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    // Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! An implementation of SipHash.

    #![allow(deprecated)]

    use marker::PhantomData;
    use ptr;
    use cmp;
    use mem;

    /// An implementation of SipHash 1-3.
    ///
    /// This is currently the default hashing function used by standard library
    /// (eg. `collections::HashMap` uses it by default).
    ///
    /// See: <https://131002.net/siphash>
    #[unstable(feature = "hashmap_internals", issue = "0")]
    #[rustc_deprecated(since = "1.13.0",
                       reason = "use `std::collections::hash_map::DefaultHasher` instead")]
    #[derive(Debug, Clone, Default)]
    #[doc(hidden)]
    pub struct SipHasher13 {
        hasher: Hasher<Sip13Rounds>,
    }

    /// An implementation of SipHash 2-4.
    ///
    /// See: <https://131002.net/siphash/>
    #[unstable(feature = "hashmap_internals", issue = "0")]
    #[rustc_deprecated(since = "1.13.0",
                       reason = "use `std::collections::hash_map::DefaultHasher` instead")]
    #[derive(Debug, Clone, Default)]
    struct SipHasher24 {
        hasher: Hasher<Sip24Rounds>,
    }

    /// An implementation of SipHash 2-4.
    ///
    /// See: <https://131002.net/siphash/>
    ///
    /// SipHash is a general-purpose hashing function: it runs at a good
    /// speed (competitive with Spooky and City) and permits strong _keyed_
    /// hashing. This lets you key your hashtables from a strong RNG, such as
    /// [`rand::os::OsRng`](https://doc.rust-lang.org/rand/rand/os/struct.OsRng.html).
    ///
    /// Although the SipHash algorithm is considered to be generally strong,
    /// it is not intended for cryptographic purposes. As such, all
    /// cryptographic uses of this implementation are _strongly discouraged_.
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_deprecated(since = "1.13.0",
                       reason = "use `std::collections::hash_map::DefaultHasher` instead")]
    #[derive(Debug, Clone, Default)]
    pub struct SipHasher(SipHasher24);

    #[derive(Debug)]
    struct Hasher<S: Sip> {
        k0: u64,
        k1: u64,
        length: usize, // how many bytes we've processed
        state: State, // hash State
        tail: u64, // unprocessed bytes le
        ntail: usize, // how many bytes in tail are valid
        _marker: PhantomData<S>,
    }

    #[derive(Debug, Clone, Copy)]
    #[repr(C)]
    struct State {
        // v0, v2 and v1, v3 show up in pairs in the algorithm,
        // and simd implementations of SipHash will use vectors
        // of v02 and v13. By placing them in this order in the struct,
        // the compiler can pick up on just a few simd optimizations by itself.
        v0: u64,
        v2: u64,
        v1: u64,
        v3: u64,
    }

    macro_rules! compress {
        ($state:expr) => ({
            compress!($state.v0, $state.v1, $state.v2, $state.v3)
        });
        ($v0:expr, $v1:expr, $v2:expr, $v3:expr) =>
        ({
            $v0 = $v0.wrapping_add($v1); $v1 = $v1.rotate_left(13); $v1 ^= $v0;
            $v0 = $v0.rotate_left(32);
            $v2 = $v2.wrapping_add($v3); $v3 = $v3.rotate_left(16); $v3 ^= $v2;
            $v0 = $v0.wrapping_add($v3); $v3 = $v3.rotate_left(21); $v3 ^= $v0;
            $v2 = $v2.wrapping_add($v1); $v1 = $v1.rotate_left(17); $v1 ^= $v2;
            $v2 = $v2.rotate_left(32);
        });
    }

    /// Load an integer of the desired type from a byte stream, in LE order. Uses
    /// `copy_nonoverlapping` to let the compiler generate the most efficient way
    /// to load it from a possibly unaligned address.
    ///
    /// Unsafe because: unchecked indexing at i..i+size_of(int_ty)
    macro_rules! load_int_le {
        ($buf:expr, $i:expr, $int_ty:ident) =>
        ({
           debug_assert!($i + mem::size_of::<$int_ty>() <= $buf.len());
           let mut data = 0 as $int_ty;
           ptr::copy_nonoverlapping($buf.get_unchecked($i),
                                    &mut data as *mut _ as *mut u8,
                                    mem::size_of::<$int_ty>());
           data.to_le()
        });
    }

