src/libcore/hash/mod.rs

   1 //! Generic hashing support.
   2 //!
   3 //! This module provides a generic way to compute the hash of a value. The
   4 //! simplest way to make a type hashable is to use `#[derive(Hash)]`:
   5 //!
   6 //! # Examples
   7 //!
   8 //! ```rust
   9 //! use std::collections::hash_map::DefaultHasher;
  10 //! use std::hash::{Hash, Hasher};
  11 //!
  12 //! #[derive(Hash)]
  13 //! struct Person {
  14 //!     id: u32,
  15 //!     name: String,
  16 //!     phone: u64,
  17 //! }
  18 //!
  19 //! let person1 = Person {
  20 //!     id: 5,
  21 //!     name: "Janet".to_string(),
  22 //!     phone: 555_666_7777,
  23 //! };
  24 //! let person2 = Person {
  25 //!     id: 5,
  26 //!     name: "Bob".to_string(),
  27 //!     phone: 555_666_7777,
  28 //! };
  29 //!
  30 //! assert!(calculate_hash(&person1) != calculate_hash(&person2));
  31 //!
  32 //! fn calculate_hash<T: Hash>(t: &T) -> u64 {
  33 //!     let mut s = DefaultHasher::new();
  34 //!     t.hash(&mut s);
  35 //!     s.finish()
  36 //! }
  37 //! ```
  38 //!
  39 //! If you need more control over how a value is hashed, you need to implement
  40 //! the [`Hash`] trait:
  41 //!
  42 //! [`Hash`]: trait.Hash.html
  43 //!
  44 //! ```rust
  45 //! use std::collections::hash_map::DefaultHasher;
  46 //! use std::hash::{Hash, Hasher};
  47 //!
  48 //! struct Person {
  49 //!     id: u32,
  50 //!     # #[allow(dead_code)]
  51 //!     name: String,
  52 //!     phone: u64,
  53 //! }
  54 //!
  55 //! impl Hash for Person {
  56 //!     fn hash<H: Hasher>(&self, state: &mut H) {
  57 //!         self.id.hash(state);
  58 //!         self.phone.hash(state);
  59 //!     }
  60 //! }
  61 //!
  62 //! let person1 = Person {
  63 //!     id: 5,
  64 //!     name: "Janet".to_string(),
  65 //!     phone: 555_666_7777,
  66 //! };
  67 //! let person2 = Person {
  68 //!     id: 5,
  69 //!     name: "Bob".to_string(),
  70 //!     phone: 555_666_7777,
  71 //! };
  72 //!
  73 //! assert_eq!(calculate_hash(&person1), calculate_hash(&person2));
  74 //!
  75 //! fn calculate_hash<T: Hash>(t: &T) -> u64 {
  76 //!     let mut s = DefaultHasher::new();
  77 //!     t.hash(&mut s);
  78 //!     s.finish()
  79 //! }
  80 //! ```
  81
  82 #![stable(feature = "rust1", since = "1.0.0")]
  83
  84 use crate::fmt;
  85 use crate::marker;
  86
  87 #[stable(feature = "rust1", since = "1.0.0")]
  88 #[allow(deprecated)]
  89 pub use self::sip::SipHasher;
  90
  91 #[unstable(feature = "hashmap_internals", issue = "0")]
  92 #[allow(deprecated)]
  93 #[doc(hidden)]
  94 pub use self::sip::SipHasher13;
  95
  96 mod sip;
  97
  98 /// A hashable type.
  99 ///
 100 /// Types implementing `Hash` are able to be [`hash`]ed with an instance of
 101 /// [`Hasher`].
 102 ///
 103 /// ## Implementing `Hash`
 104 ///
 105 /// You can derive `Hash` with `#[derive(Hash)]` if all fields implement `Hash`.
 106 /// The resulting hash will be the combination of the values from calling
 107 /// [`hash`] on each field.
