rustls/
bs_debug.rs

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1use std::fmt;
2
3/// Alternative implementation of `fmt::Debug` for byte slice.
4///
5/// Standard `Debug` implementation for `[u8]` is comma separated
6/// list of numbers. Since large amount of byte strings are in fact
7/// ASCII strings or contain a lot of ASCII strings (e. g. HTTP),
8/// it is convenient to print strings as ASCII when possible.
9///
10/// This struct wraps `&[u8]` just to override `fmt::Debug`.
11///
12/// `BsDebug` is not a part of public API of bytes crate.
13pub(crate) struct BsDebug<'a>(pub(crate) &'a [u8]);
14
15impl<'a> fmt::Debug for BsDebug<'a> {
16    fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
17        write!(fmt, "b\"")?;
18        for &c in self.0 {
19            // https://doc.rust-lang.org/reference.html#byte-escapes
20            if c == b'\n' {
21                write!(fmt, "\\n")?;
22            } else if c == b'\r' {
23                write!(fmt, "\\r")?;
24            } else if c == b'\t' {
25                write!(fmt, "\\t")?;
26            } else if c == b'\\' || c == b'"' {
27                write!(fmt, "\\{}", c as char)?;
28            } else if c == b'\0' {
29                write!(fmt, "\\0")?;
30                // ASCII printable
31            } else if (0x20..0x7f).contains(&c) {
32                write!(fmt, "{}", c as char)?;
33            } else {
34                write!(fmt, "\\x{:02x}", c)?;
35            }
36        }
37        write!(fmt, "\"")?;
38        Ok(())
39    }
40}
41
42#[cfg(test)]
43mod test {
44    use super::BsDebug;
45
46    #[test]
47    fn debug() {
48        let vec: Vec<_> = (0..0x100).map(|b| b as u8).collect();
49
50        let expected = "b\"\
51            \\0\\x01\\x02\\x03\\x04\\x05\\x06\\x07\
52            \\x08\\t\\n\\x0b\\x0c\\r\\x0e\\x0f\
53            \\x10\\x11\\x12\\x13\\x14\\x15\\x16\\x17\
54            \\x18\\x19\\x1a\\x1b\\x1c\\x1d\\x1e\\x1f\
55            \x20!\\\"#$%&'()*+,-./0123456789:;<=>?\
56            @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\\\]^_\
57            `abcdefghijklmnopqrstuvwxyz{|}~\\x7f\
58            \\x80\\x81\\x82\\x83\\x84\\x85\\x86\\x87\
59            \\x88\\x89\\x8a\\x8b\\x8c\\x8d\\x8e\\x8f\
60            \\x90\\x91\\x92\\x93\\x94\\x95\\x96\\x97\
61            \\x98\\x99\\x9a\\x9b\\x9c\\x9d\\x9e\\x9f\
62            \\xa0\\xa1\\xa2\\xa3\\xa4\\xa5\\xa6\\xa7\
63            \\xa8\\xa9\\xaa\\xab\\xac\\xad\\xae\\xaf\
64            \\xb0\\xb1\\xb2\\xb3\\xb4\\xb5\\xb6\\xb7\
65            \\xb8\\xb9\\xba\\xbb\\xbc\\xbd\\xbe\\xbf\
66            \\xc0\\xc1\\xc2\\xc3\\xc4\\xc5\\xc6\\xc7\
67            \\xc8\\xc9\\xca\\xcb\\xcc\\xcd\\xce\\xcf\
68            \\xd0\\xd1\\xd2\\xd3\\xd4\\xd5\\xd6\\xd7\
69            \\xd8\\xd9\\xda\\xdb\\xdc\\xdd\\xde\\xdf\
70            \\xe0\\xe1\\xe2\\xe3\\xe4\\xe5\\xe6\\xe7\
71            \\xe8\\xe9\\xea\\xeb\\xec\\xed\\xee\\xef\
72            \\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\xf7\
73            \\xf8\\xf9\\xfa\\xfb\\xfc\\xfd\\xfe\\xff\"";
74
75        assert_eq!(expected, format!("{:?}", BsDebug(&vec)));
76    }
77}
rustls/bs_debug.rs

rustls/
bs_debug.rs
