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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/memmem
parent3d48cd3f81164bbfc1a755dc1d4a9a02f98c8ddd (diff)
downloadfparkan-a990de90fe41456a23e58bd087d2f107d321f3a1.tar.xz
fparkan-a990de90fe41456a23e58bd087d2f107d321f3a1.zip
Deleted vendor folder
Diffstat (limited to 'vendor/memchr/src/memmem')
-rw-r--r--vendor/memchr/src/memmem/mod.rs737
-rw-r--r--vendor/memchr/src/memmem/searcher.rs1030
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diff --git a/vendor/memchr/src/memmem/mod.rs b/vendor/memchr/src/memmem/mod.rs
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--- a/vendor/memchr/src/memmem/mod.rs
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@@ -1,737 +0,0 @@
-/*!
-This module provides forward and reverse substring search routines.
-
-Unlike the standard library's substring search routines, these work on
-arbitrary bytes. For all non-empty needles, these routines will report exactly
-the same values as the corresponding routines in the standard library. For
-the empty needle, the standard library reports matches only at valid UTF-8
-boundaries, where as these routines will report matches at every position.
-
-Other than being able to work on arbitrary bytes, the primary reason to prefer
-these routines over the standard library routines is that these will generally
-be faster. In some cases, significantly so.
-
-# Example: iterating over substring matches
-
-This example shows how to use [`find_iter`] to find occurrences of a substring
-in a haystack.
-
-```
-use memchr::memmem;
-
-let haystack = b"foo bar foo baz foo";
-
-let mut it = memmem::find_iter(haystack, "foo");
-assert_eq!(Some(0), it.next());
-assert_eq!(Some(8), it.next());
-assert_eq!(Some(16), it.next());
-assert_eq!(None, it.next());
-```
-
-# Example: iterating over substring matches in reverse
-
-This example shows how to use [`rfind_iter`] to find occurrences of a substring
-in a haystack starting from the end of the haystack.
-
-**NOTE:** This module does not implement double ended iterators, so reverse
-searches aren't done by calling `rev` on a forward iterator.
-
-```
-use memchr::memmem;
-
-let haystack = b"foo bar foo baz foo";
-
-let mut it = memmem::rfind_iter(haystack, "foo");
-assert_eq!(Some(16), it.next());
-assert_eq!(Some(8), it.next());
-assert_eq!(Some(0), it.next());
-assert_eq!(None, it.next());
-```
-
-# Example: repeating a search for the same needle
-
-It may be possible for the overhead of constructing a substring searcher to be
-measurable in some workloads. In cases where the same needle is used to search
-many haystacks, it is possible to do construction once and thus to avoid it for
-subsequent searches. This can be done with a [`Finder`] (or a [`FinderRev`] for
-reverse searches).
-
-```
-use memchr::memmem;
-
-let finder = memmem::Finder::new("foo");
-
-assert_eq!(Some(4), finder.find(b"baz foo quux"));
-assert_eq!(None, finder.find(b"quux baz bar"));
-```
-*/
-
-pub use crate::memmem::searcher::PrefilterConfig as Prefilter;
-
-// This is exported here for use in the crate::arch::all::twoway
-// implementation. This is essentially an abstraction breaker. Namely, the
-// public API of twoway doesn't support providing a prefilter, but its crate
-// internal API does. The main reason for this is that I didn't want to do the
-// API design required to support it without a concrete use case.
-pub(crate) use crate::memmem::searcher::Pre;
-
-use crate::{
- arch::all::{
- packedpair::{DefaultFrequencyRank, HeuristicFrequencyRank},
- rabinkarp,
- },
- cow::CowBytes,
- memmem::searcher::{PrefilterState, Searcher, SearcherRev},
-};
-
-mod searcher;
-
-/// Returns an iterator over all non-overlapping occurrences of a substring in
-/// a haystack.
-///
-/// # Complexity
-///
-/// This routine is guaranteed to have worst case linear time complexity
-/// with respect to both the needle and the haystack. That is, this runs
-/// in `O(needle.len() + haystack.len())` time.
-///
-/// This routine is also guaranteed to have worst case constant space
-/// complexity.
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// use memchr::memmem;
-///
-/// let haystack = b"foo bar foo baz foo";
-/// let mut it = memmem::find_iter(haystack, b"foo");
-/// assert_eq!(Some(0), it.next());
-/// assert_eq!(Some(8), it.next());
-/// assert_eq!(Some(16), it.next());
-/// assert_eq!(None, it.next());
-/// ```
-#[inline]
-pub fn find_iter<'h, 'n, N: 'n + ?Sized + AsRef<[u8]>>(
- haystack: &'h [u8],
- needle: &'n N,
-) -> FindIter<'h, 'n> {
- FindIter::new(haystack, Finder::new(needle))
-}
-
-/// Returns a reverse iterator over all non-overlapping occurrences of a
-/// substring in a haystack.
-///
-/// # Complexity
-///
-/// This routine is guaranteed to have worst case linear time complexity
-/// with respect to both the needle and the haystack. That is, this runs
-/// in `O(needle.len() + haystack.len())` time.
-///
-/// This routine is also guaranteed to have worst case constant space
-/// complexity.
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// use memchr::memmem;
-///
-/// let haystack = b"foo bar foo baz foo";
-/// let mut it = memmem::rfind_iter(haystack, b"foo");
-/// assert_eq!(Some(16), it.next());
-/// assert_eq!(Some(8), it.next());
-/// assert_eq!(Some(0), it.next());
-/// assert_eq!(None, it.next());
-/// ```
-#[inline]
-pub fn rfind_iter<'h, 'n, N: 'n + ?Sized + AsRef<[u8]>>(
- haystack: &'h [u8],
- needle: &'n N,
-) -> FindRevIter<'h, 'n> {
- FindRevIter::new(haystack, FinderRev::new(needle))
-}
-
-/// Returns the index of the first occurrence of the given needle.
-///
-/// Note that if you're are searching for the same needle in many different
-/// small haystacks, it may be faster to initialize a [`Finder`] once,
-/// and reuse it for each search.
-///
-/// # Complexity
-///
-/// This routine is guaranteed to have worst case linear time complexity
-/// with respect to both the needle and the haystack. That is, this runs
-/// in `O(needle.len() + haystack.len())` time.
-///
-/// This routine is also guaranteed to have worst case constant space
-/// complexity.
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// use memchr::memmem;
-///
-/// let haystack = b"foo bar baz";
-/// assert_eq!(Some(0), memmem::find(haystack, b"foo"));
-/// assert_eq!(Some(4), memmem::find(haystack, b"bar"));
-/// assert_eq!(None, memmem::find(haystack, b"quux"));
-/// ```
-#[inline]
-pub fn find(haystack: &[u8], needle: &[u8]) -> Option<usize> {
- if haystack.len() < 64 {
- rabinkarp::Finder::new(needle).find(haystack, needle)
- } else {
- Finder::new(needle).find(haystack)
- }
-}
-
-/// Returns the index of the last occurrence of the given needle.
-///
-/// Note that if you're are searching for the same needle in many different
-/// small haystacks, it may be faster to initialize a [`FinderRev`] once,
-/// and reuse it for each search.
-///
-/// # Complexity
-///
-/// This routine is guaranteed to have worst case linear time complexity
-/// with respect to both the needle and the haystack. That is, this runs
-/// in `O(needle.len() + haystack.len())` time.
-///
-/// This routine is also guaranteed to have worst case constant space
-/// complexity.
