src/librustc_data_structures/stable_hasher.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use std::hash::{Hash, Hasher, BuildHasher};
  12 use std::marker::PhantomData;
  13 use std::mem;
  14 use sip128::SipHasher128;
  15
  16 /// When hashing something that ends up affecting properties like symbol names,
  17 /// we want these symbol names to be calculated independently of other factors
  18 /// like what architecture you're compiling *from*.
  19 ///
  20 /// To that end we always convert integers to little-endian format before
  21 /// hashing and the architecture dependent `isize` and `usize` types are
  22 /// extended to 64 bits if needed.
  23 pub struct StableHasher<W> {
  24     state: SipHasher128,
  25     bytes_hashed: u64,
  26     width: PhantomData<W>,
  27 }
  28
  29 impl<W: StableHasherResult> ::std::fmt::Debug for StableHasher<W> {
  30     fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
  31         write!(f, "{:?}", self.state)
  32     }
  33 }
  34
  35 pub trait StableHasherResult: Sized {
  36     fn finish(hasher: StableHasher<Self>) -> Self;
  37 }
  38
  39 impl<W: StableHasherResult> StableHasher<W> {
  40     pub fn new() -> Self {
  41         StableHasher {
  42             state: SipHasher128::new_with_keys(0, 0),
  43             bytes_hashed: 0,
  44             width: PhantomData,
  45         }
  46     }
  47
  48     pub fn finish(self) -> W {
  49         W::finish(self)
  50     }
  51 }
  52
  53 impl StableHasherResult for u128 {
  54     fn finish(hasher: StableHasher<Self>) -> Self {
  55         let (_0, _1) = hasher.finalize();
  56         (_0 as u128) | ((_1 as u128) << 64)
  57     }
  58 }
  59
  60 impl StableHasherResult for u64 {
  61     fn finish(hasher: StableHasher<Self>) -> Self {
  62         hasher.finalize().0
  63     }
  64 }
  65
  66 impl<W> StableHasher<W> {
  67     #[inline]
  68     pub fn finalize(self) -> (u64, u64) {
  69         self.state.finish128()
  70     }
  71
  72     #[inline]
  73     pub fn bytes_hashed(&self) -> u64 {
  74         self.bytes_hashed
  75     }
  76 }
  77
  78 impl<W> Hasher for StableHasher<W> {
  79     fn finish(&self) -> u64 {
  80         panic!("use StableHasher::finalize instead");
  81     }
  82
  83     #[inline]
  84     fn write(&mut self, bytes: &[u8]) {
  85         self.state.write(bytes);
  86         self.bytes_hashed += bytes.len() as u64;
  87     }
  88
  89     #[inline]
  90     fn write_u8(&mut self, i: u8) {
  91         self.state.write_u8(i);
  92         self.bytes_hashed += 1;
  93     }
  94
  95     #[inline]
  96     fn write_u16(&mut self, i: u16) {
  97         self.state.write_u16(i.to_le());
  98         self.bytes_hashed += 2;
  99     }
 100
 101     #[inline]
 102     fn write_u32(&mut self, i: u32) {
 103         self.state.write_u32(i.to_le());
 104         self.bytes_hashed += 4;
 105     }
 106
 107     #[inline]
 108     fn write_u64(&mut self, i: u64) {
 109         self.state.write_u64(i.to_le());
 110         self.bytes_hashed += 8;
 111     }
 112
 113     #[inline]
 114     fn write_u128(&mut self, i: u128) {
 115         self.state.write_u128(i.to_le());
 116         self.bytes_hashed += 16;
 117     }
 118
 119     #[inline]
 120     fn write_usize(&mut self, i: usize) {
 121         // Always treat usize as u64 so we get the same results on 32 and 64 bit
 122         // platforms. This is important for symbol hashes when cross compiling,
 123         // for example.
