Buffer.from for the hex string

[nlapshin]

• Version: v10.13.0
• Platform: Linux dcloud_dev 3.13.0-88-generic io.js (IO.js? iojs?) and node.js documentation fragmentation #135-Ubuntu SMP Wed Jun 8 21:10:42 UTC 2016 x86_64 GNU/Linux
• Subsystem:

I use the conversion to the hexadecimal number buffer as follows

   Buffer.from(number.toString(16), 'hex')

But, for number less that 16(15, 14 and so on) I get an empty buffer.

Example

   const buf = Buffer.from((5).toString(16), 'hex');
  
   console.log(buf); // <Buffer >

[seishun]

Works as expected. 'hex' encodes one byte as two hex characters - one character is not a valid hex string.

[addaleax]

@nlapshin To expand a bit on the answer here – the issue is that there’s no way to tell which byte(s) you mean by the hex string 5. It could be 0x05, or 0x50, or something else. Similarly, your example won’t work on numbers that lead to other odd hex string lengths – e.g. Buffer.from('abc', 'hex') will lose the c, because it doesn’t know what to do with it.

If you need a way to convert numbers into Buffers, maybe consider using the Buffer.writeInt* methods.

If you have any more questions about this, https://github.com/nodejs/help might be a good place.

[nlapshin]

@nlapshin To expand a bit on the answer here – the issue is that there’s no way to tell which byte(s) you mean by the hex string 5. It could be 0x05, or 0x50, or something else. Similarly, your example won’t work on numbers that lead to other odd hex string lengths – e.g. Buffer.from('abc', 'hex') will lose the c, because it doesn’t know what to do with it.

If you need a way to convert numbers into Buffers, maybe consider using the Buffer.writeInt* methods.

If you have any more questions about this, https://github.com/nodejs/help might be a good place.

Oh, thanks for the detailed response. I understood that hex string '5' or 'b' is one byte. And now, I understand, after your explantation, why 'Buffer.from' works that way.

Thanks a lot!

[hazae41]

Days since last bug caused by this: 0

[Trott]

@nodejs/buffer Is there any support for a breaking change that throws rather than discards data in this situation?

[Trott]

@nodejs/buffer Is there any support for a breaking change that throws rather than discards data in this situation?

And if not, how about a warning?

[jasnell]

I'd be happy with a throw but we'd have to take the current behavior through a deprecation cycle first