-///
-/// # Examples
-///
-/// Basic usage:
-///
-/// ```
-/// use memchr::memmem;
-///
-/// let haystack = b"foo bar baz";
-/// assert_eq!(Some(0), memmem::rfind(haystack, b"foo"));
-/// assert_eq!(Some(4), memmem::rfind(haystack, b"bar"));
-/// assert_eq!(Some(8), memmem::rfind(haystack, b"ba"));
-/// assert_eq!(None, memmem::rfind(haystack, b"quux"));
-/// ```
-#[inline]
-pub fn rfind(haystack: &[u8], needle: &[u8]) -> Option<usize> {
- if haystack.len() < 64 {
- rabinkarp::FinderRev::new(needle).rfind(haystack, needle)
- } else {
- FinderRev::new(needle).rfind(haystack)
- }
-}
-
-/// An iterator over non-overlapping substring matches.
-///
-/// Matches are reported by the byte offset at which they begin.
-///
-/// `'h` is the lifetime of the haystack while `'n` is the lifetime of the
-/// needle.
-#[derive(Debug, Clone)]
-pub struct FindIter<'h, 'n> {
- haystack: &'h [u8],
- prestate: PrefilterState,
- finder: Finder<'n>,
- pos: usize,
-}
-
-impl<'h, 'n> FindIter<'h, 'n> {
- #[inline(always)]
- pub(crate) fn new(
- haystack: &'h [u8],
- finder: Finder<'n>,
- ) -> FindIter<'h, 'n> {
- let prestate = PrefilterState::new();
- FindIter { haystack, prestate, finder, pos: 0 }
- }
-
- /// Convert this iterator into its owned variant, such that it no longer
- /// borrows the finder and needle.
- ///
- /// If this is already an owned iterator, then this is a no-op. Otherwise,
- /// this copies the needle.
- ///
- /// This is only available when the `alloc` feature is enabled.
- #[cfg(feature = "alloc")]
- #[inline]
- pub fn into_owned(self) -> FindIter<'h, 'static> {
- FindIter {
- haystack: self.haystack,
- prestate: self.prestate,
- finder: self.finder.into_owned(),
- pos: self.pos,
- }
- }
-}
-
-impl<'h, 'n> Iterator for FindIter<'h, 'n> {
- type Item = usize;
-
- fn next(&mut self) -> Option<usize> {
- let needle = self.finder.needle();
- let haystack = self.haystack.get(self.pos..)?;
- let idx =
- self.finder.searcher.find(&mut self.prestate, haystack, needle)?;
-
- let pos = self.pos + idx;
- self.pos = pos + needle.len().max(1);
-
- Some(pos)
- }
-
- fn size_hint(&self) -> (usize, Option<usize>) {
- // The largest possible number of non-overlapping matches is the
- // quotient of the haystack and the needle (or the length of the
- // haystack, if the needle is empty)
- match self.haystack.len().checked_sub(self.pos) {
- None => (0, Some(0)),
- Some(haystack_len) => match self.finder.needle().len() {
- // Empty needles always succeed and match at every point
- // (including the very end)
- 0 => (
- haystack_len.saturating_add(1),
- haystack_len.checked_add(1),
- ),
- needle_len => (0, Some(haystack_len / needle_len)),
- },
- }
- }
-}
-
-/// An iterator over non-overlapping substring matches in reverse.
-///
-/// Matches are reported by the byte offset at which they begin.
-///
-/// `'h` is the lifetime of the haystack while `'n` is the lifetime of the
-/// needle.
-#[derive(Clone, Debug)]
-pub struct FindRevIter<'h, 'n> {
- haystack: &'h [u8],
- finder: FinderRev<'n>,
- /// When searching with an empty needle, this gets set to `None` after
- /// we've yielded the last element at `0`.
- pos: Option<usize>,
-}
-
-impl<'h, 'n> FindRevIter<'h, 'n> {
- #[inline(always)]
- pub(crate) fn new(
- haystack: &'h [u8],
- finder: FinderRev<'n>,
- ) -> FindRevIter<'h, 'n> {
- let pos = Some(haystack.len());
- FindRevIter { haystack, finder, pos }
- }
-
- /// Convert this iterator into its owned variant, such that it no longer
- /// borrows the finder and needle.
- ///
- /// If this is already an owned iterator, then this is a no-op. Otherwise,
- /// this copies the needle.
- ///
- /// This is only available when the `std` feature is enabled.
- #[cfg(feature = "alloc")]
- #[inline]
- pub fn into_owned(self) -> FindRevIter<'h, 'static> {
- FindRevIter {
- haystack: self.haystack,
- finder: self.finder.into_owned(),
- pos: self.pos,
- }
- }
-}
-
-impl<'h, 'n> Iterator for FindRevIter<'h, 'n> {
- type Item = usize;
-
- fn next(&mut self) -> Option<usize> {
- let pos = match self.pos {
- None => return None,
- Some(pos) => pos,
- };
- let result = self.finder.rfind(&self.haystack[..pos]);
- match result {
- None => None,
- Some(i) => {
- if pos == i {
- self.pos = pos.checked_sub(1);
- } else {
- self.pos = Some(i);
- }
- Some(i)
- }
- }
- }
-}
-
-/// A single substring searcher fixed to a particular needle.
-///
-/// The purpose of this type is to permit callers to construct a substring
-/// searcher that can be used to search haystacks without the overhead of
-/// constructing the searcher in the first place. This is a somewhat niche
-/// concern when it's necessary to re-use the same needle to search multiple
-/// different haystacks with as little overhead as possible. In general, using
-/// [`find`] is good enough, but `Finder` is useful when you can meaningfully
-/// observe searcher construction time in a profile.
-///
-/// When the `std` feature is enabled, then this type has an `into_owned`
-/// version which permits building a `Finder` that is not connected to
-/// the lifetime of its needle.
-#[derive(Clone, Debug)]
-pub struct Finder<'n> {
- needle: CowBytes<'n>,
- searcher: Searcher,
-}
-
-impl<'n> Finder<'n> {
- /// Create a new finder for the given needle.
- #[inline]
- pub fn new<B: ?Sized + AsRef<[u8]>>(needle: &'n B) -> Finder<'n> {
- FinderBuilder::new().build_forward(needle)
- }
-
- /// Returns the index of the first occurrence of this needle in the given
- /// haystack.
- ///
- /// # Complexity
- ///
- /// This routine is guaranteed to have worst case linear time complexity
- /// with respect to both the needle and the haystack. That is, this runs
- /// in `O(needle.len() + haystack.len())` time.
- ///
- /// This routine is also guaranteed to have worst case constant space
- /// complexity.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// use memchr::memmem::Finder;
- ///
- /// let haystack = b"foo bar baz";
- /// assert_eq!(Some(0), Finder::new("foo").find(haystack));
- /// assert_eq!(Some(4), Finder::new("bar").find(haystack));
- /// assert_eq!(None, Finder::new("quux").find(haystack));
- /// ```
- #[inline]
- pub fn find(&self, haystack: &[u8]) -> Option<usize> {
- let mut prestate = PrefilterState::new();
- let needle = self.needle.as_slice();
- self.searcher.find(&mut prestate, haystack, needle)
- }
-
- /// Returns an iterator over all occurrences of a substring in a haystack.
- ///
- /// # Complexity
- ///
- /// This routine is guaranteed to have worst case linear time complexity
- /// with respect to both the needle and the haystack. That is, this runs
- /// in `O(needle.len() + haystack.len())` time.
- ///
- /// This routine is also guaranteed to have worst case constant space
- /// complexity.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// use memchr::memmem::Finder;
- ///
- /// let haystack = b"foo bar foo baz foo";
- /// let finder = Finder::new(b"foo");
- /// let mut it = finder.find_iter(haystack);
- /// assert_eq!(Some(0), it.next());
- /// assert_eq!(Some(8), it.next());
- /// assert_eq!(Some(16), it.next());
- /// assert_eq!(None, it.next());
- /// ```
- #[inline]
- pub fn find_iter<'a, 'h>(
- &'a self,
- haystack: &'h [u8],
- ) -> FindIter<'h, 'a> {
- FindIter::new(haystack, self.as_ref())
- }
-
- /// Convert this finder into its owned variant, such that it no longer
- /// borrows the needle.
