| /*! |
| 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::aarch64::uint8x16_t; |
| |
| 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<uint8x16_t>); |
| |
| /// 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. |
| 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 neon 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 neon 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 sse2 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 neon vectors and routines. |
| /// |
| /// # Safety |
| /// |
| /// Same as the safety for `packedpair::Finder::new`, and callers must also |
| /// ensure that neon is available. |
| #[target_feature(enable = "neon")] |
| #[inline] |
| unsafe fn with_pair_impl(needle: &[u8], pair: Pair) -> Finder { |
| let finder = packedpair::Finder::<uint8x16_t>::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 = "neon")] |
| { |
| true |
| } |
| #[cfg(not(target_feature = "neon"))] |
| { |
| false |
| } |
| } |
| |
| /// Execute a search using neon 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> { |
| // SAFETY: Building a `Finder` means it's safe to call 'neon' routines. |
| unsafe { self.find_impl(haystack, needle) } |
| } |
| |
| /// Execute a search using neon vectors and routines. |
| /// |
| /// # Panics |
| /// |
| /// When `haystack.len()` is less than [`Finder::min_haystack_len`]. |
| #[inline] |
| pub fn find_prefilter(&self, haystack: &[u8]) -> Option<usize> { |
| // SAFETY: Building a `Finder` means it's safe to call 'neon' routines. |
| unsafe { self.find_prefilter_impl(haystack) } |
| } |
| |
| /// Execute a search using neon 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 `neon` routines.) |
| #[target_feature(enable = "neon")] |
| #[inline] |
| unsafe fn find_impl( |
| &self, |
| haystack: &[u8], |
| needle: &[u8], |
| ) -> Option<usize> { |
| self.0.find(haystack, needle) |
| } |
| |
| /// Execute a prefilter search using neon 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 `neon` routines.) |
| #[target_feature(enable = "neon")] |
| #[inline] |
| unsafe fn find_prefilter_impl(&self, haystack: &[u8]) -> Option<usize> { |
| 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() |
| } |
| } |
