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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/wasm32/simd128/packedpair.rs
parent3d48cd3f81164bbfc1a755dc1d4a9a02f98c8ddd (diff)
downloadfparkan-a990de90fe41456a23e58bd087d2f107d321f3a1.tar.xz
fparkan-a990de90fe41456a23e58bd087d2f107d321f3a1.zip
Deleted vendor folder
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-/*!
-A 128-bit vector implementation of the "packed pair" SIMD algorithm.
-
-The "packed pair" algorithm is based on the [generic SIMD] algorithm. The main
-difference is that it (by default) uses a background distribution of byte
-frequencies to heuristically select the pair of bytes to search for.
-
-[generic SIMD]: http://0x80.pl/articles/simd-strfind.html#first-and-last
-*/
-
-use core::arch::wasm32::v128;
-
-use crate::arch::{all::packedpair::Pair, generic::packedpair};
-
-/// A "packed pair" finder that uses 128-bit vector operations.
-///
-/// This finder picks two bytes that it believes have high predictive power
-/// for indicating an overall match of a needle. Depending on whether
-/// `Finder::find` or `Finder::find_prefilter` is used, it reports offsets
-/// where the needle matches or could match. In the prefilter case, candidates
-/// are reported whenever the [`Pair`] of bytes given matches.
-#[derive(Clone, Copy, Debug)]
-pub struct Finder(packedpair::Finder<v128>);
-
-impl Finder {
- /// Create a new pair searcher. The searcher returned can either report
- /// exact matches of `needle` or act as a prefilter and report candidate
- /// positions of `needle`.
- ///
- /// If simd128 is unavailable in the current environment or if a [`Pair`]
- /// could not be constructed from the needle given, then `None` is
- /// returned.
- #[inline]
- pub fn new(needle: &[u8]) -> Option<Finder> {
- Finder::with_pair(needle, Pair::new(needle)?)
- }
-
- /// Create a new "packed pair" finder using the pair of bytes given.
- ///
- /// This constructor permits callers to control precisely which pair of
- /// bytes is used as a predicate.
- ///
- /// If simd128 is unavailable in the current environment, then `None` is
- /// returned.
- #[inline]
- pub fn with_pair(needle: &[u8], pair: Pair) -> Option<Finder> {
- if Finder::is_available() {
- // SAFETY: we check that simd128 is available above. We are also
- // guaranteed to have needle.len() > 1 because we have a valid
- // Pair.
- unsafe { Some(Finder::with_pair_impl(needle, pair)) }
- } else {
- None
- }
- }
-
- /// Create a new `Finder` specific to simd128 vectors and routines.
- ///
- /// # Safety
- ///
- /// Same as the safety for `packedpair::Finder::new`, and callers must also
- /// ensure that simd128 is available.
- #[target_feature(enable = "simd128")]
- #[inline]
- unsafe fn with_pair_impl(needle: &[u8], pair: Pair) -> Finder {
- let finder = packedpair::Finder::<v128>::new(needle, pair);
- Finder(finder)
- }
-
- /// Returns true when this implementation is available in the current
- /// environment.
- ///
- /// When this is true, it is guaranteed that [`Finder::with_pair`] will
- /// return a `Some` value. Similarly, when it is false, it is guaranteed
- /// that `Finder::with_pair` will return a `None` value. Notice that this
- /// does not guarantee that [`Finder::new`] will return a `Finder`. Namely,
- /// even when `Finder::is_available` is true, it is not guaranteed that a
- /// valid [`Pair`] can be found from the needle given.
- ///
- /// Note also that for the lifetime of a single program, if this returns
- /// true then it will always return true.
- #[inline]
- pub fn is_available() -> bool {
- #[cfg(target_feature = "simd128")]
- {
- true
- }
- #[cfg(not(target_feature = "simd128"))]
- {
- false
- }
- }
-
- /// Execute a search using wasm32 v128 vectors and routines.
- ///
- /// # Panics
- ///
- /// When `haystack.len()` is less than [`Finder::min_haystack_len`].
- #[inline]
- pub fn find(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
- self.find_impl(haystack, needle)
- }
-
- /// Execute a search using wasm32 v128 vectors and routines.
