/*!Generic crate-internal routines for the `memchr` family of functions.*/// What follows is a vector algorithm generic over the specific vector// type to detect the position of one, two or three needles in a haystack.// From what I know, this is a "classic" algorithm, although I don't// believe it has been published in any peer reviewed journal. I believe// it can be found in places like glibc and Go's standard library. It// appears to be well known and is elaborated on in more detail here:// https://gms.tf/stdfind-and-memchr-optimizations.html//// While the routine below is fairly long and perhaps intimidating, the basic// idea is actually very simple and can be expressed straight-forwardly in// pseudo code. The pseudo code below is written for 128 bit vectors, but the// actual code below works for anything that implements the Vector trait.////     needle = (n1 << 15) | (n1 << 14) | ... | (n1 << 1) | n1//     // Note: shift amount is in bytes////     while i <= haystack.len() - 16://       // A 16 byte vector. Each byte in chunk corresponds to a byte in//       // the haystack.//       chunk = haystack[i:i+16]//       // Compare bytes in needle with bytes in chunk. The result is a 16//       // byte chunk where each byte is 0xFF if the corresponding bytes//       // in needle and chunk were equal, or 0x00 otherwise.//       eqs = cmpeq(needle, chunk)//       // Return a 32 bit integer where the most significant 16 bits//       // are always 0 and the lower 16 bits correspond to whether the//       // most significant bit in the correspond byte in `eqs` is set.//       // In other words, `mask as u16` has bit i set if and only if//       // needle[i] == chunk[i].//       mask = movemask(eqs)////       // Mask is 0 if there is no match, and non-zero otherwise.//       if mask != 0://         // trailing_zeros tells us the position of the least significant//         // bit that is set.//         return i + trailing_zeros(mask)////     // haystack length may not be a multiple of 16, so search the rest.//     while i < haystack.len()://       if haystack[i] == n1://         return i////     // No match found.//     return NULL//// In fact, we could loosely translate the above code to Rust line-for-line// and it would be a pretty fast algorithm. But, we pull out all the stops// to go as fast as possible://// 1. We use aligned loads. That is, we do some finagling to make sure our//    primary loop not only proceeds in increments of 16 bytes, but that//    the address of haystack's pointer that we dereference is aligned to//    16 bytes. 16 is a magic number here because it is the size of SSE2//    128-bit vector. (For the AVX2 algorithm, 32 is the magic number.)//    Therefore, to get aligned loads, our pointer's address must be evenly//    divisible by 16.// 2. Our primary loop proceeds 64 bytes at a time instead of 16. It's//    kind of like loop unrolling, but we combine the equality comparisons//    using a vector OR such that we only need to extract a single mask to//    determine whether a match exists or not. If so, then we do some//    book-keeping to determine the precise location but otherwise mush on.// 3. We use our "chunk" comparison routine in as many places as possible,//    even if it means using unaligned loads. In particular, if haystack//    starts with an unaligned address, then we do an unaligned load to//    search the first 16 bytes. We then start our primary loop at the//    smallest subsequent aligned address, which will actually overlap with//    previously searched bytes. But we're OK with that. We do a similar//    dance at the end of our primary loop. Finally, to avoid a//    byte-at-a-time loop at the end, we do a final 16 byte unaligned load//    that may overlap with a previous load. This is OK because it converts//    a loop into a small number of very fast vector instructions. The overlap//    is OK because we know the place where the overlap occurs does not//    contain a match.//// And that's pretty all there is to it. Note that since the below is// generic and since it's meant to be inlined into routines with a// `#[target_feature(enable = "...")]` annotation, we must mark all routines as// both unsafe and `#[inline(always)]`.//// The fact that the code below is generic does somewhat inhibit us. For// example, I've noticed that introducing an unlineable `#[cold]` function to// handle the match case in the loop generates tighter assembly, but there is// no way to do this in the generic code below because the generic code doesn't// know what `target_feature` annotation to apply to the unlineable function.// We could make such functions part of the `Vector` trait, but we instead live// with the slightly sub-optimal codegen for now since it doesn't seem to have// a noticeable perf difference.use crate::{    ext::Pointer,    vector::{MoveMask, Vector},};/// Finds all occurrences of a single byte in a haystack.#[derive(Clone, Copy, Debug)]pub(crate) struct One<V> {    s1: u8,    v1: V,}impl<V: Vector> One<V> {    /// The number of bytes we examine per each iteration of our search loop.    const LOOP_SIZE: usize = 4 * V::BYTES;    /// Create a new searcher that finds occurrences of the byte given.    #[inline(always)]    pub(crate) unsafe fn new(needle: u8) -> One<V> {        One { s1: needle, v1: V::splat(needle) }    }    /// Returns the needle given to `One::new`.    #[inline(always)]    pub(crate) fn needle1(&self) -> u8 {        self.s1    }    /// Return a pointer to the first occurrence of the needle in the given    /// haystack. If no such occurrence exists, then `None` is returned.    ///    /// When a match is found, the pointer returned is guaranteed to be    /// `>= start` and `< end`.    ///    /// # Safety    ///    /// * It must be the case that `start < end` and that the distance between    /// them is at least equal to `V::BYTES`. That is, it must always be valid    /// to do at least an unaligned load of `V` at `start`.    /// * 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.    #[inline(always)]    pub(crate) unsafe fn find_raw(        &self,        start: *const u8,        end: *const u8,    ) -> Option<*const u8> {        // If we want to support vectors bigger than 256 bits, we probably        // need to move up to using a u64 for the masks used below. Currently        // they are 32 bits, which means we're SOL for vectors that need masks        // bigger than 32 bits. Overall unclear until there's a use case.        debug_assert!(V::BYTES <= 32, "vector cannot be bigger than 32 bytes");        let topos = V::Mask::first_offset;        let len = end.distance(start);        debug_assert!(            len >= V::BYTES,            "haystack has length {}, but must be at least {}",            len,            V::BYTES        );        // Search a possibly unaligned chunk at `start`. This covers any part        // of the haystack prior to where aligned loads can start.        if let Some(cur) = self.search_chunk(start, topos) {            return Some(cur);        }        // Set `cur` to the first V-aligned pointer greater than `start`.        let mut cur = start.add(V::BYTES - (start.as_usize() & V::ALIGN));        debug_assert!(cur > start && end.sub(V::BYTES) >= start);        if len >= Self::LOOP_SIZE {            while cur <= end.sub(Self::LOOP_SIZE) {                debug_assert_eq!(0, cur.as_usize() % V::BYTES);                let a = V::load_aligned(cur);                let b = V::load_aligned(cur.add(1 * V::BYTES));                let c = V::load_aligned(cur.add(2 * V::BYTES));                let d = V::load_aligned(cur.add(3 * V::BYTES));                let eqa = self.v1.cmpeq(a);                let eqb = self.v1.cmpeq(b);                let eqc = self.v1.cmpeq(c);                let eqd = self.v1.cmpeq(d);                let or1 = eqa.or(eqb);                let or2 = eqc.or(eqd);                let or3 = or1.or(or2);                if or3.movemask_will_have_non_zero() {                    let mask = eqa.movemask();                    if mask.has_non_zero() {                        return Some(cur.add(topos(mask)));                    }                    let mask = eqb.movemask();                    if mask.has_non_zero() {                        return Some(cur.add(1 * V::BYTES).add(topos(mask)));                    }                    let mask = eqc.movemask();                    if mask.has_non_zero() {                        return Some(cur.add(2 * V::BYTES).add(topos(mask)));                    }                    let mask = eqd.movemask();                    debug_assert!(mask.has_non_zero());                    return Some(cur.add(3 * V::BYTES).add(topos(mask)));                }                cur = cur.add(Self::LOOP_SIZE);            }        }        // Handle any leftovers after the aligned loop above. We use unaligned        // loads here, but I believe we are guaranteed that they are aligned        // since `cur` is aligned.        while cur <= end.sub(V::BYTES) {            debug_assert!(end.distance(cur) >= V::BYTES);            if let Some(cur) = self.search_chunk(cur, topos) {                return Some(cur);            }            cur = cur.add(V::BYTES);        }        // Finally handle any remaining bytes less than the size of V. In this        // case, our pointer may indeed be unaligned and the load may overlap        // with the previous one. But that's okay since we know the previous        // load didn't lead to a match (otherwise we wouldn't be here).        if cur < end {            debug_assert!(end.distance(cur) < V::BYTES);            cur = cur.sub(V::BYTES - end.distance(cur));            debug_assert_eq!(end.distance(cur), V::BYTES);            return self.search_chunk(cur, topos);        }        None    }    /// Return a pointer to the last occurrence of the needle in the given    /// haystack. If no such occurrence exists, then `None` is returned.    ///    /// When a match is found, the pointer returned is guaranteed to be    /// `>= start` and `< end`.    ///    /// # Safety    ///    /// * It must be the case that `start < end` and that the distance between    /// them is at least equal to `V::BYTES`. That is, it must always be valid    /// to do at least an unaligned load of `V` at `start`.    /// * 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.    #[inline(always)]    pub(crate) unsafe fn rfind_raw(        &self,        start: *const u8,        end: *const u8,    ) -> Option<*const u8> {        // If we want to support vectors bigger than 256 bits, we probably        // need to move up to using a u64 for the masks used below. Currently        // they are 32 bits, which means we're SOL for vectors that need masks        // bigger than 32 bits. Overall unclear until there's a use case.        debug_assert!(V::BYTES <= 32, "vector cannot be bigger than 32 bytes");        let topos = V::Mask::last_offset;        let len = end.distance(start);        debug_assert!