1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158

//! # aHash
//!
//! This hashing algorithm is intended to be a high performance, (hardware specific), keyed hash function.
//! This can be seen as a DOS resistant alternative to FxHash, or a fast equivalent to SipHash.
//! It provides a high speed hash algorithm, but where the result is not predictable without knowing a Key.
//! This allows it to be used in a HashMap without allowing for the possibility that an malicious user can
//! induce a collision.
//!
//! # How aHash works
//!
//! aHash uses the hardware AES instruction on x86 processors to provide a keyed hash function.
//! It uses two rounds of AES per hash. So it should not be considered cryptographically secure.
extern crate const_random;
extern crate arrayref;

#[macro_use]
mod convert;

mod fallback_hash;
#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes"))]
mod aes_hash;
#[cfg(test)]
mod hash_quality_test;

use const_random::const_random;
use std::collections::HashMap;
use std::hash::{BuildHasher, BuildHasherDefault};

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes"))]
pub use crate::aes_hash::AHasher;

#[cfg(not(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes")))]
pub use crate::fallback_hash::AHasher;

/// A `HashMap` using a `BuildHasherDefault` BuildHasher to hash the items.
pub type AHashMap<K, V> = HashMap<K, V, BuildHasherDefault<AHasher>>;

///Const random provides randomized keys with no runtime cost.
const DEFAULT_KEYS: [u64;2] = [const_random!(u64), const_random!(u64)];

/// Provides a default [Hasher] compile time generated constants for keys.
/// This is typically used in conjunction with [BuildHasherDefault] to create
/// [AHasher]s in order to hash the keys of the map.
///
/// # Example
/// ```
/// use std::hash::{BuildHasherDefault};
/// use ahash::AHasher;
/// use std::collections::HashMap;
///
/// let mut map: HashMap<i32, i32, BuildHasherDefault<AHasher>> = HashMap::default();
/// map.insert(12, 34);
/// ```
///
/// [BuildHasherDefault]: std::hash::BuildHasherDefault
/// [Hasher]: std::hash::Hasher
/// [HashMap]: std::collections::HashMap
impl Default for AHasher {

    /// Constructs a new [AHasher] with compile time generated constants for keys.
    /// This means the keys will be the same from one instance to another,
    /// but different from build to the next. So if it is possible for a potential
    /// attacker to have access to the compiled binary it would be better
    /// to specify keys generated at runtime.
    ///
    /// # Examples
    ///
    /// ```
    /// use ahash::AHasher;
    /// use std::hash::Hasher;
    ///
    /// let mut hasher_1 = AHasher::default();
    /// let mut hasher_2 = AHasher::default();
    ///
    /// hasher_1.write_u32(1234);
    /// hasher_2.write_u32(1234);
    ///
    /// assert_eq!(hasher_1.finish(), hasher_2.finish());
    /// ```
    #[inline]
    fn default() -> AHasher {
        AHasher::new_with_keys(DEFAULT_KEYS[0], DEFAULT_KEYS[1])
    }
}

/// Provides a [Hasher] factory. This is typically used (e.g. by [HashMap]) to create
/// [AHasher]s in order to hash the keys of the map. See `build_hasher` below.
///
/// [build_hasher]: ahash::
/// [Hasher]: std::hash::Hasher
/// [BuildHasher]: std::hash::BuildHasher
/// [HashMap]: std::collections::HashMap
pub struct ABuildHasher{}

impl ABuildHasher {
    #[inline]
    pub fn new() -> ABuildHasher {
        ABuildHasher{}
    }
}

impl BuildHasher for ABuildHasher {
    type Hasher = AHasher;

    /// Constructs a new [AHasher] with keys based on compile time generated constants and the location
    /// of the this object in memory. This means that two different [BuildHasher]s will will generate
    /// [AHasher]s that will return different hashcodes, but [Hasher]s created from the same [BuildHasher]
    /// will generate the same hashes for the same input data.
    ///
    /// # Examples
    ///
    /// ```
    /// use ahash::{AHasher, ABuildHasher};
    /// use std::hash::{Hasher, BuildHasher};
    ///
    /// let build_hasher = ABuildHasher::new();
    /// let mut hasher_1 = build_hasher.build_hasher();
    /// let mut hasher_2 = build_hasher.build_hasher();
    ///
    /// hasher_1.write_u32(1234);
    /// hasher_2.write_u32(1234);
    ///
    /// assert_eq!(hasher_1.finish(), hasher_2.finish());
    ///
    /// let other_build_hasher = ABuildHasher::new();
    /// let mut different_hasher = other_build_hasher.build_hasher();
    /// different_hasher.write_u32(1234);
    /// assert_ne!(different_hasher.finish(), hasher_1.finish());
    /// ```
    /// [Hasher]: std::hash::Hasher
    /// [BuildHasher]: std::hash::BuildHasher
    /// [HashMap]: std::collections::HashMap
    #[inline]
    fn build_hasher(&self) -> AHasher {
        let mem_loc = self as *const _ as usize as u64;
        AHasher::new_with_keys(DEFAULT_KEYS[0], DEFAULT_KEYS[1] ^ mem_loc)
    }
}


#[cfg(test)]
mod test {
    use crate::convert::Convert;
    use crate::*;

    #[test]
    fn test_builder() {
        let mut map = HashMap::<u32, u64, BuildHasherDefault<AHasher>>::default();
        map.insert(1, 3);
    }

    #[test]
    fn test_conversion() {
        let input: &[u8] = "dddddddd".as_bytes();
        let bytes: u64 = as_array!(input, 8).convert();
        assert_eq!(bytes, 0x6464646464646464);
    }
}