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
//! See [the `phf` crate's documentation][phf] for details.
//!
//! [phf]: https://docs.rs/phf

#![doc(html_root_url = "https://docs.rs/phf_shared/0.11")]
#![cfg_attr(not(feature = "std"), no_std)]

#[cfg(feature = "std")]
extern crate std as core;

use core::fmt;
use core::hash::{Hash, Hasher};
use core::num::Wrapping;
use siphasher::sip128::{Hash128, Hasher128, SipHasher13};

#[non_exhaustive]
pub struct Hashes {
    pub g: u32,
    pub f1: u32,
    pub f2: u32,
}

/// A central typedef for hash keys
///
/// Makes experimentation easier by only needing to be updated here.
pub type HashKey = u64;

#[inline]
pub fn displace(f1: u32, f2: u32, d1: u32, d2: u32) -> u32 {
    (Wrapping(d2) + Wrapping(f1) * Wrapping(d1) + Wrapping(f2)).0
}

/// `key` is from `phf_generator::HashState`.
#[inline]
pub fn hash<T: ?Sized + PhfHash>(x: &T, key: &HashKey) -> Hashes {
    let mut hasher = SipHasher13::new_with_keys(0, *key);
    x.phf_hash(&mut hasher);

    let Hash128 {
        h1: lower,
        h2: upper,
    } = hasher.finish128();

    Hashes {
        g: (lower >> 32) as u32,
        f1: lower as u32,
        f2: upper as u32,
    }
}

/// Return an index into `phf_generator::HashState::map`.
///
/// * `hash` is from `hash()` in this crate.
/// * `disps` is from `phf_generator::HashState::disps`.
/// * `len` is the length of `phf_generator::HashState::map`.
#[inline]
pub fn get_index(hashes: &Hashes, disps: &[(u32, u32)], len: usize) -> u32 {
    let (d1, d2) = disps[(hashes.g % (disps.len() as u32)) as usize];
    displace(hashes.f1, hashes.f2, d1, d2) % (len as u32)
}

/// A trait implemented by types which can be used in PHF data structures.
///
/// This differs from the standard library's `Hash` trait in that `PhfHash`'s
/// results must be architecture independent so that hashes will be consistent
/// between the host and target when cross compiling.
pub trait PhfHash {
    /// Feeds the value into the state given, updating the hasher as necessary.
    fn phf_hash<H: Hasher>(&self, state: &mut H);

    /// Feeds a slice of this type into the state provided.
    fn phf_hash_slice<H: Hasher>(data: &[Self], state: &mut H)
    where
        Self: Sized,
    {
        for piece in data {
            piece.phf_hash(state);
        }
    }
}

/// Trait for printing types with `const` constructors, used by `phf_codegen` and `phf_macros`.
pub trait FmtConst {
    /// Print a `const` expression representing this value.
    fn fmt_const(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result;
}

/// Identical to `std::borrow::Borrow` except omitting blanket impls to facilitate other
/// borrowing patterns.
///
/// The same semantic requirements apply:
///
/// > In particular `Eq`, `Ord` and `Hash` must be equivalent for borrowed and owned values:
/// `x.borrow() == y.borrow()` should give the same result as `x == y`.
///
/// (This crate's API only requires `Eq` and `PhfHash`, however.)
///
/// ### Motivation
/// The conventional signature for lookup methods on collections looks something like this:
///
/// ```rust,ignore
/// impl<K, V> Map<K, V> where K: PhfHash + Eq {
///     fn get<T: ?Sized>(&self, key: &T) -> Option<&V> where T: PhfHash + Eq, K: Borrow<T> {
///         ...
///     }
/// }
/// ```
///
/// This allows the key type used for lookup to be different than the key stored in the map so for
/// example you can use `&str` to look up a value in a `Map<String, _>`. However, this runs into
/// a problem in the case where `T` and `K` are both a `Foo<_>` type constructor but
/// the contained type is different (even being the same type with different lifetimes).
///
/// The main issue for this crate's API is that, with this method signature, you cannot perform a
/// lookup on a `Map<UniCase<&'static str>, _>` with a `UniCase<&'a str>` where `'a` is not
/// `'static`; there is no impl of `Borrow` that resolves to
/// `impl Borrow<UniCase<'a>> for UniCase<&'static str>` and one cannot be added either because of
/// all the blanket impls.
///
/// Instead, this trait is implemented conservatively, without blanket impls, so that impls like
/// this may be added. This is feasible since the set of types that implement `PhfHash` is
/// intentionally small.
///
/// This likely won't be fixable with specialization alone but will require full support for lattice
/// impls since we technically want to add overlapping blanket impls.
pub trait PhfBorrow<B: ?Sized> {
    /// Convert a reference to `self` to a reference to the borrowed type.
    fn borrow(&self) -> &B;
}