(            len >= V::BYTES,            "haystack has length {}, but must be at least {}",            len,            V::BYTES        );        if let Some(cur) = self.search_chunk(end.sub(V::BYTES), topos) {            return Some(cur);        }        let mut cur = end.sub(end.as_usize() & V::ALIGN);        debug_assert!(start <= cur && cur <= end);        if len >= Self::LOOP_SIZE {            while cur >= start.add(Self::LOOP_SIZE) {                debug_assert_eq!(0, cur.as_usize() % V::BYTES);                cur = cur.sub(Self::LOOP_SIZE);                let a = V::load_aligned(cur);                let b = V::load_aligned(cur.add(1 * V::BYTES));                let c = V::load_aligned(cur.add(2 * V::BYTES));                let d = V::load_aligned(cur.add(3 * V::BYTES));                let eqa = self.v1.cmpeq(a);                let eqb = self.v1.cmpeq(b);                let eqc = self.v1.cmpeq(c);                let eqd = self.v1.cmpeq(d);                let or1 = eqa.or(eqb);                let or2 = eqc.or(eqd);                let or3 = or1.or(or2);                if or3.movemask_will_have_non_zero() {                    let mask = eqd.movemask();                    if mask.has_non_zero() {                        return Some(cur.add(3 * V::BYTES).add(topos(mask)));                    }                    let mask = eqc.movemask();                    if mask.has_non_zero() {                        return Some(cur.add(2 * V::BYTES).add(topos(mask)));                    }                    let mask = eqb.movemask();                    if mask.has_non_zero() {                        return Some(cur.add(1 * V::BYTES).add(topos(mask)));                    }                    let mask = eqa.movemask();                    debug_assert!(mask.has_non_zero());                    return Some(cur.add(topos(mask)));                }            }        }        while cur >= start.add(V::BYTES) {            debug_assert!(cur.distance(start) >= V::BYTES);            cur = cur.sub(V::BYTES);            if let Some(cur) = self.search_chunk(cur, topos) {                return Some(cur);            }        }        if cur > start {            debug_assert!(cur.distance(start) < V::BYTES);            return self.search_chunk(start, topos);        }        None    }    /// Return a count of all matching bytes in the given haystack.    ///    /// # Safety    ///    /// * It must be the case that `start < end` and that the distance between    /// them is at least equal to `V::BYTES`. That is, it must always be valid    /// to do at least an unaligned load of `V` at `start`.    /// * 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.    #[inline(always)]    pub(crate) unsafe fn count_raw(        &self,        start: *const u8,        end: *const u8,    ) -> usize {        debug_assert!(V::BYTES <= 32, "vector cannot be bigger than 32 bytes");        let confirm = |b| b == self.needle1();        let len = end.distance(start);        debug_assert!(            len >= V::BYTES,            "haystack has length {}, but must be at least {}",            len,            V::BYTES        );        // Set `cur` to the first V-aligned pointer greater than `start`.        let mut cur = start.add(V::BYTES - (start.as_usize() & V::ALIGN));        // Count any matching bytes before we start our aligned loop.        let mut count = count_byte_by_byte(start, cur, confirm);        debug_assert!(cur > start && end.sub(V::BYTES) >= start);        if len >= Self::LOOP_SIZE {            while cur <= end.sub(Self::LOOP_SIZE) {                debug_assert_eq!(0, cur.as_usize() % V::BYTES);                let a = V::load_aligned(cur);                let b = V::load_aligned(cur.add(1 * V::BYTES));                let c = V::load_aligned(cur.add(2 * V::BYTES));                let d = V::load_aligned(cur.add(3 * V::BYTES));                let eqa = self.v1.cmpeq(a);                let eqb = self.v1.cmpeq(b);                let eqc = self.v1.cmpeq(c);                let eqd = self.v1.cmpeq(d);                count += eqa.movemask().count_ones();                count += eqb.movemask().count_ones();                count += eqc.movemask().count_ones();                count += eqd.movemask().count_ones();                cur = cur.add(Self::LOOP_SIZE);            }        }        // Handle any leftovers after the aligned loop above. We use unaligned        // loads here, but I believe we are guaranteed that they are aligned        // since `cur` is aligned.        while cur <= end.sub(V::BYTES) {            debug_assert!(end.distance(cur) >= V::BYTES);            let chunk = V::load_unaligned(cur);            count += self.v1.cmpeq(chunk).movemask().count_ones();            cur = cur.add(V::BYTES);        }        // And finally count any leftovers that weren't caught above.        count += count_byte_by_byte(cur, end, confirm);        count    }    /// Search `V::BYTES` starting at `cur` via an unaligned load.    ///    /// `mask_to_offset` should be a function that converts a `movemask` to    /// an offset such that `cur.add(offset)` corresponds to a pointer to the    /// match location if one is found. Generally it is expected to use either    /// `mask_to_first_offset` or `mask_to_last_offset`, depending on whether    /// one is implementing a forward or reverse search, respectively.    ///    /// # Safety    ///    /// `cur` must be a valid pointer and it must be valid to do an unaligned    /// load of size `V::BYTES` at `cur`.    #[inline(always)]    unsafe fn search_chunk(        &self,        cur: *const u8,        mask_to_offset: impl Fn(V::Mask) -> usize,    ) -> Option<*const u8> {        let chunk = V::load_unaligned(cur);        let mask = self.v1.cmpeq(chunk).movemask();        if mask.has_non_zero() {            Some(cur.add(mask_to_offset(mask)))        } else {            None        }    }}/// 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(crate) struct Two<V> {    s1: u8,    s2: u8,    v1: V,    v2: V,}impl<V: Vector> Two<V> {    /// The number of bytes we examine per each iteration of our search loop.    const LOOP_SIZE: usize = 2 * V::BYTES;    /// Create a new searcher that finds occurrences of the byte given.    #[inline(always)]    pub(crate) unsafe fn new(needle1: u8, needle2: u8) -> Two<V> {        Two {            s1: needle1,            s2: needle2,            v1: V::splat(needle1),            v2: V::splat(needle2),        }    }    /// Returns the first needle given to `Two::new`.    #[inline(always)]    pub(crate) fn needle1(&self) -> u8 {        self.s1    }    /// Returns the second needle given to `Two::new`.    #[inline(always)]    pub(crate) fn needle2(&self) -> u8 {        self.s2    }    /// Return a pointer to the first occurrence of one of the needles in the    /// given haystack. If no such occurrence exists, then `None` is returned.    ///    /// When a match is found, the pointer returned is guaranteed to be    /// `>= start` and `< end`.    ///    /// # Safety    ///    /// * It must be the case that `start < end` and that the distance between    /// them is at least equal to `V::BYTES`. That is, it must always be valid    /// to do at least an unaligned load of `V` at `start`.    /// * 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.    #[inline(always)]    pub(crate) unsafe fn find_raw(        &self,        start: *const u8,        end: *const u8,    ) -> Option<*const u8> {        // If we want to support vectors bigger than 256 bits, we probably        // need to move up to using a u64 for the masks used below. Currently        // they are 32 bits, which means we're SOL for vectors that need masks        // bigger than 32 bits. Overall unclear until there's a use case.        debug_assert!(V::BYTES <= 32, "vector cannot be bigger than 32 bytes");        let topos = V::Mask::first_offset;        let len = end.distance(start);        debug_assert!(            len >= V::BYTES,            "haystack has length {}, but must be at least {}",            len,            V::BYTES        );        // Search a possibly unaligned chunk at `start`. This covers any part        // of the haystack prior to where aligned loads can start.        if let Some(cur) = self.search_chunk(start, topos) {            return Some(cur);        }        // Set `cur` to the first V-aligned pointer greater than `start`.        let mut cur = start.add(V::BYTES - (start.as_usize() & V::ALIGN));        debug_assert!(cur > start && end.sub(V::BYTES) >= start);        if len >= Self::LOOP_SIZE {            while cur <= end.sub(Self::LOOP_SIZE) {                debug_assert_eq!(0, cur.as_usize() % V::BYTES);                let a = V::load_aligned(cur);                let b = V::load_aligned(cur.add(V::BYTES));                let eqa1 = self.v1.cmpeq(a);                let eqb1 = self.v1.cmpeq(b);                let eqa2 = self.v2.cmpeq(a);                let eqb2 = self.v2.cmpeq(b);                let or1 = eqa1.or(eqb1);                let or2 = eqa2.or(eqb2);                let or3 = or1.or(or2);                if or3.movemask_will_have_non_zero() {                    let mask = eqa1.movemask().or(eqa2.movemask());                    if mask.has_non_zero() {                        return Some(cur.add(topos(mask)));                    }                    let mask = eqb1.movemask().or(eqb2.movemask());                    debug_assert!(mask.has_non_zero());                    return Some(cur.add(V::BYTES).add(topos(mask)));                }                cur = cur.add(Self::LOOP_SIZE);            }        }        // Handle any leftovers after the aligned loop above. We use unaligned        // loads here, but I believe we are guaranteed that they are aligned        // since `cur` is aligned.        while cur <= end.sub(V::BYTES) {            debug_assert!(end.distance(cur) >= V::BYTES);            if let Some(cur) = self.search_chunk(cur, topos) {                return Some(cur);            }            cur = cur.add(V::BYTES);        }        // Finally handle any remaining bytes less than the size of V. In this        // case, our pointer may indeed be unaligned and the load may overlap        // with the previous one. But that's okay since we know the previous        // load didn't lead to a match (otherwise we wouldn't be here).        if cur < end {            debug_assert!(end.distance(cur) < V::BYTES);            cur = cur.sub(V::BYTES - end.distance(cur));            debug_assert_eq!(end.distance(cur), V::BYTES);            return self.search_chunk(cur, topos);        }        None    }    /// Return a pointer to the last occurrence of the needle in the given    /// haystack. If no such occurrence exists, then `None` is returned.    ///    /// When a match is found, the pointer returned is guaranteed to be    /// `>= start` and `< end`.    ///    /// # Safety    ///    /// * It must be the case that `start < end` and that the distance between    /// them is at least equal to `V::BYTES`. That is, it must always be valid    /// to do at least an unaligned load of `V` at `start`.    /// * 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.    #[inline(always)]    pub(crate) unsafe fn rfind_raw(        &self,        start: *const u8,        end: *const u8,    ) -> Option<*const u8> {        // If we want to support vectors bigger than 256 bits, we probably        // need to move up to using a u64 for the masks used below. Currently        // they are 32 bits, which means we're SOL for vectors that need masks        // bigger than 32 bits. Overall unclear until there's a use case.        debug_assert!(V::BYTES <= 32, "vector cannot be bigger than 32 bytes");        let topos = V::Mask::last_offset;        let len = end.distance(start);        debug_assert!(            len >= V::BYTES,            "haystack has length {}, but must be at least {}",            len,            V::BYTES        );        if let Some(cur) = self.search_chunk(end.sub(V::BYTES), topos) {            return Some(cur);        }        let mut cur = end.sub(end.as_usize() & V::ALIGN);        debug_assert!(start <= cur && cur <= end);        if len >= Self::LOOP_SIZE {            while cur >= start.add(Self::LOOP_SIZE) {                debug_assert_eq!(0, cur.as_usize() % V::BYTES);                cur = cur.sub(Self::LOOP_SIZE);                let a = V::load_aligned(cur);                let b = V::load_aligned(cur.add(V::BYTES));                let eqa1 = self.v1.cmpeq(a);                let eqb1 = self.v1.cmpeq(b);                let eqa2 = self.v2.cmpeq(a);                let eqb2 = self.v2.cmpeq(b);                let or1 = eqa1.or(eqb1);                let or2 = eqa2.or(eqb2);                let or3 = or1.or(or2);                if or3.movemask_will_have_non_zero() {                    let mask = eqb1.movemask().or(eqb2.movemask());                    if mask.has_non_zero() {                        return Some(cur.add(V::BYTES).add(topos(mask)));                    }                    let mask = eqa1.movemask().or(eqa2.movemask());                    debug_assert!(mask.has_non_zero());                    return Some(cur.add(topos(mask)));                }            }        }        while cur >= start.add(V::BYTES) {            debug_assert!(cur.distance(start) >= V::BYTES);            cur = cur.sub(V::BYTES);            if let Some(cur) = self.search_chunk(cur, topos) {                return Some(cur);            }        }        if cur > start {            debug_assert!(cur.distance(start) < V::BYTES);            return self.search_chunk(start, topos);        }        None    }    /// Search `V::BYTES` starting at `cur` via an unaligned load.    ///    /// `mask_to_offset` should be a function that converts a `movemask` to    /// an offset such that `cur.add(offset)` corresponds to a pointer to the    /// match location if one is found. Generally it is expected to use either    /// `mask_to_first_offset` or `mask_to_last_offset`, depending on whether    /// one is implementing a forward or reverse search, respectively.    ///    /// # Safety    ///    /// `cur` must be a valid pointer and it must be valid to do an unaligned    /// load of size `V::BYTES` at `cur`.    #[inline(always)]    unsafe fn search_chunk(        &self,        cur: *const u8,        mask_to_offset: impl Fn(V::Mask) -> usize,    ) -> Option<*const u8> {        let chunk = V::load_unaligned(cur);        let eq1 = self.v1.cmpeq(chunk);        let eq2 = self.v2.cmpeq(chunk);        let mask = eq1.or(eq2).movemask();        if mask.has_non_zero() {            let mask1 = eq1.movemask();            let mask2 = eq2.movemask();            Some(cur.add(mask_to_offset(mask1.or(mask2))))        } else {            None        }    }}/// 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(crate) struct Three<V> {    s1: u8,    s2: u8,    s3: u8,    v1: V,    v2: V,    v3: V,}impl<V: Vector> Three<V> {    /// The number of bytes we examine per each iteration of our search loop.    const LOOP_SIZE: usize = 2 * V::BYTES;    /// Create a new searcher that finds occurrences of the byte given.    #[inline(always)]    pub(crate) unsafe fn new(        needle1: u8,        needle2: u8,        needle3: u8,    ) -> Three<V> {        Three {            s1: needle1,            s2: needle2,            s3: needle3,            v1: V::splat(needle1),            v2: V::splat(needle2),            v3: V::splat(needle3),        }    }    /// Returns the first needle given to `Three::new`.    #[inline(always)]    pub(crate) fn needle1(&self) -> u8 {        self.s1    }    /// Returns the second needle given to `Three::new`.    #[inline(always)]    pub(crate) fn needle2(&self) -> u8 {        self.s2    }    /// Returns the third needle given to `Three::new`.    #[inline(always)]    pub(crate) fn needle3(&self) -> u8 {        self.s3    }    /// Return a pointer to the first occurrence of one of the needles in the    /// given haystack. If no such occurrence exists, then `None` is returned.    ///    /// When a match is found, the pointer returned is guaranteed to be    /// `>= start` and `< end`.    ///    /// # Safety    ///    /// * It must be the case that `start < end` and that the distance between    /// them is at least equal to `V::BYTES`. That is, it must always be valid    /// to do at least an unaligned load of `V` at `start`.    /// * 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.    #[inline(always)]    pub(crate) unsafe fn find_raw(        &self,        start: *const u8,        end: *const u8,    ) -> Option<*const u8> {        // If we want to support vectors bigger than 256 bits, we probably        // need to move up to using a u64 for the masks used below. Currently        // they are 32 bits, which means we're SOL for vectors that need masks        // bigger than 32 bits. Overall unclear until there's a use case.        debug_assert!(V::BYTES <= 32, "vector cannot be bigger than 32 bytes");        let topos = V::Mask::first_offset;        let len = end.distance(start);        debug_assert!(            len >= V::BYTES,            "haystack has length {}, but must be at least {}",            len,            V::BYTES        );        // Search a possibly unaligned chunk at `start`. This covers any part        // of the haystack prior to where aligned loads can start.        if let Some(cur) = self.search_chunk(start, topos) {            return Some(cur);        }        // Set `cur` to the first V-aligned pointer greater than `start`.        let mut cur = start.add(V::BYTES - (start.as_usize() & V::ALIGN));        debug_assert!(cur > start && end.sub(V::BYTES) >= start);        if len >= Self::LOOP_SIZE {            while cur <= end.sub(Self::LOOP_SIZE) {                debug_assert_eq!(0, cur.as_usize() % V::BYTES);                let a = V::load_aligned(cur);                let b = V::load_aligned(cur.add(V::BYTES));                let eqa1 = self.v1.cmpeq(a);                let eqb1 = self.v1.cmpeq(b);                let eqa2 = self.v2.cmpeq(a);                let eqb2 = self.v2.cmpeq(b);                let eqa3 = self.v3.cmpeq(a);                let eqb3 = self.v3.cmpeq(b);                let or1 = eqa1.or(eqb1);                let or2 = eqa2.or(eqb2);                let or3 = eqa3.or(eqb3);                let or4 = or1.or(or2);                let or5 = or3.or(or4);                if or5.movemask_will_have_non_zero() {                    let mask = eqa1                        .movemask()                        .or(eqa2.movemask())                        .or(eqa3.movemask());                    if mask.has_non_zero() {                        return Some(cur.add(topos(mask)));                    }                    let mask = eqb1                        .movemask()                        .or(eqb2.movemask())                        .or(eqb3.movemask());                    debug_assert!(mask.has_non_zero());                    return Some(cur.add(V::BYTES).add(topos(mask)));                }                cur = cur.add(Self::LOOP_SIZE);            }        }        // Handle any leftovers after the aligned loop above. We use unaligned        // loads here, but I believe we are guaranteed that they are aligned        // since `cur` is aligned.        while cur <= end.sub(V::BYTES) {            debug_assert!(end.distance(cur) >= V::BYTES);            if let Some(cur) = self.search_chunk(cur, topos) {                return Some(cur);            }            cur = cur.add(V::BYTES);        }        // Finally handle any remaining bytes less than the size of V. In this        // case, our pointer may indeed be unaligned and the load may overlap        // with the previous one. But that's okay since we know the previous        // load didn't lead to a match (otherwise we wouldn't be here).        if cur < end {            debug_assert!(end.distance(cur) < V::BYTES);            cur = cur.sub(V::BYTES - end.distance(cur));            debug_assert_eq!(end.distance(cur), V::BYTES);            return self.search_chunk(cur, topos);        }        None    }    /// Return a pointer to the last occurrence of the needle in the given    /// haystack. If no such occurrence exists, then `None` is returned.    ///    /// When a match is found, the pointer returned is guaranteed to be    /// `>= start` and `< end`.    ///    /// # Safety    ///    /// * It must be the case that `start < end` and that the distance between    /// them is at least equal to `V::BYTES`. That is, it must always be valid    /// to do at least an unaligned load of `V` at `start`.    /// * 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.    #[inline(always)]    pub(crate) unsafe fn rfind_raw(        &self,        start: *const u8,        end: *const u8,    ) -> Option<*const u8> {        // If we want to support vectors bigger than 256 bits, we probably        // need to move up to using a u64 for the masks used below. Currently        // they are 32 bits, which means we're SOL for vectors that need masks        // bigger than 32 bits. Overall unclear until there's a use case.        debug_assert!(V::BYTES <= 32, "vector cannot be bigger than 32 bytes");        let topos = V::Mask::last_offset;        let len = end.distance(start);        debug_assert!(            len >= V::BYTES,            "haystack has length {}, but must be at least {}",            len,            V::BYTES        );        if let Some(cur) = self.search_chunk(end.sub(V::BYTES), topos) {            return Some(cur);        }        let mut cur = end.sub(end.as_usize() & V::ALIGN);        debug_assert!(start <= cur && cur <= end);        if len >= Self::LOOP_SIZE {            while cur >= start.add(Self::LOOP_SIZE) {                debug_assert_eq!