Strongly-typed enums for registry data

[ErichDonGubler]

Hey there! I have a design-related question which I hope may eventually result in a contribution to enhance this codebase. This issue can be closed when maintainers have a consensus on whether or not this would be useful. :)

Recently, I've been developing some code in Rust that can parse Registry.pol files, and found it immensely useful to have a enum that models the data actually associated with registry values. It would be something along the lines of this:

pub enum RegistryData {
RegNone,
RegSz(String),
RegExpandSz(String),
RegBinary(Vec),
RegDwordLittleEndian(u32),
RegDwordBigEndian(u32),
RegLink(String),
RegMultiSz(Vec),
RegResourceList,
RegFullResourceDescriptor,
RegResourceRequirementsList,
RegQword(u64),
}

The key benefit I see to this model is that it allows more specific and strong types for usage with the domain that this crate handles. This is especially useful for testing -- some of the code I might write to test a sample data file in my parser might like this, and I think it's pretty easy to follow:

let parsed_reg_pol_file = RegistryPolicyFile::from_buffer(File::open("Registry.pol")?)?;
assert_eq(parsed_reg_pol_file.configuration_settings. == vec![
	RegSz("Some value"),
    RegExpandSz("APPDATA"),
	RegDword(25u32),
    RegMultiSz(vec!["just", "some", "words"]),
    // etc.
]);

This enum is not intended to replace the unparsed types like the RegValue struct or the RegType enum -- but it would be convenient to users who don't need or intend to use the intermediate types. I already have conversions defined to this enum from sequences of bytes, which might be interesting to compare with the implementation that's in this project.

There are other details I would love to discuss, too -- but first, I want to know if this is even something interesting for the winreg crate's authors! I certainly thing it would be for users.

[gentoo90]

Yes, I think this can be a part of winreg. When I started writing it I was thinking of a similar enum but ended up with RegValue struct just because it was easier to implement and I didn't need to actually use raw values anywhere outside of the crate.