1use core::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 fmt::Debug for BsDebug<'_> {
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 tests {
44 use std::format;
45 use std::prelude::v1::*;
46
47 use super::BsDebug;
48
49 #[test]
50 fn debug() {
51 let vec: Vec<_> = (0..0x100).map(|b| b as u8).collect();
52
53 let expected = "b\"\
54 \\0\\x01\\x02\\x03\\x04\\x05\\x06\\x07\
55 \\x08\\t\\n\\x0b\\x0c\\r\\x0e\\x0f\
56 \\x10\\x11\\x12\\x13\\x14\\x15\\x16\\x17\
57 \\x18\\x19\\x1a\\x1b\\x1c\\x1d\\x1e\\x1f\
58 \x20!\\\"#$%&'()*+,-./0123456789:;<=>?\
59 @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\\\]^_\
60 `abcdefghijklmnopqrstuvwxyz{|}~\\x7f\
61 \\x80\\x81\\x82\\x83\\x84\\x85\\x86\\x87\
62 \\x88\\x89\\x8a\\x8b\\x8c\\x8d\\x8e\\x8f\
63 \\x90\\x91\\x92\\x93\\x94\\x95\\x96\\x97\
64 \\x98\\x99\\x9a\\x9b\\x9c\\x9d\\x9e\\x9f\
65 \\xa0\\xa1\\xa2\\xa3\\xa4\\xa5\\xa6\\xa7\
66 \\xa8\\xa9\\xaa\\xab\\xac\\xad\\xae\\xaf\
67 \\xb0\\xb1\\xb2\\xb3\\xb4\\xb5\\xb6\\xb7\
68 \\xb8\\xb9\\xba\\xbb\\xbc\\xbd\\xbe\\xbf\
69 \\xc0\\xc1\\xc2\\xc3\\xc4\\xc5\\xc6\\xc7\
70 \\xc8\\xc9\\xca\\xcb\\xcc\\xcd\\xce\\xcf\
71 \\xd0\\xd1\\xd2\\xd3\\xd4\\xd5\\xd6\\xd7\
72 \\xd8\\xd9\\xda\\xdb\\xdc\\xdd\\xde\\xdf\
73 \\xe0\\xe1\\xe2\\xe3\\xe4\\xe5\\xe6\\xe7\
74 \\xe8\\xe9\\xea\\xeb\\xec\\xed\\xee\\xef\
75 \\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\xf7\
76 \\xf8\\xf9\\xfa\\xfb\\xfc\\xfd\\xfe\\xff\"";
77
78 assert_eq!(expected, format!("{:?}", BsDebug(&vec)));
79 }
80}
81