 124         self.state.write_u64((i as u64).to_le());
 125         self.bytes_hashed += 8;
 126     }
 127
 128     #[inline]
 129     fn write_i8(&mut self, i: i8) {
 130         self.state.write_i8(i);
 131         self.bytes_hashed += 1;
 132     }
 133
 134     #[inline]
 135     fn write_i16(&mut self, i: i16) {
 136         self.state.write_i16(i.to_le());
 137         self.bytes_hashed += 2;
 138     }
 139
 140     #[inline]
 141     fn write_i32(&mut self, i: i32) {
 142         self.state.write_i32(i.to_le());
 143         self.bytes_hashed += 4;
 144     }
 145
 146     #[inline]
 147     fn write_i64(&mut self, i: i64) {
 148         self.state.write_i64(i.to_le());
 149         self.bytes_hashed += 8;
 150     }
 151
 152     #[inline]
 153     fn write_i128(&mut self, i: i128) {
 154         self.state.write_i128(i.to_le());
 155         self.bytes_hashed += 16;
 156     }
 157
 158     #[inline]
 159     fn write_isize(&mut self, i: isize) {
 160         // Always treat isize as i64 so we get the same results on 32 and 64 bit
 161         // platforms. This is important for symbol hashes when cross compiling,
 162         // for example.
 163         self.state.write_i64((i as i64).to_le());
 164         self.bytes_hashed += 8;
 165     }
 166 }
 167
 168 /// Something that implements `HashStable<CTX>` can be hashed in a way that is
 169 /// stable across multiple compilation sessions.
 170 pub trait HashStable<CTX> {
 171     fn hash_stable<W: StableHasherResult>(&self,
 172                                           hcx: &mut CTX,
 173                                           hasher: &mut StableHasher<W>);
 174 }
 175
 176 /// Implement this for types that can be turned into stable keys like, for
 177 /// example, for DefId that can be converted to a DefPathHash. This is used for
 178 /// bringing maps into a predictable order before hashing them.
 179 pub trait ToStableHashKey<HCX> {
 180     type KeyType: Ord + Clone + Sized + HashStable<HCX>;
 181     fn to_stable_hash_key(&self, hcx: &HCX) -> Self::KeyType;
 182 }
 183
 184 // Implement HashStable by just calling `Hash::hash()`. This works fine for
 185 // self-contained values that don't depend on the hashing context `CTX`.
 186 macro_rules! impl_stable_hash_via_hash {
 187     ($t:ty) => (
 188         impl<CTX> HashStable<CTX> for $t {
 189             #[inline]
 190             fn hash_stable<W: StableHasherResult>(&self,
 191                                                   _: &mut CTX,
 192                                                   hasher: &mut StableHasher<W>) {
 193                 ::std::hash::Hash::hash(self, hasher);
 194             }
 195         }
 196     );
 197 }
 198
 199 impl_stable_hash_via_hash!(i8);
 200 impl_stable_hash_via_hash!(i16);
 201 impl_stable_hash_via_hash!(i32);
 202 impl_stable_hash_via_hash!(i64);
 203 impl_stable_hash_via_hash!(isize);
 204
 205 impl_stable_hash_via_hash!(u8);
 206 impl_stable_hash_via_hash!(u16);
 207 impl_stable_hash_via_hash!(u32);
 208 impl_stable_hash_via_hash!(u64);
 209 impl_stable_hash_via_hash!(usize);
 210
 211 impl_stable_hash_via_hash!(u128);
 212 impl_stable_hash_via_hash!(i128);
 213
 214 impl_stable_hash_via_hash!(char);
 215 impl_stable_hash_via_hash!(());
 216
 217 impl<CTX> HashStable<CTX> for f32 {
 218     fn hash_stable<W: StableHasherResult>(&self,
 219                                           ctx: &mut CTX,
 220                                           hasher: &mut StableHasher<W>) {
 221         let val: u32 = unsafe {
 222             ::std::mem::transmute(*self)
 223         };
 224         val.hash_stable(ctx, hasher);
 225     }
 226 }
 227
 228 impl<CTX> HashStable<CTX> for f64 {
 229     fn hash_stable<W: StableHasherResult>(&self,
 230                                           ctx: &mut CTX,
 231                                           hasher: &mut StableHasher<W>) {
 232         let val: u64 = unsafe {
 233             ::std::mem::transmute(*self)
 234         };
