Function bstr::B

source ·
pub fn B<'a, B: ?Sized + AsRef<[u8]>>(bytes: &'a B) -> &'a [u8] 
Expand description

A short-hand constructor for building a &[u8].

This idiosyncratic constructor is useful for concisely building byte string slices. Its primary utility is in conveniently writing byte string literals in a uniform way. For example, consider this code that does not compile:

let strs = vec![b"a", b"xy"];

The above code doesn’t compile because the type of the byte string literal b"a" is &'static [u8; 1], and the type of b"xy" is &'static [u8; 2]. Since their types aren’t the same, they can’t be stored in the same Vec. (This is dissimilar from normal Unicode string slices, where both "a" and "xy" have the same type of &'static str.)

One way of getting the above code to compile is to convert byte strings to slices. You might try this:

let strs = vec![&b"a", &b"xy"];

But this just creates values with type & &'static [u8; 1] and & &'static [u8; 2]. Instead, you need to force the issue like so:

let strs = vec![&b"a"[..], &b"xy"[..]];
// or
let strs = vec![b"a".as_ref(), b"xy".as_ref()];

But neither of these are particularly convenient to type, especially when it’s something as common as a string literal. Thus, this constructor permits writing the following instead:

use bstr::B;

let strs = vec![B("a"), B(b"xy")];

Notice that this also lets you mix and match both string literals and byte string literals. This can be quite convenient!