/// Create an impl of `FmtConst` delegating to `fmt::Debug` for types that can deal with it.
///
/// Ideally with specialization this could be just one default impl and then specialized where
/// it doesn't apply.
macro_rules! delegate_debug (
    ($ty:ty) => {
        impl FmtConst for $ty {
            fn fmt_const(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                write!(f, "{:?}", self)
            }
        }
    }
);

delegate_debug!(str);
delegate_debug!(char);
delegate_debug!(u8);
delegate_debug!(i8);
delegate_debug!(u16);
delegate_debug!(i16);
delegate_debug!(u32);
delegate_debug!(i32);
delegate_debug!(u64);
delegate_debug!(i64);
delegate_debug!(u128);
delegate_debug!(i128);
delegate_debug!(bool);

/// `impl PhfBorrow<T> for T`
macro_rules! impl_reflexive(
    ($($t:ty),*) => (
        $(impl PhfBorrow<$t> for $t {
            fn borrow(&self) -> &$t {
                self
            }
        })*
    )
);

impl_reflexive!(
    str,
    char,
    u8,
    i8,
    u16,
    i16,
    u32,
    i32,
    u64,
    i64,
    u128,
    i128,
    bool,
    [u8]
);

#[cfg(feature = "std")]
impl PhfBorrow<str> for String {
    fn borrow(&self) -> &str {
        self
    }
}

#[cfg(feature = "std")]
impl PhfBorrow<[u8]> for Vec<u8> {
    fn borrow(&self) -> &[u8] {
        self
    }
}

#[cfg(feature = "std")]
delegate_debug!(String);

#[cfg(feature = "std")]
impl PhfHash for String {
    #[inline]
    fn phf_hash<H: Hasher>(&self, state: &mut H) {
        (**self).phf_hash(state)
    }
}

#[cfg(feature = "std")]
impl PhfHash for Vec<u8> {
    #[inline]
    fn phf_hash<H: Hasher>(&self, state: &mut H) {
        (**self).phf_hash(state)
    }
}

impl<'a, T: 'a + PhfHash + ?Sized> PhfHash for &'a T {
    fn phf_hash<H: Hasher>(&self, state: &mut H) {
        (*self).phf_hash(state)
    }
}

impl<'a, T: 'a + FmtConst + ?Sized> FmtConst for &'a T {
    fn fmt_const(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        (*self).fmt_const(f)
    }
}

impl<'a> PhfBorrow<str> for &'a str {
    fn borrow(&self) -> &str {
        self
    }
}

impl<'a> PhfBorrow<[u8]> for &'a [u8] {
    fn borrow(&self) -> &[u8] {
        self
    }
}

impl PhfHash for str {
    #[inline]
    fn phf_hash<H: Hasher>(&self, state: &mut H) {
        self.as_bytes().phf_hash(state)
    }
}

impl PhfHash for [u8] {
    #[inline]
    fn phf_hash<H: Hasher>(&self, state: &mut H) {
        state.write(self);
    }
}

impl FmtConst for [u8] {
    #[inline]
    fn fmt_const(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // slices need a leading reference
        write!(f, "&{:?}", self)
    }
}

