blake2s_const/

lib.rs

//! [![GitHub](https://img.shields.io/github/tag/oconnor663/blake2_simd.svg?label=GitHub)](https://github.com/oconnor663/blake2_simd) [![crates.io](https://img.shields.io/crates/v/blake2s_simd.svg)](https://crates.io/crates/blake2s_simd) [![Build Status](https://travis-ci.org/oconnor663/blake2_simd.svg?branch=master)](https://travis-ci.org/oconnor663/blake2_simd)
//!
//! An implementation of the BLAKE2s and BLAKE2sp hash functions. See also
//! [`blake2b_simd`](https://docs.rs/blake2b_simd).
//!
//! This crate includes:
//!
//! - 100% stable Rust.
//! - SIMD implementations based on Samuel Neves' [`blake2-avx2`](https://github.com/sneves/blake2-avx2).
//!   These are very fast. For benchmarks, see [the Performance section of the
//!   README](https://github.com/oconnor663/blake2_simd#performance).
//! - Portable, safe implementations for other platforms.
//! - Dynamic CPU feature detection. Binaries include multiple implementations by default and
//!   choose the fastest one the processor supports at runtime.
//! - All the features from the [the BLAKE2 spec](https://blake2.net/blake2.pdf), like adjustable
//!   length, keying, and associated data for tree hashing.
//! - `no_std` support. The `std` Cargo feature is on by default, for CPU feature detection and
//!   for implementing `std::io::Write`.
//! - Support for computing multiple BLAKE2s hashes in parallel, matching the efficiency of
//!   BLAKE2sp. See the [`many`](many/index.html) module.
//!
//! # Example
//!
//! ```
//! use blake2s_simd::{blake2s, Params};
//!
//! let expected = "08d6cad88075de8f192db097573d0e829411cd91eb6ec65e8fc16c017edfdb74";
//! let hash = blake2s(b"foo");
//! assert_eq!(expected, &hash.to_hex());
//!
//! let hash = Params::new()
//!     .hash_length(16)
//!     .key(b"Squeamish Ossifrage")
//!     .personal(b"Shaftoe")
//!     .to_state()
//!     .update(b"foo")
//!     .update(b"bar")
//!     .update(b"baz")
//!     .finalize();
//! assert_eq!("28325512782cbf5019424fa65da9a6c7", &hash.to_hex());
//! ```

#![cfg_attr(not(feature = "std"), no_std)]

use arrayref::{array_refs, mut_array_refs};
use core::cmp;
use core::fmt;
use core::mem::size_of;

#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
mod avx2;
mod portable;
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
mod sse41;

pub mod blake2sp;
mod guts;
pub mod many;

#[cfg(test)]
mod test;

pub use guts::{Implementation, Platform};

type Word = u32;
type Count = u64;

/// The max hash length.
pub const OUTBYTES: usize = 8 * size_of::<Word>();
/// The max key length.
pub const KEYBYTES: usize = 8 * size_of::<Word>();
/// The max salt length.
pub const SALTBYTES: usize = 2 * size_of::<Word>();
/// The max personalization length.
pub const PERSONALBYTES: usize = 2 * size_of::<Word>();
/// The number input bytes passed to each call to the compression function. Small benchmarks need
/// to use an even multiple of `BLOCKBYTES`, or else their apparent throughput will be low.
pub const BLOCKBYTES: usize = 16 * size_of::<Word>();

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "avx2"))]
const EMPTY_PARAMS: Params = Params::new_for_implementation(Implementation(Platform::AVX2));

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), all(not(target_feature = "avx2"),target_feature = "sse4.1")))]
const EMPTY_PARAMS: Params = Params::new_for_implementation(Implementation(Platform::SSE41));

#[cfg(not(
    any(
        all(
            any(target_arch = "x86", target_arch = "x86_64"),
            target_feature = "avx2"
        ),
        all(
            any(target_arch = "x86", target_arch = "x86_64"), 
            target_feature = "sse4.1"
        ),
    )
))]
const EMPTY_PARAMS: Params = Params::new_for_implementation(Implementation(Platform::Portable));

const EMPTY_WORDS: [Word; 8] = EMPTY_PARAMS.empty_words();

const IV: [Word; 8] = [
    0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A, 0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19,
];