- ///
- /// If this is already an owned finder, then this is a no-op. Otherwise,
- /// this copies the needle.
- ///
- /// This is only available when the `alloc` feature is enabled.
- #[cfg(feature = "alloc")]
- #[inline]
- pub fn into_owned(self) -> Finder<'static> {
- Finder {
- needle: self.needle.into_owned(),
- searcher: self.searcher.clone(),
- }
- }
-
- /// Convert this finder into its borrowed variant.
- ///
- /// This is primarily useful if your finder is owned and you'd like to
- /// store its borrowed variant in some intermediate data structure.
- ///
- /// Note that the lifetime parameter of the returned finder is tied to the
- /// lifetime of `self`, and may be shorter than the `'n` lifetime of the
- /// needle itself. Namely, a finder's needle can be either borrowed or
- /// owned, so the lifetime of the needle returned must necessarily be the
- /// shorter of the two.
- #[inline]
- pub fn as_ref(&self) -> Finder<'_> {
- Finder {
- needle: CowBytes::new(self.needle()),
- searcher: self.searcher.clone(),
- }
- }
-
- /// Returns the needle that this finder searches for.
- ///
- /// Note that the lifetime of the needle returned is tied to the lifetime
- /// of the finder, and may be shorter than the `'n` lifetime. Namely, a
- /// finder's needle can be either borrowed or owned, so the lifetime of the
- /// needle returned must necessarily be the shorter of the two.
- #[inline]
- pub fn needle(&self) -> &[u8] {
- self.needle.as_slice()
- }
-}
-
-/// A single substring reverse searcher fixed to a particular needle.
-///
-/// The purpose of this type is to permit callers to construct a substring
-/// searcher that can be used to search haystacks without the overhead of
-/// constructing the searcher in the first place. This is a somewhat niche
-/// concern when it's necessary to re-use the same needle to search multiple
-/// different haystacks with as little overhead as possible. In general,
-/// using [`rfind`] is good enough, but `FinderRev` is useful when you can
-/// meaningfully observe searcher construction time in a profile.
-///
-/// When the `std` feature is enabled, then this type has an `into_owned`
-/// version which permits building a `FinderRev` that is not connected to
-/// the lifetime of its needle.
-#[derive(Clone, Debug)]
-pub struct FinderRev<'n> {
- needle: CowBytes<'n>,
- searcher: SearcherRev,
-}
-
-impl<'n> FinderRev<'n> {
- /// Create a new reverse finder for the given needle.
- #[inline]
- pub fn new<B: ?Sized + AsRef<[u8]>>(needle: &'n B) -> FinderRev<'n> {
- FinderBuilder::new().build_reverse(needle)
- }
-
- /// Returns the index of the last occurrence of this needle in the given
- /// haystack.
- ///
- /// The haystack may be any type that can be cheaply converted into a
- /// `&[u8]`. This includes, but is not limited to, `&str` and `&[u8]`.
- ///
- /// # Complexity
- ///
- /// This routine is guaranteed to have worst case linear time complexity
- /// with respect to both the needle and the haystack. That is, this runs
- /// in `O(needle.len() + haystack.len())` time.
- ///
- /// This routine is also guaranteed to have worst case constant space
- /// complexity.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// use memchr::memmem::FinderRev;
- ///
- /// let haystack = b"foo bar baz";
- /// assert_eq!(Some(0), FinderRev::new("foo").rfind(haystack));
- /// assert_eq!(Some(4), FinderRev::new("bar").rfind(haystack));
- /// assert_eq!(None, FinderRev::new("quux").rfind(haystack));
- /// ```
- pub fn rfind<B: AsRef<[u8]>>(&self, haystack: B) -> Option<usize> {
- self.searcher.rfind(haystack.as_ref(), self.needle.as_slice())
- }
-
- /// Returns a reverse iterator over all occurrences of a substring in a
- /// haystack.
- ///
- /// # Complexity
- ///
- /// This routine is guaranteed to have worst case linear time complexity
- /// with respect to both the needle and the haystack. That is, this runs
- /// in `O(needle.len() + haystack.len())` time.
- ///
- /// This routine is also guaranteed to have worst case constant space
- /// complexity.
- ///
- /// # Examples
- ///
- /// Basic usage:
- ///
- /// ```
- /// use memchr::memmem::FinderRev;
- ///
- /// let haystack = b"foo bar foo baz foo";
- /// let finder = FinderRev::new(b"foo");
- /// let mut it = finder.rfind_iter(haystack);
- /// assert_eq!(Some(16), it.next());
- /// assert_eq!(Some(8), it.next());
- /// assert_eq!(Some(0), it.next());
- /// assert_eq!(None, it.next());
- /// ```
- #[inline]
- pub fn rfind_iter<'a, 'h>(
- &'a self,
- haystack: &'h [u8],
- ) -> FindRevIter<'h, 'a> {
- FindRevIter::new(haystack, self.as_ref())
- }
-
- /// Convert this finder into its owned variant, such that it no longer
- /// borrows the needle.
- ///
- /// If this is already an owned finder, then this is a no-op. Otherwise,
- /// this copies the needle.
- ///
- /// This is only available when the `std` feature is enabled.
- #[cfg(feature = "alloc")]
- #[inline]
- pub fn into_owned(self) -> FinderRev<'static> {
- FinderRev {
- needle: self.needle.into_owned(),
- searcher: self.searcher.clone(),
- }
- }
-
- /// Convert this finder into its borrowed variant.
- ///
- /// This is primarily useful if your finder is owned and you'd like to
- /// store its borrowed variant in some intermediate data structure.
- ///
- /// Note that the lifetime parameter of the returned finder is tied to the
- /// lifetime of `self`, and may be shorter than the `'n` lifetime of the
- /// needle itself. Namely, a finder's needle can be either borrowed or
- /// owned, so the lifetime of the needle returned must necessarily be the
- /// shorter of the two.
- #[inline]
- pub fn as_ref(&self) -> FinderRev<'_> {
- FinderRev {
- needle: CowBytes::new(self.needle()),
- searcher: self.searcher.clone(),
- }
- }
-
- /// Returns the needle that this finder searches for.
- ///
- /// Note that the lifetime of the needle returned is tied to the lifetime
- /// of the finder, and may be shorter than the `'n` lifetime. Namely, a
- /// finder's needle can be either borrowed or owned, so the lifetime of the
- /// needle returned must necessarily be the shorter of the two.
- #[inline]
- pub fn needle(&self) -> &[u8] {
- self.needle.as_slice()
- }
-}
-
-/// A builder for constructing non-default forward or reverse memmem finders.
-///
-/// A builder is primarily useful for configuring a substring searcher.
-/// Currently, the only configuration exposed is the ability to disable
-/// heuristic prefilters used to speed up certain searches.
-#[derive(Clone, Debug, Default)]
-pub struct FinderBuilder {
- prefilter: Prefilter,
-}
-
-impl FinderBuilder {
- /// Create a new finder builder with default settings.
- pub fn new() -> FinderBuilder {
- FinderBuilder::default()
- }
-
- /// Build a forward finder using the given needle from the current
- /// settings.
- pub fn build_forward<'n, B: ?Sized + AsRef<[u8]>>(
- &self,
- needle: &'n B,
- ) -> Finder<'n> {
- self.build_forward_with_ranker(DefaultFrequencyRank, needle)
- }
-
- /// Build a forward finder using the given needle and a custom heuristic for
- /// determining the frequency of a given byte in the dataset.
- /// See [`HeuristicFrequencyRank`] for more details.
- pub fn build_forward_with_ranker<
- 'n,
- R: HeuristicFrequencyRank,
- B: ?Sized + AsRef<[u8]>,
- >(
- &self,
- ranker: R,
- needle: &'n B,
- ) -> Finder<'n> {
- let needle = needle.as_ref();
- Finder {
- needle: CowBytes::new(needle),
- searcher: Searcher::new(self.prefilter, ranker, needle),
- }
- }
-
- /// Build a reverse finder using the given needle from the current
- /// settings.
