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11356 :: Help needed: binarylang issue

• soarowl (orginal) [2024-04-04T11:32:32+02:00] view original

  I have following's code:

  import binarylang
  import strformat
  
  struct(i7, endian = l, bitEndian = r):
    u1:
      flag = 0
    7:
      value
  
  block:
    var sbs = newStringBitStream()
    for v in -127 .. 127:
      sbs.seek(0)
      let data = I7(value: v.int8)
      echo data
      i7.put(sbs, data)
      sbs.seek(0)
      let data2 = i7.get(sbs)
      echo data2
      sbs.seek(0)
      let s = sbs.readAll()
      let c = s[0].uint8
      echo fmt"{c:08b}"
      # doAssert data.value == data2.value
  Run

  The last line don't work. I have PR in github, but no response in 3 months.

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• Noraxx (orginal) [2024-04-04T18:19:20+02:00] view original

  import streams import strformat import strutils #

  I7 structure

  type

  i7 = object

  flag: bool value: int8

  Implement custom serialization and deserialization for i7

  proc putValue(sstream: var StringStream, value: i7) =

  sstream.write(value.flag) sstream.write(value.value)

  proc getValue(sstream: var StringStream): i7 =

  sstream.read(result.flag) sstream.read(result.value)

  Main code

  block:

  var sstream = newStringStream()

  for v in -127 .. 127:

  sstream.setPosition(0) let data = i7(flag: false, value: v.int8) putValue(sstream, data) sstream.setPosition(0) let data2 = getValue(sstream) doAssert data == data2, fmt"values don't match: {data.value} != {data2.value}" echo fmt"value: {data.value}, binary: {sstream.data.toHex()}"

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• soarowl (orginal) [2024-04-05T01:57:58+02:00] view original

  Thanks your code. But I need a binary parser/writer which can read/write bit-oriented fields and have big endian or little endian. for ex: https://github.com/dloss/binary-parsing those projects. BinaryLang is powerful, just declare a struct, the parser and writer will be auto generated. But it have a bug I can't fix it, the author of the project have no response my PR in 3 months.

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• Clonk (orginal) [2024-04-05T10:32:50+02:00] view original

  You can always fork the repo, fix it in your fork while the maintainer respond.

  If you use atlas for external dependencies it is quite easy to resolve the dependencies using your own fork instead of the original repo.

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• soarowl (orginal) [2024-04-05T11:37:57+02:00] view original

  Thanks your advice.

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• PMunch (orginal) [2024-04-05T14:43:11+02:00] view original

  Had a look in binaryparse which is the precursor to binarylang. Seems like the bug is caused by the extraction of the lower field just using and and not extending the sign bit. You can manually extend the sign bit, but this should definitely be fixed upstream:

  import binarylang
  import strformat
  
  struct(i7, endian = l, bitEndian = r):
    u1:
      flag = 0
    7:
      value
  
  block:
    var sbs = newStringBitStream()
    for v in -64 .. 63:
      sbs.seek(0)
      let data = I7(value: v.int8)
      echo data
      i7.put(sbs, data)
      sbs.seek(0)
      var data2 = i7.get(sbs)
      data2.value = ((data2.value shl 1) shr 1)
      echo data2
      sbs.seek(0)
      let s = sbs.readAll()
      let c = s[0].uint8
      echo fmt"{c:08b}"
      doAssert data.value == data2.value
  Run

  P.S: Also fixed the range of values so we don't try to stuff an 8 bit value into a seven bit field.

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• soarowl (orginal) [2024-04-06T02:48:21+02:00] view original

  Thanks a lot! I choose -128..127 range to test how compiler and library process those conditions.

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• PMunch (orginal) [2024-04-06T10:35:03+02:00] view original

  I agree that 1 is a bug, but 2 is really just a design choice. Since Nim doesn't have a 7 bit datatype both binaryparse and binarylang has decided to use the smallest data type which can fit a field, in this case an 8 bit integer. They also both returns tuples which makes the macro generation slightly easier so it would be a major change to go to objects with getter/setter procedures to gain this small extra security. When I first wrote binaryparse it was only intended to parse binary data (hence the name) so this wasn't a concern at all.

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• soarowl (orginal) [2024-04-06T12:54:03+02:00] view original

  Thanks your respond, I turn to Elixir to write my parsers.

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