ahash/src/operations.rs

use crate::convert::*;
#[allow(unused)]
use zerocopy::transmute;

///This constant comes from Kunth's prng (Empirically it works better than those from splitmix32).
pub(crate) const MULTIPLE: u64 = 6364136223846793005;

/// This is a constant with a lot of special properties found by automated search.
/// See the unit tests below. (Below are alternative values)
#[cfg(all(target_feature = "ssse3", not(miri)))]
const SHUFFLE_MASK: u128 = 0x020a0700_0c01030e_050f0d08_06090b04_u128;
//const SHUFFLE_MASK: u128 = 0x000d0702_0a040301_05080f0c_0e0b0609_u128;
//const SHUFFLE_MASK: u128 = 0x040A0700_030E0106_0D050F08_020B0C09_u128;

#[inline(always)]
#[cfg(feature = "folded_multiply")]
pub(crate) const fn folded_multiply(s: u64, by: u64) -> u64 {
    let result = (s as u128).wrapping_mul(by as u128);
    ((result & 0xffff_ffff_ffff_ffff) as u64) ^ ((result >> 64) as u64)
}

#[inline(always)]
#[cfg(not(feature = "folded_multiply"))]
pub(crate) const fn folded_multiply(s: u64, by: u64) -> u64 {
    let b1 = s.wrapping_mul(by.swap_bytes());
    let b2 = s.swap_bytes().wrapping_mul(!by);
    b1 ^ b2.swap_bytes()
}

/// Given a small (less than 8 byte slice) returns the same data stored in two u32s.
/// (order of and non-duplication of bytes is NOT guaranteed)
#[inline(always)]
pub(crate) fn read_small(data: &[u8]) -> [u64; 2] {
    debug_assert!(data.len() <= 8);
    if data.len() >= 2 {
        if data.len() >= 4 {
            //len 4-8
            [data.read_u32().0 as u64, data.read_last_u32() as u64]
        } else {
            //len 2-3
            [data.read_u16().0 as u64, data[data.len() - 1] as u64]
        }
    } else {
        if data.len() > 0 {
            [data[0] as u64, data[0] as u64]
        } else {
            [0, 0]
        }
    }
}

#[inline(always)]
pub(crate) fn shuffle(a: u128) -> u128 {
    #[cfg(all(target_feature = "ssse3", not(miri)))]
    {
        #[cfg(target_arch = "x86")]
        use core::arch::x86::*;
        #[cfg(target_arch = "x86_64")]
        use core::arch::x86_64::*;
        unsafe { transmute!(_mm_shuffle_epi8(transmute!(a), transmute!(SHUFFLE_MASK))) }
    }
    #[cfg(not(all(target_feature = "ssse3", not(miri))))]
    {
        a.swap_bytes()
    }
}

#[allow(unused)] //not used by fallback
#[inline(always)]
pub(crate) fn add_and_shuffle(a: u128, b: u128) -> u128 {
    let sum = add_by_64s(a.convert(), b.convert());
    shuffle(sum.convert())
}

#[allow(unused)] //not used by fallback
#[inline(always)]
pub(crate) fn shuffle_and_add(base: u128, to_add: u128) -> u128 {
    let shuffled: [u64; 2] = shuffle(base).convert();
    add_by_64s(shuffled, to_add.convert()).convert()
}

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "sse2", not(miri)))]
#[inline(always)]
pub(crate) fn add_by_64s(a: [u64; 2], b: [u64; 2]) -> [u64; 2] {
    unsafe {
        #[cfg(target_arch = "x86")]
        use core::arch::x86::*;
        #[cfg(target_arch = "x86_64")]
        use core::arch::x86_64::*;
        transmute!(_mm_add_epi64(transmute!(a), transmute!(b)))
    }
}

#[cfg(not(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "sse2", not(miri))))]
#[inline(always)]
pub(crate) fn add_by_64s(a: [u64; 2], b: [u64; 2]) -> [u64; 2] {
    [a[0].wrapping_add(b[0]), a[1].wrapping_add(b[1])]
}

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes", not(miri)))]
#[allow(unused)]
#[inline(always)]
pub(crate) fn aesenc(value: u128, xor: u128) -> u128 {
    #[cfg(target_arch = "x86")]
    use core::arch::x86::*;
    #[cfg(target_arch = "x86_64")]
    use core::arch::x86_64::*;
    unsafe {
        let value = transmute!(value);
        transmute!(_mm_aesenc_si128(value, transmute!(xor)))
    }
}

