Guide to separating the bytes of a number and placing them into an Uint8Array

Question

Guide to separating the bytes of a number and placing them into an Uint8Array

I am looking to convert a JavaScript number into the smallest possible uint8array representation.

For example :

65 535 = Uint8Array<[255,255]> (0b1111111111111111 = [0b11111111, 0b11111111])
12 356 = Uint8Array<[48,68]> (0b0011000001000100 = [0b00110000, 0b01000100])
1 142 =  Uint8Array<[4,118]> (0b0011000001000100 = [0b00000100, 0b01110110])
400 = Uint8Array<[1,144]> (0b0000000110010000 = [0b00000001, 0b10010000])
256 = Uint8Array<[1,0]> (0b0000000100000000 = [0b00000001, 0b00000000])
64 =  Uint8Array<[64]> (0b0000000001000000 = [0b01000000])
-1 = Uint8Array<[]> I do not handle negative numbers

I have been attempting to edit bytes individually as shown below:

const buffer : Uint8Array = new Uint8Array([0,0])
buffer[bytePos] &= ~(1<<bitToEdit); //to set at 0
buffer[bytePos] |= (1 <<bitToEdit) //to set at 1

The byte editing operation works, but I am unsure how to extract bytes from the number and populate them into this array.

javascript typescript binary

Answer 1

Answer №1

To achieve this functionality, you can utilize the BigInt feature along with the modulus operator (%) and the Uint8Array.from method.

In cases involving negative numbers or when dealing with a value of 0, the code provided will result in an empty Uint8Array containing zero elements. The output of this code is in Big Endian format, similar to the example given, achieved by reversing the byte array.

function convertToByteArray(number) {
  let bigIntNumber = BigInt(number);
  let byteArrayResult = [];
  while (bigIntNumber > 0n) {
    byteArrayResult.push(Number(bigIntNumber % 0x100n));
    bigIntNumber /= 0x100n;
  }
  return Uint8Array.from(byteArrayResult.reverse());
}

console.log(convertToByteArray(
  0x01_00_00_00_00_00_00_00_03n
)) // Output: Uint8Array(9) [ 1, 0, 0, 0, 0, 0, 0, 0, 3 ]

Answer 2

To achieve this functionality, you can utilize the BigInt feature along with the modulus operator (%) and the Uint8Array.from method.

In cases involving negative numbers or when dealing with a value of 0, the code provided will result in an empty Uint8Array containing zero elements. The output of this code is in Big Endian format, similar to the example given, achieved by reversing the byte array.

function convertToByteArray(number) {
  let bigIntNumber = BigInt(number);
  let byteArrayResult = [];
  while (bigIntNumber > 0n) {
    byteArrayResult.push(Number(bigIntNumber % 0x100n));
    bigIntNumber /= 0x100n;
  }
  return Uint8Array.from(byteArrayResult.reverse());
}

console.log(convertToByteArray(
  0x01_00_00_00_00_00_00_00_03n
)) // Output: Uint8Array(9) [ 1, 0, 0, 0, 0, 0, 0, 0, 3 ]

Guide to separating the bytes of a number and placing them into an Uint8Array

Answer №1

Similar questions

Utilizing Next.js named imports without server-side rendering

Sharing information between different components in React can be done using props, context, or a

An issue arises when attempting to utilize URL parameters within a loader

There was an error parsing the data from the specified URL (http://localhost:8000/src/client/assets/data.json

What is the best way to restrict the size of a table that is filled with data from a database?

Generating a clickable link for a variable within javascript

Managing JSON Forms using jQuery on Google's App Engine

How can you define the types of function arguments when destructuring arguments in TypeScript?

Converting CSS code into JavaScript

Is it possible to incorporate an additional value into the jQuery widget 'Autocomplete' by using a second variable?

Alias route for `src` in Ionic 3

Obtaining the value of an ion-toggle in Ionic2 using the ionChange

How can one authenticate an express session when sending a POST request?

Testing an asynchronous function in JavaScript can lead to the error message: "Have you neglected to utilize await?"

Are multiple click events needed for identical buttons?

Incorporating arguments within the context of a "for each" loop

Trigger event once item is selected from the jQuery combobox dropdown

Error: Unrecognized action type in Vuex

The best way to consistently execute setTimeout in order, regardless of the timing, is by utilizing a Promise

Loop through an array of arrays in JavaScript. If a match is found, add it to an existing inner array. If not, create a new