[Question] Read 3 bytes with a uint and advance only those 3 bytes on the stream

[sn4k3]

I have some situations where the format have uint's with 3 bytes, currently is it possible to define an uint and deserialize/serialize in 3 byte order? Making stream only to advance that 3 bytes so the next field will decode/encode at position 3 rather than 4?

PS: Should be cool to enable github discussions to use it as a forum board for questions instead the need to use issues for that purpose

[sn4k3]

Still struggle with this one... [FieldBitLength(24)] uint FieldName {get; set;} does not return the correct value from 3 bytes as uint. Any suggestion?

[jefffhaynes]

Can you give me some more info? I just wrote a simple test that seems to work but I might be missing something.

[sn4k3]

Sure, here my definition:

What i get:

What i expect:

File is in BIG order and use a ton of uint24

[jefffhaynes]

Ahh it's big endian. Unfortunately there is a bug involving big endian and bit fields. I've spent hours trying to fix it but unfortunately it's incredibly complex. I need to at least add a check that will throw in these cases. Sorry about that, I'll try to get back to it soon!

[sn4k3]

Thanks for looking into it.
I've not look at source code, but one thing i always do when working with bytes and convertion is to avoid C# converter functions (BitConverter), and do my own with bitwise. Those utility methods can return different outputs depending on machine endiness, unless you cover it with if (BitConverter.IsLittleEndian) Array.Reverse(bytes); which is easy forgetable.

[jefffhaynes]

As much as I would like to blame something else, it is unfortunately all my own code! The issue has to do with assumptions I made when doing bit-packing early on. Unfortunately, fixing it will mean rewriting quite a bit of the underlying bit field assemblage, which gets complicated fast. If you're interested, most of the rabbit hole is contained in BoundedStream.

[bevanweiss]

@sn4k3 could you perhaps but together a couple of Test Cases for this in Github (within the FieldBitOffset / Endianess stuff probably makes sense).

I've had a bit of a dig through the BoundedStream stuff recently, so might be able to have a look at this problem also.