- pub fn build_reverse<'n, B: ?Sized + AsRef<[u8]>>(
- &self,
- needle: &'n B,
- ) -> FinderRev<'n> {
- let needle = needle.as_ref();
- FinderRev {
- needle: CowBytes::new(needle),
- searcher: SearcherRev::new(needle),
- }
- }
-
- /// Configure the prefilter setting for the finder.
- ///
- /// See the documentation for [`Prefilter`] for more discussion on why
- /// you might want to configure this.
- pub fn prefilter(&mut self, prefilter: Prefilter) -> &mut FinderBuilder {
- self.prefilter = prefilter;
- self
- }
-}
-
-#[cfg(test)]
-mod tests {
- use super::*;
-
- define_substring_forward_quickcheck!(|h, n| Some(Finder::new(n).find(h)));
- define_substring_reverse_quickcheck!(|h, n| Some(
- FinderRev::new(n).rfind(h)
- ));
-
- #[test]
- fn forward() {
- crate::tests::substring::Runner::new()
- .fwd(|h, n| Some(Finder::new(n).find(h)))
- .run();
- }
-
- #[test]
- fn reverse() {
- crate::tests::substring::Runner::new()
- .rev(|h, n| Some(FinderRev::new(n).rfind(h)))
- .run();
- }
-}
diff --git a/vendor/memchr/src/memmem/searcher.rs b/vendor/memchr/src/memmem/searcher.rs
deleted file mode 100644
index 98b9bd6..0000000
--- a/vendor/memchr/src/memmem/searcher.rs
+++ /dev/null
@@ -1,1030 +0,0 @@
-use crate::arch::all::{
- packedpair::{HeuristicFrequencyRank, Pair},
- rabinkarp, twoway,
-};
-
-#[cfg(target_arch = "aarch64")]
-use crate::arch::aarch64::neon::packedpair as neon;
-#[cfg(target_arch = "wasm32")]
-use crate::arch::wasm32::simd128::packedpair as simd128;
-#[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
-use crate::arch::x86_64::{
- avx2::packedpair as avx2, sse2::packedpair as sse2,
-};
-
-/// A "meta" substring searcher.
-///
-/// To a first approximation, this chooses what it believes to be the "best"
-/// substring search implemnetation based on the needle at construction time.
-/// Then, every call to `find` will execute that particular implementation. To
-/// a second approximation, multiple substring search algorithms may be used,
-/// depending on the haystack. For example, for supremely short haystacks,
-/// Rabin-Karp is typically used.
-///
-/// See the documentation on `Prefilter` for an explanation of the dispatching
-/// mechanism. The quick summary is that an enum has too much overhead and
-/// we can't use dynamic dispatch via traits because we need to work in a
-/// core-only environment. (Dynamic dispatch works in core-only, but you
-/// need `&dyn Trait` and we really need a `Box<dyn Trait>` here. The latter
-/// requires `alloc`.) So instead, we use a union and an appropriately paired
-/// free function to read from the correct field on the union and execute the
-/// chosen substring search implementation.
-#[derive(Clone)]
-pub(crate) struct Searcher {
- call: SearcherKindFn,
- kind: SearcherKind,
- rabinkarp: rabinkarp::Finder,
-}
-
-impl Searcher {
- /// Creates a new "meta" substring searcher that attempts to choose the
- /// best algorithm based on the needle, heuristics and what the current
- /// target supports.
- #[inline]
- pub(crate) fn new<R: HeuristicFrequencyRank>(
- prefilter: PrefilterConfig,
- ranker: R,
- needle: &[u8],
- ) -> Searcher {
- let rabinkarp = rabinkarp::Finder::new(needle);
- if needle.len() <= 1 {
- return if needle.is_empty() {
- trace!("building empty substring searcher");
- Searcher {
- call: searcher_kind_empty,
- kind: SearcherKind { empty: () },
- rabinkarp,
- }
- } else {
- trace!("building one-byte substring searcher");
- debug_assert_eq!(1, needle.len());
- Searcher {
- call: searcher_kind_one_byte,
- kind: SearcherKind { one_byte: needle[0] },
- rabinkarp,
- }
- };
- }
- let pair = match Pair::with_ranker(needle, &ranker) {
- Some(pair) => pair,
- None => return Searcher::twoway(needle, rabinkarp, None),
- };
- debug_assert_ne!(
- pair.index1(),
- pair.index2(),
- "pair offsets should not be equivalent"
- );
- #[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
- {
- if let Some(pp) = avx2::Finder::with_pair(needle, pair) {
- if do_packed_search(needle) {
- trace!("building x86_64 AVX2 substring searcher");
- let kind = SearcherKind { avx2: pp };
- Searcher { call: searcher_kind_avx2, kind, rabinkarp }
- } else if prefilter.is_none() {
- Searcher::twoway(needle, rabinkarp, None)
- } else {
- let prestrat = Prefilter::avx2(pp, needle);
- Searcher::twoway(needle, rabinkarp, Some(prestrat))
- }
- } else if let Some(pp) = sse2::Finder::with_pair(needle, pair) {
- if do_packed_search(needle) {
- trace!("building x86_64 SSE2 substring searcher");
- let kind = SearcherKind { sse2: pp };
- Searcher { call: searcher_kind_sse2, kind, rabinkarp }
- } else if prefilter.is_none() {
- Searcher::twoway(needle, rabinkarp, None)
- } else {
- let prestrat = Prefilter::sse2(pp, needle);
- Searcher::twoway(needle, rabinkarp, Some(prestrat))
- }
- } else if prefilter.is_none() {
- Searcher::twoway(needle, rabinkarp, None)
- } else {
- // We're pretty unlikely to get to this point, but it is
- // possible to be running on x86_64 without SSE2. Namely, it's
- // really up to the OS whether it wants to support vector
- // registers or not.
- let prestrat = Prefilter::fallback(ranker, pair, needle);
- Searcher::twoway(needle, rabinkarp, prestrat)
- }
- }
- #[cfg(target_arch = "wasm32")]
- {
- if let Some(pp) = simd128::Finder::with_pair(needle, pair) {
- if do_packed_search(needle) {
- trace!("building wasm32 simd128 substring searcher");
- let kind = SearcherKind { simd128: pp };
- Searcher { call: searcher_kind_simd128, kind, rabinkarp }
- } else if prefilter.is_none() {
- Searcher::twoway(needle, rabinkarp, None)
- } else {
- let prestrat = Prefilter::simd128(pp, needle);
- Searcher::twoway(needle, rabinkarp, Some(prestrat))
- }
- } else if prefilter.is_none() {
- Searcher::twoway(needle, rabinkarp, None)
- } else {
- let prestrat = Prefilter::fallback(ranker, pair, needle);
- Searcher::twoway(needle, rabinkarp, prestrat)
- }
- }
- #[cfg(target_arch = "aarch64")]
- {
- if let Some(pp) = neon::Finder::with_pair(needle, pair) {
- if do_packed_search(needle) {
- trace!("building aarch64 neon substring searcher");
- let kind = SearcherKind { neon: pp };
- Searcher { call: searcher_kind_neon, kind, rabinkarp }
- } else if prefilter.is_none() {
- Searcher::twoway(needle, rabinkarp, None)
- } else {
- let prestrat = Prefilter::neon(pp, needle);
- Searcher::twoway(needle, rabinkarp, Some(prestrat))
- }
- } else if prefilter.is_none() {
- Searcher::twoway(needle, rabinkarp, None)
- } else {
- let prestrat = Prefilter::fallback(ranker, pair, needle);
- Searcher::twoway(needle, rabinkarp, prestrat)
- }
- }
- #[cfg(not(any(
- all(target_arch = "x86_64", target_feature = "sse2"),
- target_arch = "wasm32",
- target_arch = "aarch64"
- )))]
- {
- if prefilter.is_none() {
- Searcher::twoway(needle, rabinkarp, None)
- } else {
- let prestrat = Prefilter::fallback(ranker, pair, needle);
- Searcher::twoway(needle, rabinkarp, prestrat)
- }
- }
- }
-
- /// Creates a new searcher that always uses the Two-Way algorithm. This is
- /// typically used when vector algorithms are unavailable or inappropriate.