 108 ///
 109 /// ```
 110 /// #[derive(Hash)]
 111 /// struct Rustacean {
 112 ///     name: String,
 113 ///     country: String,
 114 /// }
 115 /// ```
 116 ///
 117 /// If you need more control over how a value is hashed, you can of course
 118 /// implement the `Hash` trait yourself:
 119 ///
 120 /// ```
 121 /// use std::hash::{Hash, Hasher};
 122 ///
 123 /// struct Person {
 124 ///     id: u32,
 125 ///     name: String,
 126 ///     phone: u64,
 127 /// }
 128 ///
 129 /// impl Hash for Person {
 130 ///     fn hash<H: Hasher>(&self, state: &mut H) {
 131 ///         self.id.hash(state);
 132 ///         self.phone.hash(state);
 133 ///     }
 134 /// }
 135 /// ```
 136 ///
 137 /// ## `Hash` and `Eq`
 138 ///
 139 /// When implementing both `Hash` and [`Eq`], it is important that the following
 140 /// property holds:
 141 ///
 142 /// ```text
 143 /// k1 == k2 -> hash(k1) == hash(k2)
 144 /// ```
 145 ///
 146 /// In other words, if two keys are equal, their hashes must also be equal.
 147 /// [`HashMap`] and [`HashSet`] both rely on this behavior.
 148 ///
 149 /// Thankfully, you won't need to worry about upholding this property when
 150 /// deriving both [`Eq`] and `Hash` with `#[derive(PartialEq, Eq, Hash)]`.
 151 ///
 152 /// [`Eq`]: ../../std/cmp/trait.Eq.html
 153 /// [`Hasher`]: trait.Hasher.html
 154 /// [`HashMap`]: ../../std/collections/struct.HashMap.html
 155 /// [`HashSet`]: ../../std/collections/struct.HashSet.html
 156 /// [`hash`]: #tymethod.hash
 157 #[stable(feature = "rust1", since = "1.0.0")]
 158 pub trait Hash {
 159     /// Feeds this value into the given [`Hasher`].
 160     ///
 161     /// # Examples
 162     ///
 163     /// ```
 164     /// use std::collections::hash_map::DefaultHasher;
 165     /// use std::hash::{Hash, Hasher};
 166     ///
 167     /// let mut hasher = DefaultHasher::new();
 168     /// 7920.hash(&mut hasher);
 169     /// println!("Hash is {:x}!", hasher.finish());
 170     /// ```
 171     ///
 172     /// [`Hasher`]: trait.Hasher.html
 173     #[stable(feature = "rust1", since = "1.0.0")]
 174     fn hash<H: Hasher>(&self, state: &mut H);
 175
 176     /// Feeds a slice of this type into the given [`Hasher`].
 177     ///
 178     /// # Examples
 179     ///
 180     /// ```
 181     /// use std::collections::hash_map::DefaultHasher;
 182     /// use std::hash::{Hash, Hasher};
 183     ///
 184     /// let mut hasher = DefaultHasher::new();
 185     /// let numbers = [6, 28, 496, 8128];
 186     /// Hash::hash_slice(&numbers, &mut hasher);
 187     /// println!("Hash is {:x}!", hasher.finish());
 188     /// ```
 189     ///
 190     /// [`Hasher`]: trait.Hasher.html
 191     #[stable(feature = "hash_slice", since = "1.3.0")]
 192     fn hash_slice<H: Hasher>(data: &[Self], state: &mut H)
 193         where Self: Sized
 194     {
 195         for piece in data {
 196             piece.hash(state);
 197         }
 198     }
 199 }
 200
 201 // Separate module to reexport the macro `Hash` from prelude without the trait `Hash`.
 202 #[cfg(not(bootstrap))]
 203 pub(crate) mod macros {
 204     /// Derive macro generating an impl of the trait `Hash`.
 205     #[rustc_builtin_macro]
 206     #[rustc_macro_transparency = "semitransparent"]
 207     #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 208     #[allow_internal_unstable(core_intrinsics)]
 209     pub macro Hash($item:item) { /* compiler built-in */ }
 210 }
 211 #[cfg(not(bootstrap))]
 212 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 213 #[doc(inline)]
 214 pub use macros::Hash;
 215
 216 /// A trait for hashing an arbitrary stream of bytes.
