bitstream2

An unaligned read/write/seek bitstream for use in various non-octet based encoding/decoding operations.

Usage

$ npm i bitstream2

const bitstream = require('bitstream2');
const myStream = bitstream([]);
myStream.write(4, 10); // write 10 as a 4 bit integer
myStream.seek(-4);
myStream.read(4); // returns 10
console.log(myStream.raw[0]); // prints 0x160 (10 << 4)
console.log(myStream.index()); // returns bit level index in stream

API

Constructor

The bitstream constructor takes a mutable reference to some array of integers, or empty, and returns a bitstream object. The initial index is always 0.

write(ct, value)

write takes two arguments, ct and value. ct is the number of bits to write at the stream index, and value is some integer to write between 0 and (1 << ct) - 1 inclusive. It advances the stream index by ct bits.

read(ct)

read rakes one argument, ct. ct is the number of bits to read from the stream index. The return value is the integer read from the stream at the stream index to the stream index + ct. It advances the stream index by ct bits.

seek(ct)

seek takes one argument, ct. The stream index is advanced by ct bits.

index()

index takes no arguments and returns the stream index.

raw

raw is a reference to the mutable array that was passed into the bitstream constructor, available for convenience. It should not be modified directly while the bitstream is in use.