 235         val.hash_stable(ctx, hasher);
 236     }
 237 }
 238
 239 impl<CTX> HashStable<CTX> for ::std::cmp::Ordering {
 240     fn hash_stable<W: StableHasherResult>(&self,
 241                                           ctx: &mut CTX,
 242                                           hasher: &mut StableHasher<W>) {
 243         (*self as i8).hash_stable(ctx, hasher);
 244     }
 245 }
 246
 247 impl<T1: HashStable<CTX>, CTX> HashStable<CTX> for (T1,) {
 248     fn hash_stable<W: StableHasherResult>(&self,
 249                                           ctx: &mut CTX,
 250                                           hasher: &mut StableHasher<W>) {
 251         let (ref _0,) = *self;
 252         _0.hash_stable(ctx, hasher);
 253     }
 254 }
 255
 256 impl<T1: HashStable<CTX>, T2: HashStable<CTX>, CTX> HashStable<CTX> for (T1, T2) {
 257     fn hash_stable<W: StableHasherResult>(&self,
 258                                           ctx: &mut CTX,
 259                                           hasher: &mut StableHasher<W>) {
 260         let (ref _0, ref _1) = *self;
 261         _0.hash_stable(ctx, hasher);
 262         _1.hash_stable(ctx, hasher);
 263     }
 264 }
 265
 266 impl<T1, T2, T3, CTX> HashStable<CTX> for (T1, T2, T3)
 267      where T1: HashStable<CTX>,
 268            T2: HashStable<CTX>,
 269            T3: HashStable<CTX>,
 270 {
 271     fn hash_stable<W: StableHasherResult>(&self,
 272                                           ctx: &mut CTX,
 273                                           hasher: &mut StableHasher<W>) {
 274         let (ref _0, ref _1, ref _2) = *self;
 275         _0.hash_stable(ctx, hasher);
 276         _1.hash_stable(ctx, hasher);
 277         _2.hash_stable(ctx, hasher);
 278     }
 279 }
 280
 281 impl<T: HashStable<CTX>, CTX> HashStable<CTX> for [T] {
 282     default fn hash_stable<W: StableHasherResult>(&self,
 283                                                   ctx: &mut CTX,
 284                                                   hasher: &mut StableHasher<W>) {
 285         self.len().hash_stable(ctx, hasher);
 286         for item in self {
 287             item.hash_stable(ctx, hasher);
 288         }
 289     }
 290 }
 291
 292 impl<T: HashStable<CTX>, CTX> HashStable<CTX> for Vec<T> {
 293     #[inline]
 294     fn hash_stable<W: StableHasherResult>(&self,
 295                                           ctx: &mut CTX,
 296                                           hasher: &mut StableHasher<W>) {
 297         (&self[..]).hash_stable(ctx, hasher);
 298     }
 299 }
 300
 301 impl<T: ?Sized + HashStable<CTX>, CTX> HashStable<CTX> for Box<T> {
 302     #[inline]
 303     fn hash_stable<W: StableHasherResult>(&self,
 304                                           ctx: &mut CTX,
 305                                           hasher: &mut StableHasher<W>) {
 306         (**self).hash_stable(ctx, hasher);
 307     }
 308 }
 309
 310 impl<T: ?Sized + HashStable<CTX>, CTX> HashStable<CTX> for ::std::rc::Rc<T> {
 311     #[inline]
 312     fn hash_stable<W: StableHasherResult>(&self,
 313                                           ctx: &mut CTX,
 314                                           hasher: &mut StableHasher<W>) {
 315         (**self).hash_stable(ctx, hasher);
 316     }
 317 }
 318
 319 impl<T: ?Sized + HashStable<CTX>, CTX> HashStable<CTX> for ::std::sync::Arc<T> {
 320     #[inline]
 321     fn hash_stable<W: StableHasherResult>(&self,
 322                                           ctx: &mut CTX,
 323                                           hasher: &mut StableHasher<W>) {
 324         (**self).hash_stable(ctx, hasher);
 325     }
 326 }
 327
 328 impl<CTX> HashStable<CTX> for str {
 329     #[inline]
 330     fn hash_stable<W: StableHasherResult>(&self,
 331                                           _: &mut CTX,
 332                                           hasher: &mut StableHasher<W>) {
 333         self.len().hash(hasher);
 334         self.as_bytes().hash(hasher);
 335     }
 336 }
 337
 338
