promise-readable

This module allows to convert Readable stream into its promisified version, which returns Promise object fulfilled when open, data, close, end or error events occurred.

The promisified stream provides async iterator so it is possible to use it with for await...of statement.

Requirements

This module requires Node >= 6.

Installation

npm install promise-readable

Additionally for Typescript:

npm install -D @types/node

Usage

const {PromiseReadable} = require("promise-readable")

Typescript:

import PromiseReadable from "promise-readable"
// or
import {PromiseReadable} from "promise-readable"

constructor

const promiseReadable = new PromiseReadable(stream)

PromiseReadable object requires Readable object to work.

Example:

const fs = require("fs")
const {PromiseReadable} = require("promise-readable")

const stream = fs.createReadStream("/etc/hosts")
const promiseReadable = new PromiseReadable(stream)

Typescript:

import fs from "fs"
import PromiseReadable from "promise-readable"

const stream = fs.createReadStream("/etc/hosts")
const promiseReadable = new PromiseReadable(stream)

stream

const stream = promiseReadable.stream

Original stream object.

Example:

console.log(promiseReadable.stream.flags)

read

const chunk = await promiseReadable.read(chunkSize)

This method returns Promise which is fulfilled when stream can return one chunk (by read method or data event) or stream is ended (end or close events).

Example:

const chunk = await promiseReadable.read(1024)

Promise returns chunk data if something has been read or undefined value if it is an end of the stream.

Example:

for (let chunk; (chunk = await promiseReadable.read()); ) {
  console.log(chunk.length)
}
console.log("stream is ended")

readAll

const content = await promiseReadable.readAll()

This method returns Promise which is fulfilled when stream is ended or closed. It is resolved to undefined value if stream is already ended or closed.

The content from the stream is buffered and then Promise returns this concatenated content.

setEncoding

promiseReadable = promiseReadable.setEncoding(encoding)

By default read and readAll methods returns Buffer objects.

This method sets the character encoding for data read from the stream. It might be used if original stream does not provide encoding option.

The method returns this object.

Example:

const asBuffer = await promiseReadable.read()

promiseReadable.setEncoding("utf8")
const asString = await promiseReadable.read()

once

const result = await promiseReadable.once(event)

This method returns Promise which is fulfilled when stream emits event. The result of this event is returned or undefined value if stream is already ended.

The promise will reject on error.

Example:

const fd = await promiseReadable.once("open")
promiseReadable.stream.pipe(process.stdout)

await promiseReadable.once("close")

promiseReadable.stream.on("data", chunk => console.log(chunk.length))
await promiseReadable.once("end")

await promiseReadable.once("error") // throws error, undefined if ended

iterate

for await (const chunk of promiseReadable.iterate(chunkSize)) {
}

This method returns async iterator which returns a content of the stream chunk-by-chunk with defined chunkSize.

Symbol.asyncIterator

for await (const chunk of promiseReadable) {
}

The PromiseReadable object is an async iterator which returns a content of the stream chunk-by-chunk with the default chunkSize.

destroy

promiseReadable.destroy()

This method calls destroy method on stream and cleans up all own handlers.

See also

PromiseWritable, PromiseDuplex, PromiseSocket, PromisePiping.

License

Copyright (c) 2017-2019 Piotr Roszatycki mailto:piotr.roszatycki@gmail.com

MIT