const SIGMA: [[u8; 16]; 10] = [
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
    [14, 10, 4, 8, 9, 15, 13, 6, 1, 12, 0, 2, 11, 7, 5, 3],
    [11, 8, 12, 0, 5, 2, 15, 13, 10, 14, 3, 6, 7, 1, 9, 4],
    [7, 9, 3, 1, 13, 12, 11, 14, 2, 6, 5, 10, 4, 0, 15, 8],
    [9, 0, 5, 7, 2, 4, 10, 15, 14, 1, 11, 12, 6, 8, 3, 13],
    [2, 12, 6, 10, 0, 11, 8, 3, 4, 13, 7, 5, 15, 14, 1, 9],
    [12, 5, 1, 15, 14, 13, 4, 10, 0, 7, 6, 3, 9, 2, 8, 11],
    [13, 11, 7, 14, 12, 1, 3, 9, 5, 0, 15, 4, 8, 6, 2, 10],
    [6, 15, 14, 9, 11, 3, 0, 8, 12, 2, 13, 7, 1, 4, 10, 5],
    [10, 2, 8, 4, 7, 6, 1, 5, 15, 11, 9, 14, 3, 12, 13, 0],
];

/// Compute the BLAKE2s hash of a slice of bytes all at once, using default
/// parameters.
///
/// # Example
///
/// ```
/// # use blake2s_simd::{blake2s, Params};
/// let expected = "08d6cad88075de8f192db097573d0e829411cd91eb6ec65e8fc16c017edfdb74";
/// let hash = blake2s(b"foo");
/// assert_eq!(expected, &hash.to_hex());
/// ```
pub fn blake2s(input: &[u8]) -> Hash {
    Params::new().hash(input)
}

pub fn blake2s_const(input: &[u8]) -> Hash {
    EMPTY_PARAMS.hash_without_state(input)
}

/// A parameter builder that exposes all the non-default BLAKE2 features.
///
/// Apart from `hash_length`, which controls the length of the final `Hash`,
/// all of these parameters are just associated data that gets mixed with the
/// input. For more details, see [the BLAKE2 spec](https://blake2.net/blake2.pdf).
///
/// Several of the parameters have a valid range defined in the spec and
/// documented below. Trying to set an invalid parameter will panic.
///
/// # Example
///
/// ```
/// # use blake2s_simd::Params;
/// // Create a Params object with a secret key and a non-default length.
/// let mut params = Params::new();
/// params.key(b"my secret key");
/// params.hash_length(16);
///
/// // Use those params to hash an input all at once.
/// let hash = params.hash(b"my input");
///
/// // Or use those params to build an incremental State.
/// let mut state = params.to_state();
/// ```
#[derive(Clone)]
pub struct Params {
    hash_length: u8,
    key_length: u8,
    key_block: [u8; BLOCKBYTES],
    salt: [u8; SALTBYTES],
    personal: [u8; PERSONALBYTES],
    fanout: u8,
    max_depth: u8,
    max_leaf_length: u32,
    node_offset: u64,
    node_depth: u8,
    inner_hash_length: u8,
    last_node: guts::LastNode,
    implementation: guts::Implementation,
}

impl Params {
    /// Equivalent to `Params::default()`.
    #[inline]
    pub fn new() -> Self {
        Self {
            hash_length: OUTBYTES as u8,
            key_length: 0,
            key_block: [0; BLOCKBYTES],
            salt: [0; SALTBYTES],
            personal: [0; PERSONALBYTES],
            // NOTE: fanout and max_depth don't default to zero!
            fanout: 1,
            max_depth: 1,
            max_leaf_length: 0,
            node_offset: 0,
            node_depth: 0,
            inner_hash_length: 0,
            last_node: guts::LastNode::No,
            implementation: guts::Implementation::detect(),
        }
    }

    /// Equivalent to `Params::default()`.
    #[inline]
    pub const fn new_for_implementation(implementation: Implementation) -> Self {
        Self {
            hash_length: OUTBYTES as u8,
            key_length: 0,
            key_block: [0; BLOCKBYTES],
            salt: [0; SALTBYTES],
            personal: [0; PERSONALBYTES],
            // NOTE: fanout and max_depth don't default to zero!
            fanout: 1,
            max_depth: 1,
            max_leaf_length: 0,
            node_offset: 0,
            node_depth: 0,
            inner_hash_length: 0,
            last_node: guts::LastNode::No,
            implementation: implementation,
        }
    }

