strtok3
A promise based streaming tokenizer
Last updated 20 days ago by borewit .
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strtok3

A promise based streaming tokenizer for Node.js and browsers.

The strtok3 module provides several methods for creating a tokenizer from various input sources. Designed for:

Features

strtok3 can read from:

Installation

npm install strtok3

Compatibility

Starting with version 7, the module has migrated from CommonJS to pure ECMAScript Module (ESM). The distributed JavaScript codebase is compliant with the ECMAScript 2020 (11th Edition) standard.

Requires a modern browser, Node.js (V8) ≥ 18 engine or Bun (JavaScriptCore) ≥ 1.2.

For TypeScript CommonJs backward compatibility, you can use load-esm.

[!NOTE] This module requires a Node.js ≥ 16 engine. It can also be used in a browser environment when bundled with a module bundler.

Support the Project

If you find this project useful and would like to support its development, consider sponsoring or contributing:

API Documentation

strtok3 methods

Use one of the methods to instantiate an abstract tokenizer:

[!NOTE] fromFile and fromStream only available when importing this module with Node.js

All methods return a Tokenizer, either directly or via a promise.

fromBlob() function

Create a tokenizer from a Blob.

function fromBlob(blob: Blob, options?: ITokenizerOptions): BlobTokenizer
Parameter Optional Type Description
blob no Blob Blob or File to read from
options yes ITokenizerOptions Tokenizer options

Returns a tokenizer.

import { fromBlob } from 'strtok3';
import { openAsBlob } from 'node:fs';
import * as Token from 'token-types';

async function parse() {
  const blob = await openAsBlob('somefile.bin');

  const tokenizer = fromBlob(blob);

  const myUint8Number = await tokenizer.readToken(Token.UINT8);
  console.log(`My number: ${myUint8Number}`);   
}

parse();

fromBuffer() function

Create a tokenizer from memory (Uint8Array or Node.js Buffer).

function fromBuffer(uint8Array: Uint8Array, options?: ITokenizerOptions): BufferTokenizer
Parameter Optional Type Description
uint8Array no Uint8Array Buffer or Uint8Array to read from
options yes ITokenizerOptions Tokenizer options

Returns a tokenizer.

import { fromBuffer } from 'strtok3';
import * as Token from 'token-types';

const tokenizer = fromBuffer(buffer);

async function parse() {
  const myUint8Number = await tokenizer.readToken(Token.UINT8);
  console.log(`My number: ${myUint8Number}`);
}

parse();

fromFile function

Creates a tokenizer from a local file.

function fromFile(sourceFilePath: string): Promise<FileTokenizer>
Parameter Type Description
sourceFilePath string Path to file to read from

[!NOTE]

  • Only available for Node.js engines
  • fromFile automatically embeds file-information

A Promise resolving to a tokenizer which can be used to parse a file.

import { fromFile } from 'strtok3';
import * as Token from 'token-types';

async function parse() {
  const tokenizer = await fromFile('somefile.bin');
  try {
    const myNumber = await tokenizer.readToken(Token.UINT8);
    console.log(`My number: ${myNumber}`);
  } finally {
    tokenizer.close(); // Close the file
  }
}

parse();

fromWebStream() function

Create a tokenizer from a WHATWG ReadableStream.

function fromWebStream(webStream: AnyWebByteStream, options?: ITokenizerOptions): ReadStreamTokenizer
Parameter Optional Type Description
webStream no ReadableStream WHATWG ReadableStream to read from
options yes ITokenizerOptions Tokenizer options

Returns a tokenizer.

import { fromWebStream } from 'strtok3';
import * as Token from 'token-types';

async function parse() {
  const tokenizer = fromWebStream(readableStream);
  try {
    const myUint8Number = await tokenizer.readToken(Token.UINT8);
    console.log(`My number: ${myUint8Number}`);
  } finally {
    await tokenizer.close();
  }
}

parse();

Tokenizer object

The tokenizer is an abstraction of a stream, file or Uint8Array, allowing reading or peeking from the stream. It can also be translated in chunked reads, as done in @tokenizer/http;

Key Features:

  • Supports seeking within the stream using tokenizer.ignore().
  • Offers peek methods to preview data without advancing the read pointer.
  • Maintains the read position via tokenizer.position.

Tokenizer functions

Read methods advance the stream pointer, while peek methods do not.

