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
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
use core::hash::Hash;
cfg_if::cfg_if! {
    if #[cfg(any(
        all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "aes", not(miri)),
        all(feature = "nightly-arm-aes", target_arch = "aarch64", target_feature = "aes", not(miri)),
        all(feature = "nightly-arm-aes", target_arch = "arm", target_feature = "aes", not(miri)),
    ))] {
        use crate::aes_hash::*;
    } else {
        use crate::fallback_hash::*;
    }
}
cfg_if::cfg_if! {
    if #[cfg(feature = "specialize")]{
        use crate::BuildHasherExt;
    }
}
cfg_if::cfg_if! {
    if #[cfg(feature = "std")] {
        extern crate std as alloc;
    } else {
        extern crate alloc;
    }
}

#[cfg(feature = "atomic-polyfill")]
use atomic_polyfill as atomic;
#[cfg(not(feature = "atomic-polyfill"))]
use core::sync::atomic;

use alloc::boxed::Box;
use atomic::{AtomicUsize, Ordering};
use core::any::{Any, TypeId};
use core::fmt;
use core::hash::BuildHasher;
use core::hash::Hasher;

pub(crate) const PI: [u64; 4] = [
    0x243f_6a88_85a3_08d3,
    0x1319_8a2e_0370_7344,
    0xa409_3822_299f_31d0,
    0x082e_fa98_ec4e_6c89,
];

pub(crate) const PI2: [u64; 4] = [
    0x4528_21e6_38d0_1377,
    0xbe54_66cf_34e9_0c6c,
    0xc0ac_29b7_c97c_50dd,
    0x3f84_d5b5_b547_0917,
];

cfg_if::cfg_if! {
    if #[cfg(all(feature = "compile-time-rng", any(test, fuzzing)))] {
        #[inline]
        fn get_fixed_seeds() -> &'static [[u64; 4]; 2] {
            use const_random::const_random;

            const RAND: [[u64; 4]; 2] = [
                [
                    const_random!(u64),
                    const_random!(u64),
                    const_random!(u64),
                    const_random!(u64),
                ], [
                    const_random!(u64),
                    const_random!(u64),
                    const_random!(u64),
                    const_random!(u64),
                ]
            ];
            &RAND
        }
    } else if #[cfg(all(feature = "runtime-rng", not(fuzzing)))] {
        #[inline]
        fn get_fixed_seeds() -> &'static [[u64; 4]; 2] {
            use crate::convert::Convert;

            static SEEDS: OnceBox<[[u64; 4]; 2]> = OnceBox::new();

            SEEDS.get_or_init(|| {
                let mut result: [u8; 64] = [0; 64];
                getrandom::getrandom(&mut result).expect("getrandom::getrandom() failed.");
                Box::new(result.convert())
            })
        }
    } else if #[cfg(feature = "compile-time-rng")] {
        #[inline]
        fn get_fixed_seeds() -> &'static [[u64; 4]; 2] {
            use const_random::const_random;

            const RAND: [[u64; 4]; 2] = [
                [
                    const_random!(u64),
                    const_random!(u64),
                    const_random!(u64),
                    const_random!(u64),
                ], [
                    const_random!(u64),
                    const_random!(u64),
                    const_random!(u64),
                    const_random!(u64),
                ]
            ];
            &RAND
        }
    } else {
        #[inline]
        fn get_fixed_seeds() -> &'static [[u64; 4]; 2] {
            &[PI, PI2]
        }
    }
}

cfg_if::cfg_if! {
    if #[cfg(not(all(target_arch = "arm", target_os = "none")))] {
        use once_cell::race::OnceBox;

        static RAND_SOURCE: OnceBox<Box<dyn RandomSource + Send + Sync>> = OnceBox::new();
    }
}
/// A supplier of Randomness used for different hashers.
/// See [set_random_source].
///
/// If [set_random_source] aHash will default to the best available source of randomness.
/// In order this is:
/// 1. OS provided random number generator (available if the `runtime-rng` flag is enabled which it is by default) - This should be very strong.
/// 2. Strong compile time random numbers used to permute a static "counter". (available if `compile-time-rng` is enabled.
/// __Enabling this is recommended if `runtime-rng` is not possible__)
/// 3. A static counter that adds the memory address of each [RandomState] created permuted with fixed constants.
/// (Similar to above but with fixed keys) - This is the weakest option. The strength of this heavily depends on whether or not ASLR is enabled.
/// (Rust enables ASLR by default)
pub trait RandomSource {
    fn gen_hasher_seed(&self) -> usize;
}

struct DefaultRandomSource {
    counter: AtomicUsize,
}

impl DefaultRandomSource {
    fn new() -> DefaultRandomSource {
        DefaultRandomSource {
            counter: AtomicUsize::new(&PI as *const _ as usize),
        }
    }