    #[inline(always)]
    fn to_words(&self) -> [Word; 8] {
        let (salt_left, salt_right) = array_refs!(&self.salt, SALTBYTES / 2, SALTBYTES / 2);
        let (personal_left, personal_right) =
            array_refs!(&self.personal, PERSONALBYTES / 2, PERSONALBYTES / 2);
        [
            IV[0]
                ^ self.hash_length as u32
                ^ (self.key_length as u32) << 8
                ^ (self.fanout as u32) << 16
                ^ (self.max_depth as u32) << 24,
            IV[1] ^ self.max_leaf_length,
            IV[2] ^ self.node_offset as u32,
            IV[3]
                ^ (self.node_offset >> 32) as u32
                ^ (self.node_depth as u32) << 16
                ^ (self.inner_hash_length as u32) << 24,
            IV[4] ^ Word::from_le_bytes(*salt_left),
            IV[5] ^ Word::from_le_bytes(*salt_right),
            IV[6] ^ Word::from_le_bytes(*personal_left),
            IV[7] ^ Word::from_le_bytes(*personal_right),
        ]
    }

    #[inline(always)]
    const fn empty_words(&self) -> [Word; 8] {
        [
            IV[0]
                ^ self.hash_length as u32
                ^ (self.key_length as u32) << 8
                ^ (self.fanout as u32) << 16
                ^ (self.max_depth as u32) << 24,
            IV[1] ^ self.max_leaf_length,
            IV[2] ^ self.node_offset as u32,
            IV[3]
                ^ (self.node_offset >> 32) as u32
                ^ (self.node_depth as u32) << 16
                ^ (self.inner_hash_length as u32) << 24,
            IV[4] ^ 0,
            IV[5] ^ 0,
            IV[6] ^ 0,
            IV[7] ^ 0,
        ]
    }

    /// Hash an input all at once with these parameters.
    #[inline]
    pub fn hash(&self, input: &[u8]) -> Hash {
        // If there's a key, just fall back to using the State.
        if self.key_length > 0 {
            return self.to_state().update(input).finalize();
        }
        let mut words = self.to_words();
        self.implementation.compress1_loop(
            input,
            &mut words,
            0,
            self.last_node,
            guts::Finalize::Yes,
            guts::Stride::Serial,
        );
        Hash {
            bytes: state_words_to_bytes(&words),
            len: self.hash_length,
        }
    }

    /// Hash an input without keying and specialization.
    #[inline]
    pub fn hash_without_state(&self, input: &[u8]) -> Hash {
        let mut words = EMPTY_WORDS;
        self.implementation.compress1_loop(
            input,
            &mut words,
            0,
            self.last_node,
            guts::Finalize::Yes,
            guts::Stride::Serial,
        );
        Hash {
            bytes: state_words_to_bytes(&words),
            len: self.hash_length,
        }
    }

    /// Construct a `State` object based on these parameters, for hashing input
    /// incrementally.
    pub fn to_state(&self) -> State {
        State::with_params(self)
    }

    /// Set the length of the final hash in bytes, from 1 to `OUTBYTES` (32). Apart from
    /// controlling the length of the final `Hash`, this is also associated data, and changing it
    /// will result in a totally different hash.
    #[inline]
    pub fn hash_length(&mut self, length: usize) -> &mut Self {
        assert!(
            1 <= length && length <= OUTBYTES,
            "Bad hash length: {}",
            length
        );
        self.hash_length = length as u8;
        self
    }

    /// Use a secret key, so that BLAKE2 acts as a MAC. The maximum key length is `KEYBYTES` (32).
    /// An empty key is equivalent to having no key at all.
    #[inline]
    pub fn key(&mut self, key: &[u8]) -> &mut Self {
        assert!(key.len() <= KEYBYTES, "Bad key length: {}", key.len());
        self.key_length = key.len() as u8;
        self.key_block = [0; BLOCKBYTES];
        self.key_block[..key.len()].copy_from_slice(key);
        self
    }

    /// At most `SALTBYTES` (8). Shorter salts are padded with null bytes. An empty salt is
    /// equivalent to having no salt at all.
    #[inline]
    pub fn salt(&mut self, salt: &[u8]) -> &mut Self {
        assert!(salt.len() <= SALTBYTES, "Bad salt length: {}", salt.len());
        self.salt = [0; SALTBYTES];
        self.salt[..salt.len()].copy_from_slice(salt);
        self
    }