 339 impl<CTX> HashStable<CTX> for String {
 340     #[inline]
 341     fn hash_stable<W: StableHasherResult>(&self,
 342                                           hcx: &mut CTX,
 343                                           hasher: &mut StableHasher<W>) {
 344         (&self[..]).hash_stable(hcx, hasher);
 345     }
 346 }
 347
 348 impl<HCX> ToStableHashKey<HCX> for String {
 349     type KeyType = String;
 350     #[inline]
 351     fn to_stable_hash_key(&self, _: &HCX) -> Self::KeyType {
 352         self.clone()
 353     }
 354 }
 355
 356 impl<CTX> HashStable<CTX> for bool {
 357     #[inline]
 358     fn hash_stable<W: StableHasherResult>(&self,
 359                                           ctx: &mut CTX,
 360                                           hasher: &mut StableHasher<W>) {
 361         (if *self { 1u8 } else { 0u8 }).hash_stable(ctx, hasher);
 362     }
 363 }
 364
 365
 366 impl<T, CTX> HashStable<CTX> for Option<T>
 367     where T: HashStable<CTX>
 368 {
 369     #[inline]
 370     fn hash_stable<W: StableHasherResult>(&self,
 371                                           ctx: &mut CTX,
 372                                           hasher: &mut StableHasher<W>) {
 373         if let Some(ref value) = *self {
 374             1u8.hash_stable(ctx, hasher);
 375             value.hash_stable(ctx, hasher);
 376         } else {
 377             0u8.hash_stable(ctx, hasher);
 378         }
 379     }
 380 }
 381
 382 impl<T1, T2, CTX> HashStable<CTX> for Result<T1, T2>
 383     where T1: HashStable<CTX>,
 384           T2: HashStable<CTX>,
 385 {
 386     #[inline]
 387     fn hash_stable<W: StableHasherResult>(&self,
 388                                           ctx: &mut CTX,
 389                                           hasher: &mut StableHasher<W>) {
 390         mem::discriminant(self).hash_stable(ctx, hasher);
 391         match *self {
 392             Ok(ref x) => x.hash_stable(ctx, hasher),
 393             Err(ref x) => x.hash_stable(ctx, hasher),
 394         }
 395     }
 396 }
 397
 398 impl<'a, T, CTX> HashStable<CTX> for &'a T
 399     where T: HashStable<CTX> + ?Sized
 400 {
 401     #[inline]
 402     fn hash_stable<W: StableHasherResult>(&self,
 403                                           ctx: &mut CTX,
 404                                           hasher: &mut StableHasher<W>) {
 405         (**self).hash_stable(ctx, hasher);
 406     }
 407 }
 408
 409 impl<T, CTX> HashStable<CTX> for ::std::mem::Discriminant<T> {
 410     #[inline]
 411     fn hash_stable<W: StableHasherResult>(&self,
 412                                           _: &mut CTX,
 413                                           hasher: &mut StableHasher<W>) {
 414         ::std::hash::Hash::hash(self, hasher);
 415     }
 416 }
 417
 418 impl<I: ::indexed_vec::Idx, T, CTX> HashStable<CTX> for ::indexed_vec::IndexVec<I, T>
 419     where T: HashStable<CTX>,
 420 {
 421     fn hash_stable<W: StableHasherResult>(&self,
 422                                           ctx: &mut CTX,
 423                                           hasher: &mut StableHasher<W>) {
 424         self.len().hash_stable(ctx, hasher);
 425         for v in &self.raw {
 426             v.hash_stable(ctx, hasher);
 427         }
 428     }
 429 }
 430
 431
 432 impl<I: ::indexed_vec::Idx, CTX> HashStable<CTX> for ::indexed_set::IdxSetBuf<I>
 433 {
 434     fn hash_stable<W: StableHasherResult>(&self,
 435                                           ctx: &mut CTX,
 436                                           hasher: &mut StableHasher<W>) {
 437         self.words().hash_stable(ctx, hasher);
 438     }
 439 }
 440
 441 impl_stable_hash_via_hash!(::std::path::Path);
 442 impl_stable_hash_via_hash!(::std::path::PathBuf);
 443
 444 impl<K, V, R, HCX> HashStable<HCX> for ::std::collections::HashMap<K, V, R>
 445     where K: ToStableHashKey<HCX> + Eq + Hash,
 446           V: HashStable<HCX>,
 447           R: BuildHasher,
 448 {
 449     #[inline]
 450     fn hash_stable<W: StableHasherResult>(&self,
