Append and consume bytes using only no-copy operations

About

A class that lets you do operations over a list of Uint8Arrays without copying them.

import { Uint8ArrayList } from 'uint8arraylist'

const list = new Uint8ArrayList()
list.append(Uint8Array.from([0, 1, 2]))
list.append(Uint8Array.from([3, 4, 5]))

list.subarray()
// -> Uint8Array([0, 1, 2, 3, 4, 5])

list.consume(3)
list.subarray()
// -> Uint8Array([3, 4, 5])

// you can also iterate over the list
for (const buf of list) {
  // ..do something with `buf`
}

list.subarray(0, 1)
// -> Uint8Array([0])

Converting Uint8ArrayLists to Uint8Arrays

There are two ways to turn a Uint8ArrayList into a Uint8Array - .slice and .subarray and one way to turn a Uint8ArrayList into a Uint8ArrayList with different contents - .sublist.

slice

Slice follows the same semantics as Uint8Array.slice in that it creates a new Uint8Array and copies bytes into it using an optional offset & length.

const list = new Uint8ArrayList()
list.append(Uint8Array.from([0, 1, 2]))
list.append(Uint8Array.from([3, 4, 5]))

list.slice(0, 1)
// -> Uint8Array([0]) - copy

list.slice(2, 5)
// -> Uint8Array([2, 3, 4]) - copy

subarray

Subarray attempts to follow the same semantics as Uint8Array.subarray with one important different - this is a no-copy operation, unless the requested bytes span two internal buffers in which case it is a copy operation.

const list = new Uint8ArrayList()
list.append(Uint8Array.from([0, 1, 2]))
list.append(Uint8Array.from([3, 4, 5]))

list.slice(0, 1)
// -> Uint8Array([0]) - no-copy

list.slice(2, 5)
// -> Uint8Array([2, 3, 4]) - copy

sublist

Sublist creates and returns a new Uint8ArrayList that shares the underlying buffers with the original so is always a no-copy operation.

const list = new Uint8ArrayList()
list.append(Uint8Array.from([0, 1, 2]))
list.append(Uint8Array.from([3, 4, 5]))

list.sublist(0, 1)
// -> Uint8ArrayList([0]) - no-copy

list.sublist(2, 5)
// -> Uint8ArrayList([2], [3, 4]) - no-copy

Inspiration

Borrows liberally from bl but only uses native JS types.

Install

$ npm i uint8arraylist

Browser <script> tag

Loading this module through a script tag will make it's exports available as Uint8arraylist in the global namespace.

<script src="https://unpkg.com/uint8arraylist/dist/index.min.js"></script>

API Docs

• https://achingbrain.github.io/uint8arraylist

License

Licensed under either of

• Apache 2.0, (LICENSE-APACHE / http://www.apache.org/licenses/LICENSE-2.0)
• MIT (LICENSE-MIT / http://opensource.org/licenses/MIT)

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.