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Use indexing instead of .get_unchecked() for LUT lookup

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Based on @paolobarbolini's tip that the unsafe block was unnecessary in
this case.

Not much left of `hexify()` after this, so seemed clearer to just inline
it.
This commit is contained in:
Martin Gammelsæter 2022-03-09 22:21:35 +01:00
parent 876142417c
commit 7f4f4fc34c
1 changed files with 2 additions and 14 deletions
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16
library/core/src/ascii.rs
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@ -99,24 +99,12 @@ pub fn escape_default(c: u8) -> EscapeDefault {
b'"' => ([b'\\', b'"', 0, 0], 2),
b'\x20'..=b'\x7e' => ([c, 0, 0, 0], 1),
_ => {
let (b1, b2) = hexify(c);
([b'\\', b'x', b1, b2], 4)
let hex_digits: &[u8; 16] = b"0123456789abcdef";
([b'\\', b'x', hex_digits[(c >> 4) as usize], hex_digits[(c & 0xf) as usize]], 4)
}
};
return EscapeDefault { range: 0..len, data };
#[inline]
fn hexify(b: u8) -> (u8, u8) {
let hex_digits: &[u8; 16] = b"0123456789abcdef";
// SAFETY: For all n: u8, n >> 4 < 16 and n & 0xf < 16
unsafe {
(
*hex_digits.get_unchecked((b >> 4) as usize),
*hex_digits.get_unchecked((b & 0xf) as usize),
)
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]