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Diffstat (limited to 'vendor/memchr/src/arch/all/memchr.rs')
| -rw-r--r-- | vendor/memchr/src/arch/all/memchr.rs | 1015 |
1 files changed, 1015 insertions, 0 deletions
diff --git a/vendor/memchr/src/arch/all/memchr.rs b/vendor/memchr/src/arch/all/memchr.rs new file mode 100644 index 000000000..b211ad9ec --- /dev/null +++ b/vendor/memchr/src/arch/all/memchr.rs @@ -0,0 +1,1015 @@ +/*! +Provides architecture independent implementations of `memchr` and friends. + +The main types in this module are [`One`], [`Two`] and [`Three`]. They are for +searching for one, two or three distinct bytes, respectively, in a haystack. +Each type also has corresponding double ended iterators. These searchers +are typically slower than hand-coded vector routines accomplishing the same +task, but are also typically faster than naive scalar code. These routines +effectively work by treating a `usize` as a vector of 8-bit lanes, and thus +achieves some level of data parallelism even without explicit vector support. + +The `One` searcher also provides a [`One::count`] routine for efficiently +counting the number of times a single byte occurs in a haystack. This is +useful, for example, for counting the number of lines in a haystack. This +routine exists because it is usually faster, especially with a high match +count, then using [`One::find`] repeatedly. ([`OneIter`] specializes its +`Iterator::count` implementation to use this routine.) + +Only one, two and three bytes are supported because three bytes is about +the point where one sees diminishing returns. Beyond this point and it's +probably (but not necessarily) better to just use a simple `[bool; 256]` array +or similar. However, it depends mightily on the specific work-load and the +expected match frequency. +*/ + +use crate::{arch::generic::memchr as generic, ext::Pointer}; + +/// The number of bytes in a single `usize` value. +const USIZE_BYTES: usize = (usize::BITS / 8) as usize; +/// The bits that must be zero for a `*const usize` to be properly aligned. +const USIZE_ALIGN: usize = USIZE_BYTES - 1; + +/// Finds all occurrences of a single byte in a haystack. +#[derive(Clone, Copy, Debug)] +pub struct One { + s1: u8, + v1: usize, +} + +impl One { + /// The number of bytes we examine per each iteration of our search loop. + const LOOP_BYTES: usize = 2 * USIZE_BYTES; + + /// Create a new searcher that finds occurrences of the byte given. + #[inline] + pub fn new(needle: u8) -> One { + One { s1: needle, v1: splat(needle) } + } + + /// A test-only routine so that we can bundle a bunch of quickcheck + /// properties into a single macro. Basically, this provides a constructor + /// that makes it identical to most other memchr implementations, which + /// have fallible constructors. + #[cfg(test)] + pub(crate) fn try_new(needle: u8) -> Option<One> { + Some(One::new(needle)) + } + + /// Return the first occurrence of the needle in the given haystack. If no + /// such occurrence exists, then `None` is returned. + /// + /// The occurrence is reported as an offset into `haystack`. Its maximum + /// value for a non-empty haystack is `haystack.len() - 1`. + #[inline] + pub fn find(&self, haystack: &[u8]) -> Option<usize> { + // SAFETY: `find_raw` guarantees that if a pointer is returned, it + // falls within the bounds of the start and end pointers. + unsafe { + generic::search_slice_with_raw(haystack, |s, e| { + self.find_raw(s, e) + }) + } + } + + /// Return the last occurrence of the needle in the given haystack. If no + /// such occurrence exists, then `None` is returned. + /// + /// The occurrence is reported as an offset into `haystack`. Its maximum + /// value for a non-empty haystack is `haystack.len() - 1`. + #[inline] + pub fn rfind(&self, haystack: &[u8]) -> Option<usize> { + // SAFETY: `find_raw` guarantees that if a pointer is returned, it + // falls within the bounds of the start and end pointers. + unsafe { + generic::search_slice_with_raw(haystack, |s, e| { + self.rfind_raw(s, e) + }) + } + } + + /// Counts all occurrences of this byte in the given haystack. + #[inline] + pub fn count(&self, haystack: &[u8]) -> usize { + // SAFETY: All of our pointers are derived directly from a borrowed + // slice, which is guaranteed to be valid. + unsafe { + let start = haystack.as_ptr(); + let end = start.add(haystack.len()); + self.count_raw(start, end) + } + } + + /// Like `find`, but accepts and returns raw pointers. + /// + /// When a match is found, the pointer returned is guaranteed to be + /// `>= start` and `< end`. + /// + /// This routine is useful if you're already using raw pointers and would + /// like to avoid converting back to a slice before executing a search. + /// + /// # Safety + /// + /// * Both `start` and `end` must be valid for reads. + /// * Both `start` and `end` must point to an initialized value. + /// * Both `start` and `end` must point to the same allocated object and + /// must either be in bounds or at most one byte past the end of the + /// allocated object. + /// * Both `start` and `end` must be _derived from_ a pointer to the same + /// object. + /// * The distance between `start` and `end` must not overflow `isize`. + /// * The distance being in bounds must not rely on "wrapping around" the + /// address space. + /// + /// Note that callers may pass a pair of pointers such that `start >= end`. + /// In that case, `None` will always be returned. + #[inline] + pub unsafe fn find_raw( + &self, + start: *const u8, + end: *const u8, + ) -> Option<*const u8> { + if start >= end { + return None; + } + let confirm = |b| self.confirm(b); + let len = end.distance(start); + if len < USIZE_BYTES { + return generic::fwd_byte_by_byte(start, end, confirm); + } + + // The start of the search may not be aligned to `*const usize`, + // so we do an unaligned load here. + let chunk = start.cast::<usize>().read_unaligned(); + if self.has_needle(chunk) { + return generic::fwd_byte_by_byte(start, end, confirm); + } + + // And now we start our search at a guaranteed aligned position. + // The first iteration of the loop below will overlap with the the + // unaligned chunk above in cases where the search starts at an + // unaligned offset, but that's okay as we're only here if that + // above didn't find a match. + let mut cur = + start.add(USIZE_BYTES - (start.as_usize() & USIZE_ALIGN)); + debug_assert!(cur > start); + if len <= One::LOOP_BYTES { + return generic::fwd_byte_by_byte(cur, end, confirm); + } + debug_assert!(end.sub(One::LOOP_BYTES) >= start); + while cur <= end.sub(One::LOOP_BYTES) { + debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES); + + let a = cur.cast::<usize>().read(); + let b = cur.add(USIZE_BYTES).cast::<usize>().read(); + if self.has_needle(a) || self.has_needle(b) { + break; + } + cur = cur.add(One::LOOP_BYTES); + } + generic::fwd_byte_by_byte(cur, end, confirm) + } + + /// Like `rfind`, but accepts and returns raw pointers. + /// + /// When a match is found, the pointer returned is guaranteed to be + /// `>= start` and `< end`. + /// + /// This routine is useful if you're already using raw pointers and would + /// like to avoid converting back to a slice before executing a search. + /// + /// # Safety + /// + /// * Both `start` and `end` must be valid for reads. + /// * Both `start` and `end` must point to an initialized value. + /// * Both `start` and `end` must point to the same allocated object and + /// must either be in bounds or at most one byte past the end of the + /// allocated object. + /// * Both `start` and `end` must be _derived from_ a pointer to the same + /// object. + /// * The distance between `start` and `end` must not overflow `isize`. + /// * The distance being in bounds must not rely on "wrapping around" the + /// address space. + /// + /// Note that callers may pass a pair of pointers such that `start >= end`. + /// In that case, `None` will always be returned. + #[inline] + pub unsafe fn rfind_raw( + &self, + start: *const u8, + end: *const u8, + ) -> Option<*const u8> { + if start >= end { + return None; + } + let confirm = |b| self.confirm(b); + let len = end.distance(start); + if len < USIZE_BYTES { + return generic::rev_byte_by_byte(start, end, confirm); + } + + let chunk = end.sub(USIZE_BYTES).cast::<usize>().read_unaligned(); + if self.has_needle(chunk) { + return generic::rev_byte_by_byte(start, end, confirm); + } + + let mut cur = end.sub(end.as_usize() & USIZE_ALIGN); + debug_assert!