- /// (For example, when the needle is "too long.")
- ///
- /// If a prefilter is given, then the searcher returned will be accelerated
- /// by the prefilter.
- #[inline]
- fn twoway(
- needle: &[u8],
- rabinkarp: rabinkarp::Finder,
- prestrat: Option<Prefilter>,
- ) -> Searcher {
- let finder = twoway::Finder::new(needle);
- match prestrat {
- None => {
- trace!("building scalar two-way substring searcher");
- let kind = SearcherKind { two_way: finder };
- Searcher { call: searcher_kind_two_way, kind, rabinkarp }
- }
- Some(prestrat) => {
- trace!(
- "building scalar two-way \
- substring searcher with a prefilter"
- );
- let two_way_with_prefilter =
- TwoWayWithPrefilter { finder, prestrat };
- let kind = SearcherKind { two_way_with_prefilter };
- Searcher {
- call: searcher_kind_two_way_with_prefilter,
- kind,
- rabinkarp,
- }
- }
- }
- }
-
- /// Searches the given haystack for the given needle. The needle given
- /// should be the same as the needle that this finder was initialized
- /// with.
- ///
- /// Inlining this can lead to big wins for latency, and #[inline] doesn't
- /// seem to be enough in some cases.
- #[inline(always)]
- pub(crate) fn find(
- &self,
- prestate: &mut PrefilterState,
- haystack: &[u8],
- needle: &[u8],
- ) -> Option<usize> {
- if haystack.len() < needle.len() {
- None
- } else {
- // SAFETY: By construction, we've ensured that the function
- // in `self.call` is properly paired with the union used in
- // `self.kind`.
- unsafe { (self.call)(self, prestate, haystack, needle) }
- }
- }
-}
-
-impl core::fmt::Debug for Searcher {
- fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
- f.debug_struct("Searcher")
- .field("call", &"<searcher function>")
- .field("kind", &"<searcher kind union>")
- .field("rabinkarp", &self.rabinkarp)
- .finish()
- }
-}
-
-/// A union indicating one of several possible substring search implementations
-/// that are in active use.
-///
-/// This union should only be read by one of the functions prefixed with
-/// `searcher_kind_`. Namely, the correct function is meant to be paired with
-/// the union by the caller, such that the function always reads from the
-/// designated union field.
-#[derive(Clone, Copy)]
-union SearcherKind {
- empty: (),
- one_byte: u8,
- two_way: twoway::Finder,
- two_way_with_prefilter: TwoWayWithPrefilter,
- #[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
- sse2: crate::arch::x86_64::sse2::packedpair::Finder,
- #[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
- avx2: crate::arch::x86_64::avx2::packedpair::Finder,
- #[cfg(target_arch = "wasm32")]
- simd128: crate::arch::wasm32::simd128::packedpair::Finder,
- #[cfg(target_arch = "aarch64")]
- neon: crate::arch::aarch64::neon::packedpair::Finder,
-}
-
-/// A two-way substring searcher with a prefilter.
-#[derive(Copy, Clone, Debug)]
-struct TwoWayWithPrefilter {
- finder: twoway::Finder,
- prestrat: Prefilter,
-}
-
-/// The type of a substring search function.
-///
-/// # Safety
-///
-/// When using a function of this type, callers must ensure that the correct
-/// function is paired with the value populated in `SearcherKind` union.
-type SearcherKindFn = unsafe fn(
- searcher: &Searcher,
- prestate: &mut PrefilterState,
- haystack: &[u8],
- needle: &[u8],
-) -> Option<usize>;
-
-/// Reads from the `empty` field of `SearcherKind` to handle the case of
-/// searching for the empty needle. Works on all platforms.
-///
-/// # Safety
-///
-/// Callers must ensure that the `searcher.kind.empty` union field is set.
-unsafe fn searcher_kind_empty(
- _searcher: &Searcher,
- _prestate: &mut PrefilterState,
- _haystack: &[u8],
- _needle: &[u8],
-) -> Option<usize> {
- Some(0)
-}
-
-/// Reads from the `one_byte` field of `SearcherKind` to handle the case of
-/// searching for a single byte needle. Works on all platforms.
-///
-/// # Safety
-///
-/// Callers must ensure that the `searcher.kind.one_byte` union field is set.
-unsafe fn searcher_kind_one_byte(
- searcher: &Searcher,
- _prestate: &mut PrefilterState,
- haystack: &[u8],
- _needle: &[u8],
-) -> Option<usize> {
- let needle = searcher.kind.one_byte;
- crate::memchr(needle, haystack)
-}
-
-/// Reads from the `two_way` field of `SearcherKind` to handle the case of
-/// searching for an arbitrary needle without prefilter acceleration. Works on
-/// all platforms.
-///
-/// # Safety
-///
-/// Callers must ensure that the `searcher.kind.two_way` union field is set.
-unsafe fn searcher_kind_two_way(
- searcher: &Searcher,
- _prestate: &mut PrefilterState,
- haystack: &[u8],
- needle: &[u8],
-) -> Option<usize> {
- if rabinkarp::is_fast(haystack, needle) {
- searcher.rabinkarp.find(haystack, needle)
- } else {
- searcher.kind.two_way.find(haystack, needle)
- }
-}
-
-/// Reads from the `two_way_with_prefilter` field of `SearcherKind` to handle
-/// the case of searching for an arbitrary needle with prefilter acceleration.
-/// Works on all platforms.
-///
-/// # Safety
-///
-/// Callers must ensure that the `searcher.kind.two_way_with_prefilter` union
-/// field is set.
-unsafe fn searcher_kind_two_way_with_prefilter(
- searcher: &Searcher,
- prestate: &mut PrefilterState,
- haystack: &[u8],
- needle: &[u8],
-) -> Option<usize> {
- if rabinkarp::is_fast(haystack, needle) {
- searcher.rabinkarp.find(haystack, needle)
- } else {
- let TwoWayWithPrefilter { ref finder, ref prestrat } =
- searcher.kind.two_way_with_prefilter;
- let pre = Pre { prestate, prestrat };
- finder.find_with_prefilter(Some(pre), haystack, needle)
- }
-}
-
-/// Reads from the `sse2` field of `SearcherKind` to execute the x86_64 SSE2
-/// vectorized substring search implementation.
-///
-/// # Safety
-///
-/// Callers must ensure that the `searcher.kind.sse2` union field is set.
-#[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
-unsafe fn searcher_kind_sse2(
- searcher: &Searcher,
- _prestate: &mut PrefilterState,
- haystack: &[u8],
- needle: &[u8],
-) -> Option<usize> {
- let finder = &searcher.kind.sse2;
- if haystack.len() < finder.min_haystack_len() {
- searcher.rabinkarp.find(haystack, needle)
- } else {
- finder.find(haystack, needle)
- }
-}
-
-/// Reads from the `avx2` field of `SearcherKind` to execute the x86_64 AVX2
-/// vectorized substring search implementation.
-///
-/// # Safety
-///
-/// Callers must ensure that the `searcher.kind.avx2` union field is set.
-#[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
-unsafe fn searcher_kind_avx2(
- searcher: &Searcher,
- _prestate: &mut PrefilterState,
- haystack: &[u8],
- needle: &[u8],
-) -> Option<usize> {
- let finder = &searcher.kind.avx2;
- if haystack.len() < finder.min_haystack_len() {
- searcher.rabinkarp.find(haystack, needle)
- } else {
- finder.find(haystack, needle)
- }
-}
-
-/// Reads from the `simd128` field of `SearcherKind` to execute the wasm32
-/// simd128 vectorized substring search implementation.
