chunk-reader2

chunk-reader2

Asynchronous, buffered, chunk-by-chunk file reader with customizable buffer size.

Install

NPM

npm install chunk-reader2

yarn

yarn add chunk-reader2

Usage

Import

ES6

import { ChunkReader } from 'chunk-reader2';

CommonJS

const { ChunkReader } = require('chunk-reader2');

Example

const reader = new ChunkReader({
  filePath: './file.txt',
  bufferSize: 1024,
});

while (!reader.isClosed) {
  const chunk = await reader.read();
  console.log(chunk);
}

API

new ChunkReader(options: ChunkReaderOptions): ChunkReader

The options you can pass are:

Name	Type	Default	Description
filePath	string	none	The path or location of your file (required)
bufferSize	number	1024	Chunk/buffer size in bytes
bufferEncoding	'ascii' | 'utf8' | 'utf-8' | 'utf16le' | 'ucs2' | 'ucs-2' | 'base64' | 'latin1' | 'binary' | 'hex'	'utf8'	Character encoding to use on read() operation
removeInvisibleUnicode	boolean	false	Remove all (or perhaps just "common") non-printable Unicode characters except line breaks. Using regex: /[\x00-\x09\x0B-\x0C\x0E-\x1F\x7F-\x9F]/g

Instance Methods

read(): Promise<string>

Asynchronously read next chunk of current file stream.

Example:

const reader = new ChunkReader({
  filePath: './file.txt',
  bufferSize: 8,
});

while (!reader.isClosed) {
  const chunk = await reader.read();
  console.log(chunk);
}

./file.txt

aaaabbbbccccddddeeeeffffgggghhhhiiiijjjjkkkkllllmmmmnnnnoooo

Output:

aaaabbbb
ccccdddd
eeeeffff
gggghhhh
iiiijjjj
kkkkllll
mmmmnnnn
oooo

NOTE: This method can be called concurrently with safe because it used async-mutex module to handle Mutual Exclusion.

reset(): void

Reset the reader, so it will repeat the reading from the beginning.

Example:

const reader = new ChunkReader({
  filePath: './file.txt',
  bufferSize: 1,
});

for (let i = 0; i < 2; i++) {
  const chunk = await reader.read();
  console.log(chunk);
}

console.log('reset');
reader.reset();

while (!reader.isClosed) {
  const chunk = await reader.read();
  console.log(chunk);
}

./file.txt

12345

Output:

1
2
reset
1
2
3
4
5

open(): void

Manually open the file descriptor and get bytesLength. This method will be called automatically on the first read() operation. Throws an error when file doesn't exist.

close(): void

Manually close the file descriptor. This method will be called automatically on the last read() operation (last file stream).

Instance Property

The property of ChunkReader instance you can access are:

Name	Type	Description
bytesLength	number	Size of the file in bytes. Value assigned on open() operation
bytesRead	number	Size of the bytes read in the file by read() operation
readCount	number	Count of read() operation called
isOpened	boolean	Indicates whether the reader has opened the file or open() has been called
isClosed	boolean	Indicates whether the reader has closed the file or close() has been called

Testing

This library is well tested. You can test the code as follows:

NPM

npm test

yarn

yarn test

Related

• line-reader2 - Asynchronous, buffered, line-by-line file reader with customizable buffer size and separator.

Contribute

If you have anything to contribute, or functionality that you lack - you are more than welcome to participate in this!

License

Feel free to use this library under the conditions of the MIT license.