(start <= cur && cur <= end); + if len <= One::LOOP_BYTES { + return generic::rev_byte_by_byte(start, cur, confirm); + } + while cur >= start.add(One::LOOP_BYTES) { + debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES); + + let a = cur.sub(2 * USIZE_BYTES).cast::<usize>().read(); + let b = cur.sub(1 * USIZE_BYTES).cast::<usize>().read(); + if self.has_needle(a) || self.has_needle(b) { + break; + } + cur = cur.sub(One::LOOP_BYTES); + } + generic::rev_byte_by_byte(start, cur, confirm) + } + + /// Counts all occurrences of this byte in the given haystack represented + /// by raw pointers. + /// + /// This routine is useful if you're already using raw pointers and would + /// like to avoid converting back to a slice before executing a search. + /// + /// # Safety + /// + /// * Both `start` and `end` must be valid for reads. + /// * Both `start` and `end` must point to an initialized value. + /// * Both `start` and `end` must point to the same allocated object and + /// must either be in bounds or at most one byte past the end of the + /// allocated object. + /// * Both `start` and `end` must be _derived from_ a pointer to the same + /// object. + /// * The distance between `start` and `end` must not overflow `isize`. + /// * The distance being in bounds must not rely on "wrapping around" the + /// address space. + /// + /// Note that callers may pass a pair of pointers such that `start >= end`. + /// In that case, `0` will always be returned. + #[inline] + pub unsafe fn count_raw(&self, start: *const u8, end: *const u8) -> usize { + if start >= end { + return 0; + } + let confirm = |b| self.confirm(b); + let len = end.distance(start); + if len < USIZE_BYTES { + return generic::count_byte_by_byte(start, end, confirm); + } + + // And now we start our search at a guaranteed aligned position. + let mut cur = + start.add(USIZE_BYTES - (start.as_usize() & USIZE_ALIGN)); + debug_assert!(cur > start); + // Count any bytes that start before the first aligned boundary. + let mut count = generic::count_byte_by_byte(start, cur, confirm); + if len <= One::LOOP_BYTES { + return count + generic::count_byte_by_byte(cur, end, confirm); + } + debug_assert!(end.sub(One::LOOP_BYTES) >= start); + while cur <= end.sub(One::LOOP_BYTES) { + debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES); + + let a = cur.cast::<usize>().read(); + let b = cur.add(USIZE_BYTES).cast::<usize>().read(); + count += self.count_bytes(a); + count += self.count_bytes(b); + cur = cur.add(One::LOOP_BYTES); + } + count += generic::count_byte_by_byte(cur, end, confirm); + count + } + + /// Returns an iterator over all occurrences of the needle byte in the + /// given haystack. + /// + /// The iterator returned implements `DoubleEndedIterator`. This means it + /// can also be used to find occurrences in reverse order. + pub fn iter<'a, 'h>(&'a self, haystack: &'h [u8]) -> OneIter<'a, 'h> { + OneIter { searcher: self, it: generic::Iter::new(haystack) } + } + + #[inline(always)] + fn has_needle(&self, chunk: usize) -> bool { + has_zero_byte(self.v1 ^ chunk) + } + + #[inline(always)] + fn count_bytes(&self, chunk: usize) -> usize { + count_bytes(self.v1 ^ chunk) + } + + #[inline(always)] + fn confirm(&self, haystack_byte: u8) -> bool { + self.s1 == haystack_byte + } +} + +/// An iterator over all occurrences of a single byte in a haystack. +/// +/// This iterator implements `DoubleEndedIterator`, which means it can also be +/// used to find occurrences in reverse order. +/// +/// This iterator is created by the [`One::iter`] method. +/// +/// The lifetime parameters are as follows: +/// +/// * `'a` refers to the lifetime of the underlying [`One`] searcher. +/// * `'h` refers to the lifetime of the haystack being searched. +#[derive(Clone, Debug)] +pub struct OneIter<'a, 'h> { + /// The underlying memchr searcher. + searcher: &'a One, + /// Generic iterator implementation. + it: generic::Iter<'h>, +} + +impl<'a, 'h> Iterator for OneIter<'a, 'h> { + type Item = usize; + + #[inline] + fn next(&mut self) -> Option<usize> { + // SAFETY: We rely on the generic iterator to provide valid start + // and end pointers, but we guarantee that any pointer returned by + // 'find_raw' falls within the bounds of the start and end pointer. + unsafe { self.it.next(|s, e| self.searcher.find_raw(s, e)) } + } + + #[inline] + fn count(self) -> usize { + self.it.count(|s, e| { + // SAFETY: We rely on our generic iterator to return valid start + // and end pointers. + unsafe { self.searcher.count_raw(s, e) } + }) + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.it.size_hint() + } +} + +impl<'a, 'h> DoubleEndedIterator for OneIter<'a, 'h> { + #[inline] + fn next_back(&mut self) -> Option<usize> { + // SAFETY: We rely on the generic iterator to provide valid start + // and end pointers, but we guarantee that any pointer returned by + // 'rfind_raw' falls within the bounds of the start and end pointer. + unsafe { self.it.next_back(|s, e| self.searcher.rfind_raw(s, e)) } + } +} + +/// Finds all occurrences of two bytes in a haystack. +/// +/// That is, this reports matches of one of two possible bytes. For example, +/// searching for `a` or `b` in `afoobar` would report matches at offsets `0`, +/// `4` and `5`. +#[derive(Clone, Copy, Debug)] +pub struct Two { + s1: u8, + s2: u8, + v1: usize, + v2: usize, +} + +impl Two { + /// Create a new searcher that finds occurrences of the two needle bytes + /// given. + #[inline] + pub fn new(needle1: u8, needle2: u8) -> Two { + Two { + s1: needle1, + s2: needle2, + v1: splat(needle1), + v2: splat(needle2), + } + } + + /// A test-only routine so that we can bundle a bunch of quickcheck + /// properties into a single macro. Basically, this provides a constructor + /// that makes it identical to most other memchr implementations, which + /// have fallible constructors. + #[cfg(test)] + pub(crate) fn try_new(needle1: u8, needle2: u8) -> Option<Two> { + Some(Two::new(needle1, needle2)) + } + + /// Return the first occurrence of one of the needle bytes in the given + /// haystack. If no such occurrence exists, then `None` is returned. + /// + /// The occurrence is reported as an offset into `haystack`. Its maximum + /// value for a non-empty haystack is `haystack.len() - 1`. + #[inline] + pub fn find(&self, haystack: &[u8]) -> Option<usize> { + // SAFETY: `find_raw` guarantees that if a pointer is returned, it + // falls within the bounds of the start and end pointers. + unsafe { + generic::search_slice_with_raw(haystack, |s, e| { + self.find_raw(s, e) + }) + } + } + + /// Return the last occurrence of one of the needle bytes in the given + /// haystack. If no such occurrence exists, then `None` is returned. + /// + /// The occurrence is reported as an offset into `haystack`. Its maximum + /// value for a non-empty haystack is `haystack.len() - 1`. + #[inline] + pub fn rfind(&self, haystack: &[u8]) -> Option<usize> { + // SAFETY: `find_raw` guarantees that if a pointer is returned, it + // falls within the bounds of the start and end pointers. + unsafe { + generic::search_slice_with_raw(haystack, |s, e| { + self.rfind_raw(s, e) + }) + } + } + + /// Like `find`, but accepts and returns raw pointers. + /// + /// When a match is found, the pointer returned is guaranteed to be + /// `>= start` and `< end`. + /// + /// This routine is useful if you're already using raw pointers and would + /// like to avoid converting back to a slice before executing a search. + /// + /// # Safety + /// + /// * Both `start` and `end` must be valid for reads. + /// * Both `start` and `end` must point to an initialized value. + /// * Both `start` and `end` must point to the same allocated object and + /// must either be in bounds or at most one byte past the end of the + /// allocated object. + /// * Both `start` and `end` must be _derived from_ a pointer to the same + /// object. + /// * The distance between `start` and `end` must not overflow `isize`. + /// * The distance being in bounds must not rely on "wrapping around" the + /// address space. + /// + /// Note that callers may pass a pair of pointers such that `start >= end`. + /// In that case, `None` will always be returned. + #[inline] + pub unsafe fn find_raw( + &self, + start: *const u8, + end: *const u8, + ) -> Option<*const u8> { + if start >= end { + return None; + } + let confirm = |b| self.confirm(b); + let len = end.distance(start); + if len < USIZE_BYTES { + return generic::fwd_byte_by_byte(start, end, confirm); + } + + // The start of the search may not be aligned to `*const usize`, + // so we do an unaligned load here. + let chunk = start.cast::<usize>().read_unaligned(); + if self.has_needle(chunk) { + return generic::fwd_byte_by_byte(start, end, confirm); + } + + // And now we start our search at a guaranteed aligned position. + // The first iteration of the loop below will overlap with the the + // unaligned chunk above in cases where the search starts at an + // unaligned offset, but that's okay as we're only here if that + // above didn't find a match. + let mut cur = + start.add(USIZE_BYTES - (start.as_usize() & USIZE_ALIGN)); + debug_assert!