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    // Copyright 2015-2016 Brian Smith.
    // Copyright 2016 Simon Sapin.
    //
    // Permission to use, copy, modify, and/or distribute this software for any
    // purpose with or without fee is hereby granted, provided that the above
    // copyright notice and this permission notice appear in all copies.
    //
    // THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
    // WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
    // MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
    // SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    // WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
    // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
    // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

    use {c, polyfill};
    use core;
    use core::num::Wrapping;

    // XXX: This duplicates super::State and shouldn't need to be public.
    // TODO: Remove the duplication, but be wary of
    // https://github.com/rust-lang/rust/issues/30905.
    pub type State = [u64; super::MAX_CHAINING_LEN / 8];

    pub const BLOCK_LEN: usize = 512 / 8;
    pub const CHAINING_LEN: usize = 160 / 8;
    pub const OUTPUT_LEN: usize = 160 / 8;
    const CHAINING_WORDS: usize = CHAINING_LEN / 4;

    type W32 = Wrapping<u32>;

    #[inline]
    fn ch(x: W32, y: W32, z: W32) -> W32 { (x & y) | (!x & z) }

    #[inline]
    fn parity(x: W32, y: W32, z: W32) -> W32 { x ^ y ^ z }

    #[inline]
    fn maj(x: W32, y: W32, z: W32) -> W32 { (x & y) | (x & z) | (y & z) }

    /// The main purpose in retaining this is to support legacy protocols and OCSP,
    /// none of which need a fast SHA-1 implementation.
    /// This implementation therefore favors size and simplicity over speed.
    /// Unlike SHA-256, SHA-384, and SHA-512,
    /// there is no assembly language implementation.
    pub unsafe extern fn block_data_order(state: &mut State,
                                          data: *const u8, num: c::size_t) {
        let data = data as *const [u8; BLOCK_LEN];
        let blocks = core::slice::from_raw_parts(data, num);
        block_data_order_safe(state, blocks)
    }

    fn block_data_order_safe(state: &mut State, blocks: &[[u8; BLOCK_LEN]]) {
        let state = polyfill::slice::u64_as_u32_mut(state);
        let state = polyfill::slice::as_wrapping_mut(state);
        let state = &mut state[..CHAINING_WORDS];
        let state = slice_as_array_ref_mut!(state, CHAINING_WORDS).unwrap();

        let mut w: [W32; 80] = [Wrapping(0); 80];
        for block in blocks {
            for t in 0..16 {
                let word = slice_as_array_ref!(&block[t * 4..][..4], 4).unwrap();
                w[t] = Wrapping(polyfill::slice::u32_from_be_u8(word))
            }
            for t in 16..80 {
                let wt = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16];
                w[t] = polyfill::wrapping_rotate_left_u32(wt, 1);
            }

            let mut a = state[0];
            let mut b = state[1];
            let mut c = state[2];
            let mut d = state[3];
            let mut e = state[4];

            for t in 0..80 {
                let (k, f) = match t {
                    0...19 => (0x5a827999, ch(b, c, d)),
                    20...39 => (0x6ed9eba1, parity(b, c, d)),
                    40...59 => (0x8f1bbcdc, maj(b, c, d)),
                    60...79 => (0xca62c1d6, parity(b, c, d)),
                    _ => unreachable!(),
                };
                let tt = polyfill::wrapping_rotate_left_u32(a, 5) + f + e +
                         Wrapping(k) + w[t];
                e = d;
                d = c;
                c = polyfill::wrapping_rotate_left_u32(b, 30);
                b = a;
                a = tt;
            }

            state[0] = state[0] + a;
            state[1] = state[1] + b;
            state[2] = state[2] + c;
            state[3] = state[3] + d;
            state[4] = state[4] + e;
        }
    }

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