Parsing binary protocols #31

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1. indutny commented on Nov 28, 2019

   

   indutny

   on Nov 28, 2019

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   Maybe...?
2. arthurschreiber commented on Dec 2, 2019

   

   arthurschreiber

   on Dec 2, 2019

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   So I played around with this a bit more.

   I added a new node type called Byte, that works like a mix between Invoke and Match - it matches any byte and then passes it on to a given code function.

   It works something like this:

   const p = new LLParse('example');
   
   p.property('i16', 'value');
   
   const uint16be = p.byte(p.code.store('value'));
   uint16be.skipTo(
     p.byte(p.code.mulAdd('value', { base: 2 ** 8 })).skipTo(uint16be)
   );
   
   const artifacts = p.build(uint16be);

   I've yet to figure the best way out to expose reading of values coming in in little endian order. 🤔

   Anyway, is this how you'd implement binary reading in llparse? Or do you have any other ideas how this could be exposed in a nicer / more consistent fashion?
3. arthurschreiber commented on Dec 2, 2019

   

   arthurschreiber

   on Dec 2, 2019

   Last edited by arthurschreiber

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   Maybe it would be better to just add two new nodes for reading signed/unsigned LE and BE encoded bytes into a field:

   const p = new LLParse('example');
   
   p.property('i8', 'type')
   p.property('i16', 'value');
   
   const type = p.uIntLE('type', 1);
   const valueLength = p.uIntLE('valueLength', 2);
   
   type.skipTo(valueLength.skipTo(p.consume('valueLength').skipTo(type)));

   This could automatically check that the field is large enough to read the required number of bytes into it.

   This would already cover most of my needs, and should be pretty straightforward to implement, I think. @indutny What do you think?
4. Vizonex commented on May 28, 2026

   

   Vizonex

   on May 28, 2026

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   Sorry if I am choosing to reopen a dead issue but I am making a PR that attempts the same thing but is a lot simpler and has active tools to help prevent errors from occurring nodejs/llparse-builder#197