 217 ///
 218 /// Instances of `Hasher` usually represent state that is changed while hashing
 219 /// data.
 220 ///
 221 /// `Hasher` provides a fairly basic interface for retrieving the generated hash
 222 /// (with [`finish`]), and writing integers as well as slices of bytes into an
 223 /// instance (with [`write`] and [`write_u8`] etc.). Most of the time, `Hasher`
 224 /// instances are used in conjunction with the [`Hash`] trait.
 225 ///
 226 /// # Examples
 227 ///
 228 /// ```
 229 /// use std::collections::hash_map::DefaultHasher;
 230 /// use std::hash::Hasher;
 231 ///
 232 /// let mut hasher = DefaultHasher::new();
 233 ///
 234 /// hasher.write_u32(1989);
 235 /// hasher.write_u8(11);
 236 /// hasher.write_u8(9);
 237 /// hasher.write(b"Huh?");
 238 ///
 239 /// println!("Hash is {:x}!", hasher.finish());
 240 /// ```
 241 ///
 242 /// [`Hash`]: trait.Hash.html
 243 /// [`finish`]: #tymethod.finish
 244 /// [`write`]: #tymethod.write
 245 /// [`write_u8`]: #method.write_u8
 246 #[stable(feature = "rust1", since = "1.0.0")]
 247 pub trait Hasher {
 248     /// Returns the hash value for the values written so far.
 249     ///
 250     /// Despite its name, the method does not reset the hasher’s internal
 251     /// state. Additional [`write`]s will continue from the current value.
 252     /// If you need to start a fresh hash value, you will have to create
 253     /// a new hasher.
 254     ///
 255     /// # Examples
 256     ///
 257     /// ```
 258     /// use std::collections::hash_map::DefaultHasher;
 259     /// use std::hash::Hasher;
 260     ///
 261     /// let mut hasher = DefaultHasher::new();
 262     /// hasher.write(b"Cool!");
 263     ///
 264     /// println!("Hash is {:x}!", hasher.finish());
 265     /// ```
 266     ///
 267     /// [`write`]: #tymethod.write
 268     #[stable(feature = "rust1", since = "1.0.0")]
 269     fn finish(&self) -> u64;
 270
 271     /// Writes some data into this `Hasher`.
 272     ///
 273     /// # Examples
 274     ///
 275     /// ```
 276     /// use std::collections::hash_map::DefaultHasher;
 277     /// use std::hash::Hasher;
 278     ///
 279     /// let mut hasher = DefaultHasher::new();
 280     /// let data = [0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef];
 281     ///
 282     /// hasher.write(&data);
 283     ///
 284     /// println!("Hash is {:x}!", hasher.finish());
 285     /// ```
 286     #[stable(feature = "rust1", since = "1.0.0")]
 287     fn write(&mut self, bytes: &[u8]);
 288
 289     /// Writes a single `u8` into this hasher.
 290     #[inline]
 291     #[stable(feature = "hasher_write", since = "1.3.0")]
 292     fn write_u8(&mut self, i: u8) {
 293         self.write(&[i])
 294     }
 295     /// Writes a single `u16` into this hasher.
 296     #[inline]
 297     #[stable(feature = "hasher_write", since = "1.3.0")]
 298     fn write_u16(&mut self, i: u16) {
 299         self.write(&i.to_ne_bytes())
 300     }
 301     /// Writes a single `u32` into this hasher.
 302     #[inline]
 303     #[stable(feature = "hasher_write", since = "1.3.0")]
 304     fn write_u32(&mut self, i: u32) {
 305         self.write(&i.to_ne_bytes())
 306     }
 307     /// Writes a single `u64` into this hasher.
 308     #[inline]
 309     #[stable(feature = "hasher_write", since = "1.3.0")]
 310     fn write_u64(&mut self, i: u64) {
 311         self.write(&i.to_ne_bytes())
 312     }
 313     /// Writes a single `u128` into this hasher.
