strtok3

A promise based streaming tokenizer for Node.js and browsers. This node module is a successor of strtok2.

The strtok3 contains a few methods to turn different input into a tokenizer. Designed to

• Support a streaming environment
• Decoding of binary data, strings and numbers in mind
• Read custom tokens.
• Optimized tokenizers for reading from file, stream or buffer.

It can read from:

• A file (taking a file path as an input)
• A Node.js stream.
• A Buffer
• HTTP chunked transfer provided by streaming-http-token-reader.

Usage

Use one of the methods to instantiate an abstract tokenizer:

• strtok3.fromFile
• strtok3.fromStream
• strtok3.fromBuffer

strtok3 methods

All of the strtok3 methods return a tokenizer, either directly or via a promise.

Method strtok3.fromFile()

Returns, via a promise, a tokenizer which can be used to parse a file.

import strtok3 from 'strtok3';
import Token from 'token-types';
    
strtok3.fromFile("somefile.bin").then(tokenizer => {
  return tokenizer.readToken<number>(Token.UINT8).then(myUint8Number => {
    console.log("My number: %s", myUint8Number);
  });
})

Method strtok3.fromStream()

Create tokenizer from a node.js readable stream.

import strtok3 from 'strtok3';
import Token from 'token-types';

strtok3.fromStream(stream).then(tokenizer => {
  return tokenizer.readToken<number>(Token.UINT8).then(myUint8Number => {
    console.log("My number: %s", myUint8Number);
  });
});

Returns a tokenizer, via a Promise, which can be used to parse a buffer.

Method strtok3.fromBuffer()

Returns a tokenizer which can be used to parse a buffer.

import strtok3 from 'strtok3';
    
const tokenizer = strtok3.fromBuffer(buffer);

tokenizer.readToken<number>(Token.UINT8).then(myUint8Number => {
  console.log("My number: %s", myUint8Number);
});

Tokenizer

The tokenizer allows us to read or peek from the tokenizer-stream. The tokenizer-stream is an abstraction of a stream, file or Buffer. It can also be translated in chunked reads, as done in streaming-http-token-reader;

What is the difference with Nodejs.js stream?

• The tokenizer-stream supports jumping / seeking in a the tokenizer-stream using tokenizer.ignore()
• In addition to read methods, it has peek methods, to read a ahead and check what is coming.

The tokenizer.position keeps tracks of

Tokenizer attributes

Attribute tokenizer.fileSize

Optional attribute of the total file or stream length in bytes

Attribute tokenizer.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.

Tokenizer methods

There are to groups of methods

• 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.
• peek methods: same as the read, but it will not advance the pointer. It allows to read (peek) ahead.

Method tokenizer.readBuffer()

Read buffer from stream. readBuffer(buffer, offset?, length?, position?, maybeless?)

Return value Promise<number> Promise with number of bytes read

Method tokenizer.peekBuffer()

Peek (read ahead) buffer from tokenizer peekBuffer(buffer, offset?, length?, position?, maybeless?)

Return value Promise<number> Promise with number of bytes read

Method tokenizer.readToken()

Read a token from the tokenizer-stream. readToken(token, position?, maybeless?)

Return value Promise<T>. Promise with token value read from the tokenizer-stream.

Method tokenizer.peekToken()

Peek a token from the tokenizer-stream. peekToken(token, position?, maybeless?)

Return value Promise<T> Promise with token value peeked from the tokenizer-stream.

Method tokenizer.readNumber()

Peek a numeric token from the tokenizer-stream.

  readNumber(token)

Return value Promise<number> Promise with number peeked from the tokenizer-stream.

Method tokenizer.ignore()

Peek a numeric token from the tokenizer-stream. ignore(length)

Return value Promise<number> Promise with number peeked from the tokenizer-stream.

Method tokenizer.close()

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

=======

Return value Promise<number> Promise with number of bytes read

Method tokenizer.readToken()

Read a token from the tokenizer-stream. readToken(token, position?, maybeless?)

Return value Promise<T>. Promise with token value read from the tokenizer-stream.

Method tokenizer.peekToken()

Peek a token from the tokenizer-stream. peekToken(token, position?, maybeless?)

Return value Promise<T> Promise with token value peeked from the tokenizer-stream.

Method tokenizer.readNumber()

Peek a numeric token from the tokenizer-stream. readNumber(token)

Return value Promise<number> Promise with number peeked from the tokenizer-stream.

Method tokenizer.ignore()

Peek a numeric token from the tokenizer-stream. ignore(length)

Return value Promise<number> Promise with number peeked from the tokenizer-stream.

Method tokenizer.close()

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

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Token

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

Below is an example of parsing the the first byte from a readable stream as an unsigned-integer:

import strtok3 from 'strtok3';
import Token from 'token-types';
    
let readableStream; // stream.Readable;

strtok3.fromStream(readableStream).then(tokenizer => {
  return tokenizer.readToken<number>(Token.UINT8).then(myUint8Number => {
    console.log("My number: %s", myUint8Number);
  });
})

Browser

To exclude fs based dependencies, you can use a submodule-import from 'strtok3/lib/core'.

Example submodule-import:

import strtok3core from 'strtok3/lib/core';

const tokenizer = strtok3core.fromStream(stream);

If you plan to use fromStream you need to polyfill:

1. buffer: buffer
2. stream: web-streams-polyfill