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93 lines
3.2 KiB
Rust
93 lines
3.2 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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///
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/// Safety: `ptr` must be writable for `len` bytes.
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#[inline]
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pub unsafe fn encode_utf8(ch: char, ptr: *mut u8, len: usize) -> 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 && len >= 1 {
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ptr.add(0).write(code as u8);
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return Ok(1);
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} else if code < MAX_TWO_B && len >= 2 {
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ptr.add(0).write((code >> 6 & 0x1F) as u8 | TAG_TWO_B);
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ptr.add(1).write((code & 0x3F) as u8 | TAG_CONT);
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return Ok(2);
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} else if code < MAX_THREE_B && len >= 3 {
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ptr.add(0).write((code >> 12 & 0x0F) as u8 | TAG_THREE_B);
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ptr.add(1).write((code >> 6 & 0x3F) as u8 | TAG_CONT);
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ptr.add(2).write((code & 0x3F) as u8 | TAG_CONT);
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return Ok(3);
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} else if len >= 4 {
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ptr.add(0).write((code >> 18 & 0x07) as u8 | TAG_FOUR_B);
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ptr.add(1).write((code >> 12 & 0x3F) as u8 | TAG_CONT);
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ptr.add(2).write((code >> 6 & 0x3F) as u8 | TAG_CONT);
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ptr.add(3).write((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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#[test]
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#[cfg_attr(miri, ignore)] // Miri is too slow
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fn test_encode_utf8() {
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// Test that all codepoints are encoded correctly
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let mut data = [0u8; 16];
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for codepoint in 0..=(std::char::MAX as u32) {
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if let Some(ch) = std::char::from_u32(codepoint) {
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for elt in &mut data { *elt = 0; }
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let ptr = data.as_mut_ptr();
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let len = data.len();
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unsafe {
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let res = encode_utf8(ch, ptr, len).ok().unwrap();
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assert_eq!(res, ch.len_utf8());
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}
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let string = std::str::from_utf8(&data).unwrap();
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assert_eq!(string.chars().next(), Some(ch));
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}
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}
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}
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#[test]
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fn test_encode_utf8_oob() {
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// test that we report oob if the buffer is too short
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let mut data = [0u8; 16];
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let chars = ['a', 'α', '<27>', '𐍈'];
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for (len, &ch) in (1..=4).zip(&chars) {
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assert_eq!(len, ch.len_utf8(), "Len of ch={}", ch);
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let ptr = data.as_mut_ptr();
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unsafe {
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assert!(matches::matches!(encode_utf8(ch, ptr, len - 1), Err(_)));
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assert!(matches::matches!(encode_utf8(ch, ptr, len), Ok(_)));
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}
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}
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}
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