-///
-/// # Safety
-///
-/// Callers must ensure that the `searcher.kind.simd128` union field is set.
-#[cfg(target_arch = "wasm32")]
-unsafe fn searcher_kind_simd128(
- searcher: &Searcher,
- _prestate: &mut PrefilterState,
- haystack: &[u8],
- needle: &[u8],
-) -> Option<usize> {
- let finder = &searcher.kind.simd128;
- if haystack.len() < finder.min_haystack_len() {
- searcher.rabinkarp.find(haystack, needle)
- } else {
- finder.find(haystack, needle)
- }
-}
-
-/// Reads from the `neon` field of `SearcherKind` to execute the aarch64 neon
-/// vectorized substring search implementation.
-///
-/// # Safety
-///
-/// Callers must ensure that the `searcher.kind.neon` union field is set.
-#[cfg(target_arch = "aarch64")]
-unsafe fn searcher_kind_neon(
- searcher: &Searcher,
- _prestate: &mut PrefilterState,
- haystack: &[u8],
- needle: &[u8],
-) -> Option<usize> {
- let finder = &searcher.kind.neon;
- if haystack.len() < finder.min_haystack_len() {
- searcher.rabinkarp.find(haystack, needle)
- } else {
- finder.find(haystack, needle)
- }
-}
-
-/// A reverse substring searcher.
-#[derive(Clone, Debug)]
-pub(crate) struct SearcherRev {
- kind: SearcherRevKind,
- rabinkarp: rabinkarp::FinderRev,
-}
-
-/// The kind of the reverse searcher.
-///
-/// For the reverse case, we don't do any SIMD acceleration or prefilters.
-/// There is no specific technical reason why we don't, but rather don't do it
-/// because it's not clear it's worth the extra code to do so. If you have a
-/// use case for it, please file an issue.
-///
-/// We also don't do the union trick as we do with the forward case and
-/// prefilters. Basically for the same reason we don't have prefilters or
-/// vector algorithms for reverse searching: it's not clear it's worth doing.
-/// Please file an issue if you have a compelling use case for fast reverse
-/// substring search.
-#[derive(Clone, Debug)]
-enum SearcherRevKind {
- Empty,
- OneByte { needle: u8 },
- TwoWay { finder: twoway::FinderRev },
-}
-
-impl SearcherRev {
- /// Creates a new searcher for finding occurrences of the given needle in
- /// reverse. That is, it reports the last (instead of the first) occurrence
- /// of a needle in a haystack.
- #[inline]
- pub(crate) fn new(needle: &[u8]) -> SearcherRev {
- let kind = if needle.len() <= 1 {
- if needle.is_empty() {
- trace!("building empty reverse substring searcher");
- SearcherRevKind::Empty
- } else {
- trace!("building one-byte reverse substring searcher");
- debug_assert_eq!(1, needle.len());
- SearcherRevKind::OneByte { needle: needle[0] }
- }
- } else {
- trace!("building scalar two-way reverse substring searcher");
- let finder = twoway::FinderRev::new(needle);
- SearcherRevKind::TwoWay { finder }
- };
- let rabinkarp = rabinkarp::FinderRev::new(needle);
- SearcherRev { kind, rabinkarp }
- }
-
- /// Searches the given haystack for the last occurrence of the given
- /// needle. The needle given should be the same as the needle that this
- /// finder was initialized with.
- #[inline]
- pub(crate) fn rfind(
- &self,
- haystack: &[u8],
- needle: &[u8],
- ) -> Option<usize> {
- if haystack.len() < needle.len() {
- return None;
- }
- match self.kind {
- SearcherRevKind::Empty => Some(haystack.len()),
- SearcherRevKind::OneByte { needle } => {
- crate::memrchr(needle, haystack)
- }
- SearcherRevKind::TwoWay { ref finder } => {
- if rabinkarp::is_fast(haystack, needle) {
- self.rabinkarp.rfind(haystack, needle)
- } else {
- finder.rfind(haystack, needle)
- }
- }
- }
- }
-}
-
-/// Prefilter controls whether heuristics are used to accelerate searching.
-///
-/// A prefilter refers to the idea of detecting candidate matches very quickly,
-/// and then confirming whether those candidates are full matches. This
-/// idea can be quite effective since it's often the case that looking for
-/// candidates can be a lot faster than running a complete substring search
-/// over the entire input. Namely, looking for candidates can be done with
-/// extremely fast vectorized code.
-///
-/// The downside of a prefilter is that it assumes false positives (which are
-/// candidates generated by a prefilter that aren't matches) are somewhat rare
-/// relative to the frequency of full matches. That is, if a lot of false
-/// positives are generated, then it's possible for search time to be worse
-/// than if the prefilter wasn't enabled in the first place.
-///
-/// Another downside of a prefilter is that it can result in highly variable
-/// performance, where some cases are extraordinarily fast and others aren't.
-/// Typically, variable performance isn't a problem, but it may be for your use
-/// case.
-///
-/// The use of prefilters in this implementation does use a heuristic to detect
-/// when a prefilter might not be carrying its weight, and will dynamically
-/// disable its use. Nevertheless, this configuration option gives callers
-/// the ability to disable prefilters if you have knowledge that they won't be
-/// useful.
-#[derive(Clone, Copy, Debug)]
-#[non_exhaustive]
-pub enum PrefilterConfig {
- /// Never used a prefilter in substring search.
- None,
- /// Automatically detect whether a heuristic prefilter should be used. If
- /// it is used, then heuristics will be used to dynamically disable the
- /// prefilter if it is believed to not be carrying its weight.
- Auto,
-}
-
-impl Default for PrefilterConfig {
- fn default() -> PrefilterConfig {
- PrefilterConfig::Auto
- }
-}
-
-impl PrefilterConfig {
- /// Returns true when this prefilter is set to the `None` variant.
- fn is_none(&self) -> bool {
- matches!(*self, PrefilterConfig::None)
- }
-}
-
-/// The implementation of a prefilter.
-///
-/// This type encapsulates dispatch to one of several possible choices for a
-/// prefilter. Generally speaking, all prefilters have the same approximate
-/// algorithm: they choose a couple of bytes from the needle that are believed
-/// to be rare, use a fast vector algorithm to look for those bytes and return
-/// positions as candidates for some substring search algorithm (currently only
-/// Two-Way) to confirm as a match or not.
-///
-/// The differences between the algorithms are actually at the vector
-/// implementation level. Namely, we need different routines based on both
-/// which target architecture we're on and what CPU features are supported.
-///
-/// The straight-forwardly obvious approach here is to use an enum, and make
-/// `Prefilter::find` do case analysis to determine which algorithm was
-/// selected and invoke it. However, I've observed that this leads to poor
-/// codegen in some cases, especially in latency sensitive benchmarks. That is,
-/// this approach comes with overhead that I wasn't able to eliminate.
-///
-/// The second obvious approach is to use dynamic dispatch with traits. Doing
-/// that in this context where `Prefilter` owns the selection generally
-/// requires heap allocation, and this code is designed to run in core-only
-/// environments.
-///
-/// So we settle on using a union (that's `PrefilterKind`) and a function
-/// pointer (that's `PrefilterKindFn`). We select the right function pointer
-/// based on which field in the union we set, and that function in turn
-/// knows which field of the union to access. The downside of this approach
-/// is that it forces us to think about safety, but the upside is that
-/// there are some nice latency improvements to benchmarks. (Especially the
-/// `memmem/sliceslice/short` benchmark.)
-///
-/// In cases where we've selected a vector algorithm and the haystack given
-/// is too short, we fallback to the scalar version of `memchr` on the
-/// `rarest_byte`. (The scalar version of `memchr` is still better than a naive
-/// byte-at-a-time loop because it will read in `usize`-sized chunks at a
-/// time.)
