# guts.rs - source
Source of the Rust file `/home/key/.cargo/registry/src/github.com-1ecc6299db9ec823/rand_chacha-0.3.1/src/guts.rs`.
Keywords: rust, rustlang, rust-lang

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    // Copyright 2019 The CryptoCorrosion Contributors
    // Copyright 2020 Developers of the Rand project.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! The ChaCha random number generator.

    use ppv_lite86::{dispatch, dispatch_light128};

    pub use ppv_lite86::Machine;
    use ppv_lite86::{vec128_storage, ArithOps, BitOps32, LaneWords4, MultiLane, StoreBytes, Vec4};

    pub(crate) const BLOCK: usize = 64;
    pub(crate) const BLOCK64: u64 = BLOCK as u64;
    const LOG2_BUFBLOCKS: u64 = 2;
    const BUFBLOCKS: u64 = 1 << LOG2_BUFBLOCKS;
    pub(crate) const BUFSZ64: u64 = BLOCK64 * BUFBLOCKS;
    pub(crate) const BUFSZ: usize = BUFSZ64 as usize;

    const STREAM_PARAM_NONCE: u32 = 1;
    const STREAM_PARAM_BLOCK: u32 = 0;

    #[derive(Clone, PartialEq, Eq)]
    pub struct ChaCha {
        pub(crate) b: vec128_storage,
        pub(crate) c: vec128_storage,
        pub(crate) d: vec128_storage,
    }

    #[derive(Clone)]
    pub struct State<V> {
        pub(crate) a: V,
        pub(crate) b: V,
        pub(crate) c: V,
        pub(crate) d: V,
    }

    #[inline(always)]
    pub(crate) fn round<V: ArithOps + BitOps32>(mut x: State<V>) -> State<V> {
        x.a += x.b;
        x.d = (x.d ^ x.a).rotate_each_word_right16();
        x.c += x.d;
        x.b = (x.b ^ x.c).rotate_each_word_right20();
        x.a += x.b;
        x.d = (x.d ^ x.a).rotate_each_word_right24();
        x.c += x.d;
        x.b = (x.b ^ x.c).rotate_each_word_right25();
        x
    }

    #[inline(always)]
    pub(crate) fn diagonalize<V: LaneWords4>(mut x: State<V>) -> State<V> {
        x.b = x.b.shuffle_lane_words3012();
        x.c = x.c.shuffle_lane_words2301();
        x.d = x.d.shuffle_lane_words1230();
        x
    }
    #[inline(always)]
    pub(crate) fn undiagonalize<V: LaneWords4>(mut x: State<V>) -> State<V> {
        x.b = x.b.shuffle_lane_words1230();
        x.c = x.c.shuffle_lane_words2301();
        x.d = x.d.shuffle_lane_words3012();
        x
    }

    impl ChaCha {
        #[inline(always)]
        pub fn new(key: &[u8; 32], nonce: &[u8]) -> Self {
            init_chacha(key, nonce)
        }

        #[inline(always)]
        fn pos64<M: Machine>(&self, m: M) -> u64 {
            let d: M::u32x4 = m.unpack(self.d);
            ((d.extract(1) as u64) << 32) | d.extract(0) as u64
        }

        /// Produce 4 blocks of output, advancing the state
        #[inline(always)]
        pub fn refill4(&mut self, drounds: u32, out: &mut [u8; BUFSZ]) {
            refill_wide(self, drounds, out)
        }

        #[inline(always)]
        pub fn set_block_pos(&mut self, value: u64) {
            set_stream_param(self, STREAM_PARAM_BLOCK, value)
        }

        #[inline(always)]
        pub fn get_block_pos(&self) -> u64 {
            get_stream_param(self, STREAM_PARAM_BLOCK)
        }

        #[inline(always)]
        pub fn set_nonce(&mut self, value: u64) {
            set_stream_param(self, STREAM_PARAM_NONCE, value)
        }

        #[inline(always)]
        pub fn get_nonce(&self) -> u64 {
            get_stream_param(self, STREAM_PARAM_NONCE)
        }

        #[inline(always)]
        pub fn get_seed(&self) -> [u8; 32] {
            get_seed(self)
        }
    }

    #[allow(clippy::many_single_char_names)]
    #[inline(always)]
    fn refill_wide_impl<Mach: Machine>(
        m: Mach, state: &mut ChaCha, drounds: u32, out: &mut [u8; BUFSZ],
    ) {
        let k = m.vec([0x6170_7865, 0x3320_646e, 0x7962_2d32, 0x6b20_6574]);
        let mut pos = state.pos64(m);
        let d0: Mach::u32x4 = m.unpack(state.d);
        pos = pos.wrapping_add(1);
        let d1 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
        pos = pos.wrapping_add(1);
        let d2 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
        pos = pos.wrapping_add(1);
        let d3 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);

