mega-evm 1.6.1

The evm tailored for the MegaETH
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// Derived from AHash v0.8.12 - see NOTICE.md for full attribution

use super::convert::ReadFromSlice;

#[inline(always)]
fn read_small(data: &[u8]) -> [u64; 2] {
    debug_assert!(data.len() <= 8);
    if data.len() >= 2 {
        if data.len() >= 4 {
            [data.read_u32().0 as u64, data.read_last_u32() as u64]
        } else {
            [data.read_u16().0 as u64, data[data.len() - 1] as u64]
        }
    } else if !data.is_empty() {
        [data[0] as u64, data[0] as u64]
    } else {
        [0, 0]
    }
}

const PI2: [u64; 4] =
    [0x4528_21e6_38d0_1377, 0xbe54_66cf_34e9_0c6c, 0xc0ac_29b7_c97c_50dd, 0x3f84_d5b5_b547_0917];

const MULTIPLE: u64 = 6364136223846793005;
const ROT: u32 = 23;

#[inline(always)]
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)
}

#[derive(Debug, Clone)]
pub(crate) struct RandomState {
    k0: u64,
    k1: u64,
    k2: u64,
    k3: u64,
}

impl RandomState {
    #[inline]
    pub(super) const fn with_seeds(k0: u64, k1: u64, k2: u64, k3: u64) -> Self {
        Self { k0: k0 ^ PI2[0], k1: k1 ^ PI2[1], k2: k2 ^ PI2[2], k3: k3 ^ PI2[3] }
    }
}

#[derive(Debug, Clone)]
pub(crate) struct DeterministicHasher {
    buffer: u64,
    pad: u64,
    extra_keys: [u64; 2],
}

impl DeterministicHasher {
    #[inline(always)]
    fn update(&mut self, new_data: u64) {
        self.buffer = folded_multiply(new_data ^ self.buffer, MULTIPLE);
    }

    #[inline(always)]
    fn large_update(&mut self, new_data: u128) {
        let block: [u64; 2] = [new_data as u64, (new_data >> 64) as u64];
        let combined =
            folded_multiply(block[0] ^ self.extra_keys[0], block[1] ^ self.extra_keys[1]);
        self.buffer = (self.buffer.wrapping_add(self.pad) ^ combined).rotate_left(ROT);
    }
}

impl core::hash::Hasher for DeterministicHasher {
    #[inline]
    fn write_u8(&mut self, i: u8) {
        self.update(i as u64);
    }

    #[inline]
    fn write_u16(&mut self, i: u16) {
        self.update(i as u64);
    }

    #[inline]
    fn write_u32(&mut self, i: u32) {
        self.update(i as u64);
    }

    #[inline]
    fn write_u64(&mut self, i: u64) {
        self.update(i);
    }

    #[inline]
    fn write_u128(&mut self, i: u128) {
        self.large_update(i);
    }

    #[inline]
    fn write_usize(&mut self, i: usize) {
        self.write_u64(i as u64);
    }

    #[inline]
    fn write(&mut self, input: &[u8]) {
        let mut data = input;
        let length = data.len() as u64;

        self.buffer = self.buffer.wrapping_add(length).wrapping_mul(MULTIPLE);

        if data.len() > 8 {
            if data.len() > 16 {
                let tail = data.read_last_u128();
                self.large_update(tail);
                while data.len() > 16 {
                    let (block, rest) = data.read_u128();
                    self.large_update(block);
                    data = rest;
                }
            } else {
                let front = data.read_u64().0;
                let back = data.read_last_u64();
                let combined = (front as u128) | ((back as u128) << 64);
                self.large_update(combined);
            }
        } else {
            let value = read_small(data);
            let combined = (value[0] as u128) | ((value[1] as u128) << 64);
            self.large_update(combined);
        }
    }

    #[inline]
    fn finish(&self) -> u64 {
        let rot = (self.buffer & 63) as u32;
        folded_multiply(self.buffer, self.pad).rotate_left(rot)
    }
}

impl core::hash::BuildHasher for RandomState {
    type Hasher = DeterministicHasher;

    #[inline]
    fn build_hasher(&self) -> Self::Hasher {
        DeterministicHasher { buffer: self.k1, pad: self.k0, extra_keys: [self.k2, self.k3] }
    }
}