- ///
- /// # Panics
- ///
- /// When `haystack.len()` is less than [`Finder::min_haystack_len`].
- #[inline]
- pub fn find_prefilter(&self, haystack: &[u8]) -> Option<usize> {
- self.find_prefilter_impl(haystack)
- }
-
- /// Execute a search using wasm32 v128 vectors and routines.
- ///
- /// # Panics
- ///
- /// When `haystack.len()` is less than [`Finder::min_haystack_len`].
- ///
- /// # Safety
- ///
- /// (The target feature safety obligation is automatically fulfilled by
- /// virtue of being a method on `Finder`, which can only be constructed
- /// when it is safe to call `simd128` routines.)
- #[target_feature(enable = "simd128")]
- #[inline]
- fn find_impl(&self, haystack: &[u8], needle: &[u8]) -> Option<usize> {
- // SAFETY: The target feature safety obligation is automatically
- // fulfilled by virtue of being a method on `Finder`, which can only be
- // constructed when it is safe to call `simd128` routines.
- unsafe { self.0.find(haystack, needle) }
- }
-
- /// Execute a prefilter search using wasm32 v128 vectors and routines.
- ///
- /// # Panics
- ///
- /// When `haystack.len()` is less than [`Finder::min_haystack_len`].
- ///
- /// # Safety
- ///
- /// (The target feature safety obligation is automatically fulfilled by
- /// virtue of being a method on `Finder`, which can only be constructed
- /// when it is safe to call `simd128` routines.)
- #[target_feature(enable = "simd128")]
- #[inline]
- fn find_prefilter_impl(&self, haystack: &[u8]) -> Option<usize> {
- // SAFETY: The target feature safety obligation is automatically
- // fulfilled by virtue of being a method on `Finder`, which can only be
- // constructed when it is safe to call `simd128` routines.
- unsafe { self.0.find_prefilter(haystack) }
- }
-
- /// Returns the pair of offsets (into the needle) used to check as a
- /// predicate before confirming whether a needle exists at a particular
- /// position.
- #[inline]
- pub fn pair(&self) -> &Pair {
- self.0.pair()
- }
-
- /// Returns the minimum haystack length that this `Finder` can search.
- ///
- /// Using a haystack with length smaller than this in a search will result
- /// in a panic. The reason for this restriction is that this finder is
- /// meant to be a low-level component that is part of a larger substring
- /// strategy. In that sense, it avoids trying to handle all cases and
- /// instead only handles the cases that it can handle very well.
- #[inline]
- pub fn min_haystack_len(&self) -> usize {
- self.0.min_haystack_len()
- }
-}
-
-#[cfg(test)]
-mod tests {
- use super::*;
-
- fn find(haystack: &[u8], needle: &[u8]) -> Option<Option<usize>> {
- let f = Finder::new(needle)?;
- if haystack.len() < f.min_haystack_len() {
- return None;
- }
- Some(f.find(haystack, needle))
- }
-
- define_substring_forward_quickcheck!(find);
-
- #[test]
- fn forward_substring() {
- crate::tests::substring::Runner::new().fwd(find).run()
- }
-
- #[test]
- fn forward_packedpair() {
- fn find(
- haystack: &[u8],
- needle: &[u8],
- index1: u8,
- index2: u8,
- ) -> Option<Option<usize>> {
- let pair = Pair::with_indices(needle, index1, index2)?;
- let f = Finder::with_pair(needle, pair)?;
- if haystack.len() < f.min_haystack_len() {
- return None;
- }
- Some(f.find(haystack, needle))
- }
- crate::tests::packedpair::Runner::new().fwd(find).run()
- }
-
- #[test]
- fn forward_packedpair_prefilter() {
- fn find(
- haystack: &[u8],
- needle: &[u8],
- index1: u8,
- index2: u8,
- ) -> Option<Option<usize>> {
- let pair = Pair::with_indices(needle, index1, index2)?;
- let f = Finder::with_pair(needle, pair)?;
- if haystack.len() < f.min_haystack_len() {
- return None;
- }
- Some(f.find_prefilter(haystack))
- }
- crate::tests::packedpair::Runner::new().fwd(find).run()
- }
-}