    #[cfg(all(target_arch = "arm", target_os = "none"))]
    const fn default() -> DefaultRandomSource {
        DefaultRandomSource {
            counter: AtomicUsize::new(PI[3] as usize),
        }
    }
}

impl RandomSource for DefaultRandomSource {
    cfg_if::cfg_if! {
        if #[cfg(all(target_arch = "arm", target_os = "none"))] {
            fn gen_hasher_seed(&self) -> usize {
                let stack = self as *const _ as usize;
                let previous = self.counter.load(Ordering::Relaxed);
                let new = previous.wrapping_add(stack);
                self.counter.store(new, Ordering::Relaxed);
                new
            }
        } else {
            fn gen_hasher_seed(&self) -> usize {
                let stack = self as *const _ as usize;
                self.counter.fetch_add(stack, Ordering::Relaxed)
            }
        }
    }
}

cfg_if::cfg_if! {
        if #[cfg(all(target_arch = "arm", target_os = "none"))] {
            #[inline]
            fn get_src() -> &'static dyn RandomSource {
                static RAND_SOURCE: DefaultRandomSource = DefaultRandomSource::default();
                &RAND_SOURCE
            }
        } else {
            /// Provides an optional way to manually supply a source of randomness for Hasher keys.
            ///
            /// The provided [RandomSource] will be used to be used as a source of randomness by [RandomState] to generate new states.
            /// If this method is not invoked the standard source of randomness is used as described in the Readme.
            ///
            /// The source of randomness can only be set once, and must be set before the first RandomState is created.
            /// If the source has already been specified `Err` is returned with a `bool` indicating if the set failed because
            /// method was previously invoked (true) or if the default source is already being used (false).
            #[cfg(not(all(target_arch = "arm", target_os = "none")))]
            pub fn set_random_source(source: impl RandomSource + Send + Sync + 'static) -> Result<(), bool> {
                RAND_SOURCE.set(Box::new(Box::new(source))).map_err(|s| s.as_ref().type_id() != TypeId::of::<&DefaultRandomSource>())
            }

            #[inline]
            fn get_src() -> &'static dyn RandomSource {
                RAND_SOURCE.get_or_init(|| Box::new(Box::new(DefaultRandomSource::new()))).as_ref()
            }
        }
}

/// 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
///
/// There are multiple constructors each is documented in more detail below:
///
/// | Constructor   | Dynamically random? | Seed |
/// |---------------|---------------------|------|
/// |`new`          | Each instance unique|_[RandomSource]_|
/// |`generate_with`| Each instance unique|`u64` x 4 + [RandomSource]|
/// |`with_seed`    | Fixed per process   |`u64` + static random number|
/// |`with_seeds`   | Fixed               |`u64` x 4|
///
#[derive(Clone)]
pub struct RandomState {
    pub(crate) k0: u64,
    pub(crate) k1: u64,
    pub(crate) k2: u64,
    pub(crate) k3: u64,
}

impl fmt::Debug for RandomState {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.pad("RandomState { .. }")
    }
}

impl RandomState {
    /// Create a new `RandomState` `BuildHasher` using random keys.
    ///
    /// Each instance will have a unique set of keys derived from [RandomSource].
    ///
    #[inline]
    pub fn new() -> RandomState {
        let src = get_src();
        let fixed = get_fixed_seeds();
        Self::from_keys(&fixed[0], &fixed[1], src.gen_hasher_seed())
    }