(cur > start); + debug_assert!(end.sub(USIZE_BYTES) >= start); + while cur <= end.sub(USIZE_BYTES) { + debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES); + + let chunk = cur.cast::<usize>().read(); + if self.has_needle(chunk) { + break; + } + cur = cur.add(USIZE_BYTES); + } + generic::fwd_byte_by_byte(cur, end, confirm) + } + + /// Like `rfind`, but accepts and returns raw pointers. + /// + /// When a match is found, the pointer returned is guaranteed to be + /// `>= start` and `< end`. + /// + /// This routine is useful if you're already using raw pointers and would + /// like to avoid converting back to a slice before executing a search. + /// + /// # Safety + /// + /// * Both `start` and `end` must be valid for reads. + /// * Both `start` and `end` must point to an initialized value. + /// * Both `start` and `end` must point to the same allocated object and + /// must either be in bounds or at most one byte past the end of the + /// allocated object. + /// * Both `start` and `end` must be _derived from_ a pointer to the same + /// object. + /// * The distance between `start` and `end` must not overflow `isize`. + /// * The distance being in bounds must not rely on "wrapping around" the + /// address space. + /// + /// Note that callers may pass a pair of pointers such that `start >= end`. + /// In that case, `None` will always be returned. + #[inline] + pub unsafe fn rfind_raw( + &self, + start: *const u8, + end: *const u8, + ) -> Option<*const u8> { + if start >= end { + return None; + } + let confirm = |b| self.confirm(b); + let len = end.distance(start); + if len < USIZE_BYTES { + return generic::rev_byte_by_byte(start, end, confirm); + } + + let chunk = end.sub(USIZE_BYTES).cast::<usize>().read_unaligned(); + if self.has_needle(chunk) { + return generic::rev_byte_by_byte(start, end, confirm); + } + + let mut cur = end.sub(end.as_usize() & USIZE_ALIGN); + debug_assert!(start <= cur && cur <= end); + while cur >= start.add(USIZE_BYTES) { + debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES); + + let chunk = cur.sub(USIZE_BYTES).cast::<usize>().read(); + if self.has_needle(chunk) { + break; + } + cur = cur.sub(USIZE_BYTES); + } + generic::rev_byte_by_byte(start, cur, confirm) + } + + /// Returns an iterator over all occurrences of one of the needle bytes in + /// the given haystack. + /// + /// The iterator returned implements `DoubleEndedIterator`. This means it + /// can also be used to find occurrences in reverse order. + pub fn iter<'a, 'h>(&'a self, haystack: &'h [u8]) -> TwoIter<'a, 'h> { + TwoIter { searcher: self, it: generic::Iter::new(haystack) } + } + + #[inline(always)] + fn has_needle(&self, chunk: usize) -> bool { + has_zero_byte(self.v1 ^ chunk) || has_zero_byte(self.v2 ^ chunk) + } + + #[inline(always)] + fn confirm(&self, haystack_byte: u8) -> bool { + self.s1 == haystack_byte || self.s2 == haystack_byte + } +} + +/// An iterator over all occurrences of two possible bytes in a haystack. +/// +/// This iterator implements `DoubleEndedIterator`, which means it can also be +/// used to find occurrences in reverse order. +/// +/// This iterator is created by the [`Two::iter`] method. +/// +/// The lifetime parameters are as follows: +/// +/// * `'a` refers to the lifetime of the underlying [`Two`] searcher. +/// * `'h` refers to the lifetime of the haystack being searched. +#[derive(Clone, Debug)] +pub struct TwoIter<'a, 'h> { + /// The underlying memchr searcher. + searcher: &'a Two, + /// Generic iterator implementation. + it: generic::Iter<'h>, +} + +impl<'a, 'h> Iterator for TwoIter<'a, 'h> { + type Item = usize; + + #[inline] + fn