 314     #[inline]
 315     #[stable(feature = "i128", since = "1.26.0")]
 316     fn write_u128(&mut self, i: u128) {
 317         self.write(&i.to_ne_bytes())
 318     }
 319     /// Writes a single `usize` into this hasher.
 320     #[inline]
 321     #[stable(feature = "hasher_write", since = "1.3.0")]
 322     fn write_usize(&mut self, i: usize) {
 323         self.write(&i.to_ne_bytes())
 324     }
 325
 326     /// Writes a single `i8` into this hasher.
 327     #[inline]
 328     #[stable(feature = "hasher_write", since = "1.3.0")]
 329     fn write_i8(&mut self, i: i8) {
 330         self.write_u8(i as u8)
 331     }
 332     /// Writes a single `i16` into this hasher.
 333     #[inline]
 334     #[stable(feature = "hasher_write", since = "1.3.0")]
 335     fn write_i16(&mut self, i: i16) {
 336         self.write(&i.to_ne_bytes())
 337     }
 338     /// Writes a single `i32` into this hasher.
 339     #[inline]
 340     #[stable(feature = "hasher_write", since = "1.3.0")]
 341     fn write_i32(&mut self, i: i32) {
 342         self.write(&i.to_ne_bytes())
 343     }
 344     /// Writes a single `i64` into this hasher.
 345     #[inline]
 346     #[stable(feature = "hasher_write", since = "1.3.0")]
 347     fn write_i64(&mut self, i: i64) {
 348         self.write(&i.to_ne_bytes())
 349     }
 350     /// Writes a single `i128` into this hasher.
 351     #[inline]
 352     #[stable(feature = "i128", since = "1.26.0")]
 353     fn write_i128(&mut self, i: i128) {
 354         self.write(&i.to_ne_bytes())
 355     }
 356     /// Writes a single `isize` into this hasher.
 357     #[inline]
 358     #[stable(feature = "hasher_write", since = "1.3.0")]
 359     fn write_isize(&mut self, i: isize) {
 360         self.write(&i.to_ne_bytes())
 361     }
 362 }
 363
 364 #[stable(feature = "indirect_hasher_impl", since = "1.22.0")]
 365 impl<H: Hasher + ?Sized> Hasher for &mut H {
 366     fn finish(&self) -> u64 {
 367         (**self).finish()
 368     }
 369     fn write(&mut self, bytes: &[u8]) {
 370         (**self).write(bytes)
 371     }
 372     fn write_u8(&mut self, i: u8) {
 373         (**self).write_u8(i)
 374     }
 375     fn write_u16(&mut self, i: u16) {
 376         (**self).write_u16(i)
 377     }
 378     fn write_u32(&mut self, i: u32) {
 379         (**self).write_u32(i)
 380     }
 381     fn write_u64(&mut self, i: u64) {
 382         (**self).write_u64(i)
 383     }
 384     fn write_u128(&mut self, i: u128) {
 385         (**self).write_u128(i)
 386     }
 387     fn write_usize(&mut self, i: usize) {
 388         (**self).write_usize(i)
 389     }
 390     fn write_i8(&mut self, i: i8) {
 391         (**self).write_i8(i)
 392     }
 393     fn write_i16(&mut self, i: i16) {
 394         (**self).write_i16(i)
 395     }
 396     fn write_i32(&mut self, i: i32) {
 397         (**self).write_i32(i)
 398     }
 399     fn write_i64(&mut self, i: i64) {
 400         (**self).write_i64(i)
 401     }
 402     fn write_i128(&mut self, i: i128) {
 403         (**self).write_i128(i)
 404     }
 405     fn write_isize(&mut self, i: isize) {
 406         (**self).write_isize(i)
 407     }
 408 }
 409
 410 /// A trait for creating instances of [`Hasher`].
 411 ///
 412 /// A `BuildHasher` is typically used (e.g., by [`HashMap`]) to create
 413 /// [`Hasher`]s for each key such that they are hashed independently of one
 414 /// another, since [`Hasher`]s contain state.
