How to read buffer object byte by byte in JS

Question

Is it possible to read buffer line by line in JS?

I currently have a JS buffer object.

If i do console.log(buff) it will print something like this

<Buffer 0c 00 00 00 99 4e 98 3a f0 9d 09 3b 00 00 00 00 68 48 12 3c f0 77 1f 4a 6c 6c 0a 4a 0f 32 5f 31 31 39 38 36 31 5f 31 33 33 39 33 39 40 fc 11 00 09 00 ... 336 more bytes>

I am wondering if there is a way in Javascript to read this like a stream. I know in python for instance I can read the buffer like a stream byte byte.. something like (below)

buff.read(1) 
0c
buff.read(2)
00 00
buff.read(4)
00 99 4e 98

Why has someone tagged this question for close? Can you clarify? — Dinero
– Dinero, Commented Feb 13, 2020 at 18:14

Ashish Modi · Accepted Answer · 2020-02-13 19:10:27Z

2

I am not sure what your use case is but Buffer implements Uint8Array which effectively makes it iterable. So you can get the values like this

const buffer = Buffer.from("This is string");

for (const b of buffer) {
  console.log(b);
}

You could also consider creating a read function which can do similar thing for you

function read(size) {
  return buffer.slice(0, size);
}

You can use it like this

read(3);

You could also use buffer.keys(), buffer.values() and buffer.entries() to get keys, values and key value respectively using these functions.

Hope this helps.

answered Feb 13, 2020 at 19:10

Ashish Modi

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T.J. Crowder · Accepted Answer · 2020-05-20 16:07:27Z

1

The Buffer documentation shows that Buffer has a subarray method (and also a slice method), either of which can be used directly or to implement a utility method to do this.

Using it directly:

let n = 0;
buff.slice(n, n += 1);
// [0c]
buff.slice(n, n += 2);
// [00, 00]
buff.slice(n, n += 4);
// [00, 99, 4e, 98]

You could encapsulate that into a function if you don't want to keep track of n.

edited May 20, 2020 at 16:07

answered Feb 13, 2020 at 19:04

T.J. Crowder

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