Buffer treats decimal numbers mod 100??  #317

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1. vweevers commented on Aug 2, 2022

   

   vweevers

   on Aug 2, 2022

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   That's a parseInt() behavior, unrelated to Buffer: parseInt(0x61, 16) === 0x97.
2. nanaknihal commented on Aug 2, 2022

   

   nanaknihal

   on Aug 2, 2022

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   That's a parseInt() behavior, unrelated to Buffer: parseInt(0x61, 16) === 0x97.

   That's approximately what parseInt does, which is fine. The problem seems to be from Buffer, not parseInt:

   Buffer.from("abcde").map(x=>parseInt(x,16)) returns

   <Buffer 97 98 99 00 01> instead of

   <Buffer 97 98 99 100 101> or

   some other array with 97, 98, 99, 100, 101.
3. vweevers commented on Aug 2, 2022

   

   vweevers

   on Aug 2, 2022

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   The maximum value of a byte is 255. Buffer is a Uint8Array (rather than a Uint8ClampedArray), so values get wrapped.

   $ node
   > new Uint8Array([255, 256, 257])
   Uint8Array(3) [ 255, 0, 1 ]
   > new Uint8ClampedArray([255, 256, 257])
   Uint8ClampedArray(3) [ 255, 255, 255 ]
   
4. nanaknihal commented on Aug 2, 2022

   

   nanaknihal

   on Aug 2, 2022

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   Yes. Although it oddly wraps at 100 instead of 256. I think Buffer is treating the result of parseInt as 0x100 instead of 100.

   I don't know the exact interface between Buffer and parseInt; perhaps this is difficult to fix and best remain a "feature" rather than a bug. It is unintuitive but perhaps it's just how Buffers work and there's no way around it.
5. vweevers commented on Aug 2, 2022

   

   vweevers

   on Aug 2, 2022

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   Yes. Although it oddly wraps at 100

   A hexadecimal 100. Perhaps that's where the confusion comes from: console.log(buffer) prints a hexadecimal representation of the bytes. Here's an easy way to demonstrate that:

   $ node
   > Buffer.from('abcde')
   <Buffer 61 62 63 64 65>
   > Buffer.from('abcde').toString('hex')
   '6162636465'
   

   There's no bug here.