 415 ///
 416 /// For each instance of `BuildHasher`, the [`Hasher`]s created by
 417 /// [`build_hasher`] should be identical. That is, if the same stream of bytes
 418 /// is fed into each hasher, the same output will also be generated.
 419 ///
 420 /// # Examples
 421 ///
 422 /// ```
 423 /// use std::collections::hash_map::RandomState;
 424 /// use std::hash::{BuildHasher, Hasher};
 425 ///
 426 /// let s = RandomState::new();
 427 /// let mut hasher_1 = s.build_hasher();
 428 /// let mut hasher_2 = s.build_hasher();
 429 ///
 430 /// hasher_1.write_u32(8128);
 431 /// hasher_2.write_u32(8128);
 432 ///
 433 /// assert_eq!(hasher_1.finish(), hasher_2.finish());
 434 /// ```
 435 ///
 436 /// [`build_hasher`]: #tymethod.build_hasher
 437 /// [`Hasher`]: trait.Hasher.html
 438 /// [`HashMap`]: ../../std/collections/struct.HashMap.html
 439 #[stable(since = "1.7.0", feature = "build_hasher")]
 440 pub trait BuildHasher {
 441     /// Type of the hasher that will be created.
 442     #[stable(since = "1.7.0", feature = "build_hasher")]
 443     type Hasher: Hasher;
 444
 445     /// Creates a new hasher.
 446     ///
 447     /// Each call to `build_hasher` on the same instance should produce identical
 448     /// [`Hasher`]s.
 449     ///
 450     /// # Examples
 451     ///
 452     /// ```
 453     /// use std::collections::hash_map::RandomState;
 454     /// use std::hash::BuildHasher;
 455     ///
 456     /// let s = RandomState::new();
 457     /// let new_s = s.build_hasher();
 458     /// ```
 459     ///
 460     /// [`Hasher`]: trait.Hasher.html
 461     #[stable(since = "1.7.0", feature = "build_hasher")]
 462     fn build_hasher(&self) -> Self::Hasher;
 463 }
 464
 465 /// Used to create a default [`BuildHasher`] instance for types that implement
 466 /// [`Hasher`] and [`Default`].
 467 ///
 468 /// `BuildHasherDefault<H>` can be used when a type `H` implements [`Hasher`] and
 469 /// [`Default`], and you need a corresponding [`BuildHasher`] instance, but none is
 470 /// defined.
 471 ///
 472 /// Any `BuildHasherDefault` is [zero-sized]. It can be created with
 473 /// [`default`][method.Default]. When using `BuildHasherDefault` with [`HashMap`] or
 474 /// [`HashSet`], this doesn't need to be done, since they implement appropriate
 475 /// [`Default`] instances themselves.
 476 ///
 477 /// # Examples
 478 ///
 479 /// Using `BuildHasherDefault` to specify a custom [`BuildHasher`] for
 480 /// [`HashMap`]:
 481 ///
 482 /// ```
 483 /// use std::collections::HashMap;
 484 /// use std::hash::{BuildHasherDefault, Hasher};
 485 ///
 486 /// #[derive(Default)]
 487 /// struct MyHasher;
 488 ///
 489 /// impl Hasher for MyHasher {
 490 ///     fn write(&mut self, bytes: &[u8]) {
 491 ///         // Your hashing algorithm goes here!
 492 ///        unimplemented!()
 493 ///     }
 494 ///
 495 ///     fn finish(&self) -> u64 {
 496 ///         // Your hashing algorithm goes here!
