377 lines
8.8 KiB
Rust
377 lines
8.8 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/*!
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* Generic hashing support.
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*
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* This module provides a generic way to compute the hash of a value. The
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* simplest way to make a type hashable is to use `#[deriving(Hash)]`:
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*
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* # Example
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*
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* ```rust
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* use std::hash;
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* use std::hash::Hash;
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*
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* #[deriving(Hash)]
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* struct Person {
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* id: uint,
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* name: ~str,
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* phone: u64,
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* }
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*
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* let person1 = Person { id: 5, name: ~"Janet", phone: 555_666_7777 };
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* let person2 = Person { id: 5, name: ~"Bob", phone: 555_666_7777 };
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*
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* assert!(hash::hash(&person1) != hash::hash(&person2));
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* ```
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*
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* If you need more control over how a value is hashed, you need to implement
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* the trait `Hash`:
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*
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* ```rust
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* use std::hash;
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* use std::hash::Hash;
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* use std::hash::sip::SipState;
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*
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* struct Person {
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* id: uint,
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* name: ~str,
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* phone: u64,
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* }
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*
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* impl Hash for Person {
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* fn hash(&self, state: &mut SipState) {
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* self.id.hash(state);
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* self.phone.hash(state);
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* }
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* }
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*
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* let person1 = Person { id: 5, name: ~"Janet", phone: 555_666_7777 };
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* let person2 = Person { id: 5, name: ~"Bob", phone: 555_666_7777 };
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*
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* assert!(hash::hash(&person1) == hash::hash(&person2));
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* ```
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*/
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#[allow(unused_must_use)];
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use container::Container;
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use io::Writer;
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use iter::Iterator;
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use option::{Option, Some, None};
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use rc::Rc;
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use str::{Str, StrSlice};
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use slice::{Vector, ImmutableVector};
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use vec::Vec;
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/// Reexport the `sip::hash` function as our default hasher.
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pub use hash = self::sip::hash;
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pub mod sip;
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/// A trait that represents a hashable type. The `S` type parameter is an
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/// abstract hash state that is used by the `Hash` to compute the hash.
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/// It defaults to `std::hash::sip::SipState`.
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pub trait Hash<S = sip::SipState> {
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/// Compute a hash of the value.
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fn hash(&self, state: &mut S);
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}
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/// A trait that computes a hash for a value. The main users of this trait are
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/// containers like `HashMap`, which need a generic way hash multiple types.
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pub trait Hasher<S> {
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/// Compute a hash of the value.
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fn hash<T: Hash<S>>(&self, value: &T) -> u64;
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}
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//////////////////////////////////////////////////////////////////////////////
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macro_rules! impl_hash(
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( $( $ty:ty => $method:ident;)* ) => (
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$(
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impl<S: Writer> Hash<S> for $ty {
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#[inline]
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fn hash(&self, state: &mut S) {
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state.$method(*self);
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}
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}
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)*
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)
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)
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impl_hash!(
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u8 => write_u8;
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u16 => write_le_u16;
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u32 => write_le_u32;
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u64 => write_le_u64;
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uint => write_le_uint;
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i8 => write_i8;
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i16 => write_le_i16;
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i32 => write_le_i32;
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i64 => write_le_i64;
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int => write_le_int;
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)
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impl<S: Writer> Hash<S> for bool {
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#[inline]
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fn hash(&self, state: &mut S) {
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(*self as u8).hash(state);
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}
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}
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impl<S: Writer> Hash<S> for char {
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#[inline]
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fn hash(&self, state: &mut S) {
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(*self as u32).hash(state);
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}
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}
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impl<'a, S: Writer> Hash<S> for &'a str {
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#[inline]
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fn hash(&self, state: &mut S) {
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state.write(self.as_bytes());
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state.write_u8(0xFF);
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}
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}
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impl<S: Writer> Hash<S> for ~str {
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#[inline]
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fn hash(&self, state: &mut S) {
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self.as_slice().hash(state);
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}
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}
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macro_rules! impl_hash_tuple(
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() => (
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impl<S: Writer> Hash<S> for () {
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#[inline]
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fn hash(&self, state: &mut S) {
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state.write([]);
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}
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}
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);
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($A:ident $($B:ident)*) => (
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impl<
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S: Writer,
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$A: Hash<S> $(, $B: Hash<S>)*
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> Hash<S> for ($A, $($B),*) {
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#[inline]
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fn hash(&self, state: &mut S) {
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match *self {
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(ref $A, $(ref $B),*) => {
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$A.hash(state);
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$(
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$B.hash(state);
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)*
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}
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}
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}
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}
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impl_hash_tuple!($($B)*)
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);
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)
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impl_hash_tuple!(a0 a1 a2 a3 a4 a5 a6 a7)
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impl<'a, S: Writer, T: Hash<S>> Hash<S> for &'a [T] {
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#[inline]
