konst_kernel/chr/
char_formatting.rspub const fn encode_utf8(char: char) -> Utf8Encoded {
let u32 = char as u32;
match u32 {
0..=127 => Utf8Encoded {
encoded: [u32 as u8, 0, 0, 0],
len: 1,
},
0x80..=0x7FF => {
let b0 = 0b1100_0000 | (u32 >> 6) as u8;
let b1 = 0b1000_0000 | (u32 & 0b0011_1111) as u8;
Utf8Encoded {
encoded: [b0, b1, 0, 0],
len: 2,
}
}
0x800..=0xFFFF => {
let b0 = 0b1110_0000 | (u32 >> 12) as u8;
let b1 = 0b1000_0000 | ((u32 >> 6) & 0b0011_1111) as u8;
let b2 = 0b1000_0000 | (u32 & 0b0011_1111) as u8;
Utf8Encoded {
encoded: [b0, b1, b2, 0],
len: 3,
}
}
0x10000..=u32::MAX => {
let b0 = 0b1111_0000 | (u32 >> 18) as u8;
let b1 = 0b1000_0000 | ((u32 >> 12) & 0b0011_1111) as u8;
let b2 = 0b1000_0000 | ((u32 >> 6) & 0b0011_1111) as u8;
let b3 = 0b1000_0000 | (u32 & 0b0011_1111) as u8;
Utf8Encoded {
encoded: [b0, b1, b2, b3],
len: 4,
}
}
}
}
#[derive(Copy, Clone)]
pub struct Utf8Encoded {
encoded: [u8; 4],
len: u8,
}
impl Utf8Encoded {
pub const fn as_str(&self) -> &str {
unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }
}
pub const fn as_bytes(&self) -> &[u8] {
crate::slice::slice_up_to(&self.encoded, self.len as usize)
}
}
#[cfg(all(test, not(miri)))]
mod tests {
use super::{encode_utf8, Utf8Encoded};
fn as_bytes(fmt: &Utf8Encoded) -> &[u8] {
&fmt.encoded[..fmt.len as usize]
}
#[test]
fn char_to_utf8_encoding_test() {
for c in '\0'..=core::char::MAX {
let mut utf8_std = [0u8; 4];
let utf8_std = c.encode_utf8(&mut utf8_std);
let utf8_konst = encode_utf8(c);
assert_eq!(utf8_std.as_bytes(), as_bytes(&utf8_konst));
assert_eq!(utf8_std.as_bytes(), utf8_konst.as_bytes());
{
assert_eq!(
core::str::from_utf8(utf8_std.as_bytes()).unwrap(),
utf8_konst.as_str(),
);
}
}
}
}