#[cfg(any(
    all(feature = "nightly-arm-aes", target_arch = "aarch64", target_feature = "aes", not(miri)),
    all(feature = "nightly-arm-aes", target_arch = "arm", target_feature = "aes", not(miri)),
))]
#[allow(unused)]
#[inline(always)]
pub(crate) fn aesenc(value: u128, xor: u128) -> u128 {
    #[cfg(target_arch = "aarch64")]
    use core::arch::aarch64::*;
    #[cfg(target_arch = "arm")]
    use core::arch::arm::*;
    let res = unsafe { vaesmcq_u8(vaeseq_u8(transmute!(value), transmute!(0u128))) };
    let value: u128 = transmute!(res);
    xor ^ value
}

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes", not(miri)))]
#[allow(unused)]
#[inline(always)]
pub(crate) fn aesdec(value: u128, xor: u128) -> u128 {
    #[cfg(target_arch = "x86")]
    use core::arch::x86::*;
    #[cfg(target_arch = "x86_64")]
    use core::arch::x86_64::*;
    unsafe {
        let value = transmute!(value);
        transmute!(_mm_aesdec_si128(value, transmute!(xor)))
    }
}

#[cfg(any(
    all(feature = "nightly-arm-aes", target_arch = "aarch64", target_feature = "aes", not(miri)),
    all(feature = "nightly-arm-aes", target_arch = "arm", target_feature = "aes", not(miri)),
))]
#[allow(unused)]
#[inline(always)]
pub(crate) fn aesdec(value: u128, xor: u128) -> u128 {
    #[cfg(target_arch = "aarch64")]
    use core::arch::aarch64::*;
    #[cfg(target_arch = "arm")]
    use core::arch::arm::*;
    let res = unsafe { vaesimcq_u8(vaesdq_u8(transmute!(value), transmute!(0u128))) };
    let value: u128 = transmute!(res);
    xor ^ value
}

#[allow(unused)]
#[inline(always)]
pub(crate) fn add_in_length(enc: &mut u128, len: u64) {
    #[cfg(all(target_arch = "x86_64", target_feature = "sse2", not(miri)))]
    {
        #[cfg(target_arch = "x86_64")]
        use core::arch::x86_64::*;

        unsafe {
            let enc = enc as *mut u128;
            let len = _mm_cvtsi64_si128(len as i64);
            let data = _mm_loadu_si128(enc.cast());
            let sum = _mm_add_epi64(data, len);
            _mm_storeu_si128(enc.cast(), sum);
        }
    }
    #[cfg(not(all(target_arch = "x86_64", target_feature = "sse2", not(miri))))]
    {
        let mut t: [u64; 2] = enc.convert();
        t[0] = t[0].wrapping_add(len);
        *enc = t.convert();
    }
}

#[cfg(test)]
mod test {
    use super::*;

    // This is code to search for the shuffle constant
    //
    //thread_local! { static MASK: Cell<u128> = Cell::new(0); }
    //
    // fn shuffle(a: u128) -> u128 {
    //     use std::intrinsics::transmute;
    //     #[cfg(target_arch = "x86")]
    //     use core::arch::x86::*;
    //     #[cfg(target_arch = "x86_64")]
    //     use core::arch::x86_64::*;
    //     MASK.with(|mask| {
    //         unsafe { transmute!(_mm_shuffle_epi8(transmute!(a), transmute!(mask.get()))) }
    //     })
    // }
    //
    // #[test]
    // fn find_shuffle() {
    //     use rand::prelude::*;
    //     use SliceRandom;
    //     use std::panic;
    //     use std::io::Write;
    //
    //     let mut value: [u8; 16] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 ,13, 14, 15];
    //     let mut rand = thread_rng();
    //     let mut successful_list = HashMap::new();
    //     for _attempt in 0..10000000 {
    //         rand.shuffle(&mut value);
    //         let test_val = value.convert();
    //         MASK.with(|mask| {
    //             mask.set(test_val);
    //         });
    //         if let Ok(successful) = panic::catch_unwind(|| {
    //             test_shuffle_does_not_collide_with_aes();
    //             test_shuffle_moves_high_bits();
    //             test_shuffle_moves_every_value();
    //             //test_shuffle_does_not_loop();
    //             value
    //         }) {
    //             let successful: u128 = successful.convert();
    //             successful_list.insert(successful, iters_before_loop());
    //         }
    //     }
    //     let write_file = File::create("/tmp/output").unwrap();
    //     let mut writer = BufWriter::new(&write_file);
    //
    //     for success in successful_list {
    //         writeln!(writer, "Found successful: {:x?} - {:?}", success.0, success.1);
    //     }
    // }
    //
    // fn iters_before_loop() -> u32 {
    //     let numbered = 0x00112233_44556677_8899AABB_CCDDEEFF;
    //     let mut shuffled = shuffle(numbered);
    //     let mut count = 0;
    //     loop {
    //         // println!("{:>16x}", shuffled);
    //         if numbered == shuffled {
    //             break;
    //         }
    //         count += 1;
    //         shuffled = shuffle(shuffled);
    //     }
    //     count
    // }