There are two kind of functions:

  1. read methods: used to read a token of Buffer from the tokenizer. The position of the tokenizer-stream will advance with the size of the token.
  2. peek methods: same as the read, but it will not advance the pointer. It allows to read (peek) ahead.

readBuffer function

Read data from the tokenizer into provided "buffer" (Uint8Array). readBuffer(buffer, options?)

readBuffer(buffer: Uint8Array, options?: IReadChunkOptions): Promise<number>;
Parameter Type Description
buffer Buffer | Uint8Array Target buffer to write the data read to
options IReadChunkOptions An integer specifying the number of bytes to read

Return promise with number of bytes read. The number of bytes read may be less than requested if the mayBeLess flag is set.

peekBuffer function

Peek (read ahead), from tokenizer, into the buffer without advancing the stream pointer.

peekBuffer(uint8Array: Uint8Array, options?: IReadChunkOptions): Promise<number>;
Parameter Type Description
buffer Buffer | Uint8Array Target buffer to write the data read (peeked) to.
options IReadChunkOptions An integer specifying the number of bytes to read.

Return value Promise<number> Promise with number of bytes read. The number of bytes read may be less if the mayBeLess flag was set.

readToken function

Read a token from the tokenizer-stream.

readToken<Value>(token: IGetToken<Value>, position: number = this.position): Promise<Value>
Parameter Type Description
token IGetToken Token to read from the tokenizer-stream.
position? number Offset where to begin reading within the file. If position is null, data will be read from the current file position.

Return value Promise<number>. Promise with number of bytes read. The number of bytes read maybe if less, mayBeLess flag was set.

peek function

Peek a token from the tokenizer.

peekToken<Value>(token: IGetToken<Value>, position: number = this.position): Promise<Value>
Parameter Type Description
token IGetToken<T> Token to read from the tokenizer-stream.
position? number Offset where to begin reading within the file. If position is null, data will be read from the current file position.

Return a promise with the token value peeked from the tokenizer.

readNumber function

Read a numeric token from the tokenizer.

readNumber(token: IToken<number>): Promise<number>
Parameter Type Description
token IGetToken<number> Numeric token to read from the tokenizer-stream.

A promise resolving to a numeric value read and decoded from the tokenizer-stream.

ignore function

Advance the offset pointer with the token number of bytes provided.

ignore(length: number): Promise<number>
Parameter Type Description
length number Number of bytes to ignore. Will advance the tokenizer.position

A promise resolving to the number of bytes ignored from the tokenizer-stream.

close function

Clean up resources, such as closing a file pointer if applicable.

Tokenizer attributes

  • fileInfo

    Optional attribute describing the file information, see IFileInfo

  • position

    Pointer to the current position in the tokenizer stream. If a position is provided to a read or peek method, is should be, at least, equal or greater than this value.

IReadChunkOptions interface

Each attribute is optional:

Attribute Type Description
length number Requested number of bytes to read.
position number Position where to peek from the file. If position is null, data will be read from the current file position. Position may not be less then tokenizer.position
mayBeLess boolean If and only if set, will not throw an EOF error if less than the requested mayBeLess could be read.

Example usage:

  tokenizer.peekBuffer(buffer, {mayBeLess: true});

IFileInfo interface

Provides optional metadata about the file being tokenized.

Attribute Type Description
size number File size in bytes
mimeType string MIME-type of file.
path string File path
url string File URL

Token object

The token is basically a description of what to read from the tokenizer-stream. A basic set of token types can be found here: token-types.

A token is something which implements the following interface:

export interface IGetToken<T> {

  /**
   * Length in bytes of encoded value
   */
  len: number;

  /**
   * Decode value from buffer at offset
   * @param buf Buffer to read the decoded value from
   * @param off Decode offset
   */
  get(buf: Uint8Array, off: number): T;
}

The tokenizer reads token.len bytes from the tokenizer-stream into a Buffer. The token.get will be called with the Buffer. token.get is responsible for conversion from the buffer to the desired output type.

Working with Web-API readable stream

To convert a Web-API readable stream into a Node.js readable stream, you can use readable-web-to-node-stream to convert one in another.

import { fromWebStream } from 'strtok3';
import { ReadableWebToNodeStream } from 'readable-web-to-node-stream';

(async () => {

  const response = await fetch(url);
  const readableWebStream = response.body; // Web-API readable stream
  const webStream = new ReadableWebToNodeStream(readableWebStream); // convert to Node.js readable stream

  const tokenizer = fromWebStream(webStream); // And we now have tokenizer in a web environment
})();

Dependencies

Dependencies:

  • @tokenizer/token: Provides token definitions and utilities used by strtok3 for interpreting binary data.

Licence

This project is licensed under the MIT License. Feel free to use, modify, and distribute as needed.

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