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I have a bit array that represents a data protocol, 1024 bytes. The range of the fields go from very small, to int32s in size. For example, ProtoID = bits 0-3, Source = bits 4-6, Value1 = bits 7-14, value2 = Bit2

Something like

BitArray.SetValue(int value, startIndex, maxBitstoSet) //Or maybe i can make it a generic insert byte[] and use BitConverter.GetBytes(value)? //The maxbits to set is to isolate just those bits, so they don't cross boundaries of another field in case the user enters a value that is more than it can old.

I am struggling on the way to implement this. Would i need to create a mask based on the value data type ( or based on the lenght of the byte[]) and just OR them to set those bits?

EDIT: Someone suggested a custom struct might work, something like this:

[StructLayout(LayoutKind.Explicit, Size = 56, Pack = 1)]
public struct NewStuff
{
    [MarshalAs(UnmanagedType.U1)]
    [FieldOffset(0)]
    public byte ProtoID = 0b011;

    [MarshalAs(UnmanagedType.U1)]
    [FieldOffset(3)]
    public byte value1;

    [MarshalAs(UnmanagedType.U1)]
    [FieldOffset(7)]
    public byte value2;

}

Value1 is can only be 3 bits only, so the max should be 0x07. But what if the user enters 0x08, that would cross bit boundaries and overwrite value2 LSB?

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  • Do you have a more specific example we can help you with and which you can use as a "template" on how to deal with this in general? Commented May 15, 2023 at 17:52
  • 1
    Can't you create a struct which matches the memory layout of that byte array. Something like; stackoverflow.com/questions/2871/… Commented May 15, 2023 at 17:55
  • @rene. That might work, I am not overly familiar with struct layout in c#, but looking at the example, it seems that it would work. The FieldOffset attribute is the BIT position, yes? It looks i should be able to assign each property directly. However for those values that only take < 8 bits, the smallest property data type would be a byte. Would that cross byte boundaries? IE. byte value1=0b011. It should only take 3 bits, 0x07 as it max value. But if the user enters 10, would it cross into the boundary of the next date type? Commented May 15, 2023 at 18:26
  • FieldOffset is byte so you would still need to fiddle with masks for some setters and getters on your struct. See also: learn.microsoft.com/en-us/dotnet/api/… Commented May 15, 2023 at 18:37
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