 497 ///         unimplemented!()
 498 ///     }
 499 /// }
 500 ///
 501 /// type MyBuildHasher = BuildHasherDefault<MyHasher>;
 502 ///
 503 /// let hash_map = HashMap::<u32, u32, MyBuildHasher>::default();
 504 /// ```
 505 ///
 506 /// [`BuildHasher`]: trait.BuildHasher.html
 507 /// [`Default`]: ../default/trait.Default.html
 508 /// [method.default]: #method.default
 509 /// [`Hasher`]: trait.Hasher.html
 510 /// [`HashMap`]: ../../std/collections/struct.HashMap.html
 511 /// [`HashSet`]: ../../std/collections/struct.HashSet.html
 512 /// [zero-sized]: https://doc.rust-lang.org/nomicon/exotic-sizes.html#zero-sized-types-zsts
 513 #[stable(since = "1.7.0", feature = "build_hasher")]
 514 pub struct BuildHasherDefault<H>(marker::PhantomData<H>);
 515
 516 #[stable(since = "1.9.0", feature = "core_impl_debug")]
 517 impl<H> fmt::Debug for BuildHasherDefault<H> {
 518     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 519         f.pad("BuildHasherDefault")
 520     }
 521 }
 522
 523 #[stable(since = "1.7.0", feature = "build_hasher")]
 524 impl<H: Default + Hasher> BuildHasher for BuildHasherDefault<H> {
 525     type Hasher = H;
 526
 527     fn build_hasher(&self) -> H {
 528         H::default()
 529     }
 530 }
 531
 532 #[stable(since = "1.7.0", feature = "build_hasher")]
 533 impl<H> Clone for BuildHasherDefault<H> {
 534     fn clone(&self) -> BuildHasherDefault<H> {
 535         BuildHasherDefault(marker::PhantomData)
 536     }
 537 }
 538
 539 #[stable(since = "1.7.0", feature = "build_hasher")]
 540 impl<H> Default for BuildHasherDefault<H> {
 541     fn default() -> BuildHasherDefault<H> {
 542         BuildHasherDefault(marker::PhantomData)
 543     }
 544 }
 545
 546 #[stable(since = "1.29.0", feature = "build_hasher_eq")]
 547 impl<H> PartialEq for BuildHasherDefault<H> {
 548     fn eq(&self, _other: &BuildHasherDefault<H>) -> bool {
 549         true
 550     }
 551 }
 552
 553 #[stable(since = "1.29.0", feature = "build_hasher_eq")]
 554 impl<H> Eq for BuildHasherDefault<H> {}
 555
 556 //////////////////////////////////////////////////////////////////////////////
 557
 558 mod impls {
 559     use crate::mem;
 560     use crate::slice;
 561
 562     use super::*;
 563
 564     macro_rules! impl_write {
 565         ($(($ty:ident, $meth:ident),)*) => {$(
 566             #[stable(feature = "rust1", since = "1.0.0")]
 567             impl Hash for $ty {
 568                 fn hash<H: Hasher>(&self, state: &mut H) {
 569                     state.$meth(*self)
 570                 }
 571
 572                 fn hash_slice<H: Hasher>(data: &[$ty], state: &mut H) {
 573                     let newlen = data.len() * mem::size_of::<$ty>();
 574                     let ptr = data.as_ptr() as *const u8;
 575                     state.write(unsafe { slice::from_raw_parts(ptr, newlen) })
 576                 }
 577             }
 578         )*}
 579     }
 580
 581     impl_write! {
 582         (u8, write_u8),
 583         (u16, write_u16),
 584         (u32, write_u32),
 585         (u64, write_u64),
 586         (usize, write_usize),
 587         (i8, write_i8),
 588         (i16, write_i16),
 589         (i32, write_i32),
 590         (i64, write_i64),
 591         (isize, write_isize),
 592         (u128, write_u128),
 593         (i128, write_i128),
 594     }
 595
 596     #[stable(feature = "rust1", since = "1.0.0")]
 597     impl Hash for bool {
 598         fn hash<H: Hasher>(&self, state: &mut H) {
 599             state.write_u8(*self as u8)
 600         }
 601     }
 602
 603     #[stable(feature = "rust1", since = "1.0.0")]
 604     impl Hash for char {
 605         fn hash<H: Hasher>(&self, state: &mut H) {
 606             state.write_u32(*self as u32)
 607         }
 608     }
 609
 610     #[stable(feature = "rust1", since = "1.0.0")]
 611     impl Hash for str {