next(&mut self) -> Option<usize> { + // SAFETY: We rely on the generic iterator to provide valid start + // and end pointers, but we guarantee that any pointer returned by + // 'find_raw' falls within the bounds of the start and end pointer. + unsafe { self.it.next(|s, e| self.searcher.find_raw(s, e)) } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.it.size_hint() + } +} + +impl<'a, 'h> DoubleEndedIterator for TwoIter<'a, 'h> { + #[inline] + fn next_back(&mut self) -> Option<usize> { + // SAFETY: We rely on the generic iterator to provide valid start + // and end pointers, but we guarantee that any pointer returned by + // 'rfind_raw' falls within the bounds of the start and end pointer. + unsafe { self.it.next_back(|s, e| self.searcher.rfind_raw(s, e)) } + } +} + +/// Finds all occurrences of three bytes in a haystack. +/// +/// That is, this reports matches of one of three possible bytes. For example, +/// searching for `a`, `b` or `o` in `afoobar` would report matches at offsets +/// `0`, `2`, `3`, `4` and `5`. +#[derive(Clone, Copy, Debug)] +pub struct Three { + s1: u8, + s2: u8, + s3: u8, + v1: usize, + v2: usize, + v3: usize, +} + +impl Three { + /// Create a new searcher that finds occurrences of the three needle bytes + /// given. + #[inline] + pub fn new(needle1: u8, needle2: u8, needle3: u8) -> Three { + Three { + s1: needle1, + s2: needle2, + s3: needle3, + v1: splat(needle1), + v2: splat(needle2), + v3: splat(needle3), + } + } + + /// A test-only routine so that we can bundle a bunch of quickcheck + /// properties into a single macro. Basically, this provides a constructor + /// that makes it identical to most other memchr implementations, which + /// have fallible constructors. + #[cfg(test)] + pub(crate) fn try_new( + needle1: u8, + needle2: u8, + needle3: u8, + ) -> Option<Three> { + Some(Three::new(needle1, needle2, needle3)) + } + + /// Return the first occurrence of one of the needle bytes in the given + /// haystack. If no such occurrence exists, then `None` is returned. + /// + /// The occurrence is reported as an offset into `haystack`. Its maximum + /// value for a non-empty haystack is `haystack.len() - 1`. + #[inline] + pub fn find(&self, haystack: &[u8]) -> Option<usize> { + // SAFETY: `find_raw` guarantees that if a pointer is returned, it + // falls within the bounds of the start and end pointers. + unsafe { + generic::search_slice_with_raw(haystack, |s, e| { + self.find_raw(s, e) + }) + } + } + + /// Return the last occurrence of one of the needle bytes in the given + /// haystack. If no such occurrence exists, then `None` is returned. + /// + /// The occurrence is reported as an offset into `haystack`. Its maximum + /// value for a non-empty haystack is `haystack.len() - 1`. + #[inline] + pub fn rfind(&self, haystack: &[u8]) -> Option<usize> { + // SAFETY: `find_raw` guarantees that if a pointer is returned, it + // falls within the bounds of the start and end pointers. + unsafe { + generic::search_slice_with_raw(haystack, |s, e| { + self.rfind_raw(s, e) + }) + } + } + + /// Like `find`, but accepts and returns raw pointers. + /// + /// When a match is found, the pointer returned is guaranteed to be + /// `>= start` and `< end`. + /// + /// This routine is useful if you're already using raw pointers and would + /// like to avoid converting back to a slice before executing a search. + /// + /// # Safety + /// + /// * Both `start` and `end` must be valid for reads. + /// * Both `start` and `end` must point to an initialized value. + /// * Both `start` and `end` must point to the same allocated object and + /// must either be in bounds or at most one byte past the end of the + /// allocated object. + /// * Both `start` and `end` must be _derived from_ a pointer to the same + /// object. + /// * The distance between `start` and `end` must not overflow `isize`. + /// * The distance being in bounds must not rely on "wrapping around" the + /// address space. + /// + /// Note that callers may pass a pair of pointers such that `start >= end`. + /// In that case, `None` will always be returned. + #[inline] + pub unsafe fn find_raw( + &self, + start: *const u8, + end: *const u8, + ) -> Option<*const u8> { + if start >= end { + return None; + } + let