Function with_str_bytes

pub fn with_str_bytes<R, F>(s: &mut str, f: F) -> R
where
    F: FnOnce(&mut [u8]) -> R,

Executes a function on the bytes of a string, asserting that it is valid UTF-8.

Panics

This will panic if the function causes the string to become invalid UTF-8. In this case, the bytes up to the point of the first invalid UTF-8 byte will remain the same, and the contents of the rest of the string is unspecified, although it will be valid UTF-8.

If the callback itself panics, the entire string’s contents is unspecified, but it will be valid UTF-8. Even if the byte slice was set to invalid UTF-8, there will not be a double panic.

Examples

Replace all spaces in a string with dashes in-place:

let mut data: Box<str> = Box::from("Lorem ipsum dolor sit amet");
with_str_bytes::with_str_bytes(&mut data, |bytes| {
    for byte in bytes {
        if *byte == b' ' {
            *byte = b'-';
        }
    }
});
assert_eq!(&*data, "Lorem-ipsum-dolor-sit-amet");