Why is NextUInt64 not a public method

[Xyncgas]

https://github.com/dotnet/runtime/blob/508fef51e841aa16ffed1aae32bf4793a2cea363/src/libraries/System.Private.CoreLib/src/System/Random.Xoshiro256StarStarImpl.cs

In the source code the ability to produce NextUInt64 is clearly there but not available for System.Random so I suggest in one way or another allow me to produce UInt64 with System.Random instead of having to use stack allocated bytes as span to do so

[huoyaoyuan]

Because there's no NextUInt32 either. Just cast the result of NextInt64.

[Xyncgas]

Oh yea I... I am sorry

[VesperGarment]

That doesn't work quite properly. NextInt64 only returns positive integers - 63 bits of random. If you actually want all 64 bits random I think you have to do a little dance getting 4 bytes and BitConverter-ing it._

[elgonzo]

@VesperGarment that's not quite accurate. The NextInt64(Int64, Int64) overload can return negative values if you set the value range accordingly. For example, NextInt64(long.MinValue, long.MaxValue) should give you a value from almost the entire 64-bit value range. Almost only because it won't ever return the long.MaxValue value.

[tannergooding]

Please feel free to open an API proposal request UInt32 and UInt64 APIs: https://github.com/dotnet/runtime/issues/new?assignees=&labels=api-suggestion&template=02_api_proposal.yml&title=%5BAPI+Proposal%5D%3A+

Our API Review Process is detailed here: https://github.com/dotnet/runtime/blob/main/docs/project/api-review-process.md

While casting the result of NextInt64 to UInt64 will indeed work for some scenarios, it also makes the code significantly harder to read, understand, and maintain.

Given that integers in .NET are two's complement, getting values above long.MaxValue is also "difficult", because long.MaxValue + 1 is long.MinValue and -1 is ulong.MaxValue; so providing this functionality would allow valid unsigned ranges to be more easily returned.

[tannergooding]

Notably, we also use such APIs or similar APIs internally for our own tests and other scenarios. So it is completely within reason that other developers would benefit as well.