(0, cur.as_usize() % V::BYTES);                cur = cur.sub(Self::LOOP_SIZE);                let a = V::load_aligned(cur);                let b = V::load_aligned(cur.add(V::BYTES));                let eqa1 = self.v1.cmpeq(a);                let eqb1 = self.v1.cmpeq(b);                let eqa2 = self.v2.cmpeq(a);                let eqb2 = self.v2.cmpeq(b);                let eqa3 = self.v3.cmpeq(a);                let eqb3 = self.v3.cmpeq(b);                let or1 = eqa1.or(eqb1);                let or2 = eqa2.or(eqb2);                let or3 = eqa3.or(eqb3);                let or4 = or1.or(or2);                let or5 = or3.or(or4);                if or5.movemask_will_have_non_zero() {                    let mask = eqb1                        .movemask()                        .or(eqb2.movemask())                        .or(eqb3.movemask());                    if mask.has_non_zero() {                        return Some(cur.add(V::BYTES).add(topos(mask)));                    }                    let mask = eqa1                        .movemask()                        .or(eqa2.movemask())                        .or(eqa3.movemask());                    debug_assert!(mask.has_non_zero());                    return Some(cur.add(topos(mask)));                }            }        }        while cur >= start.add(V::BYTES) {            debug_assert!(cur.distance(start) >= V::BYTES);            cur = cur.sub(V::BYTES);            if let Some(cur) = self.search_chunk(cur, topos) {                return Some(cur);            }        }        if cur > start {            debug_assert!(cur.distance(start) < V::BYTES);            return self.search_chunk(start, topos);        }        None    }    /// Search `V::BYTES` starting at `cur` via an unaligned load.    ///    /// `mask_to_offset` should be a function that converts a `movemask` to    /// an offset such that `cur.add(offset)` corresponds to a pointer to the    /// match location if one is found. Generally it is expected to use either    /// `mask_to_first_offset` or `mask_to_last_offset`, depending on whether    /// one is implementing a forward or reverse search, respectively.    ///    /// # Safety    ///    /// `cur` must be a valid pointer and it must be valid to do an unaligned    /// load of size `V::BYTES` at `cur`.    #[inline(always)]    unsafe fn search_chunk(        &self,        cur: *const u8,        mask_to_offset: impl Fn(V::Mask) -> usize,    ) -> Option<*const u8> {        let chunk = V::load_unaligned(cur);        let eq1 = self.v1.cmpeq(chunk);        let eq2 = self.v2.cmpeq(chunk);        let eq3 = self.v3.cmpeq(chunk);        let mask = eq1.or(eq2).or(eq3).movemask();        if mask.has_non_zero() {            let mask1 = eq1.movemask();            let mask2 = eq2.movemask();            let mask3 = eq3.movemask();            Some(cur.add(mask_to_offset(mask1.or(mask2).or(mask3))))        } else {            None        }    }}/// An iterator over all occurrences of a set of bytes in a haystack.////// This iterator implements the routines necessary to provide a/// `DoubleEndedIterator` impl, which means it can also be used to find/// occurrences in reverse order.////// The lifetime parameters are as follows:////// * `'h` refers to the lifetime of the haystack being searched.////// This type is intended to be used to implement all iterators for the/// `memchr` family of functions. It handles a tiny bit of marginally tricky/// raw pointer math, but otherwise expects the caller to provide `find_raw`/// and `rfind_raw` routines for each call of `next` and `next_back`,/// respectively.#[derive(Clone, Debug)]pub(crate) struct Iter<'h> {    /// The original starting point into the haystack. We use this to convert    /// pointers to offsets.    original_start: *const u8,    /// The current starting point into the haystack. That is, where the next    /// search will begin.    start: *const u8,    /// The current ending point into the haystack. That is, where the next    /// reverse search will begin.    end: *const u8,    /// A marker for tracking the lifetime of the start/cur_start/cur_end    /// pointers above, which all point into the haystack.    haystack: core::marker::PhantomData<&'h [u8]>,}// SAFETY: Iter contains no shared references to anything that performs any// interior mutations. Also, the lifetime guarantees that Iter will not outlive// the haystack.unsafe impl<'h> Send for Iter<'h> {}// SAFETY: Iter perform no interior mutations, therefore no explicit// synchronization is necessary. Also, the lifetime guarantees that Iter will// not outlive the haystack.unsafe impl<'h> Sync for Iter<'h> {}impl<'h> Iter<'h> {    /// Create a new generic memchr iterator.    #[inline(always)]    pub(crate) fn new(haystack: &'h [u8]) -> Iter<'h> {        Iter {            original_start: haystack.as_ptr(),            start: haystack.as_ptr(),            end: haystack.as_ptr().wrapping_add(haystack.len()),            haystack: core::marker::PhantomData,        }    }    /// Returns the next occurrence in the forward direction.    ///    /// # Safety    ///    /// Callers must ensure that if a pointer is returned from the closure    /// provided, then it must be greater than or equal to the start pointer    /// and less than the end pointer.    #[inline(always)]    pub(crate) unsafe fn next(        &mut self,        mut find_raw: impl FnMut(*const u8, *const u8) -> Option<*const u8>,    ) -> Option<usize> {        // SAFETY: Pointers are derived directly from the same &[u8] haystack.        // We only ever modify start/end corresponding to a matching offset        // found between start and end. Thus all changes to start/end maintain        // our safety requirements.        //        // The only other assumption we rely on is that the pointer returned        // by `find_raw` satisfies `self.start <= found < self.end`, and that        // safety contract is forwarded to the caller.        let found = find_raw(self.start, self.end)?;        let result = found.distance(self.original_start);        self.start = found.add(1);        Some(result)    }    /// Returns the number of remaining elements in this iterator.    #[inline(always)]    pub(crate) fn count(        self,        mut count_raw: impl FnMut(*const u8, *const u8) -> usize,    ) -> usize {        // SAFETY: Pointers are derived directly from the same &[u8] haystack.        // We only ever modify start/end corresponding to a matching offset        // found between start and end. Thus all changes to start/end maintain        // our safety requirements.        count_raw(self.start, self.end)    }    /// Returns the next occurrence in reverse.    ///    /// # Safety    ///    /// Callers must ensure that if a pointer is returned from the closure    /// provided, then it must be greater than or equal to the start pointer    /// and less than the end pointer.    #[inline(always)]    pub(crate) unsafe fn next_back(        &mut self,        mut rfind_raw: impl FnMut(*const u8, *const u8) -> Option<*const u8>,    ) -> Option<usize> {        // SAFETY: Pointers are derived directly from the same &[u8] haystack.        // We only ever modify start/end corresponding to a matching offset        // found between start and end. Thus all changes to start/end maintain        // our safety requirements.        //        // The only other assumption we rely on is that the pointer returned        // by `rfind_raw` satisfies `self.start <= found < self.end`, and that        // safety contract is forwarded to the caller.        let found = rfind_raw(self.start, self.end)?;        let result = found.distance(self.original_start);        self.end = found;        Some(result)    }    /// Provides an implementation of `Iterator::size_hint`.    #[inline(always)]    pub(crate) fn size_hint(&self) -> (usize, Option<usize>) {        (0, Some(self.end.as_usize().saturating_sub(self.start.as_usize())))    }}/// Search a slice using a function that operates on raw pointers.////// Given a function to search a contiguous sequence of memory for the location/// of a non-empty set of bytes, this will execute that search on a slice of/// bytes. The pointer returned by the given function will be converted to an/// offset relative to the starting point of the given slice. That is, if a/// match is found, the offset returned by this routine is guaranteed to be a/// valid index into `haystack`.////// Callers may use this for a forward or reverse search.////// # Safety////// Callers must ensure that if a pointer is returned by `find_raw`, then the/// pointer must be greater than or equal to the starting pointer and less than/// the end pointer.#[inline(always)]pub(crate) unsafe fn search_slice_with_raw(    haystack: &[u8],    mut find_raw: impl FnMut(*const u8, *const u8) -> Option<*const u8>,) -> Option<usize> {    // SAFETY: We rely on `find_raw` to return a correct and valid pointer, but    // otherwise, `start` and `end` are valid due to the guarantees provided by    // a &[u8].    let start = haystack.as_ptr();    let end = start.add(haystack.len());    let found = find_raw(start, end)?;    Some(found.distance(start))}/// Performs a forward byte-at-a-time loop until either `ptr >= end_ptr` or/// until `confirm(*ptr)` returns `true`. If the former occurs, then `None` is/// returned. If the latter occurs, then the pointer at which `confirm` returns/// `true` is returned.////// # Safety////// Callers must provide valid pointers and they must satisfy `start_ptr <=/// ptr` and `ptr <= end_ptr`.#[inline(always)]pub(crate) unsafe fn fwd_byte_by_byte<F: Fn(u8) -> bool>(    start: *const u8,    end: *const u8,    confirm: F,) -> Option<*const u8> {    debug_assert!(start <= end);    let mut ptr = start;    while ptr < end {        if confirm(*ptr) {            return Some(ptr);        }        ptr = ptr.offset(1);    }    None}/// Performs a reverse byte-at-a-time loop until either `ptr < start_ptr` or/// until `confirm(*ptr)` returns `true`. If the former occurs, then `None` is/// returned. If the latter occurs, then the pointer at which `confirm` returns/// `true` is returned.////// # Safety////// Callers must provide valid pointers and they must satisfy `start_ptr <=/// ptr` and `ptr <= end_ptr`.#[inline(always)]pub(crate) unsafe fn rev_byte_by_byte<F: Fn(u8) -> bool>(    start: *const u8,    end: *const u8,    confirm: F,) -> Option<*const u8> {    debug_assert!(start <= end);    let mut ptr = end;    while ptr > start {        ptr = ptr.offset(-1);        if confirm(*ptr) {            return Some(ptr);        }    }    None}/// Performs a forward byte-at-a-time loop until `ptr >= end_ptr` and returns/// the number of times `confirm(*ptr)` returns `true`.////// # Safety////// Callers must provide valid pointers and they must satisfy `start_ptr <=/// ptr` and `ptr <= end_ptr`.#[inline(always)]pub(crate) unsafe fn count_byte_by_byte<F: Fn(u8) -> bool>(    start: *const u8,    end: *const u8,    confirm: F,) -> usize {    debug_assert!(start <= end);    let mut ptr = start;    let mut count = 0;    while ptr < end {        if confirm(*ptr) {            count += 1;        }        ptr = ptr.offset(1);    }    count}