    /// Create a new `RandomState` `BuildHasher` based on the provided seeds, but in such a way
    /// that each time it is called the resulting state will be different and of high quality.
    /// This allows fixed constant or poor quality seeds to be provided without the problem of different
    /// `BuildHasher`s being identical or weak.
    ///
    /// This is done via permuting the provided values with the value of a static counter and memory address.
    /// (This makes this method somewhat more expensive than `with_seeds` below which does not do this).
    ///
    /// The provided values (k0-k3) do not need to be of high quality but they should not all be the same value.
    #[inline]
    pub fn generate_with(k0: u64, k1: u64, k2: u64, k3: u64) -> RandomState {
        let src = get_src();
        let fixed = get_fixed_seeds();
        RandomState::from_keys(&fixed[0], &[k0, k1, k2, k3], src.gen_hasher_seed())
    }

    fn from_keys(a: &[u64; 4], b: &[u64; 4], c: usize) -> RandomState {
        let &[k0, k1, k2, k3] = a;
        let mut hasher = AHasher::from_random_state(&RandomState { k0, k1, k2, k3 });
        hasher.write_usize(c);
        let mix = |l: u64, r: u64| {
            let mut h = hasher.clone();
            h.write_u64(l);
            h.write_u64(r);
            h.finish()
        };
        RandomState {
            k0: mix(b[0], b[2]),
            k1: mix(b[1], b[3]),
            k2: mix(b[2], b[1]),
            k3: mix(b[3], b[0]),
        }
    }

    /// Internal. Used by Default.
    #[inline]
    pub(crate) fn with_fixed_keys() -> RandomState {
        let [k0, k1, k2, k3] = get_fixed_seeds()[0];
        RandomState { k0, k1, k2, k3 }
    }

    /// Build a `RandomState` from a single key. The provided key does not need to be of high quality,
    /// but all `RandomState`s created from the same key will produce identical hashers.
    /// (In contrast to `generate_with` above)
    ///
    /// This allows for explicitly setting the seed to be used.
    ///
    /// Note: This method does not require the provided seed to be strong.
    #[inline]
    pub fn with_seed(key: usize) -> RandomState {
        let fixed = get_fixed_seeds();
        RandomState::from_keys(&fixed[0], &fixed[1], key)
    }

    /// Allows for explicitly setting the seeds to used.
    /// All `RandomState`s created with the same set of keys key will produce identical hashers.
    /// (In contrast to `generate_with` above)
    ///
    /// Note: If DOS resistance is desired one of these should be a decent quality random number.
    /// If 4 high quality random number are not cheaply available this method is robust against 0s being passed for
    /// one or more of the parameters or the same value being passed for more than one parameter.
    /// It is recommended to pass numbers in order from highest to lowest quality (if there is any difference).
    #[inline]
    pub const fn with_seeds(k0: u64, k1: u64, k2: u64, k3: u64) -> RandomState {
        RandomState {
            k0: k0 ^ PI2[0],
            k1: k1 ^ PI2[1],
            k2: k2 ^ PI2[2],
            k3: k3 ^ PI2[3],
        }
    }

    /// Calculates the hash of a single value. This provides a more convenient (and faster) way to obtain a hash:
    /// For example:
    #[cfg_attr(
        feature = "std",
        doc = r##" # Examples
```
    use std::hash::BuildHasher;
    use ahash::RandomState;

    let hash_builder = RandomState::new();
    let hash = hash_builder.hash_one("Some Data");
```
    "##
    )]
    /// This is similar to:
    #[cfg_attr(
        feature = "std",
        doc = r##" # Examples
```
    use std::hash::{BuildHasher, Hash, Hasher};
    use ahash::RandomState;

    let hash_builder = RandomState::new();
    let mut hasher = hash_builder.build_hasher();
    "Some Data".hash(&mut hasher);
    let hash = hasher.finish();
```
    "##
    )]
    /// (Note that these two ways to get a hash may not produce the same value for the same data)
    ///
    /// This is intended as a convenience for code which *consumes* hashes, such
    /// as the implementation of a hash table or in unit tests that check
    /// whether a custom [`Hash`] implementation behaves as expected.
    ///
    /// This must not be used in any code which *creates* hashes, such as in an
    /// implementation of [`Hash`].  The way to create a combined hash of
    /// multiple values is to call [`Hash::hash`] multiple times using the same
    /// [`Hasher`], not to call this method repeatedly and combine the results.
    #[inline]
    pub fn hash_one<T: Hash>(&self, x: T) -> u64
    where
        Self: Sized,
    {
        use crate::specialize::CallHasher;
        T::get_hash(&x, self)
    }
}

