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authorValentin Popov <valentin@popov.link>2024-07-19 15:37:58 +0300
committerValentin Popov <valentin@popov.link>2024-07-19 15:37:58 +0300
commita990de90fe41456a23e58bd087d2f107d321f3a1 (patch)
tree15afc392522a9e85dc3332235e311b7d39352ea9 /vendor/memchr/src/arch/all/shiftor.rs
parent3d48cd3f81164bbfc1a755dc1d4a9a02f98c8ddd (diff)
downloadfparkan-a990de90fe41456a23e58bd087d2f107d321f3a1.tar.xz
fparkan-a990de90fe41456a23e58bd087d2f107d321f3a1.zip
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diff --git a/vendor/memchr/src/arch/all/shiftor.rs b/vendor/memchr/src/arch/all/shiftor.rs
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-/*!
-An implementation of the [Shift-Or substring search algorithm][shiftor].
-
-[shiftor]: https://en.wikipedia.org/wiki/Bitap_algorithm
-*/
-
-use alloc::boxed::Box;
-
-/// The type of our mask.
-///
-/// While we don't expose anyway to configure this in the public API, if one
-/// really needs less memory usage or support for longer needles, then it is
-/// suggested to copy the code from this module and modify it to fit your
-/// needs. The code below is written to be correct regardless of whether Mask
-/// is a u8, u16, u32, u64 or u128.
-type Mask = u16;
-
-/// A forward substring searcher using the Shift-Or algorithm.
-#[derive(Debug)]
-pub struct Finder {
- masks: Box<[Mask; 256]>,
- needle_len: usize,
-}
-
-impl Finder {
- const MAX_NEEDLE_LEN: usize = (Mask::BITS - 1) as usize;
-
- /// Create a new Shift-Or forward searcher for the given `needle`.
- ///
- /// The needle may be empty. The empty needle matches at every byte offset.
- #[inline]
- pub fn new(needle: &[u8]) -> Option<Finder> {
- let needle_len = needle.len();
- if needle_len > Finder::MAX_NEEDLE_LEN {
- // A match is found when bit 7 is set in 'result' in the search
- // routine below. So our needle can't be bigger than 7. We could
- // permit bigger needles by using u16, u32 or u64 for our mask
- // entries. But this is all we need for this example.
- return None;
- }
- let mut searcher = Finder { masks: Box::from([!0; 256]), needle_len };
- for (i, &byte) in needle.iter().enumerate() {
- searcher.masks[usize::from(byte)] &= !(1 << i);
- }
- Some(searcher)
- }
-
- /// Return the first occurrence of the needle given to `Finder::new` in
- /// the `haystack` given. If no such occurrence exists, then `None` is
- /// returned.
- ///
- /// Unlike most other substring search implementations in this crate, this
- /// finder does not require passing the needle at search time. A match can
- /// be determined without the needle at all since the required information
- /// is already encoded into this finder at construction time.
- ///
- /// The maximum value this can return is `haystack.len()`, which can only
- /// occur when the needle and haystack both have length zero. Otherwise,
- /// for non-empty haystacks, the maximum value is `haystack.len() - 1`.
- #[inline]
- pub fn find(&self, haystack: &[u8]) -> Option<usize> {
- if self.needle_len == 0 {
- return Some(0);
- }
- let mut result = !1;
- for (i, &byte) in haystack.iter().enumerate() {
- result |= self.masks[usize::from(byte)];
- result <<= 1;
- if result & (1 << self.needle_len) == 0 {
- return Some(i + 1 - self.needle_len);
- }
- }
- None
- }
-}
-
-#[cfg(test)]
-mod tests {
- use super::*;
-
- define_substring_forward_quickcheck!(|h, n| Some(Finder::new(n)?.find(h)));
-
- #[test]
- fn forward() {
- crate::tests::substring::Runner::new()
- .fwd(|h, n| Some(Finder::new(n)?.find(h)))
- .run();
- }
-}