csv_async/
debug.rs

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1/// A type that provides a human readable debug impl for arbitrary bytes.
2///
3/// This generally works best when the bytes are presumed to be mostly UTF-8,
4/// but will work for anything.
5///
6/// N.B. This is copied nearly verbatim from regex-automata. Sigh.
7pub(crate) struct Bytes<'a>(pub(crate) &'a [u8]);
8
9impl<'a> core::fmt::Debug for Bytes<'a> {
10    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
11        write!(f, "\"")?;
12        // This is a sad re-implementation of a similar impl found in bstr.
13        let mut bytes = self.0;
14        while let Some(result) = utf8_decode(bytes) {
15            let ch = match result {
16                Ok(ch) => ch,
17                Err(byte) => {
18                    write!(f, r"\x{:02x}", byte)?;
19                    bytes = &bytes[1..];
20                    continue;
21                }
22            };
23            bytes = &bytes[ch.len_utf8()..];
24            match ch {
25                '\0' => write!(f, "\\0")?,
26                // ASCII control characters except \0, \n, \r, \t
27                '\x01'..='\x08'
28                | '\x0b'
29                | '\x0c'
30                | '\x0e'..='\x19'
31                | '\x7f' => {
32                    write!(f, "\\x{:02x}", u32::from(ch))?;
33                }
34                _ => {
35                    write!(f, "{}", ch.escape_debug())?;
36                }
37            }
38        }
39        write!(f, "\"")?;
40        Ok(())
41    }
42}
43
44/// Decodes the next UTF-8 encoded codepoint from the given byte slice.
45///
46/// If no valid encoding of a codepoint exists at the beginning of the given
47/// byte slice, then the first byte is returned instead.
48///
49/// This returns `None` if and only if `bytes` is empty.
50pub(crate) fn utf8_decode(bytes: &[u8]) -> Option<Result<char, u8>> {
51    fn len(byte: u8) -> Option<usize> {
52        if byte <= 0x7F {
53            Some(1)
54        } else if byte & 0b1100_0000 == 0b1000_0000 {
55            None
56        } else if byte <= 0b1101_1111 {
57            Some(2)
58        } else if byte <= 0b1110_1111 {
59            Some(3)
60        } else if byte <= 0b1111_0111 {
61            Some(4)
62        } else {
63            None
64        }
65    }
66
67    if bytes.is_empty() {
68        return None;
69    }
70    let len = match len(bytes[0]) {
71        None => return Some(Err(bytes[0])),
72        Some(len) if len > bytes.len() => return Some(Err(bytes[0])),
73        Some(1) => return Some(Ok(char::from(bytes[0]))),
74        Some(len) => len,
75    };
76    match core::str::from_utf8(&bytes[..len]) {
77        Ok(s) => Some(Ok(s.chars().next().unwrap())),
78        Err(_) => Some(Err(bytes[0])),
79    }
80}
csv_async/debug.rs

csv_async/
debug.rs