-#[derive(Clone, Copy)]
-struct Prefilter {
- call: PrefilterKindFn,
- kind: PrefilterKind,
- rarest_byte: u8,
- rarest_offset: u8,
-}
-
-impl Prefilter {
- /// Return a "fallback" prefilter, but only if it is believed to be
- /// effective.
- #[inline]
- fn fallback<R: HeuristicFrequencyRank>(
- ranker: R,
- pair: Pair,
- needle: &[u8],
- ) -> Option<Prefilter> {
- /// The maximum frequency rank permitted for the fallback prefilter.
- /// If the rarest byte in the needle has a frequency rank above this
- /// value, then no prefilter is used if the fallback prefilter would
- /// otherwise be selected.
- const MAX_FALLBACK_RANK: u8 = 250;
-
- trace!("building fallback prefilter");
- let rarest_offset = pair.index1();
- let rarest_byte = needle[usize::from(rarest_offset)];
- let rarest_rank = ranker.rank(rarest_byte);
- if rarest_rank > MAX_FALLBACK_RANK {
- None
- } else {
- let finder = crate::arch::all::packedpair::Finder::with_pair(
- needle,
- pair.clone(),
- )?;
- let call = prefilter_kind_fallback;
- let kind = PrefilterKind { fallback: finder };
- Some(Prefilter { call, kind, rarest_byte, rarest_offset })
- }
- }
-
- /// Return a prefilter using a x86_64 SSE2 vector algorithm.
- #[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
- #[inline]
- fn sse2(finder: sse2::Finder, needle: &[u8]) -> Prefilter {
- trace!("building x86_64 SSE2 prefilter");
- let rarest_offset = finder.pair().index1();
- let rarest_byte = needle[usize::from(rarest_offset)];
- Prefilter {
- call: prefilter_kind_sse2,
- kind: PrefilterKind { sse2: finder },
- rarest_byte,
- rarest_offset,
- }
- }
-
- /// Return a prefilter using a x86_64 AVX2 vector algorithm.
- #[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
- #[inline]
- fn avx2(finder: avx2::Finder, needle: &[u8]) -> Prefilter {
- trace!("building x86_64 AVX2 prefilter");
- let rarest_offset = finder.pair().index1();
- let rarest_byte = needle[usize::from(rarest_offset)];
- Prefilter {
- call: prefilter_kind_avx2,
- kind: PrefilterKind { avx2: finder },
- rarest_byte,
- rarest_offset,
- }
- }
-
- /// Return a prefilter using a wasm32 simd128 vector algorithm.
- #[cfg(target_arch = "wasm32")]
- #[inline]
- fn simd128(finder: simd128::Finder, needle: &[u8]) -> Prefilter {
- trace!("building wasm32 simd128 prefilter");
- let rarest_offset = finder.pair().index1();
- let rarest_byte = needle[usize::from(rarest_offset)];
- Prefilter {
- call: prefilter_kind_simd128,
- kind: PrefilterKind { simd128: finder },
- rarest_byte,
- rarest_offset,
- }
- }
-
- /// Return a prefilter using a aarch64 neon vector algorithm.
- #[cfg(target_arch = "aarch64")]
- #[inline]
- fn neon(finder: neon::Finder, needle: &[u8]) -> Prefilter {
- trace!("building aarch64 neon prefilter");
- let rarest_offset = finder.pair().index1();
- let rarest_byte = needle[usize::from(rarest_offset)];
- Prefilter {
- call: prefilter_kind_neon,
- kind: PrefilterKind { neon: finder },
- rarest_byte,
- rarest_offset,
- }
- }
-
- /// Return a *candidate* position for a match.
- ///
- /// When this returns an offset, it implies that a match could begin at
- /// that offset, but it may not. That is, it is possible for a false
- /// positive to be returned.
- ///
- /// When `None` is returned, then it is guaranteed that there are no
- /// matches for the needle in the given haystack. That is, it is impossible
- /// for a false negative to be returned.
- ///
- /// The purpose of this routine is to look for candidate matching positions
- /// as quickly as possible before running a (likely) slower confirmation
- /// step.
- #[inline]
- fn find(&self, haystack: &[u8]) -> Option<usize> {
- // SAFETY: By construction, we've ensured that the function in
- // `self.call` is properly paired with the union used in `self.kind`.
- unsafe { (self.call)(self, haystack) }
- }
-
- /// A "simple" prefilter that just looks for the occurrence of the rarest
- /// byte from the needle. This is generally only used for very small
- /// haystacks.
- #[inline]
- fn find_simple(&self, haystack: &[u8]) -> Option<usize> {
- // We don't use crate::memchr here because the haystack should be small
- // enough that memchr won't be able to use vector routines anyway. So
- // we just skip straight to the fallback implementation which is likely
- // faster. (A byte-at-a-time loop is only used when the haystack is
- // smaller than `size_of::<usize>()`.)
- crate::arch::all::memchr::One::new(self.rarest_byte)
- .find(haystack)
- .map(|i| i.saturating_sub(usize::from(self.rarest_offset)))
- }
-}
-
-impl core::fmt::Debug for Prefilter {
- fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
- f.debug_struct("Prefilter")
- .field("call", &"<prefilter function>")
- .field("kind", &"<prefilter kind union>")
- .field("rarest_byte", &self.rarest_byte)
- .field("rarest_offset", &self.rarest_offset)
- .finish()
- }
-}
-
-/// A union indicating one of several possible prefilters that are in active
-/// use.
-///
-/// This union should only be read by one of the functions prefixed with
-/// `prefilter_kind_`. Namely, the correct function is meant to be paired with
-/// the union by the caller, such that the function always reads from the
-/// designated union field.
-#[derive(Clone, Copy)]
-union PrefilterKind {
- fallback: crate::arch::all::packedpair::Finder,
- #[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
- sse2: crate::arch::x86_64::sse2::packedpair::Finder,
- #[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
- avx2: crate::arch::x86_64::avx2::packedpair::Finder,
- #[cfg(target_arch = "wasm32")]
- simd128: crate::arch::wasm32::simd128::packedpair::Finder,
- #[cfg(target_arch = "aarch64")]
- neon: crate::arch::aarch64::neon::packedpair::Finder,
-}
-
-/// The type of a prefilter function.
-///
-/// # Safety
-///
-/// When using a function of this type, callers must ensure that the correct
-/// function is paired with the value populated in `PrefilterKind` union.
-type PrefilterKindFn =
- unsafe fn(strat: &Prefilter, haystack: &[u8]) -> Option<usize>;
-
-/// Reads from the `fallback` field of `PrefilterKind` to execute the fallback
-/// prefilter. Works on all platforms.
-///
-/// # Safety
-///
-/// Callers must ensure that the `strat.kind.fallback` union field is set.
-unsafe fn prefilter_kind_fallback(
- strat: &Prefilter,
- haystack: &[u8],
-) -> Option<usize> {
- strat.kind.fallback.find_prefilter(haystack)
-}
-
-/// Reads from the `sse2` field of `PrefilterKind` to execute the x86_64 SSE2
-/// prefilter.
-///
-/// # Safety
-///
-/// Callers must ensure that the `strat.kind.sse2` union field is set.
-#[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
-unsafe fn prefilter_kind_sse2(
- strat: &Prefilter,
- haystack: &[u8],
-) -> Option<usize> {
- let finder = &strat.kind.sse2;
- if haystack.len() < finder.min_haystack_len() {
- strat.find_simple(haystack)
- } else {
- finder.find_prefilter(haystack)
- }
-}
-
-/// Reads from the `avx2` field of `PrefilterKind` to execute the x86_64 AVX2
-/// prefilter.
-///
-/// # Safety
-///
-/// Callers must ensure that the `strat.kind.avx2` union field is set.
