Unicode Scalar value转utf-8编码

2023-03-30 21:08 2023-03-30 21:08 作者: xmh0511

````rust
fn unicode_to_utf8(code: u32) -> Vec<u8> {
    match code {
        0..=0x7f => [code as u8].into(),
        0x80..=0x7FF => {
            // 2 byes
            let unit_low = ((0b00111111 & code) | 0b10000000) as u8;
            let code = code >> 6;
            let unit_high = ((0b00111111 & code) | 0b11000000) as u8;
            [unit_high, unit_low].into()
        }
        0x800..=0xFFFF => {
            // 3 bytes
            let mut result = Vec::new();
            let mut code = code;
            for _ in 0..2 {
                let unit_low = ((0b00111111 & code) | 0b10000000) as u8;
                result.push(unit_low);
                code = code >> 6;
            }
            let unit_high = ((0b00111111 & code) | 0b11100000) as u8;
            result.push(unit_high);
            result.reverse();
            result
        }
        0x10000..=0x1FFFFF => {
            // 4 bytes
            let mut result = Vec::new();
            let mut code = code;
            for _ in 0..3 {
                let unit_low = ((0b00111111 & code) | 0b10000000) as u8;
                result.push(unit_low);
                code = code >> 6;
            }
            let unit_high = ((0b00111111 & code) | 0b11110000) as u8;
            result.push(unit_high);
            result.reverse();
            result
        }
        0x200000..=0x3FFFFFF => {
            // 5 bytes
            let mut result = Vec::new();
            let mut code = code;
            for _ in 0..4 {
                let unit_low = ((0b00111111 & code) | 0b10000000) as u8;
                result.push(unit_low);
                code = code >> 6;
            }
            let unit_high = ((0b00111111 & code) | 0b11111000) as u8;
            result.push(unit_high);
            result.reverse();
            result
        }
        0x4000000..=0x7FFFFFFF => {
            // 6 bytes
            let mut result = Vec::new();
            let mut code = code;
            for _ in 0..5 {
                let unit_low = ((0b00111111 & code) | 0b10000000) as u8;
                result.push(unit_low);
                code = code >> 6;
            }
            let unit_high = ((0b00111111 & code) | 0b11111100) as u8;
            result.push(unit_high);
            result.reverse();
            result
        }
        _ => {
            panic!("cannot be represented in unicode scalar values");
        }
    }
}
fn main() {
    // let bytes = [0xce_u8,0xb3_u8];
    // let r = std::str::from_utf8(&bytes).unwrap();
    // println!("{r}");
    // let v:Vec<char>  = r.chars().collect();
    // let r = char::from_str(r).unwrap();
    // println!("{r}");

let r = unicode_to_utf8(0x1300);
    println!("{r:X?}");
}

````