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/*!
Provides convenience routines for escaping raw bytes.
Since this crate tends to deal with `&[u8]` everywhere and the default
`Debug` implementation just shows decimal integers, it makes debugging those
representations quite difficult. This module provides types that show `&[u8]`
as if it were a string, with invalid UTF-8 escaped into its byte-by-byte hex
representation.
*/
use crate::util::utf8;
/// Provides a convenient `Debug` implementation for a `u8`.
///
/// The `Debug` impl treats the byte as an ASCII, and emits a human readable
/// representation of it. If the byte isn't ASCII, then it's emitted as a hex
/// escape sequence.
#[derive(Clone, Copy)]
pub struct DebugByte(pub u8);
impl core::fmt::Debug for DebugByte {
fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
// Special case ASCII space. It's too hard to read otherwise, so
// put quotes around it. I sometimes wonder whether just '\x20' would
// be better...
if self.0 == b' ' {
return write!(f, "' '");
}
// 10 bytes is enough to cover any output from ascii::escape_default.
let mut bytes = [0u8; 10];
let mut len = 0;
for (i, mut b) in core::ascii::escape_default(self.0).enumerate() {
// capitalize \xab to \xAB
if i >= 2 && b'a' <= b && b <= b'f' {
b -= 32;
}
bytes[len] = b;
len += 1;
}
write!(f, "{}", core::str::from_utf8(&bytes[..len]).unwrap())
}
}
/// Provides a convenient `Debug` implementation for `&[u8]`.
///
/// This generally works best when the bytes are presumed to be mostly UTF-8,
/// but will work for anything. For any bytes that aren't UTF-8, they are
/// emitted as hex escape sequences.
pub struct DebugHaystack<'a>(pub &'a [u8]);
impl<'a> core::fmt::Debug for DebugHaystack<'a> {
fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
write!(f, "\"")?;
// This is a sad re-implementation of a similar impl found in bstr.
let mut bytes = self.0;
while let Some(result) = utf8::decode(bytes) {
let ch = match result {
Ok(ch) => ch,
Err(byte) => {
write!(f, r"\x{:02x}", byte)?;
bytes = &bytes[1..];
continue;
}
};
bytes = &bytes[ch.len_utf8()..];
match ch {
'\0' => write!(f, "\\0")?,
// ASCII control characters except \0, \n, \r, \t
'\x01'..='\x08'
| '\x0b'
| '\x0c'
| '\x0e'..='\x19'
| '\x7f' => {
write!(f, "\\x{:02x}", u32::from(ch))?;
}
'\n' | '\r' | '\t' | _ => {
write!(f, "{}", ch.escape_debug())?;
}
}
}
write!(f, "\"")?;
Ok(())
}
}