CODEWITHSUNDEEP
node.js
Dimitrios Desyllas
Dimitrios Desyllas

Reputation: 10032

Convert Hex string into binary data into a buffer

Sometimes from network transmissions/usdb devices you receive the data has a hexadimal string eg:

"12ADFF1345"

These type of string I want somehow to be converted into a binary equivalent into a buffer, in order to perform a some mathematical or binary operations on them.

Do you know how I can achieve that?

Upvotes: 3

Views: 1980

Answers (2)

corn3lius
corn3lius

Reputation: 4985

Use the builtin Buffer class :

let buf1 = Buffer.from('12ADFF1345', 'hex');

let value = buf1.readInt32LE(0);
let value2 = buf1.readInt16LE(2);
console.log(value,value2);


>> 335523090 5119
// '13ffad12' '13FF' (LE) 
>> 313392915 -237
// '12ADFF13' 'ff13' (BE)

https://nodejs.org/api/buffer.html#buffer_class_method_buffer_from_string_encoding

Upvotes: 5

Dimitrios Desyllas
Dimitrios Desyllas

Reputation: 10032

Yes I know how to do that, the algorithm is simple (assuming that you have no escape characters):

  1. Split the read string into a character.
  2. Group each character pair.
  3. Then generate the string 0x^first_character_pair^
  4. parseInt the string above with base 16

In other words consult the following code:

const hexStringToBinaryBuffer = (string) => {
  const subStrings = Array.from(string);
  let previous = null;
  const bytes = [];
  _.each(subStrings, (val) => {
    if (previous === null) { // Converting every 2 chars as binary data
      previous = val;
    } else {
      const value = parseInt(`0x${previous}${val}`, 16);
      bytes.push(value);
      previous = null;
    }
  });

  return Buffer.from(bytes);
};

This is usefull if you pass as string the result of a Buffer.toString('hex') or equivalent method via a network socket or a usb port and the other end received it.

Upvotes: 0

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