copstr: COPy STRing module using const generic for capacity

[copstr::Str] wraps a fixed-size array of u8 and provides a string-like interface on top. The size is specified using a const generic argument.

The internal u8 array corresponds to UTF-8 encoded chars. All functions guarantee that the contents are valid UTF-8 and return an error if they are not. Truncation only happens at UTF-8 boundaries.

[copstr] is very useful when we want to add a string-like field to a struct that implements Copy but we don't want to give up this trait.

Example usage

```rust use copstr; use std::convert::TryFrom;

// Create an owned fixed-size string with size 6 on the stack: let mut string = copstr::Str::<6>::try_from("string")?;

// Use it as a regular string: println!("contents: {}", string);

// Replace the contents with another string that fits the size 6: string.replace("str")?;

// Append a letter: string.push('i')?;

// Instead of returning a potential error, we can instead use // truncating methods: string.replacetrunc("stringification"); asserteq!(string.as_str(), "string");

// copstr::Str also Deref, so all str methods are // available: let split = format!("{:?}", string.splitat(3)); asserteq!(split, r#"("str", "ing")"#);

// We can add a copstr to a struct without having to give up the // Copy trait:

[derive(Clone, Copy)]

pub struct Mystruct { // ... comment: copstr::Str<10>, } ```