/// Creates an instance of RandomState using keys obtained from the random number generator.
/// Each instance created in this way will have a unique set of keys. (But the resulting instance
/// can be used to create many hashers each or which will have the same keys.)
///
/// This is the same as [RandomState::new()]
///
/// NOTE: For safety this trait impl is only available available if either of the flags `runtime-rng` (on by default) or
/// `compile-time-rng` are enabled. This is to prevent weakly keyed maps from being accidentally created. Instead one of
/// constructors for [RandomState] must be used.
#[cfg(any(feature = "compile-time-rng", feature = "runtime-rng", feature = "no-rng"))]
impl Default for RandomState {
    #[inline]
    fn default() -> Self {
        Self::new()
    }
}

impl BuildHasher for RandomState {
    type Hasher = AHasher;

    /// Constructs a new [AHasher] with keys based on this [RandomState] object.
    /// This means that two different [RandomState]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.
    ///
    #[cfg_attr(
        feature = "std",
        doc = r##" # Examples
```
        use ahash::{AHasher, RandomState};
        use std::hash::{Hasher, BuildHasher};
    
        let build_hasher = RandomState::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 = RandomState::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 {
        AHasher::from_random_state(self)
    }

    /// Calculates the hash of a single value. This provides a more convenient (and faster) way to obtain a hash:
    /// For example:
    #[cfg_attr(
        feature = "std",
        doc = r##" # Examples
```
    use std::hash::BuildHasher;
    use ahash::RandomState;

    let hash_builder = RandomState::new();
    let hash = hash_builder.hash_one("Some Data");
```
    "##
    )]
    /// This is similar to:
    #[cfg_attr(
        feature = "std",
        doc = r##" # Examples
```
    use std::hash::{BuildHasher, Hash, Hasher};
    use ahash::RandomState;

    let hash_builder = RandomState::new();
    let mut hasher = hash_builder.build_hasher();
    "Some Data".hash(&mut hasher);
    let hash = hasher.finish();
```
    "##
    )]
    /// (Note that these two ways to get a hash may not produce the same value for the same data)
    ///
    /// This is intended as a convenience for code which *consumes* hashes, such
    /// as the implementation of a hash table or in unit tests that check
    /// whether a custom [`Hash`] implementation behaves as expected.
    ///
    /// This must not be used in any code which *creates* hashes, such as in an
    /// implementation of [`Hash`].  The way to create a combined hash of
    /// multiple values is to call [`Hash::hash`] multiple times using the same
    /// [`Hasher`], not to call this method repeatedly and combine the results.
    #[cfg(feature = "specialize")]
    #[inline]
    fn hash_one<T: Hash>(&self, x: T) -> u64 {
        RandomState::hash_one(self, x)
    }
}

#[cfg(feature = "specialize")]
impl BuildHasherExt for RandomState {
    #[inline]
    fn hash_as_u64<T: Hash + ?Sized>(&self, value: &T) -> u64 {
        let mut hasher = AHasherU64 {
            buffer: self.k0,
            pad: self.k1,
        };
        value.hash(&mut hasher);
        hasher.finish()
    }

    #[inline]
    fn hash_as_fixed_length<T: Hash + ?Sized>(&self, value: &T) -> u64 {
        let mut hasher = AHasherFixed(self.build_hasher());
        value.hash(&mut hasher);
        hasher.finish()
    }

    #[inline]
    fn hash_as_str<T: Hash + ?Sized>(&self, value: &T) -> u64 {
        let mut hasher = AHasherStr(self.build_hasher());
        value.hash(&mut hasher);
        hasher.finish()
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_unique() {
        let a = RandomState::generate_with(1, 2, 3, 4);
        let b = RandomState::generate_with(1, 2, 3, 4);
        assert_ne!(a.build_hasher().finish(), b.build_hasher().finish());
    }

    #[cfg(all(feature = "runtime-rng", not(all(feature = "compile-time-rng", test))))]
    #[test]
    fn test_not_pi() {
        assert_ne!(PI, get_fixed_seeds()[0]);
    }

    #[cfg(all(feature = "compile-time-rng", any(not(feature = "runtime-rng"), test)))]
    #[test]
    fn test_not_pi_const() {
        assert_ne!(PI, get_fixed_seeds()[0]);
    }

    #[cfg(all(not(feature = "runtime-rng"), not(feature = "compile-time-rng")))]
    #[test]
    fn test_pi() {
        assert_eq!(PI, get_fixed_seeds()[0]);
    }

    #[test]
    fn test_with_seeds_const() {
        const _CONST_RANDOM_STATE: RandomState = RandomState::with_seeds(17, 19, 21, 23);
    }
}