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fn hash(&self, state: &mut S) {
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self.len().hash(state);
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for elt in self.iter() {
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elt.hash(state);
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}
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}
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}
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impl<'a, S: Writer, T: Hash<S>> Hash<S> for &'a mut [T] {
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#[inline]
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fn hash(&self, state: &mut S) {
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self.as_slice().hash(state);
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}
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}
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impl<S: Writer, T: Hash<S>> Hash<S> for ~[T] {
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#[inline]
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fn hash(&self, state: &mut S) {
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self.as_slice().hash(state);
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}
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}
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impl<S: Writer, T: Hash<S>> Hash<S> for Vec<T> {
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#[inline]
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fn hash(&self, state: &mut S) {
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self.as_slice().hash(state);
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}
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}
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impl<'a, S: Writer, T: Hash<S>> Hash<S> for &'a T {
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#[inline]
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fn hash(&self, state: &mut S) {
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(**self).hash(state);
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}
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}
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impl<'a, S: Writer, T: Hash<S>> Hash<S> for &'a mut T {
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#[inline]
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fn hash(&self, state: &mut S) {
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(**self).hash(state);
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}
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}
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impl<S: Writer, T: Hash<S>> Hash<S> for ~T {
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#[inline]
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fn hash(&self, state: &mut S) {
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(**self).hash(state);
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}
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}
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impl<S: Writer, T: Hash<S>> Hash<S> for @T {
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#[inline]
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fn hash(&self, state: &mut S) {
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(**self).hash(state);
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}
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}
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impl<S: Writer, T: Hash<S>> Hash<S> for Rc<T> {
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#[inline]
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fn hash(&self, state: &mut S) {
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(**self).hash(state);
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}
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}
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impl<S: Writer, T: Hash<S>> Hash<S> for Option<T> {
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#[inline]
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fn hash(&self, state: &mut S) {
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match *self {
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Some(ref x) => {
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0u8.hash(state);
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x.hash(state);
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}
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None => {
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1u8.hash(state);
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}
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}
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}
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}
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impl<S: Writer, T> Hash<S> for *T {
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#[inline]
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fn hash(&self, state: &mut S) {
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// NB: raw-pointer Hash does _not_ dereference
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// to the target; it just gives you the pointer-bytes.
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(*self as uint).hash(state);
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}
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}
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impl<S: Writer, T> Hash<S> for *mut T {
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#[inline]
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fn hash(&self, state: &mut S) {
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// NB: raw-pointer Hash does _not_ dereference
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// to the target; it just gives you the pointer-bytes.
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(*self as uint).hash(state);
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}
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}
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//////////////////////////////////////////////////////////////////////////////
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#[cfg(test)]
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mod tests {
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use cast;
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use io::{IoResult, Writer};
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use iter::{Iterator};
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use option::{Some, None};
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use result::Ok;
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use slice::ImmutableVector;
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use super::{Hash, Hasher};
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struct MyWriterHasher;
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impl Hasher<MyWriter> for MyWriterHasher {
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fn hash<T: Hash<MyWriter>>(&self, value: &T) -> u64 {
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let mut state = MyWriter { hash: 0 };
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value.hash(&mut state);
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state.hash
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}
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}
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struct MyWriter {
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hash: u64,
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}
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impl Writer for MyWriter {
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// Most things we'll just add up the bytes.
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fn write(&mut self, buf: &[u8]) -> IoResult<()> {
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for byte in buf.iter() {
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self.hash += *byte as u64;
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}
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Ok(())
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}
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}
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#[test]
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fn test_writer_hasher() {
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let hasher = MyWriterHasher;
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assert_eq!(hasher.hash(&()), 0);
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assert_eq!(hasher.hash(&5u8), 5);
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assert_eq!(hasher.hash(&5u16), 5);
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assert_eq!(hasher.hash(&5u32), 5);
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assert_eq!(hasher.hash(&5u64), 5);
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assert_eq!(hasher.hash(&5u), 5);
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assert_eq!(hasher.hash(&5i8), 5);
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assert_eq!(hasher.hash(&5i16), 5);
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assert_eq!(hasher.hash(&5i32), 5);
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assert_eq!(hasher.hash(&5i64), 5);
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assert_eq!(hasher.hash(&5i), 5);
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assert_eq!(hasher.hash(&false), 0);
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assert_eq!(hasher.hash(&true), 1);
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assert_eq!(hasher.hash(&'a'), 97);
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assert_eq!(hasher.hash(& &"a"), 97 + 0xFF);
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assert_eq!(hasher.hash(& &[1u8, 2u8, 3u8]), 9);
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unsafe {
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let ptr: *int = cast::transmute(5);
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assert_eq!(hasher.hash(&ptr), 5);
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}
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unsafe {
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let ptr: *mut int = cast::transmute(5);
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assert_eq!(hasher.hash(&ptr), 5);
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}
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}
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struct Custom {
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hash: u64
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}
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impl Hash<u64> for Custom {
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fn hash(&self, state: &mut u64) {
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*state = self.hash;
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}
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}
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#[test]
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fn test_custom_state() {
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let custom = Custom { hash: 5 };
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let mut state = 0;
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custom.hash(&mut state);
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assert_eq!(state, 5);
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}
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}
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