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jisotalo / ads-client

Unofficial Node.js ADS library for connecting to Beckhoff TwinCAT automation systems using ADS protocol.

Home Page:https://jisotalo.fi/ads-client/

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_parseDataType: Incorrect parsing of flags

mycroes opened this issue · comments

commented

In the following excerpt from _parseDataType:

  //20..23 Offset
  dataType.offset = data.readUInt32LE(pos)
  pos += 4

  //24..27 ADS data type (AdsDataType)
  dataType.adsDataType = data.readUInt32LE(pos)
  dataType.adsDataTypeStr = ADS.ADS_DATA_TYPES.toString(dataType.adsDataType)
  pos += 4

  //27..30 Flags (AdsDataTypeFlags)
  dataType.flags = data.readUInt16LE(pos)
  dataType.flagsStr = ADS.ADS_DATA_TYPE_FLAGS.toStringArray(dataType.flags)
  pos += 4

  //31..32 Name length
  dataType.nameLength = data.readUInt16LE(pos)
  pos += 2

  //33..34 Type length
  dataType.typeLength = data.readUInt16LE(pos)
  pos += 2

The offsets in the comments are off by one starting at Flags (should have been 28..31) and flags is parsed using readUInt16LE, while ADS_DATA_TYPE_FLAGS actually contains values > 16 bits. pos is incremented by 4, so it's mostly comments that are messed up.

Noticed this while expanding the AdsClient library, so big thank you for the detailed implementation.

commented

Hi @mycroes!

Thank you for reporting this, it indeed seems to be a bug! Also by looking at ADS_DATA_TYPE_FLAGS we can see that these values go over 16 bits.

I will merge your pull request, thanks.

Your library looks nice, keep up the good work!

commented

You're welcome! It's actually not my library, as in, I'm not the original author. However, I've recently acquired ownership of the GitHub repository and am in the process of expanding and refactoring the library to make it well-suited and performant for professional use.

I fixed at least one issue by using your code as reference and I'm making use of a lot of the other code to implement (or extend) things like retrieving symbols and datatypes. I still have to tackle updates to symbols though, but I guess your library provides enough information to handle that as well. So again, a big thanks for the detailed implementation, I'll put it to good use!

commented

Sounds good! Let me know if you have any issues by email, for example. It's always interesting to help.