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// Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// 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.
///
/// Safety: `ptr` must be writable for `len` bytes.
#[inline]
pub unsafe fn encode_utf8(ch: char, ptr: *mut u8, len: usize) -> Result<usize, EncodeUtf8Error>
{
let code = ch as u32;
if code < MAX_ONE_B && len >= 1 {
ptr.add(0).write(code as u8);
return Ok(1);
} else if code < MAX_TWO_B && len >= 2 {
ptr.add(0).write((code >> 6 & 0x1F) as u8 | TAG_TWO_B);
ptr.add(1).write((code & 0x3F) as u8 | TAG_CONT);
return Ok(2);
} else if code < MAX_THREE_B && len >= 3 {
ptr.add(0).write((code >> 12 & 0x0F) as u8 | TAG_THREE_B);
ptr.add(1).write((code >> 6 & 0x3F) as u8 | TAG_CONT);
ptr.add(2).write((code & 0x3F) as u8 | TAG_CONT);
return Ok(3);
} else if len >= 4 {
ptr.add(0).write((code >> 18 & 0x07) as u8 | TAG_FOUR_B);
ptr.add(1).write((code >> 12 & 0x3F) as u8 | TAG_CONT);
ptr.add(2).write((code >> 6 & 0x3F) as u8 | TAG_CONT);
ptr.add(3).write((code & 0x3F) as u8 | TAG_CONT);
return Ok(4);
};
Err(EncodeUtf8Error)
}
#[test]
#[cfg_attr(miri, ignore)] // Miri is too slow
fn test_encode_utf8() {
// Test that all codepoints are encoded correctly
let mut data = [0u8; 16];
for codepoint in 0..=(std::char::MAX as u32) {
if let Some(ch) = std::char::from_u32(codepoint) {
for elt in &mut data { *elt = 0; }
let ptr = data.as_mut_ptr();
let len = data.len();
unsafe {
let res = encode_utf8(ch, ptr, len).ok().unwrap();
assert_eq!(res, ch.len_utf8());
}
let string = std::str::from_utf8(&data).unwrap();
assert_eq!(string.chars().next(), Some(ch));
}
}
}
#[test]
fn test_encode_utf8_oob() {
// test that we report oob if the buffer is too short
let mut data = [0u8; 16];
let chars = ['a', 'α', '�', '𐍈'];
for (len, &ch) in (1..=4).zip(&chars) {
assert_eq!(len, ch.len_utf8(), "Len of ch={}", ch);
let ptr = data.as_mut_ptr();
unsafe {
assert!(matches::matches!(encode_utf8(ch, ptr, len - 1), Err(_)));
assert!(matches::matches!(encode_utf8(ch, ptr, len), Ok(_)));
}
}
}