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1 | // Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT |
2 | // file at the top-level directory of this distribution and at | |
3 | // http://rust-lang.org/COPYRIGHT. | |
4 | // | |
5 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | |
6 | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | |
7 | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | |
8 | // option. This file may not be copied, modified, or distributed | |
9 | // except according to those terms. | |
10 | // | |
11 | // Original authors: alexchrichton, bluss | |
12 | ||
f035d41b XL |
13 | use std::ptr; |
14 | ||
2c00a5a8 XL |
15 | // UTF-8 ranges and tags for encoding characters |
16 | const TAG_CONT: u8 = 0b1000_0000; | |
17 | const TAG_TWO_B: u8 = 0b1100_0000; | |
18 | const TAG_THREE_B: u8 = 0b1110_0000; | |
19 | const TAG_FOUR_B: u8 = 0b1111_0000; | |
20 | const MAX_ONE_B: u32 = 0x80; | |
21 | const MAX_TWO_B: u32 = 0x800; | |
22 | const MAX_THREE_B: u32 = 0x10000; | |
23 | ||
24 | /// Placeholder | |
25 | pub struct EncodeUtf8Error; | |
26 | ||
f035d41b XL |
27 | #[inline] |
28 | unsafe fn write(ptr: *mut u8, index: usize, byte: u8) { | |
29 | ptr::write(ptr.add(index), byte) | |
30 | } | |
31 | ||
2c00a5a8 XL |
32 | /// Encode a char into buf using UTF-8. |
33 | /// | |
34 | /// On success, return the byte length of the encoding (1, 2, 3 or 4).<br> | |
35 | /// On error, return `EncodeUtf8Error` if the buffer was too short for the char. | |
f035d41b XL |
36 | /// |
37 | /// Safety: `ptr` must be writable for `len` bytes. | |
2c00a5a8 | 38 | #[inline] |
f035d41b | 39 | pub unsafe fn encode_utf8(ch: char, ptr: *mut u8, len: usize) -> Result<usize, EncodeUtf8Error> |
2c00a5a8 XL |
40 | { |
41 | let code = ch as u32; | |
f035d41b XL |
42 | if code < MAX_ONE_B && len >= 1 { |
43 | write(ptr, 0, code as u8); | |
2c00a5a8 | 44 | return Ok(1); |
f035d41b XL |
45 | } else if code < MAX_TWO_B && len >= 2 { |
46 | write(ptr, 0, (code >> 6 & 0x1F) as u8 | TAG_TWO_B); | |
47 | write(ptr, 1, (code & 0x3F) as u8 | TAG_CONT); | |
2c00a5a8 | 48 | return Ok(2); |
f035d41b XL |
49 | } else if code < MAX_THREE_B && len >= 3 { |
50 | write(ptr, 0, (code >> 12 & 0x0F) as u8 | TAG_THREE_B); | |
51 | write(ptr, 1, (code >> 6 & 0x3F) as u8 | TAG_CONT); | |
52 | write(ptr, 2, (code & 0x3F) as u8 | TAG_CONT); | |
2c00a5a8 | 53 | return Ok(3); |
f035d41b XL |
54 | } else if len >= 4 { |
55 | write(ptr, 0, (code >> 18 & 0x07) as u8 | TAG_FOUR_B); | |
56 | write(ptr, 1, (code >> 12 & 0x3F) as u8 | TAG_CONT); | |
57 | write(ptr, 2, (code >> 6 & 0x3F) as u8 | TAG_CONT); | |
58 | write(ptr, 3, (code & 0x3F) as u8 | TAG_CONT); | |
2c00a5a8 XL |
59 | return Ok(4); |
60 | }; | |
61 | Err(EncodeUtf8Error) | |
62 | } | |
63 | ||
f035d41b XL |
64 | |
65 | #[test] | |
5869c6ff | 66 | #[cfg_attr(miri, ignore)] // Miri is too slow |
f035d41b XL |
67 | fn test_encode_utf8() { |
68 | // Test that all codepoints are encoded correctly | |
69 | let mut data = [0u8; 16]; | |
70 | for codepoint in 0..=(std::char::MAX as u32) { | |
71 | if let Some(ch) = std::char::from_u32(codepoint) { | |
72 | for elt in &mut data { *elt = 0; } | |
73 | let ptr = data.as_mut_ptr(); | |
74 | let len = data.len(); | |
75 | unsafe { | |
76 | let res = encode_utf8(ch, ptr, len).ok().unwrap(); | |
77 | assert_eq!(res, ch.len_utf8()); | |
78 | } | |
79 | let string = std::str::from_utf8(&data).unwrap(); | |
80 | assert_eq!(string.chars().next(), Some(ch)); | |
81 | } | |
82 | } | |
83 | } | |
84 | ||
85 | #[test] | |
86 | fn test_encode_utf8_oob() { | |
87 | // test that we report oob if the buffer is too short | |
88 | let mut data = [0u8; 16]; | |
89 | let chars = ['a', 'α', '�', '𐍈']; | |
90 | for (len, &ch) in (1..=4).zip(&chars) { | |
91 | assert_eq!(len, ch.len_utf8(), "Len of ch={}", ch); | |
92 | let ptr = data.as_mut_ptr(); | |
93 | unsafe { | |
94 | assert!(matches::matches!(encode_utf8(ch, ptr, len - 1), Err(_))); | |
95 | assert!(matches::matches!(encode_utf8(ch, ptr, len), Ok(_))); | |
96 | } | |
97 | } | |
98 | } | |
99 |