0b3c0725a2
Research-grade code, treat with care. Change-Id: I99804df93e64101ef24928238ef0a8a02b59c2aa Reviewed-on: https://cl.tvl.fyi/c/depot/+/7686 Reviewed-by: edef <edef@edef.eu> Tested-by: BuildkiteCI
53 lines
1.6 KiB
Rust
53 lines
1.6 KiB
Rust
use packed_simd::{m8x32, u8x32};
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fn prefilter(haystack: u8x32) -> m8x32 {
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let alp = haystack.gt(u8x32::splat(b'a' - 1)) & haystack.lt(u8x32::splat(b'z' + 1));
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let num = haystack.gt(u8x32::splat(b'0' - 1)) & haystack.lt(u8x32::splat(b'9' + 1));
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alp | num
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}
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/// scan_clean returns `Err(&buffer[..n])` of known pointer-free data,
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/// or `Ok(buffer)` if the entire buffer is pointer-free.
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pub fn scan_clean(buffer: &[u8]) -> Result<&[u8], &[u8]> {
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let buffer = {
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let n = buffer.len() & !31;
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&buffer[..n]
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};
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let mut masks = buffer
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.chunks_exact(32)
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.map(|chunk| prefilter(u8x32::from_slice_unaligned(chunk)).bitmask())
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.enumerate()
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.map(|e| (e.0 * 32, e.1))
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.peekable();
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while let Some((offset, mask)) = masks.next() {
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let peek = masks.peek().map(|x| x.1).unwrap_or(!0 >> 1);
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let n = (!mask).leading_zeros() + (!peek).trailing_zeros();
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if n >= 32 {
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let offset = offset + mask.trailing_zeros() as usize;
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return Err(&buffer[..offset]);
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}
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}
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Ok(buffer)
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}
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#[cfg(test)]
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mod test {
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#[test]
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fn scan_tail() {
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let buffer = b"_xfbmj7sl2ikicym9x3yq7cms5qx1w39k";
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assert_eq!(crate::scan_clean(buffer), Err(&buffer[..1]));
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}
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#[test]
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fn scan_straddle() {
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let buffer = b"________________xfbmj7sl2ikicym9x3yq7cms5qx1w39k________________";
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assert_eq!(crate::scan_clean(buffer), Err(&buffer[..16]));
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}
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#[test]
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fn scan_clean() {
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let buffer = b"x_______________xfbmj7sl2ikicym9x3yq-cms5qx1w3-k________________";
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assert_eq!(crate::scan_clean(buffer), Ok(&buffer[..]));
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}
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}
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