confirm = |b| self.confirm(b); + let len = end.distance(start); + if len < USIZE_BYTES { + return generic::fwd_byte_by_byte(start, end, confirm); + } + + // The start of the search may not be aligned to `*const usize`, + // so we do an unaligned load here. + let chunk = start.cast::<usize>().read_unaligned(); + if self.has_needle(chunk) { + return generic::fwd_byte_by_byte(start, end, confirm); + } + + // And now we start our search at a guaranteed aligned position. + // The first iteration of the loop below will overlap with the the + // unaligned chunk above in cases where the search starts at an + // unaligned offset, but that's okay as we're only here if that + // above didn't find a match. + let mut cur = + start.add(USIZE_BYTES - (start.as_usize() & USIZE_ALIGN)); + debug_assert!(cur > start); + debug_assert!(end.sub(USIZE_BYTES) >= start); + while cur <= end.sub(USIZE_BYTES) { + debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES); + + let chunk = cur.cast::<usize>().read(); + if self.has_needle(chunk) { + break; + } + cur = cur.add(USIZE_BYTES); + } + generic::fwd_byte_by_byte(cur, end, confirm) + } + + /// Like `rfind`, but accepts and returns raw pointers. + /// + /// When a match is found, the pointer returned is guaranteed to be + /// `>= start` and `< end`. + /// + /// This routine is useful if you're already using raw pointers and would + /// like to avoid converting back to a slice before executing a search. + /// + /// # Safety + /// + /// * Both `start` and `end` must be valid for reads. + /// * Both `start` and `end` must point to an initialized value. + /// * Both `start` and `end` must point to the same allocated object and + /// must either be in bounds or at most one byte past the end of the + /// allocated object. + /// * Both `start` and `end` must be _derived from_ a pointer to the same + /// object. + /// * The distance between `start` and `end` must not overflow `isize`. + /// * The distance being in bounds must not rely on "wrapping around" the + /// address space. + /// + /// Note that callers may pass a pair of pointers such that `start >= end`. + /// In that case, `None` will always be returned. + #[inline] + pub unsafe fn rfind_raw( + &self, + start: *const u8, + end: *const u8, + ) -> Option<*const u8> { + if start >= end { + return None; + } + let confirm = |b| self.confirm(b); + let len = end.distance(start); + if len < USIZE_BYTES { + return generic::rev_byte_by_byte(start, end, confirm); + } + + let chunk = end.sub(USIZE_BYTES).cast::<usize>().read_unaligned(); + if self.has_needle(chunk) { + return generic::rev_byte_by_byte(start, end, confirm); + } + + let mut cur = end.sub(end.as_usize() & USIZE_ALIGN); + debug_assert!(start <= cur && cur <= end); + while cur >= start.add(USIZE_BYTES) { + debug_assert_eq!(0, cur.as_usize() % USIZE_BYTES); + + let chunk = cur.sub(USIZE_BYTES).cast::<usize>().read(); + if self.has_needle(chunk) { + break; + } + cur = cur.sub(USIZE_BYTES); + } + generic::rev_byte_by_byte(start, cur, confirm) + } + + /// Returns an iterator over all occurrences of one of the needle bytes in + /// the given haystack. + /// + /// The iterator returned implements `DoubleEndedIterator`. This means it + /// can also be used to find occurrences in reverse order. + pub fn iter<'a, 'h>(&'a self, haystack: &'h [u8]) -> ThreeIter<'a, 'h> { + ThreeIter { searcher: self, it: generic::Iter::new(haystack) } + } + + #[inline(always)] + fn has_needle(&self, chunk: usize) -> bool { + has_zero_byte(self.v1 ^ chunk) + || has_zero_byte(self.v2 ^ chunk) + || has_zero_byte(self.v3 ^ chunk) + } + + #[inline(always)] + fn confirm(&self, haystack_byte: u8) -> bool { + self.s1 == haystack_byte + || self.s2 == haystack_byte + || self.s3 == haystack_byte + } +} + +/// An iterator over all occurrences of three possible bytes in a haystack. +/// +/// This iterator implements `DoubleEndedIterator`, which means it can also be +/// used to find occurrences in reverse order. +/// +/// This iterator is created by the [`Three::iter`] method. +/// +/// The lifetime parameters are as follows: +/// +/// * `'a` refers to the lifetime of the underlying [`Three`] searcher. +/// * `'h` refers to the lifetime of the haystack being searched. +#[derive(Clone, Debug)] +pub