 612         fn hash<H: Hasher>(&self, state: &mut H) {
 613             state.write(self.as_bytes());
 614             state.write_u8(0xff)
 615         }
 616     }
 617
 618     #[stable(feature = "never_hash", since = "1.29.0")]
 619     impl Hash for ! {
 620         fn hash<H: Hasher>(&self, _: &mut H) {
 621             *self
 622         }
 623     }
 624
 625     macro_rules! impl_hash_tuple {
 626         () => (
 627             #[stable(feature = "rust1", since = "1.0.0")]
 628             impl Hash for () {
 629                 fn hash<H: Hasher>(&self, _state: &mut H) {}
 630             }
 631         );
 632
 633         ( $($name:ident)+) => (
 634             #[stable(feature = "rust1", since = "1.0.0")]
 635             impl<$($name: Hash),+> Hash for ($($name,)+) where last_type!($($name,)+): ?Sized {
 636                 #[allow(non_snake_case)]
 637                 fn hash<S: Hasher>(&self, state: &mut S) {
 638                     let ($(ref $name,)+) = *self;
 639                     $($name.hash(state);)+
 640                 }
 641             }
 642         );
 643     }
 644
 645     macro_rules! last_type {
 646         ($a:ident,) => { $a };
 647         ($a:ident, $($rest_a:ident,)+) => { last_type!($($rest_a,)+) };
 648     }
 649
 650     impl_hash_tuple! {}
 651     impl_hash_tuple! { A }
 652     impl_hash_tuple! { A B }
 653     impl_hash_tuple! { A B C }
 654     impl_hash_tuple! { A B C D }
 655     impl_hash_tuple! { A B C D E }
 656     impl_hash_tuple! { A B C D E F }
 657     impl_hash_tuple! { A B C D E F G }
 658     impl_hash_tuple! { A B C D E F G H }
 659     impl_hash_tuple! { A B C D E F G H I }
 660     impl_hash_tuple! { A B C D E F G H I J }
 661     impl_hash_tuple! { A B C D E F G H I J K }
 662     impl_hash_tuple! { A B C D E F G H I J K L }
 663
 664     #[stable(feature = "rust1", since = "1.0.0")]
 665     impl<T: Hash> Hash for [T] {
 666         fn hash<H: Hasher>(&self, state: &mut H) {
 667             self.len().hash(state);
 668             Hash::hash_slice(self, state)
 669         }
 670     }
 671
 672
 673     #[stable(feature = "rust1", since = "1.0.0")]
 674     impl<T: ?Sized + Hash> Hash for &T {
 675         fn hash<H: Hasher>(&self, state: &mut H) {
 676             (**self).hash(state);
 677         }
 678     }
 679
 680     #[stable(feature = "rust1", since = "1.0.0")]
 681     impl<T: ?Sized + Hash> Hash for &mut T {
 682         fn hash<H: Hasher>(&self, state: &mut H) {
 683             (**self).hash(state);
 684         }
 685     }
 686
 687     #[stable(feature = "rust1", since = "1.0.0")]
 688     impl<T: ?Sized> Hash for *const T {
 689         fn hash<H: Hasher>(&self, state: &mut H) {
 690             if mem::size_of::<Self>() == mem::size_of::<usize>() {
 691                 // Thin pointer
 692                 state.write_usize(*self as *const () as usize);
 693             } else {
 694                 // Fat pointer
 695                 let (a, b) = unsafe {
 696                     *(self as *const Self as *const (usize, usize))
 697                 };
 698                 state.write_usize(a);
 699                 state.write_usize(b);
 700             }
 701         }
 702     }
 703
 704     #[stable(feature = "rust1", since = "1.0.0")]
 705     impl<T: ?Sized> Hash for *mut T {
 706         fn hash<H: Hasher>(&self, state: &mut H) {
 707             if mem::size_of::<Self>() == mem::size_of::<usize>() {
 708                 // Thin pointer
 709                 state.write_usize(*self as *const () as usize);
 710             } else {
 711                 // Fat pointer
 712                 let (a, b) = unsafe {
 713                     *(self as *const Self as *const (usize, usize))
 714                 };
 715                 state.write_usize(a);
 716                 state.write_usize(b);
 717             }
 718         }
 719     }
 720 }