dots.node.fs.write-stream — io.github.dots-cljs/dots-node 20.12.12-9

• Extends stream.Writable

Instances of fs.WriteStream are created and returned using the {@link createWriteStream } function.

add-listener cljs

(add-listener write-stream event listener)

events.EventEmitter

1. open
2. close
3. ready

Parameters:

• event: string | symbol
• listener: (...args: any[]) => void

Returns: WriteStream

bytes-written cljs

(bytes-written write-stream)

The number of bytes written so far. Does not include data that is still queued for writing.

close cljs

(close write-stream)

(close write-stream callback)

Closes writeStream. Optionally accepts a callback that will be executed once the writeStreamis closed.

Parameters:

• callback: ((err?: ErrnoException | null | undefined) => void) | undefined

Returns: void

closed? cljs

(closed? write-stream)

Is true after 'close' has been emitted.

compose cljs

(compose write-stream stream)

(compose write-stream stream options)

Parameters:

• stream: ComposeFnParam | T | Iterable<T> | AsyncIterable<T>
• options: { signal: AbortSignal; } | undefined

Returns: T

cork cljs

(cork write-stream)

The writable.cork() method forces all written data to be buffered in memory. The buffered data will be flushed when either the {@link uncork } or {@link end } methods are called.

The primary intent of writable.cork() is to accommodate a situation in which several small chunks are written to the stream in rapid succession. Instead of immediately forwarding them to the underlying destination, writable.cork() buffers all the chunks until writable.uncork() is called, which will pass them all to writable._writev(), if present. This prevents a head-of-line blocking situation where data is being buffered while waiting for the first small chunk to be processed. However, use of writable.cork() without implementing writable._writev() may have an adverse effect on throughput.

See also: writable.uncork(), writable._writev().

Returns: void

destroy cljs

(destroy write-stream)

(destroy write-stream error)

Destroy the stream. Optionally emit an 'error' event, and emit a 'close' event (unless emitClose is set to false). After this call, the writable stream has ended and subsequent calls to write() or end() will result in an ERR_STREAM_DESTROYED error. This is a destructive and immediate way to destroy a stream. Previous calls to write() may not have drained, and may trigger an ERR_STREAM_DESTROYED error. Use end() instead of destroy if data should flush before close, or wait for the 'drain' event before destroying the stream.

Once destroy() has been called any further calls will be a no-op and no further errors except from _destroy() may be emitted as 'error'.

Implementors should not override this method, but instead implement writable._destroy().

Parameters:

• error: Error | undefined - Optional, an error to emit with 'error' event.

Returns: WriteStream

destroyed? cljs

(destroyed? write-stream)

Is true after writable.destroy() has been called.

emit? cljs

(emit? write-stream & event)

(emit? write-stream event err)

(emit? write-stream event src)

(emit? write-stream event & args)

Parameters:

• event: string | symbol
• args: any[]
• err: Error
• src: Readable

Returns: boolean

end cljs

(end write-stream)

(end write-stream cb)

(end write-stream chunk)

(end write-stream chunk cb)

(end write-stream chunk encoding)

(end write-stream chunk encoding cb)

Calling the writable.end() method signals that no more data will be written to the Writable. The optional chunk and encoding arguments allow one final additional chunk of data to be written immediately before closing the stream.

Calling the {@link write } method after calling {@link end } will raise an error.

// Write 'hello, ' and then end with 'world!'.
const fs = require('node:fs');
const file = fs.createWriteStream('example.txt');
file.write('hello, ');
file.end('world!');
// Writing more now is not allowed!

Parameters:

• chunk: any
• encoding: BufferEncoding
• cb: (() => void) | undefined

Returns: WriteStream

errored cljs

(errored write-stream)

Returns error if the stream has been destroyed with an error.

event-names cljs

(event-names write-stream)

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

import { EventEmitter } from 'node:events';

const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns: (string | symbol)[]

listener-count cljs

(listener-count write-stream event-name)

(listener-count write-stream event-name listener)

Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

Parameters:

• event-name: string | symbol - The name of the event being listened for
• listener: Function | undefined - The event handler function

Returns: number

listeners cljs

(listeners write-stream event-name)

Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

Parameters:

• event-name: string | symbol

Returns: Function[]

max-listeners cljs

(max-listeners write-stream)

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to {@link defaultMaxListeners }.

Returns: number

off cljs

(off write-stream event-name listener)

Alias for emitter.removeListener().

Parameters:

• event-name: string | symbol
• listener: (...args: any[]) => void

Returns: WriteStream

on cljs

(on write-stream event listener)

Parameters:

• event: string | symbol
• listener: (...args: any[]) => void

Returns: WriteStream

once cljs

(once write-stream event listener)

Parameters:

• event: string | symbol
• listener: (...args: any[]) => void

Returns: WriteStream

path cljs

(path write-stream)

The path to the file the stream is writing to as specified in the first argument to {@link createWriteStream }. If path is passed as a string, thenwriteStream.path will be a string. If path is passed as a Buffer, thenwriteStream.path will be a Buffer.

pending? cljs

(pending? write-stream)

This property is true if the underlying file has not been opened yet, i.e. before the 'ready' event is emitted.

pipe cljs

(pipe write-stream destination)

(pipe write-stream destination options)

Parameters:

• destination: T
• options: { end?: boolean | undefined; } | undefined

Returns: T

prepend-listener cljs

(prepend-listener write-stream event listener)

Parameters:

• event: string | symbol
• listener: (...args: any[]) => void

Returns: WriteStream

prepend-once-listener cljs

(prepend-once-listener write-stream event listener)

