bluss
456aeaf557
Copy the encode_utf8 function from odds. std encode_utf8 requires Rust 1.15 and has a different signature, this one seems to fit us better.
55 lines
1.9 KiB
Rust
55 lines
1.9 KiB
Rust
// Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//
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// Original authors: alexchrichton, bluss
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// UTF-8 ranges and tags for encoding characters
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const TAG_CONT: u8 = 0b1000_0000;
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const TAG_TWO_B: u8 = 0b1100_0000;
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const TAG_THREE_B: u8 = 0b1110_0000;
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const TAG_FOUR_B: u8 = 0b1111_0000;
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const MAX_ONE_B: u32 = 0x80;
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const MAX_TWO_B: u32 = 0x800;
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const MAX_THREE_B: u32 = 0x10000;
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/// Placeholder
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pub struct EncodeUtf8Error;
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/// Encode a char into buf using UTF-8.
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///
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/// On success, return the byte length of the encoding (1, 2, 3 or 4).<br>
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/// On error, return `EncodeUtf8Error` if the buffer was too short for the char.
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#[inline]
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pub fn encode_utf8(ch: char, buf: &mut [u8]) -> Result<usize, EncodeUtf8Error>
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{
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let code = ch as u32;
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if code < MAX_ONE_B && buf.len() >= 1 {
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buf[0] = code as u8;
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return Ok(1);
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} else if code < MAX_TWO_B && buf.len() >= 2 {
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buf[0] = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
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buf[1] = (code & 0x3F) as u8 | TAG_CONT;
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return Ok(2);
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} else if code < MAX_THREE_B && buf.len() >= 3 {
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buf[0] = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
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buf[1] = (code >> 6 & 0x3F) as u8 | TAG_CONT;
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buf[2] = (code & 0x3F) as u8 | TAG_CONT;
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return Ok(3);
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} else if buf.len() >= 4 {
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buf[0] = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
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buf[1] = (code >> 12 & 0x3F) as u8 | TAG_CONT;
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buf[2] = (code >> 6 & 0x3F) as u8 | TAG_CONT;
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buf[3] = (code & 0x3F) as u8 | TAG_CONT;
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return Ok(4);
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};
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Err(EncodeUtf8Error)
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}
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