    #[cfg(all(
        any(target_arch = "x86", target_arch = "x86_64"),
        target_feature = "ssse3",
        target_feature = "aes",
        not(miri)
    ))]
    #[test]
    fn test_shuffle_does_not_collide_with_aes() {
        let mut value: [u8; 16] = [0; 16];
        let zero_mask_enc = aesenc(0, 0);
        let zero_mask_dec = aesdec(0, 0);
        for index in 0..16 {
            value[index] = 1;
            let excluded_positions_enc: [u8; 16] = aesenc(value.convert(), zero_mask_enc).convert();
            let excluded_positions_dec: [u8; 16] = aesdec(value.convert(), zero_mask_dec).convert();
            let actual_location: [u8; 16] = shuffle(value.convert()).convert();
            for pos in 0..16 {
                if actual_location[pos] != 0 {
                    assert_eq!(
                        0, excluded_positions_enc[pos],
                        "Forward Overlap between {:?} and {:?} at {}",
                        excluded_positions_enc, actual_location, index
                    );
                    assert_eq!(
                        0, excluded_positions_dec[pos],
                        "Reverse Overlap between {:?} and {:?} at {}",
                        excluded_positions_dec, actual_location, index
                    );
                }
            }
            value[index] = 0;
        }
    }

    #[test]
    fn test_shuffle_contains_each_value() {
        let value: [u8; 16] = 0x00010203_04050607_08090A0B_0C0D0E0F_u128.convert();
        let shuffled: [u8; 16] = shuffle(value.convert()).convert();
        for index in 0..16_u8 {
            assert!(shuffled.contains(&index), "Value is missing {}", index);
        }
    }

    #[test]
    fn test_shuffle_moves_every_value() {
        let mut value: [u8; 16] = [0; 16];
        for index in 0..16 {
            value[index] = 1;
            let shuffled: [u8; 16] = shuffle(value.convert()).convert();
            assert_eq!(0, shuffled[index], "Value is not moved {}", index);
            value[index] = 0;
        }
    }

    #[test]
    fn test_shuffle_moves_high_bits() {
        assert!(
            shuffle(1) > (1_u128 << 80),
            "Low bits must be moved to other half {:?} -> {:?}",
            0,
            shuffle(1)
        );

        assert!(
            shuffle(1_u128 << 58) >= (1_u128 << 64),
            "High bits must be moved to other half {:?} -> {:?}",
            7,
            shuffle(1_u128 << 58)
        );
        assert!(
            shuffle(1_u128 << 58) < (1_u128 << 112),
            "High bits must not remain high {:?} -> {:?}",
            7,
            shuffle(1_u128 << 58)
        );
        assert!(
            shuffle(1_u128 << 64) < (1_u128 << 64),
            "Low bits must be moved to other half {:?} -> {:?}",
            8,
            shuffle(1_u128 << 64)
        );
        assert!(
            shuffle(1_u128 << 64) >= (1_u128 << 16),
            "Low bits must not remain low {:?} -> {:?}",
            8,
            shuffle(1_u128 << 64)
        );

        assert!(
            shuffle(1_u128 << 120) < (1_u128 << 50),
            "High bits must be moved to low half {:?} -> {:?}",
            15,
            shuffle(1_u128 << 120)
        );
    }

    #[cfg(all(
        any(target_arch = "x86", target_arch = "x86_64"),
        target_feature = "ssse3",
        not(miri)
    ))]
    #[test]
    fn test_shuffle_does_not_loop() {
        let numbered = 0x00112233_44556677_8899AABB_CCDDEEFF;
        let mut shuffled = shuffle(numbered);
        for count in 0..100 {
            // println!("{:>16x}", shuffled);
            assert_ne!(numbered, shuffled, "Equal after {} vs {:x}", count, shuffled);
            shuffled = shuffle(shuffled);
        }
    }

    #[test]
    fn test_add_length() {
        let mut enc = (u64::MAX as u128) << 64 | 50;
        add_in_length(&mut enc, u64::MAX);
        assert_eq!(enc >> 64, u64::MAX as u128);
        assert_eq!(enc as u64, 49);
    }
}