jopohl/urh

Enhancement: Variable protocol field positions depending on LENGTH type fields

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#801 opened on Sep 18, 2020

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 (6 comments) (0 reactions) (0 assignees)Python (10,093 stars) (859 forks)batch import
discussionfeaturegood first issuehelp wanted

Description

A common protocol structure is to have a header containing a length field, followed by data of length bytes, followed by additional protocol fields such as a CRC. If the length field is variable, the position of subsequent URH-specified protocol fields defined by fixed position will not be in the correct location.

I do not know the best way to address this, but quick and easy way to support this would be through allowing field values to be used as variables in the Start and End location columns in the Edit Protocol Labels from Message Type UI Window. This is not a great solution because of the number of edge cases. A better option might be to create an Advanced Settings option where LENGTH type fields could specify which fields they apply to and the behavior of downstream fields. Alternatively, DATA type segments could have an Advanced menu where their length could be assigned to depend on the value of a LENGTH type field.

The CHECKSUM type advanced menu is incredibly useful and expanding this could be very powerful for other field types.

Contributor guide

Tech stack
python
Domain
backendtooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
needs investigation
Prerequisites
Understanding of URH protocol field systemPython
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
The issue requests variable field positions based on LENGTH fields. Multiple approaches are suggested: allowing variables in Start/End columns, an Advanced Settings for LENGTH fields, or extending DATA segment properties. The CHECKSUM advanced menu is cited as a model. To proceed, review the protocol field definition code (likely in src/urh/), the 'Edit Protocol Labels from Message Type' UI (likely in src/urh/ui/), and examine how CHECKSUM fields handle advanced settings. The issue is from 2020 and lacks a clear preferred solution; maintainer input is needed to decide on an approach.
Enhancement: Variable protocol field positions depending on LENGTH type fields · jopohl/urh#801 | Good First Issue