    /// At most `PERSONALBYTES` (8). Shorter personalizations are padded with null bytes. An empty
    /// personalization is equivalent to having no personalization at all.
    #[inline]
    pub fn personal(&mut self, personalization: &[u8]) -> &mut Self {
        assert!(
            personalization.len() <= PERSONALBYTES,
            "Bad personalization length: {}",
            personalization.len()
        );
        self.personal = [0; PERSONALBYTES];
        self.personal[..personalization.len()].copy_from_slice(personalization);
        self
    }

    /// From 0 (meaning unlimited) to 255. The default is 1 (meaning sequential).
    #[inline]
    pub fn fanout(&mut self, fanout: u8) -> &mut Self {
        self.fanout = fanout;
        self
    }

    /// From 0 (meaning BLAKE2X B2 hashes), through 1 (the default, meaning sequential) to 255 (meaning unlimited).
    #[inline]
    pub fn max_depth(&mut self, depth: u8) -> &mut Self {
        self.max_depth = depth;
        self
    }

    /// From 0 (the default, meaning unlimited or sequential) to `2^32 - 1`.
    #[inline]
    pub fn max_leaf_length(&mut self, length: u32) -> &mut Self {
        self.max_leaf_length = length;
        self
    }

    /// From 0 (the default, meaning first, leftmost, leaf, or sequential) to `2^48 - 1`.
    #[inline]
    pub fn node_offset(&mut self, offset: u64) -> &mut Self {
        assert!(offset < (1 << 48), "Bad node offset: {}", offset);
        self.node_offset = offset;
        self
    }

    /// From 0 (the default, meaning leaf or sequential) to 255.
    #[inline]
    pub fn node_depth(&mut self, depth: u8) -> &mut Self {
        self.node_depth = depth;
        self
    }

    /// From 0 (the default, meaning sequential) to `OUTBYTES` (32).
    #[inline]
    pub fn inner_hash_length(&mut self, length: usize) -> &mut Self {
        assert!(length <= OUTBYTES, "Bad inner hash length: {}", length);
        self.inner_hash_length = length as u8;
        self
    }

    /// Indicates the rightmost node in a row. This can also be changed on the
    /// `State` object, potentially after hashing has begun. See
    /// [`State::set_last_node`].
    ///
    /// [`State::set_last_node`]: struct.State.html#method.set_last_node
    #[inline]
    pub fn last_node(&mut self, last_node: bool) -> &mut Self {
        self.last_node = if last_node {
            guts::LastNode::Yes
        } else {
            guts::LastNode::No
        };
        self
    }
}

impl Default for Params {
    fn default() -> Self {
        Self::new()
    }
}

impl fmt::Debug for Params {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "Params {{ hash_length: {}, key_length: {}, salt: {:?}, personal: {:?}, fanout: {}, \
             max_depth: {}, max_leaf_length: {}, node_offset: {}, node_depth: {}, \
             inner_hash_length: {}, last_node: {} }}",
            self.hash_length,
            // NB: Don't print the key itself. Debug shouldn't leak secrets.
            self.key_length,
            &self.salt,
            &self.personal,
            self.fanout,
            self.max_depth,
            self.max_leaf_length,
            self.node_offset,
            self.node_depth,
            self.inner_hash_length,
            self.last_node.yes(),
        )
    }
}

/// An incremental hasher for BLAKE2s.
///
/// To construct a `State` with non-default parameters, see `Params::to_state`.
///
/// # Example
///
/// ```
/// use blake2s_simd::{State, blake2s};
///
/// let mut state = blake2s_simd::State::new();
///
/// state.update(b"foo");
/// assert_eq!(blake2s(b"foo"), state.finalize());
///
/// state.update(b"bar");
/// assert_eq!(blake2s(b"foobar"), state.finalize());
/// ```
#[derive(Clone)]
pub struct State {
    words: [Word; 8],
    count: Count,
    buf: [u8; BLOCKBYTES],
    buflen: u8,
    last_node: guts::LastNode,
    hash_length: u8,
    implementation: guts::Implementation,
    is_keyed: bool,
}

impl State {
    /// Equivalent to `State::default()` or `Params::default().to_state()`.
    pub fn new() -> Self {
        Self::with_params(&Params::default())
    }

    fn with_params(params: &Params) -> Self {
        let mut state = Self {
            words: params.to_words(),
            count: 0,
            buf: [0; BLOCKBYTES],
            buflen: 0,
            last_node: params.last_node,
            hash_length: params.hash_length,
            implementation: params.implementation,
            is_keyed: params.key_length > 0,
        };
        if state.is_keyed {
            state.buf = params.key_block;
            state.buflen = state.buf.len() as u8;
        }
        state
    }

    fn fill_buf(&mut self, input: &mut &[u8]) {
        let take = cmp::min(BLOCKBYTES - self.buflen as usize, input.len());
        self.buf[self.buflen as usize..self.buflen as usize + take].copy_from_slice(&input[..take]);
        self.buflen += take as u8;
        *input = &input[take..];
    }

