chunkreader2

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

Install

NPM

npm install chunkreader2

yarn

yarn add chunkreader2

Usage

Import

ES6

import { ChunkReader } from 'chunkreader2';

CommonJS

const { ChunkReader } = require('chunkreader2');

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 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 |

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).

Testing

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

NPM

npm test

yarn

yarn test

Related

• linereader2 - 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.