format_escape_default/
lib.rs

1//! A library for printing (formatting) arbitrary byte arrays using [`std::ascii::escape_default`].
2//!
3//! [`std::ascii::escape_default`]: https://doc.rust-lang.org/std/ascii/fn.escape_default.html
4// #![no_std] // can't do this because ascii isn't in core
5use std::fmt;
6
7/// Wraps the byte array and implements display
8///
9/// See [`format_escape_default`] method.
10///
11/// [`format_escape_default`]: fn.format_escape_default.html
12#[derive(Debug, Eq, PartialEq, Hash)]
13pub struct EscapeDefaultFmt<'a> {
14    inner: &'a [u8],
15}
16
17impl<'a> fmt::Display for EscapeDefaultFmt<'a> {
18    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
19        use std::ascii;
20        use std::char;
21        for ch in self.inner {
22            for esc_ch in ascii::escape_default(*ch) {
23                // safe because escape_default guarantees a valid unicode character
24                write!(f, "{}", unsafe { char::from_u32_unchecked(esc_ch as u32) })?;
25            }
26        }
27        Ok(())
28    }
29}
30
31/// Takes a byte array and wraps it in a struct that knows how to format it using
32/// [`std::ascii::escape_default`].
33///
34/// # Examples
35///
36/// ```
37/// use format_escape_default::format_escape_default;
38///
39/// let unescaped = b"\t\nsometext\r\n";
40/// let escaped = "\\t\\nsometext\\r\\n";
41/// assert_eq!(escaped, format!("{}", format_escape_default(unescaped)));
42/// ```
43///
44/// [`std::ascii::escape_default`]: https://doc.rust-lang.org/std/ascii/fn.escape_default.html
45pub fn format_escape_default<'a>(i: &'a [u8]) -> EscapeDefaultFmt<'a> {
46    EscapeDefaultFmt { inner: i }
47}
48
49#[cfg(test)]
50mod tests {
51    use super::format_escape_default;
52    #[test]
53    fn smoke() {
54        assert_eq!(format!("{}", format_escape_default(b"\t\r\ntest\\")), "\\t\\r\\ntest\\\\");
55    }
56}
format_escape_default/lib.rs

format_escape_default/
lib.rs