struct ThreeIter<'a, 'h> { + /// The underlying memchr searcher. + searcher: &'a Three, + /// Generic iterator implementation. + it: generic::Iter<'h>, +} + +impl<'a, 'h> Iterator for ThreeIter<'a, 'h> { + type Item = usize; + + #[inline] + fn next(&mut self) -> Option<usize> { + // SAFETY: We rely on the generic iterator to provide valid start + // and end pointers, but we guarantee that any pointer returned by + // 'find_raw' falls within the bounds of the start and end pointer. + unsafe { self.it.next(|s, e| self.searcher.find_raw(s, e)) } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.it.size_hint() + } +} + +impl<'a, 'h> DoubleEndedIterator for ThreeIter<'a, 'h> { + #[inline] + fn next_back(&mut self) -> Option<usize> { + // SAFETY: We rely on the generic iterator to provide valid start + // and end pointers, but we guarantee that any pointer returned by + // 'rfind_raw' falls within the bounds of the start and end pointer. + unsafe { self.it.next_back(|s, e| self.searcher.rfind_raw(s, e)) } + } +} + +/// Return `true` if `x` contains any zero byte. +/// +/// That is, this routine treats `x` as a register of 8-bit lanes and returns +/// true when any of those lanes is `0`. +/// +/// From "Matters Computational" by J. Arndt. +#[inline(always)] +fn has_zero_byte(x: usize) -> bool { + // "The idea is to subtract one from each of the bytes and then look for + // bytes where the borrow propagated all the way to the most significant + // bit." + const LO: usize = splat(0x01); + const HI: usize = splat(0x80); + + (x.wrapping_sub(LO) & !x & HI) != 0 +} + +#[inline(always)] +fn count_bytes(chunk: usize) -> usize { + const LO: usize = splat(0x01); + const HI: usize = splat(0x80); + + (chunk.wrapping_sub(LO) & !chunk & HI).count_ones() as usize +} + +/// Repeat the given byte into a word size number. That is, every 8 bits +/// is equivalent to the given byte. For example, if `b` is `\x4E` or +/// `01001110` in binary, then the returned value on a 32-bit system would be: +/// `01001110_01001110_01001110_01001110`. +#[inline(always)] +const fn splat(b: u8) -> usize { + // TODO: use `usize::from` once it can be used in const context. + (b as usize) * (usize::MAX / 255) +} + +#[cfg(test)] +mod tests { + use super::*; + + define_memchr_quickcheck!(super, try_new); + + #[test] + fn forward_one() { + crate::tests::memchr::Runner::new(1).forward_iter( + |haystack, needles| { + Some(One::new(needles[0]).iter(haystack).collect()) + }, + ) + } + + #[test] + fn reverse_one() { + crate::tests::memchr::Runner::new(1).reverse_iter( + |haystack, needles| { + Some(One::new(needles[0]).iter(haystack).rev().collect()) + }, + ) + } + + #[test] + fn count_one() { + crate::tests::memchr::Runner::new(1).count_iter(|haystack, needles| { + Some(One::new(needles[0]).iter(haystack).count()) + }) + } + + #[test] + fn forward_two() { + crate::tests::memchr::Runner::new(2).forward_iter( + |haystack, needles| { + let n1 = needles.get(0).copied()?; + let n2 = needles.get(1).copied()?; + Some(Two::new(n1, n2).iter(haystack).collect()) + }, + ) + } + + #[test] + fn reverse_two() { + crate::tests::memchr::Runner::new(2).reverse_iter( + |haystack, needles| { + let n1 = needles.get(0).copied()?; + let n2 = needles.get(1).copied()?; + Some(Two::new(n1, n2).iter(haystack).rev().collect()) + }, + ) + } + + #[test] + fn forward_three() { + crate::tests::memchr::Runner::new(3).forward_iter( + |haystack, needles| { + let n1 = needles.get(0).copied()?; + let n2 = needles.get(1).copied()?; + let n3 = needles.get(2).copied()?; + Some(Three::new(n1, n2, n3).iter(haystack).collect()) + }, + ) + } + + #[test] + fn reverse_three() { + crate::tests::memchr::Runner::new(3).reverse_iter( + |haystack, needles| { + let n1 = needles.get(0).copied()?; + let n2 = needles.get(1).copied()?; + let n3 = needles.get(2).copied()?; + Some(Three::new(n1, n2, n3).iter(haystack).rev().collect()) + }, + ) + } + + // This was found by quickcheck in the course of refactoring this crate + // after memchr 2.5.0. + #[test] + fn regression_double_ended_iterator() { + let finder = One::new(b'a'); + let haystack = "a"; + let mut it = finder.iter(haystack.as_bytes()); + assert_eq!(Some(0), it.next()); + assert_eq!(None, it.next_back()); + } +} |