    // If the state already has some input in its buffer, try to fill the buffer and perform a
    // compression. However, only do the compression if there's more input coming, otherwise it
    // will give the wrong hash it the caller finalizes immediately after.
    fn compress_buffer_if_possible(&mut self, input: &mut &[u8]) {
        if self.buflen > 0 {
            self.fill_buf(input);
            if !input.is_empty() {
                self.implementation.compress1_loop(
                    &self.buf,
                    &mut self.words,
                    self.count,
                    self.last_node,
                    guts::Finalize::No,
                    guts::Stride::Serial,
                );
                self.count = self.count.wrapping_add(BLOCKBYTES as Count);
                self.buflen = 0;
            }
        }
    }

    /// Add input to the hash. You can call `update` any number of times.
    pub fn update(&mut self, mut input: &[u8]) -> &mut Self {
        // If we have a partial buffer, try to complete it.
        self.compress_buffer_if_possible(&mut input);
        // While there's more than a block of input left (which also means we cleared the buffer
        // above), compress blocks directly without copying.
        let mut end = input.len().saturating_sub(1);
        end -= end % BLOCKBYTES;
        if end > 0 {
            self.implementation.compress1_loop(
                &input[..end],
                &mut self.words,
                self.count,
                self.last_node,
                guts::Finalize::No,
                guts::Stride::Serial,
            );
            self.count = self.count.wrapping_add(end as Count);
            input = &input[end..];
        }
        // Buffer any remaining input, to be either compressed or finalized in a subsequent call.
        // Note that this represents some copying overhead, which in theory we could avoid in
        // all-at-once setting. A function hardcoded for exactly BLOCKSIZE input bytes is about 10%
        // faster than using this implementation for the same input.
        self.fill_buf(&mut input);
        self
    }

    /// Finalize the state and return a `Hash`. This method is idempotent, and calling it multiple
    /// times will give the same result. It's also possible to `update` with more input in between.
    pub fn finalize(&self) -> Hash {
        let mut words_copy = self.words;
        self.implementation.compress1_loop(
            &self.buf[..self.buflen as usize],
            &mut words_copy,
            self.count,
            self.last_node,
            guts::Finalize::Yes,
            guts::Stride::Serial,
        );
        Hash {
            bytes: state_words_to_bytes(&words_copy),
            len: self.hash_length,
        }
    }

    /// Set a flag indicating that this is the last node of its level in a tree hash. This is
    /// equivalent to [`Params::last_node`], except that it can be set at any time before calling
    /// `finalize`. That allows callers to begin hashing a node without knowing ahead of time
    /// whether it's the last in its level. For more details about the intended use of this flag
    /// [the BLAKE2 spec].
    ///
    /// [`Params::last_node`]: struct.Params.html#method.last_node
    /// [the BLAKE2 spec]: https://blake2.net/blake2.pdf
    pub fn set_last_node(&mut self, last_node: bool) -> &mut Self {
        self.last_node = if last_node {
            guts::LastNode::Yes
        } else {
            guts::LastNode::No
        };
        self
    }

    /// Return the total number of bytes input so far.
    ///
    /// Note that `count` doesn't include the bytes of the key block, if any.
    /// It's exactly the total number of input bytes fed to `update`.
    pub fn count(&self) -> Count {
        let mut ret = self.count.wrapping_add(self.buflen as Count);
        if self.is_keyed {
            ret -= BLOCKBYTES as Count;
        }
        ret
    }
}

