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    /*!
    The `memchr` crate provides heavily optimized routines for searching bytes.

    The `memchr` function is traditionally provided by libc, however, the
    performance of `memchr` can vary significantly depending on the specific
    implementation of libc that is used. They can range from manually tuned
    Assembly implementations (like that found in GNU's libc) all the way to
    non-vectorized C implementations (like that found in MUSL).

    To smooth out the differences between implementations of libc, at least
    on `x86_64` for Rust 1.27+, this crate provides its own implementation of
    `memchr` that should perform competitively with the one found in GNU's libc.
    The implementation is in pure Rust and has no dependency on a C compiler or an
    Assembler.

    Additionally, GNU libc also provides an extension, `memrchr`. This crate
    provides its own implementation of `memrchr` as well, on top of `memchr2`,
    `memchr3`, `memrchr2` and `memrchr3`. The difference between `memchr` and
    `memchr2` is that that `memchr2` permits finding all occurrences of two bytes
    instead of one. Similarly for `memchr3`.
    */

    #![cfg_attr(not(feature = "use_std"), no_std)]

    #![deny(missing_docs)]
    #![doc(html_root_url = "https://docs.rs/memchr/2.0.0")]

    // Supporting 16-bit would be fine. If you need it, please submit a bug report
    // at https://github.com/BurntSushi/rust-memchr
    #[cfg(not(any(target_pointer_width = "32", target_pointer_width = "64")))]
    compile_error!("memchr currently not supported on non-32 or non-64 bit");

    #[cfg(feature = "use_std")]
    extern crate core;

    #[cfg(test)]
    #[macro_use]
    extern crate quickcheck;

    use core::iter::Rev;

    pub use iter::{Memchr, Memchr2, Memchr3};

    // N.B. If you're looking for the cfg knobs for libc, see build.rs.
    #[cfg(memchr_libc)]
    mod c;
    #[allow(dead_code)]
    mod fallback;
    mod iter;
    mod naive;
    #[cfg(all(target_arch = "x86_64", memchr_runtime_simd))]
    mod x86;
    #[cfg(test)]
    mod tests;

    /// An iterator over all occurrences of the needle in a haystack.
    #[inline]
    pub fn memchr_iter(needle: u8, haystack: &[u8]) -> Memchr {
        Memchr::new(needle, haystack)
    }

    /// An iterator over all occurrences of the needles in a haystack.
    #[inline]
    pub fn memchr2_iter(
        needle1: u8,
        needle2: u8,
        haystack: &[u8],
    ) -> Memchr2 {
        Memchr2::new(needle1, needle2, haystack)
    }

    /// An iterator over all occurrences of the needles in a haystack.
    #[inline]
    pub fn memchr3_iter(
        needle1: u8,
        needle2: u8,
        needle3: u8,
        haystack: &[u8],
    ) -> Memchr3 {
        Memchr3::new(needle1, needle2, needle3, haystack)
    }

    /// An iterator over all occurrences of the needle in a haystack, in reverse.
    #[inline]
    pub fn memrchr_iter(needle: u8, haystack: &[u8]) -> Rev<Memchr> {
        Memchr::new(needle, haystack).rev()
    }

    /// An iterator over all occurrences of the needles in a haystack, in reverse.
    #[inline]
    pub fn memrchr2_iter(
        needle1: u8,
        needle2: u8,
        haystack: &[u8],
    ) -> Rev<Memchr2> {
        Memchr2::new(needle1, needle2, haystack).rev()
    }

    /// An iterator over all occurrences of the needles in a haystack, in reverse.
    #[inline]
    pub fn memrchr3_iter(
        needle1: u8,
        needle2: u8,
        needle3: u8,
        haystack: &[u8],
    ) -> Rev<Memchr3> {
        Memchr3::new(needle1, needle2, needle3, haystack).rev()
    }

    /// Search for the first occurrence of a byte in a slice.
    ///
    /// This returns the index corresponding to the first occurrence of `needle` in
    /// `haystack`, or `None` if one is not found.
    ///
    /// While this is operationally the same as something like
    /// `haystack.iter().position(|&b| b == needle)`, `memchr` will use a highly
    /// optimized routine that can be up to an order of magnitude faster in some
    /// cases.
    ///
    /// # Example
    ///
    /// This shows how to find the first position of a byte in a byte string.
    ///
    /// ```
    /// use memchr::memchr;
    ///
    /// let haystack = b"the quick brown fox";
    /// assert_eq!(memchr(b'k', haystack), Some(8));
    /// ```
    #[inline]
    pub fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
        #[cfg(all(target_arch = "x86_64", memchr_runtime_simd))]
        #[inline(always)]
        fn imp(n1: u8, haystack: &[u8]) -> Option<usize> {
            x86::memchr(n1, haystack)
        }

        #[cfg(all(
            memchr_libc,
            not(all(target_arch = "x86_64", memchr_runtime_simd))
        ))]
        #[inline(always)]
        fn imp(n1: u8, haystack: &[u8]) -> Option<usize> {
            c::memchr(n1, haystack)
        }

        #[cfg(all(
            not(memchr_libc),
            not(all(target_arch = "x86_64", memchr_runtime_simd))
        ))]
        #[inline(always)]
        fn imp(n1: u8, haystack: &[u8]) -> Option<usize> {
            fallback::memchr(n1, haystack)
        }

        if haystack.is_empty() {
            None
        } else {
            imp(needle, haystack)
        }
    }