Parameters:

• event: string | symbol
• listener: (...args: any[]) => void

Returns: WriteStream

raw-listeners cljs

(raw-listeners write-stream event-name)

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

Parameters:

• event-name: string | symbol

Returns: Function[]

remove-all-listeners cljs

(remove-all-listeners write-stream)

(remove-all-listeners write-stream event-name)

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters:

• event-name: string | symbol | undefined

Returns: WriteStream

remove-listener cljs

(remove-listener write-stream event listener)

Parameters:

• event: string | symbol
• listener: (...args: any[]) => void

Returns: WriteStream

set-bytes-written! cljs

(set-bytes-written! write-stream value)

The number of bytes written so far. Does not include data that is still queued for writing.

set-default-encoding cljs

(set-default-encoding write-stream encoding)

The writable.setDefaultEncoding() method sets the default encoding for a Writable stream.

Parameters:

• encoding: BufferEncoding - The new default encoding

Returns: WriteStream

set-destroyed! cljs

(set-destroyed! write-stream value)

Is true after writable.destroy() has been called.

set-max-listeners cljs

(set-max-listeners write-stream n)

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters:

• n: number

Returns: WriteStream

set-path! cljs

(set-path! write-stream value)

The path to the file the stream is writing to as specified in the first argument to {@link createWriteStream }. If path is passed as a string, thenwriteStream.path will be a string. If path is passed as a Buffer, thenwriteStream.path will be a Buffer.

set-pending! cljs

(set-pending! write-stream value)

This property is true if the underlying file has not been opened yet, i.e. before the 'ready' event is emitted.

uncork cljs

(uncork write-stream)

The writable.uncork() method flushes all data buffered since {@link cork } was called.

When using writable.cork() and writable.uncork() to manage the buffering of writes to a stream, defer calls to writable.uncork() using process.nextTick(). Doing so allows batching of all writable.write() calls that occur within a given Node.js event loop phase.

stream.cork();
stream.write('some ');
stream.write('data ');
process.nextTick(() => stream.uncork());

If the writable.cork() method is called multiple times on a stream, the same number of calls to writable.uncork() must be called to flush the buffered data.

stream.cork();
stream.write('some ');
stream.cork();
stream.write('data ');
process.nextTick(() => {
  stream.uncork();
  // The data will not be flushed until uncork() is called a second time.
  stream.uncork();
});

See also: writable.cork().

Returns: void

writable-corked cljs

(writable-corked write-stream)

Number of times writable.uncork() needs to be called in order to fully uncork the stream.

writable-ended? cljs

(writable-ended? write-stream)

Is true after writable.end() has been called. This property does not indicate whether the data has been flushed, for this use writable.writableFinished instead.

writable-finished? cljs

(writable-finished? write-stream)

Is set to true immediately before the 'finish' event is emitted.

writable-high-water-mark cljs

(writable-high-water-mark write-stream)

Return the value of highWaterMark passed when creating this Writable.

writable-length cljs

(writable-length write-stream)

This property contains the number of bytes (or objects) in the queue ready to be written. The value provides introspection data regarding the status of the highWaterMark.

writable-need-drain? cljs

(writable-need-drain? write-stream)

Is true if the stream's buffer has been full and stream will emit 'drain'.

writable-object-mode? cljs

(writable-object-mode? write-stream)

Getter for the property objectMode of a given Writable stream.

writable? cljs

(writable? write-stream)

Is true if it is safe to call writable.write(), which means the stream has not been destroyed, errored, or ended.

write? cljs

(write? write-stream chunk)

(write? write-stream chunk callback)

(write? write-stream chunk encoding)

(write? write-stream chunk encoding callback)

The writable.write() method writes some data to the stream, and calls the supplied callback once the data has been fully handled. If an error occurs, the callback will be called with the error as its first argument. The callback is called asynchronously and before 'error' is emitted.

The return value is true if the internal buffer is less than the highWaterMark configured when the stream was created after admitting chunk. If false is returned, further attempts to write data to the stream should stop until the 'drain' event is emitted.

While a stream is not draining, calls to write() will buffer chunk, and return false. Once all currently buffered chunks are drained (accepted for delivery by the operating system), the 'drain' event will be emitted. Once write() returns false, do not write more chunks until the 'drain' event is emitted. While calling write() on a stream that is not draining is allowed, Node.js will buffer all written chunks until maximum memory usage occurs, at which point it will abort unconditionally. Even before it aborts, high memory usage will cause poor garbage collector performance and high RSS (which is not typically released back to the system, even after the memory is no longer required). Since TCP sockets may never drain if the remote peer does not read the data, writing a socket that is not draining may lead to a remotely exploitable vulnerability.

Writing data while the stream is not draining is particularly problematic for a Transform, because the Transform streams are paused by default until they are piped or a 'data' or 'readable' event handler is added.

If the data to be written can be generated or fetched on demand, it is recommended to encapsulate the logic into a Readable and use {@link pipe }. However, if calling write() is preferred, it is possible to respect backpressure and avoid memory issues using the 'drain' event:

function write(data, cb) {
  if (!stream.write(data)) {
    stream.once('drain', cb);
  } else {
    process.nextTick(cb);
  }
}

// Wait for cb to be called before doing any other write.
write('hello', () => {
  console.log('Write completed, do more writes now.');
});

A Writable stream in object mode will always ignore the encoding argument.

Parameters:

• chunk: any
• encoding: BufferEncoding
• callback: ((error: Error | null | undefined) => void) | undefined

Returns: boolean