#[cfg(feature = "unicase")]
impl<S> PhfHash for unicase::UniCase<S>
where
    unicase::UniCase<S>: Hash,
{
    #[inline]
    fn phf_hash<H: Hasher>(&self, state: &mut H) {
        self.hash(state)
    }
}

#[cfg(feature = "unicase")]
impl<S> FmtConst for unicase::UniCase<S>
where
    S: AsRef<str>,
{
    fn fmt_const(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.is_ascii() {
            f.write_str("UniCase::ascii(")?;
        } else {
            f.write_str("UniCase::unicode(")?;
        }

        self.as_ref().fmt_const(f)?;
        f.write_str(")")
    }
}

#[cfg(feature = "unicase")]
impl<'b, 'a: 'b, S: ?Sized + 'a> PhfBorrow<unicase::UniCase<&'b S>> for unicase::UniCase<&'a S> {
    fn borrow(&self) -> &unicase::UniCase<&'b S> {
        self
    }
}

#[cfg(feature = "uncased")]
impl PhfHash for uncased::UncasedStr {
    #[inline]
    fn phf_hash<H: Hasher>(&self, state: &mut H) {
        self.hash(state)
    }
}

#[cfg(feature = "uncased")]
impl FmtConst for uncased::UncasedStr {
    fn fmt_const(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // transmute is not stable in const fns (rust-lang/rust#53605), so
        // `UncasedStr::new` can't be a const fn itself, but we can inline the
        // call to transmute here in the meantime.
        f.write_str("unsafe { ::core::mem::transmute::<&'static str, &'static UncasedStr>(")?;
        self.as_str().fmt_const(f)?;
        f.write_str(") }")
    }
}

#[cfg(feature = "uncased")]
impl PhfBorrow<uncased::UncasedStr> for &uncased::UncasedStr {
    fn borrow(&self) -> &uncased::UncasedStr {
        self
    }
}

macro_rules! sip_impl (
    (le $t:ty) => (
        impl PhfHash for $t {
            #[inline]
            fn phf_hash<H: Hasher>(&self, state: &mut H) {
                self.to_le().hash(state);
            }
        }
    );
    ($t:ty) => (
        impl PhfHash for $t {
            #[inline]
            fn phf_hash<H: Hasher>(&self, state: &mut H) {
                self.hash(state);
            }
        }
    )
);

sip_impl!(u8);
sip_impl!(i8);
sip_impl!(le u16);
sip_impl!(le i16);
sip_impl!(le u32);
sip_impl!(le i32);
sip_impl!(le u64);
sip_impl!(le i64);
sip_impl!(le u128);
sip_impl!(le i128);
sip_impl!(bool);

impl PhfHash for char {
    #[inline]
    fn phf_hash<H: Hasher>(&self, state: &mut H) {
        (*self as u32).phf_hash(state)
    }
}

// minimize duplicated code since formatting drags in quite a bit
fn fmt_array<T: core::fmt::Debug>(array: &[T], f: &mut fmt::Formatter<'_>) -> fmt::Result {
    write!(f, "{:?}", array)
}

macro_rules! array_impl (
    ($t:ty) => (
        impl<const N: usize> PhfHash for [$t; N] {
            #[inline]
            fn phf_hash<H: Hasher>(&self, state: &mut H) {
                for v in &self[..] {
                    v.phf_hash(state);
                }
            }
        }

        impl<const N: usize> FmtConst for [$t; N] {
            fn fmt_const(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                fmt_array(self, f)
            }
        }

        impl<const N: usize> PhfBorrow<[$t]> for [$t; N] {
            fn borrow(&self) -> &[$t] {
                self
            }
        }
    )
);

array_impl!(u8);
array_impl!(i8);
array_impl!(u16);
array_impl!(i16);
array_impl!(u32);
array_impl!(i32);
array_impl!(u64);
array_impl!(i64);
array_impl!(u128);
array_impl!(i128);
array_impl!(bool);
array_impl!(char);