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Mark \u parsing as cold

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This counterintuitively speeds up War and Peace 275 -> 290 MB/s (+5%) by
enabling inlining of encode_utf8 and extend_from_slice.
This commit is contained in:
Alisa Sireneva 2024-08-12 19:34:06 +03:00
parent cf771a0471
commit a38dbf3708
1 changed files with 86 additions and 76 deletions
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24
src/read.rs
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@ -882,7 +882,23 @@ fn parse_escape<'de, R: Read<'de>>(
b'n' => scratch.push(b'\n'), b'n' => scratch.push(b'\n'),
b'r' => scratch.push(b'\r'), b'r' => scratch.push(b'\r'),
b't' => scratch.push(b'\t'), b't' => scratch.push(b'\t'),
b'u' => { b'u' => return parse_unicode_escape(read, validate, scratch),
_ => {
return error(read, ErrorCode::InvalidEscape);
}
}
Ok(())
}
/// Parses a JSON \u escape and appends it into the scratch space. Assumes \u
/// has just been read.
#[cold]
fn parse_unicode_escape<'de, R: Read<'de>>(
read: &mut R,
validate: bool,
scratch: &mut Vec<u8>,
) -> Result<()> {
fn encode_surrogate(scratch: &mut Vec<u8>, n: u16) { fn encode_surrogate(scratch: &mut Vec<u8>, n: u16) {
scratch.extend_from_slice(&[ scratch.extend_from_slice(&[
(n >> 12 & 0b0000_1111) as u8 | 0b1110_0000, (n >> 12 & 0b0000_1111) as u8 | 0b1110_0000,
@ -957,12 +973,6 @@ fn parse_escape<'de, R: Read<'de>>(
}; };
scratch.extend_from_slice(c.encode_utf8(&mut [0_u8; 4]).as_bytes()); scratch.extend_from_slice(c.encode_utf8(&mut [0_u8; 4]).as_bytes());
}
_ => {
return error(read, ErrorCode::InvalidEscape);
}
}
Ok(()) Ok(())
} }