-#[cfg(all(target_arch = "x86_64", target_feature = "sse2"))]
-unsafe fn prefilter_kind_avx2(
- strat: &Prefilter,
- haystack: &[u8],
-) -> Option<usize> {
- let finder = &strat.kind.avx2;
- if haystack.len() < finder.min_haystack_len() {
- strat.find_simple(haystack)
- } else {
- finder.find_prefilter(haystack)
- }
-}
-
-/// Reads from the `simd128` field of `PrefilterKind` to execute the wasm32
-/// simd128 prefilter.
-///
-/// # Safety
-///
-/// Callers must ensure that the `strat.kind.simd128` union field is set.
-#[cfg(target_arch = "wasm32")]
-unsafe fn prefilter_kind_simd128(
- strat: &Prefilter,
- haystack: &[u8],
-) -> Option<usize> {
- let finder = &strat.kind.simd128;
- if haystack.len() < finder.min_haystack_len() {
- strat.find_simple(haystack)
- } else {
- finder.find_prefilter(haystack)
- }
-}
-
-/// Reads from the `neon` field of `PrefilterKind` to execute the aarch64 neon
-/// prefilter.
-///
-/// # Safety
-///
-/// Callers must ensure that the `strat.kind.neon` union field is set.
-#[cfg(target_arch = "aarch64")]
-unsafe fn prefilter_kind_neon(
- strat: &Prefilter,
- haystack: &[u8],
-) -> Option<usize> {
- let finder = &strat.kind.neon;
- if haystack.len() < finder.min_haystack_len() {
- strat.find_simple(haystack)
- } else {
- finder.find_prefilter(haystack)
- }
-}
-
-/// PrefilterState tracks state associated with the effectiveness of a
-/// prefilter. It is used to track how many bytes, on average, are skipped by
-/// the prefilter. If this average dips below a certain threshold over time,
-/// then the state renders the prefilter inert and stops using it.
-///
-/// A prefilter state should be created for each search. (Where creating an
-/// iterator is treated as a single search.) A prefilter state should only be
-/// created from a `Freqy`. e.g., An inert `Freqy` will produce an inert
-/// `PrefilterState`.
-#[derive(Clone, Copy, Debug)]
-pub(crate) struct PrefilterState {
- /// The number of skips that has been executed. This is always 1 greater
- /// than the actual number of skips. The special sentinel value of 0
- /// indicates that the prefilter is inert. This is useful to avoid
- /// additional checks to determine whether the prefilter is still
- /// "effective." Once a prefilter becomes inert, it should no longer be
- /// used (according to our heuristics).
- skips: u32,
- /// The total number of bytes that have been skipped.
- skipped: u32,
-}
-
-impl PrefilterState {
- /// The minimum number of skip attempts to try before considering whether
- /// a prefilter is effective or not.
- const MIN_SKIPS: u32 = 50;
-
- /// The minimum amount of bytes that skipping must average.
- ///
- /// This value was chosen based on varying it and checking
- /// the microbenchmarks. In particular, this can impact the
- /// pathological/repeated-{huge,small} benchmarks quite a bit if it's set
- /// too low.
- const MIN_SKIP_BYTES: u32 = 8;
-
- /// Create a fresh prefilter state.
- #[inline]
- pub(crate) fn new() -> PrefilterState {
- PrefilterState { skips: 1, skipped: 0 }
- }
-
- /// Update this state with the number of bytes skipped on the last
- /// invocation of the prefilter.
- #[inline]
- fn update(&mut self, skipped: usize) {
- self.skips = self.skips.saturating_add(1);
- // We need to do this dance since it's technically possible for
- // `skipped` to overflow a `u32`. (And we use a `u32` to reduce the
- // size of a prefilter state.)
- self.skipped = match u32::try_from(skipped) {
- Err(_) => core::u32::MAX,
- Ok(skipped) => self.skipped.saturating_add(skipped),
- };
- }
-
- /// Return true if and only if this state indicates that a prefilter is
- /// still effective.
- #[inline]
- fn is_effective(&mut self) -> bool {
- if self.is_inert() {
- return false;
- }
- if self.skips() < PrefilterState::MIN_SKIPS {
- return true;
- }
- if self.skipped >= PrefilterState::MIN_SKIP_BYTES * self.skips() {
- return true;
- }
-
- // We're inert.
- self.skips = 0;
- false
- }
-
- /// Returns true if the prefilter this state represents should no longer
- /// be used.
- #[inline]
- fn is_inert(&self) -> bool {
- self.skips == 0
- }
-
- /// Returns the total number of times the prefilter has been used.
- #[inline]
- fn skips(&self) -> u32 {
- // Remember, `0` is a sentinel value indicating inertness, so we
- // always need to subtract `1` to get our actual number of skips.
- self.skips.saturating_sub(1)
- }
-}
-
-/// A combination of prefilter effectiveness state and the prefilter itself.
-#[derive(Debug)]
-pub(crate) struct Pre<'a> {
- /// State that tracks the effectiveness of a prefilter.
- prestate: &'a mut PrefilterState,
- /// The actual prefilter.
- prestrat: &'a Prefilter,
-}
-
-impl<'a> Pre<'a> {
- /// Call this prefilter on the given haystack with the given needle.
- #[inline]
- pub(crate) fn find(&mut self, haystack: &[u8]) -> Option<usize> {
- let result = self.prestrat.find(haystack);
- self.prestate.update(result.unwrap_or(haystack.len()));
- result
- }
-
- /// Return true if and only if this prefilter should be used.
- #[inline]
- pub(crate) fn is_effective(&mut self) -> bool {
- self.prestate.is_effective()
- }
-}
-
-/// Returns true if the needle has the right characteristics for a vector
-/// algorithm to handle the entirety of substring search.
-///
-/// Vector algorithms can be used for prefilters for other substring search
-/// algorithms (like Two-Way), but they can also be used for substring search
-/// on their own. When used for substring search, vector algorithms will
-/// quickly identify candidate match positions (just like in the prefilter
-/// case), but instead of returning the candidate position they will try to
-/// confirm the match themselves. Confirmation happens via `memcmp`. This
-/// works well for short needles, but can break down when many false candidate
-/// positions are generated for large needles. Thus, we only permit vector
-/// algorithms to own substring search when the needle is of a certain length.
-#[inline]
-fn do_packed_search(needle: &[u8]) -> bool {
- /// The minimum length of a needle required for this algorithm. The minimum
- /// is 2 since a length of 1 should just use memchr and a length of 0 isn't
- /// a case handled by this searcher.
- const MIN_LEN: usize = 2;
-
- /// The maximum length of a needle required for this algorithm.
- ///
- /// In reality, there is no hard max here. The code below can handle any
- /// length needle. (Perhaps that suggests there are missing optimizations.)
- /// Instead, this is a heuristic and a bound guaranteeing our linear time
- /// complexity.
- ///
- /// It is a heuristic because when a candidate match is found, memcmp is
- /// run. For very large needles with lots of false positives, memcmp can
- /// make the code run quite slow.
- ///
- /// It is a bound because the worst case behavior with memcmp is
- /// multiplicative in the size of the needle and haystack, and we want
- /// to keep that additive. This bound ensures we still meet that bound
- /// theoretically, since it's just a constant. We aren't acting in bad
- /// faith here, memcmp on tiny needles is so fast that even in pathological
- /// cases (see pathological vector benchmarks), this is still just as fast
- /// or faster in practice.
- ///
- /// This specific number was chosen by tweaking a bit and running
- /// benchmarks. The rare-medium-needle, for example, gets about 5% faster
- /// by using this algorithm instead of a prefilter-accelerated Two-Way.
- /// There's also a theoretical desire to keep this number reasonably
- /// low, to mitigate the impact of pathological cases. I did try 64, and
- /// some benchmarks got a little better, and others (particularly the
- /// pathological ones), got a lot worse. So... 32 it is?
- const MAX_LEN: usize = 32;
- MIN_LEN <= needle.len() && needle.len() <= MAX_LEN
-}