arrayvec/src/char.rs at master · Simteract/arrayvec · GitHub

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// file at the top-level directory of this distribution and at

// http://rust-lang.org/COPYRIGHT.

// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or

// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license

// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your

// option. This file may not be copied, modified, or distributed

// except according to those terms.

// Original authors: alexchrichton, bluss

// UTF-8 ranges and tags for encoding characters

const TAG_CONT: u8 = 0b1000_0000;

const TAG_TWO_B: u8 = 0b1100_0000;

const TAG_THREE_B: u8 = 0b1110_0000;

const TAG_FOUR_B: u8 = 0b1111_0000;

const MAX_ONE_B: u32 = 0x80;

const MAX_TWO_B: u32 = 0x800;

const MAX_THREE_B: u32 = 0x10000;

/// Placeholder

pub struct EncodeUtf8Error;

/// Encode a char into buf using UTF-8.

///

/// On success, return the byte length of the encoding (1, 2, 3 or 4).<br>

/// On error, return `EncodeUtf8Error` if the buffer was too short for the char.

#[inline]

pub fn encode_utf8(ch: char, buf: &mut [u8]) -> Result<usize, EncodeUtf8Error>

{

let code = ch as u32;

if code < MAX_ONE_B && buf.len() >= 1 {

buf[0] = code as u8;

return Ok(1);

} else if code < MAX_TWO_B && buf.len() >= 2 {

buf[0] = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;

buf[1] = (code & 0x3F) as u8 | TAG_CONT;

return Ok(2);

} else if code < MAX_THREE_B && buf.len() >= 3 {

buf[0] = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;

buf[1] = (code >> 6 & 0x3F) as u8 | TAG_CONT;

buf[2] = (code & 0x3F) as u8 | TAG_CONT;

return Ok(3);

} else if buf.len() >= 4 {

buf[0] = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;

buf[1] = (code >> 12 & 0x3F) as u8 | TAG_CONT;

buf[2] = (code >> 6 & 0x3F) as u8 | TAG_CONT;

buf[3] = (code & 0x3F) as u8 | TAG_CONT;

return Ok(4);

};

Err(EncodeUtf8Error)

}

arrayvec/src/char.rs at master · Simteract/arrayvec · GitHub

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