| // Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT |
| // 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) |
| } |
| |