    /// Load an u64 using up to 7 bytes of a byte slice.
    ///
    /// Unsafe because: unchecked indexing at start..start+len
    #[inline]
    unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
        debug_assert!(len < 8);
        let mut i = 0; // current byte index (from LSB) in the output u64
        let mut out = 0;
        if i + 3 < len {
            out = load_int_le!(buf, start + i, u32) as u64;
            i += 4;
        }
        if i + 1 < len {
            out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8);
            i += 2
        }
        if i < len {
            out |= (*buf.get_unchecked(start + i) as u64) << (i * 8);
            i += 1;
        }
        debug_assert_eq!(i, len);
        out
    }

    impl SipHasher {
        /// Creates a new `SipHasher` with the two initial keys set to 0.
        #[inline]
        #[stable(feature = "rust1", since = "1.0.0")]
        #[rustc_deprecated(since = "1.13.0",
                           reason = "use `std::collections::hash_map::DefaultHasher` instead")]
        pub fn new() -> SipHasher {
            SipHasher::new_with_keys(0, 0)
        }

        /// Creates a `SipHasher` that is keyed off the provided keys.
        #[inline]
        #[stable(feature = "rust1", since = "1.0.0")]
        #[rustc_deprecated(since = "1.13.0",
                           reason = "use `std::collections::hash_map::DefaultHasher` instead")]
        pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher {
            SipHasher(SipHasher24 {
                hasher: Hasher::new_with_keys(key0, key1)
            })
        }
    }

    impl SipHasher13 {
        /// Creates a new `SipHasher13` with the two initial keys set to 0.
        #[inline]
        #[unstable(feature = "hashmap_internals", issue = "0")]
        #[rustc_deprecated(since = "1.13.0",
                           reason = "use `std::collections::hash_map::DefaultHasher` instead")]
        pub fn new() -> SipHasher13 {
            SipHasher13::new_with_keys(0, 0)
        }

        /// Creates a `SipHasher13` that is keyed off the provided keys.
        #[inline]
        #[unstable(feature = "hashmap_internals", issue = "0")]
        #[rustc_deprecated(since = "1.13.0",
                           reason = "use `std::collections::hash_map::DefaultHasher` instead")]
        pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
            SipHasher13 {
                hasher: Hasher::new_with_keys(key0, key1)
            }
        }
    }

    impl<S: Sip> Hasher<S> {
        #[inline]
        fn new_with_keys(key0: u64, key1: u64) -> Hasher<S> {
            let mut state = Hasher {
                k0: key0,
                k1: key1,
                length: 0,
                state: State {
                    v0: 0,
                    v1: 0,
                    v2: 0,
                    v3: 0,
                },
                tail: 0,
                ntail: 0,
                _marker: PhantomData,
            };
            state.reset();
            state
        }

        #[inline]
        fn reset(&mut self) {
            self.length = 0;
            self.state.v0 = self.k0 ^ 0x736f6d6570736575;
            self.state.v1 = self.k1 ^ 0x646f72616e646f6d;
            self.state.v2 = self.k0 ^ 0x6c7967656e657261;
            self.state.v3 = self.k1 ^ 0x7465646279746573;
            self.ntail = 0;
        }

        // Specialized write function that is only valid for buffers with len <= 8.
        // It's used to force inlining of write_u8 and write_usize, those would normally be inlined
        // except for composite types (that includes slices and str hashing because of delimiter).
        // Without this extra push the compiler is very reluctant to inline delimiter writes,
        // degrading performance substantially for the most common use cases.
        #[inline]
        fn short_write(&mut self, msg: &[u8]) {
            debug_assert!(msg.len() <= 8);
            let length = msg.len();
            self.length += length;

            let needed = 8 - self.ntail;
            let fill = cmp::min(length, needed);
            if fill == 8 {
                self.tail = unsafe { load_int_le!(msg, 0, u64) };
            } else {
                self.tail |= unsafe { u8to64_le(msg, 0, fill) } << (8 * self.ntail);
                if length < needed {
                    self.ntail += length;
                    return;
                }
            }
            self.state.v3 ^= self.tail;
            S::c_rounds(&mut self.state);
            self.state.v0 ^= self.tail;

