Fix ReadUBits(32) masking out all bits. Thanks to @in0finite

[saul]

Fixes #37

[github-actions]

BenchmarkDotNet v0.13.9+228a464e8be6c580ad9408e98f18813f6407fb5a, Ubuntu 22.04.4 LTS (Jammy Jellyfish)
AMD EPYC 7763, 1 CPU, 4 logical and 2 physical cores
.NET SDK 8.0.203
  [Host]     : .NET 8.0.3 (8.0.324.11423), X64 RyuJIT AVX2
  Job-IGJYAE : .NET 8.0.3 (8.0.324.11423), X64 RyuJIT AVX2
  Job-FVCKUP : .NET 8.0.3 (8.0.324.11423), X64 RyuJIT AVX2

InvocationCount=1  MaxIterationCount=16  UnrollFactor=1  
WarmupCount=1  

Method	Job	Arguments	Mean	Error	StdDev	Ratio	Gen0	Gen1	Allocated	Alloc Ratio
ParseDemo	Job-IGJYAE	/p:Baseline=true	2.263 s	0.0115 s	0.0096 s	1.00	5000.0000	2000.0000	489.9 MB	1.00
ParseDemo	Job-FVCKUP	Default	2.207 s	0.0241 s	0.0226 s	0.97	5000.0000	2000.0000	489.9 MB	1.00

[in0finite]

Can you please add a safeguard here, so it's easier to catch similar bugs :

#if DEBUG
if (numBits > 32 || numBits < 0)
    throw ...;
#endif

[saul]

This will throw as the code is already written

[in0finite]

Maybe I am missing something, but if the code goes into else branch and if numBits is 50 and _bitsAvail is 32, it will not throw, but instead decrease numBits to 18.

Anyways, it's not intuitive as it is, so adding Debug.Assert() would not hurt.

[in0finite]

Could you also add a safeguard after reading all entities from BitBuffer here, to make sure everything is read from it:

if (entityBitBuffer.RemainingBytes >= 4)
    throw "not all data read";