#[inline(always)]
fn state_words_to_bytes(state_words: &[Word; 8]) -> [u8; OUTBYTES] {
    let mut bytes = [0; OUTBYTES];
    {
        const W: usize = size_of::<Word>();
        let refs = mut_array_refs!(&mut bytes, W, W, W, W, W, W, W, W);
        *refs.0 = state_words[0].to_le_bytes();
        *refs.1 = state_words[1].to_le_bytes();
        *refs.2 = state_words[2].to_le_bytes();
        *refs.3 = state_words[3].to_le_bytes();
        *refs.4 = state_words[4].to_le_bytes();
        *refs.5 = state_words[5].to_le_bytes();
        *refs.6 = state_words[6].to_le_bytes();
        *refs.7 = state_words[7].to_le_bytes();
    }
    bytes
}

#[cfg(feature = "std")]
impl std::io::Write for State {
    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
        self.update(buf);
        Ok(buf.len())
    }

    fn flush(&mut self) -> std::io::Result<()> {
        Ok(())
    }
}

impl fmt::Debug for State {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        // NB: Don't print the words. Leaking them would allow length extension.
        write!(
            f,
            "State {{ count: {}, hash_length: {}, last_node: {} }}",
            self.count(),
            self.hash_length,
            self.last_node.yes(),
        )
    }
}

impl Default for State {
    fn default() -> Self {
        Self::with_params(&Params::default())
    }
}

type HexString = arrayvec::ArrayString<[u8; 2 * OUTBYTES]>;

/// A finalized BLAKE2 hash, with constant-time equality.
#[derive(Clone, Copy)]
pub struct Hash {
    bytes: [u8; OUTBYTES],
    len: u8,
}

impl Hash {
    /// Convert the hash to a byte slice. Note that if you're using BLAKE2 as a MAC, you need
    /// constant time equality, which `&[u8]` doesn't provide.
    pub fn as_bytes(&self) -> &[u8] {
        &self.bytes[..self.len as usize]
    }

    /// Convert the hash to a byte array. Note that if you're using BLAKE2 as a
    /// MAC, you need constant time equality, which arrays don't provide. This
    /// panics in debug mode if the length of the hash isn't `OUTBYTES`.
    #[inline]
    pub fn as_array(&self) -> &[u8; OUTBYTES] {
        debug_assert_eq!(self.len as usize, OUTBYTES);
        &self.bytes
    }

    /// Convert the hash to a lowercase hexadecimal
    /// [`ArrayString`](https://docs.rs/arrayvec/0.4/arrayvec/struct.ArrayString.html).
    pub fn to_hex(&self) -> HexString {
        bytes_to_hex(self.as_bytes())
    }
}

fn bytes_to_hex(bytes: &[u8]) -> HexString {
    let mut s = arrayvec::ArrayString::new();
    let table = b"0123456789abcdef";
    for &b in bytes {
        s.push(table[(b >> 4) as usize] as char);
        s.push(table[(b & 0xf) as usize] as char);
    }
    s
}

/// This implementation is constant time, if the two hashes are the same length.
impl PartialEq for Hash {
    fn eq(&self, other: &Hash) -> bool {
        constant_time_eq::constant_time_eq(&self.as_bytes(), &other.as_bytes())
    }
}

/// This implementation is constant time, if the slice is the same length as the hash.
impl PartialEq<[u8]> for Hash {
    fn eq(&self, other: &[u8]) -> bool {
        constant_time_eq::constant_time_eq(&self.as_bytes(), other)
    }
}

impl Eq for Hash {}

impl AsRef<[u8]> for Hash {
    fn as_ref(&self) -> &[u8] {
        self.as_bytes()
    }
}

impl fmt::Debug for Hash {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Hash(0x{})", self.to_hex())
    }
}

// Paint a byte pattern that won't repeat, so that we don't accidentally miss
// buffer offset bugs. This is the same as what Bao uses in its tests.
#[cfg(test)]
fn paint_test_input(buf: &mut [u8]) {
    let mut offset = 0;
    let mut counter: u32 = 1;
    while offset < buf.len() {
        let bytes = counter.to_le_bytes();
        let take = cmp::min(bytes.len(), buf.len() - offset);
        buf[offset..][..take].copy_from_slice(&bytes[..take]);
        counter += 1;
        offset += take;
    }
}

// This module is pub for internal benchmarks only. Please don't use it.
#[doc(hidden)]
pub mod benchmarks {
    use super::*;

    pub fn force_portable(params: &mut Params) {
        params.implementation = guts::Implementation::portable();
    }

    pub fn force_portable_blake2sp(params: &mut blake2sp::Params) {
        blake2sp::force_portable(params);
    }
}