nonmaxunsigned-1.1.0 has been yanked.

NonMax-Unsigned

This crate provides an implementation for non-max integer types with null-pointer-optimization.

This crate is usable in a no-std environment.

Example

use nonmaxunsigned::NonMaxU8;

fn main() {
    let a = NonMaxU8::new(5).unwrap();
    let b = NonMaxU8::new(12).unwrap();

    assert_eq!(NonMaxU8::new(17).unwrap(), a + b);
    assert_eq!(None, NonMaxU8::new(u8::MAX));
}

Features

endian-conversion

This feature provides access to little and big endian versions of the non-max integer types as well as conversions between them. The native version for the non-max integers is just a type alias for the correct endianness.

non_max.get() will always return the native endian integer.

use nonmaxunsigned::{NonMaxU32Le, NonMaxU32Be, NonMaxU32};

fn main() {
# #[cfg(feature = "endian-conversion")]
# {
    let native = NonMaxU32::new(37).unwrap();
    let little = native.to_le();
    let big = native.to_be();

    assert_eq!(little.get(), big.get());
    assert_eq!(native.get(), big.get());
    assert_eq!(native.get(), little.get());

    assert_eq!(little.to_native(), native);
    assert_eq!(little.to_be(), big);
# }
}

Similar Crates

There are a few similar crates already existing on crates.io:

Unlike those crates this implementation does not NonZero. Those crates store the value as value ^ max which is never 0 as long as value != max. However this means the binary/hex representation of the stored value is hard to parse.

This implementation instead relies on a large enum NonMaxU8Internal which has 254 variants. Such an enum also leads to null-pointer-optimization but does not require the xor trick to prevent 0 values. Instead it relies on core::mem::transmute_copy.

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)