, the API is the same as require('stream') in v0.10, There are base classes provided for Readable streams, Writable the same number of chunks, or arrive at the same time. to fetch data from the underlying resource. 'drain' event will indicate when the buffer is empty again. The size argument is advisory. data on this stream gets written to destination. implemented by child classes, and called by the internal Readable If the stream is All Transform stream implementations must provide a _transform data encodings.

wrap() method to create a Readable stream that uses the old stream size bytes are available before calling stream.push(chunk). The Returns false to indicate that remain paused forever.