    /// Like `memchr`, but searches for two bytes instead of one.
    #[inline]
    pub fn memchr2(needle1: u8, needle2: u8, haystack: &[u8]) -> Option<usize> {
        #[cfg(all(target_arch = "x86_64", memchr_runtime_simd))]
        #[inline(always)]
        fn imp(n1: u8, n2: u8, haystack: &[u8]) -> Option<usize> {
            x86::memchr2(n1, n2, haystack)
        }

        #[cfg(not(all(target_arch = "x86_64", memchr_runtime_simd)))]
        #[inline(always)]
        fn imp(n1: u8, n2: u8, haystack: &[u8]) -> Option<usize> {
            fallback::memchr2(n1, n2, haystack)
        }

        if haystack.is_empty() {
            None
        } else {
            imp(needle1, needle2, haystack)
        }
    }

    /// Like `memchr`, but searches for three bytes instead of one.
    #[inline]
    pub fn memchr3(
        needle1: u8,
        needle2: u8,
        needle3: u8,
        haystack: &[u8],
    ) -> Option<usize> {
        #[cfg(all(target_arch = "x86_64", memchr_runtime_simd))]
        #[inline(always)]
        fn imp(n1: u8, n2: u8, n3: u8, haystack: &[u8]) -> Option<usize> {
            x86::memchr3(n1, n2, n3, haystack)
        }

        #[cfg(not(all(target_arch = "x86_64", memchr_runtime_simd)))]
        #[inline(always)]
        fn imp(n1: u8, n2: u8, n3: u8, haystack: &[u8]) -> Option<usize> {
            fallback::memchr3(n1, n2, n3, haystack)
        }

        if haystack.is_empty() {
            None
        } else {
            imp(needle1, needle2, needle3, haystack)
        }
    }

    /// Search for the last occurrence of a byte in a slice.
    ///
    /// This returns the index corresponding to the last occurrence of `needle` in
    /// `haystack`, or `None` if one is not found.
    ///
    /// While this is operationally the same as something like
    /// `haystack.iter().rposition(|&b| b == needle)`, `memrchr` will use a highly
    /// optimized routine that can be up to an order of magnitude faster in some
    /// cases.
    ///
    /// # Example
    ///
    /// This shows how to find the last position of a byte in a byte string.
    ///
    /// ```
    /// use memchr::memrchr;
    ///
    /// let haystack = b"the quick brown fox";
    /// assert_eq!(memrchr(b'o', haystack), Some(17));
    /// ```
    #[inline]
    pub fn memrchr(needle: u8, haystack: &[u8]) -> Option<usize> {
        #[cfg(all(target_arch = "x86_64", memchr_runtime_simd))]
        #[inline(always)]
        fn imp(n1: u8, haystack: &[u8]) -> Option<usize> {
            x86::memrchr(n1, haystack)
        }

        #[cfg(all(
            all(memchr_libc, target_os = "linux"),
            not(all(target_arch = "x86_64", memchr_runtime_simd))
        ))]
        #[inline(always)]
        fn imp(n1: u8, haystack: &[u8]) -> Option<usize> {
            c::memrchr(n1, haystack)
        }

        #[cfg(all(
            not(all(memchr_libc, target_os = "linux")),
            not(all(target_arch = "x86_64", memchr_runtime_simd))
        ))]
        #[inline(always)]
        fn imp(n1: u8, haystack: &[u8]) -> Option<usize> {
            fallback::memrchr(n1, haystack)
        }

        if haystack.is_empty() {
            None
        } else {
            imp(needle, haystack)
        }
    }

    /// Like `memrchr`, but searches for two bytes instead of one.
    #[inline]
    pub fn memrchr2(needle1: u8, needle2: u8, haystack: &[u8]) -> Option<usize> {
        #[cfg(all(target_arch = "x86_64", memchr_runtime_simd))]
        #[inline(always)]
        fn imp(n1: u8, n2: u8, haystack: &[u8]) -> Option<usize> {
            x86::memrchr2(n1, n2, haystack)
        }

        #[cfg(not(all(target_arch = "x86_64", memchr_runtime_simd)))]
        #[inline(always)]
        fn imp(n1: u8, n2: u8, haystack: &[u8]) -> Option<usize> {
            fallback::memrchr2(n1, n2, haystack)
        }

        if haystack.is_empty() {
            None
        } else {
            imp(needle1, needle2, haystack)
        }
    }

    /// Like `memrchr`, but searches for three bytes instead of one.
    #[inline]
    pub fn memrchr3(
        needle1: u8,
        needle2: u8,
        needle3: u8,
        haystack: &[u8],
    ) -> Option<usize> {
        #[cfg(all(target_arch = "x86_64", memchr_runtime_simd))]
        #[inline(always)]
        fn imp(n1: u8, n2: u8, n3: u8, haystack: &[u8]) -> Option<usize> {
            x86::memrchr3(n1, n2, n3, haystack)
        }

        #[cfg(not(all(target_arch = "x86_64", memchr_runtime_simd)))]
        #[inline(always)]
        fn imp(n1: u8, n2: u8, n3: u8, haystack: &[u8]) -> Option<usize> {
            fallback::memrchr3(n1, n2, n3, haystack)
        }

        if haystack.is_empty() {
            None
        } else {
            imp(needle1, needle2, needle3, haystack)
        }
    }

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