 451                                           hcx: &mut HCX,
 452                                           hasher: &mut StableHasher<W>) {
 453         hash_stable_hashmap(hcx, hasher, self, ToStableHashKey::to_stable_hash_key);
 454     }
 455 }
 456
 457 impl<K, R, HCX> HashStable<HCX> for ::std::collections::HashSet<K, R>
 458     where K: ToStableHashKey<HCX> + Eq + Hash,
 459           R: BuildHasher,
 460 {
 461     fn hash_stable<W: StableHasherResult>(&self,
 462                                           hcx: &mut HCX,
 463                                           hasher: &mut StableHasher<W>) {
 464         let mut keys: Vec<_> = self.iter()
 465                                    .map(|k| k.to_stable_hash_key(hcx))
 466                                    .collect();
 467         keys.sort_unstable();
 468         keys.hash_stable(hcx, hasher);
 469     }
 470 }
 471
 472 impl<K, V, HCX> HashStable<HCX> for ::std::collections::BTreeMap<K, V>
 473     where K: ToStableHashKey<HCX>,
 474           V: HashStable<HCX>,
 475 {
 476     fn hash_stable<W: StableHasherResult>(&self,
 477                                           hcx: &mut HCX,
 478                                           hasher: &mut StableHasher<W>) {
 479         let mut entries: Vec<_> = self.iter()
 480                                       .map(|(k, v)| (k.to_stable_hash_key(hcx), v))
 481                                       .collect();
 482         entries.sort_unstable_by(|&(ref sk1, _), &(ref sk2, _)| sk1.cmp(sk2));
 483         entries.hash_stable(hcx, hasher);
 484     }
 485 }
 486
 487 impl<K, HCX> HashStable<HCX> for ::std::collections::BTreeSet<K>
 488     where K: ToStableHashKey<HCX>,
 489 {
 490     fn hash_stable<W: StableHasherResult>(&self,
 491                                           hcx: &mut HCX,
 492                                           hasher: &mut StableHasher<W>) {
 493         let mut keys: Vec<_> = self.iter()
 494                                    .map(|k| k.to_stable_hash_key(hcx))
 495                                    .collect();
 496         keys.sort_unstable();
 497         keys.hash_stable(hcx, hasher);
 498     }
 499 }
 500
 501 pub fn hash_stable_hashmap<HCX, K, V, R, SK, F, W>(
 502     hcx: &mut HCX,
 503     hasher: &mut StableHasher<W>,
 504     map: &::std::collections::HashMap<K, V, R>,
 505     to_stable_hash_key: F)
 506     where K: Eq + Hash,
 507           V: HashStable<HCX>,
 508           R: BuildHasher,
 509           SK: HashStable<HCX> + Ord + Clone,
 510           F: Fn(&K, &HCX) -> SK,
 511           W: StableHasherResult,
 512 {
 513     let mut entries: Vec<_> = map.iter()
 514                                   .map(|(k, v)| (to_stable_hash_key(k, hcx), v))
 515                                   .collect();
 516     entries.sort_unstable_by(|&(ref sk1, _), &(ref sk2, _)| sk1.cmp(sk2));
 517     entries.hash_stable(hcx, hasher);
 518 }
 519
 520
 521 /// A vector container that makes sure that its items are hashed in a stable
 522 /// order.
 523 pub struct StableVec<T>(Vec<T>);
 524
 525 impl<T> StableVec<T> {
 526     pub fn new(v: Vec<T>) -> Self {
 527         StableVec(v)
 528     }
 529 }
 530
 531 impl<T> ::std::ops::Deref for StableVec<T> {
 532     type Target = Vec<T>;
 533
 534     fn deref(&self) -> &Vec<T> {
 535         &self.0
 536     }
 537 }
 538
 539 impl<T, HCX> HashStable<HCX> for StableVec<T>
 540     where T: HashStable<HCX> + ToStableHashKey<HCX>
 541 {
 542     fn hash_stable<W: StableHasherResult>(&self,
 543                                           hcx: &mut HCX,
 544                                           hasher: &mut StableHasher<W>) {
 545         let StableVec(ref v) = *self;
 546
 547         let mut sorted: Vec<_> = v.iter()
 548                                   .map(|x| x.to_stable_hash_key(hcx))
 549                                   .collect();
 550         sorted.sort_unstable();
 551         sorted.hash_stable(hcx, hasher);
 552     }
 553 }