        let b = m.unpack(state.b);
        let c = m.unpack(state.c);
        let mut x = State {
            a: Mach::u32x4x4::from_lanes([k, k, k, k]),
            b: Mach::u32x4x4::from_lanes([b, b, b, b]),
            c: Mach::u32x4x4::from_lanes([c, c, c, c]),
            d: m.unpack(Mach::u32x4x4::from_lanes([d0, d1, d2, d3]).into()),
        };
        for _ in 0..drounds {
            x = round(x);
            x = undiagonalize(round(diagonalize(x)));
        }
        let mut pos = state.pos64(m);
        let d0: Mach::u32x4 = m.unpack(state.d);
        pos = pos.wrapping_add(1);
        let d1 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
        pos = pos.wrapping_add(1);
        let d2 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
        pos = pos.wrapping_add(1);
        let d3 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);
        pos = pos.wrapping_add(1);
        let d4 = d0.insert((pos >> 32) as u32, 1).insert(pos as u32, 0);

        let (a, b, c, d) = (
            x.a.to_lanes(),
            x.b.to_lanes(),
            x.c.to_lanes(),
            x.d.to_lanes(),
        );
        let sb = m.unpack(state.b);
        let sc = m.unpack(state.c);
        let sd = [m.unpack(state.d), d1, d2, d3];
        state.d = d4.into();
        let mut words = out.chunks_exact_mut(16);
        for ((((&a, &b), &c), &d), &sd) in a.iter().zip(&b).zip(&c).zip(&d).zip(&sd) {
            (a + k).write_le(words.next().unwrap());
            (b + sb).write_le(words.next().unwrap());
            (c + sc).write_le(words.next().unwrap());
            (d + sd).write_le(words.next().unwrap());
        }
    }

    dispatch!(m, Mach, {
        fn refill_wide(state: &mut ChaCha, drounds: u32, out: &mut [u8; BUFSZ]) {
            refill_wide_impl(m, state, drounds, out);
        }
    });

    // Single-block, rounds-only; shared by try_apply_keystream for tails shorter than BUFSZ
    // and XChaCha's setup step.
    dispatch!(m, Mach, {
        fn refill_narrow_rounds(state: &mut ChaCha, drounds: u32) -> State<vec128_storage> {
            let k: Mach::u32x4 = m.vec([0x6170_7865, 0x3320_646e, 0x7962_2d32, 0x6b20_6574]);
            let mut x = State {
                a: k,
                b: m.unpack(state.b),
                c: m.unpack(state.c),
                d: m.unpack(state.d),
            };
            for _ in 0..drounds {
                x = round(x);
                x = undiagonalize(round(diagonalize(x)));
            }
            State {
                a: x.a.into(),
                b: x.b.into(),
                c: x.c.into(),
                d: x.d.into(),
            }
        }
    });

    dispatch_light128!(m, Mach, {
        fn set_stream_param(state: &mut ChaCha, param: u32, value: u64) {
            let d: Mach::u32x4 = m.unpack(state.d);
            state.d = d
                .insert((value >> 32) as u32, (param << 1) | 1)
                .insert(value as u32, param << 1)
                .into();
        }
    });

    dispatch_light128!(m, Mach, {
        fn get_stream_param(state: &ChaCha, param: u32) -> u64 {
            let d: Mach::u32x4 = m.unpack(state.d);
            ((d.extract((param << 1) | 1) as u64) << 32) | d.extract(param << 1) as u64
        }
    });

    dispatch_light128!(m, Mach, {
        fn get_seed(state: &ChaCha) -> [u8; 32] {
            let b: Mach::u32x4 = m.unpack(state.b);
            let c: Mach::u32x4 = m.unpack(state.c);
            let mut key = [0u8; 32];
            b.write_le(&mut key[..16]);
            c.write_le(&mut key[16..]);
            key
        }
    });

    fn read_u32le(xs: &[u8]) -> u32 {
        assert_eq!(xs.len(), 4);
        u32::from(xs[0]) | (u32::from(xs[1]) << 8) | (u32::from(xs[2]) << 16) | (u32::from(xs[3]) << 24)
    }

    dispatch_light128!(m, Mach, {
        fn init_chacha(key: &[u8; 32], nonce: &[u8]) -> ChaCha {
            let ctr_nonce = [
                0,
                if nonce.len() == 12 {
                    read_u32le(&nonce[0..4])
                } else {
                    0
                },
                read_u32le(&nonce[nonce.len() - 8..nonce.len() - 4]),
                read_u32le(&nonce[nonce.len() - 4..]),
            ];
            let key0: Mach::u32x4 = m.read_le(&key[..16]);
            let key1: Mach::u32x4 = m.read_le(&key[16..]);
            ChaCha {
                b: key0.into(),
                c: key1.into(),
                d: ctr_nonce.into(),
            }
        }
    });

    dispatch_light128!(m, Mach, {
        fn init_chacha_x(key: &[u8; 32], nonce: &[u8; 24], rounds: u32) -> ChaCha {
            let key0: Mach::u32x4 = m.read_le(&key[..16]);
            let key1: Mach::u32x4 = m.read_le(&key[16..]);
            let nonce0: Mach::u32x4 = m.read_le(&nonce[..16]);
            let mut state = ChaCha {
                b: key0.into(),
                c: key1.into(),
                d: nonce0.into(),
            };
            let x = refill_narrow_rounds(&mut state, rounds);
            let ctr_nonce1 = [0, 0, read_u32le(&nonce[16..20]), read_u32le(&nonce[20..24])];
            state.b = x.a;
            state.c = x.d;
            state.d = ctr_nonce1.into();
            state
        }
    });