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concat-stream

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    concat-stream

writable stream that concatenates strings or binary data and calls a callback with the result


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2
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Package description

What is concat-stream?

The concat-stream npm package is a writable stream that concatenates data and calls a callback with the result. It can be used to collect stream data and concatenate it into a single buffer, string, or array. It is useful for collecting stream data from sources like HTTP requests, file reads, and other stream sources.

What are concat-stream's main functionalities?

Concatenate stream data into a buffer

This code sample demonstrates how to use concat-stream to read data from a file and concatenate it into a buffer. The buffer is then converted to a string and logged to the console.

const concat = require('concat-stream');
const fs = require('fs');

const readStream = fs.createReadStream('file.txt');
const concatStream = concat(function(buffer) {
  console.log(buffer.toString());
});

readStream.pipe(concatStream);

Concatenate stream data into a string

This code sample shows how to use concat-stream to collect HTTP response data and concatenate it into a string. The string is then logged to the console.

const concat = require('concat-stream');
const http = require('http');

http.get('http://example.com', function(response) {
  response.pipe(concat(function(data) {
    console.log(data.toString());
  }));
});

Concatenate stream data into an array

This example demonstrates how to use concat-stream to collect data from a readable stream and concatenate it into an array. The resulting array is then logged to the console.

const concat = require('concat-stream');
const { Readable } = require('stream');

const arrayStream = Readable.from(['hello', ' ', 'world']);
const concatStream = concat({ encoding: 'array' }, function(array) {
  console.log(array);
});

arrayStream.pipe(concatStream);

Other packages similar to concat-stream

Readme

Source

concat-stream

Writable stream that concatenates strings or binary data and calls a callback with the result. Not a transform stream -- more of a stream sink.

Build Status

NPM

description

Streams emit many buffers. If you want to collect all of the buffers, and when the stream ends concatenate all of the buffers together and receive a single buffer then this is the module for you.

Only use this if you know you can fit all of the output of your stream into a single Buffer (e.g. in RAM).

There are also objectMode streams that emit things other than Buffers, and you can concatenate these too. See below for details.

examples

Buffers
var fs = require('fs')
var concat = require('concat-stream')

var readStream = fs.createReadStream('cat.png')
var concatStream = concat(gotPicture)

readStream.on('error', handleError)
readStream.pipe(concatStream)

function gotPicture(imageBuffer) {
  // imageBuffer is all of `cat.png` as a node.js Buffer
}

function handleError(err) {
  // handle your error appropriately here, e.g.:
  console.error(err) // print the error to STDERR
  process.exit(1) // exit program with non-zero exit code
}

Arrays
var write = concat(function(data) {})
write.write([1,2,3])
write.write([4,5,6])
write.end()
// data will be [1,2,3,4,5,6] in the above callback
Uint8Arrays
var write = concat(function(data) {})
var a = new Uint8Array(3)
a[0] = 97; a[1] = 98; a[2] = 99
write.write(a)
write.write('!')
write.end(Buffer('!!1'))

See test/ for more examples

methods

var concat = require('concat-stream')

var writable = concat(opts={}, cb)

Return a writable stream that will fire cb(data) with all of the data that was written to the stream. Data can be written to writable as strings, Buffers, arrays of byte integers, and Uint8Arrays.

By default concat-stream will give you back the same data type as the type of the first buffer written to the stream. Use opts.encoding to set what format data should be returned as, e.g. if you if you don't want to rely on the built-in type checking or for some other reason.

  • string - get a string
  • buffer - get back a Buffer
  • array - get an array of byte integers
  • uint8array, u8, uint8 - get back a Uint8Array
  • object, get back an array of Objects

If you don't specify an encoding, and the types can't be inferred (e.g. you write things that aren't in the list above), it will try to convert concat them into a Buffer.

error handling

concat-stream does not handle errors for you, so you must handle errors on whatever streams you pipe into concat-stream. This is a general rule when programming with node.js streams: always handle errors on each and every stream. Since concat-stream is not itself a stream it does not emit errors.

license

MIT LICENSE

FAQs

Last updated on 01 Mar 2018

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