            // Buffered tail is now flushed, process new input.
            self.ntail = length - needed;
            self.tail = unsafe { u8to64_le(msg, needed, self.ntail) };
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl super::Hasher for SipHasher {
        #[inline]
        fn write(&mut self, msg: &[u8]) {
            self.0.hasher.write(msg)
        }

        #[inline]
        fn finish(&self) -> u64 {
            self.0.hasher.finish()
        }
    }

    #[unstable(feature = "hashmap_internals", issue = "0")]
    impl super::Hasher for SipHasher13 {
        #[inline]
        fn write(&mut self, msg: &[u8]) {
            self.hasher.write(msg)
        }

        #[inline]
        fn finish(&self) -> u64 {
            self.hasher.finish()
        }
    }

    impl<S: Sip> super::Hasher for Hasher<S> {
        // see short_write comment for explanation
        #[inline]
        fn write_usize(&mut self, i: usize) {
            let bytes = unsafe {
                ::slice::from_raw_parts(&i as *const usize as *const u8, mem::size_of::<usize>())
            };
            self.short_write(bytes);
        }

        // see short_write comment for explanation
        #[inline]
        fn write_u8(&mut self, i: u8) {
            self.short_write(&[i]);
        }

        #[inline]
        fn write(&mut self, msg: &[u8]) {
            let length = msg.len();
            self.length += length;

            let mut needed = 0;

            if self.ntail != 0 {
                needed = 8 - self.ntail;
                self.tail |= unsafe { u8to64_le(msg, 0, cmp::min(length, needed)) } << 8 * self.ntail;
                if length < needed {
                    self.ntail += length;
                    return
                } else {
                    self.state.v3 ^= self.tail;
                    S::c_rounds(&mut self.state);
                    self.state.v0 ^= self.tail;
                    self.ntail = 0;
                }
            }

            // Buffered tail is now flushed, process new input.
            let len = length - needed;
            let left = len & 0x7;

            let mut i = needed;
            while i < len - left {
                let mi = unsafe { load_int_le!(msg, i, u64) };

                self.state.v3 ^= mi;
                S::c_rounds(&mut self.state);
                self.state.v0 ^= mi;

                i += 8;
            }

            self.tail = unsafe { u8to64_le(msg, i, left) };
            self.ntail = left;
        }

        #[inline]
        fn finish(&self) -> u64 {
            let mut state = self.state;

            let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;

            state.v3 ^= b;
            S::c_rounds(&mut state);
            state.v0 ^= b;

            state.v2 ^= 0xff;
            S::d_rounds(&mut state);

            state.v0 ^ state.v1 ^ state.v2 ^ state.v3
        }
    }

    impl<S: Sip> Clone for Hasher<S> {
        #[inline]
        fn clone(&self) -> Hasher<S> {
            Hasher {
                k0: self.k0,
                k1: self.k1,
                length: self.length,
                state: self.state,
                tail: self.tail,
                ntail: self.ntail,
                _marker: self._marker,
            }
        }
    }

    impl<S: Sip> Default for Hasher<S> {
        /// Creates a `Hasher<S>` with the two initial keys set to 0.
        #[inline]
        fn default() -> Hasher<S> {
            Hasher::new_with_keys(0, 0)
        }
    }

    #[doc(hidden)]
    trait Sip {
        fn c_rounds(_: &mut State);
        fn d_rounds(_: &mut State);
    }

    #[derive(Debug, Clone, Default)]
    struct Sip13Rounds;

    impl Sip for Sip13Rounds {
        #[inline]
        fn c_rounds(state: &mut State) {
            compress!(state);
        }

        #[inline]
        fn d_rounds(state: &mut State) {
            compress!(state);
            compress!(state);
            compress!(state);
        }
    }

    #[derive(Debug, Clone, Default)]
    struct Sip24Rounds;

    impl Sip for Sip24Rounds {
        #[inline]
        fn c_rounds(state: &mut State) {
            compress!(state);
            compress!(state);
        }

        #[inline]
        fn d_rounds(state: &mut State) {
            compress!(state);
            compress!(state);
            compress!(state);
            compress!(state);
        }
    }

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