serde/de/
utf8.rs

1use lib::*;
2
3const TAG_CONT: u8 = 0b1000_0000;
4const TAG_TWO_B: u8 = 0b1100_0000;
5const TAG_THREE_B: u8 = 0b1110_0000;
6const TAG_FOUR_B: u8 = 0b1111_0000;
7const MAX_ONE_B: u32 = 0x80;
8const MAX_TWO_B: u32 = 0x800;
9const MAX_THREE_B: u32 = 0x10000;
10
11#[inline]
12pub fn encode(c: char) -> Encode {
13    let code = c as u32;
14    let mut buf = [0; 4];
15    let pos = if code < MAX_ONE_B {
16        buf[3] = code as u8;
17        3
18    } else if code < MAX_TWO_B {
19        buf[2] = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
20        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
21        2
22    } else if code < MAX_THREE_B {
23        buf[1] = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
24        buf[2] = (code >> 6 & 0x3F) as u8 | TAG_CONT;
25        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
26        1
27    } else {
28        buf[0] = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
29        buf[1] = (code >> 12 & 0x3F) as u8 | TAG_CONT;
30        buf[2] = (code >> 6 & 0x3F) as u8 | TAG_CONT;
31        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
32        0
33    };
34    Encode { buf: buf, pos: pos }
35}
36
37pub struct Encode {
38    buf: [u8; 4],
39    pos: usize,
40}
41
42impl Encode {
43    pub fn as_str(&self) -> &str {
44        str::from_utf8(&self.buf[self.pos..]).unwrap()
45    }
46}