pub trait Hash {
// Required method
fn hash<H>(&self, state: &mut H)
where H: Hasher;
// Provided method
fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher,
Self: Sized { ... }
}
Expand description
A hashable type.
Types implementing Hash
are able to be hash
ed with an instance of
Hasher
.
Implementing Hash
You can derive Hash
with #[derive(Hash)]
if all fields implement Hash
.
The resulting hash will be the combination of the values from calling
hash
on each field.
#[derive(Hash)]
struct Rustacean {
name: String,
country: String,
}
If you need more control over how a value is hashed, you can of course
implement the Hash
trait yourself:
use std::hash::{Hash, Hasher};
struct Person {
id: u32,
name: String,
phone: u64,
}
impl Hash for Person {
fn hash<H: Hasher>(&self, state: &mut H) {
self.id.hash(state);
self.phone.hash(state);
}
}
Hash
and Eq
When implementing both Hash
and Eq
, it is important that the following
property holds:
k1 == k2 -> hash(k1) == hash(k2)
In other words, if two keys are equal, their hashes must also be equal.
HashMap
and HashSet
both rely on this behavior.
Thankfully, you won’t need to worry about upholding this property when
deriving both Eq
and Hash
with #[derive(PartialEq, Eq, Hash)]
.
Prefix collisions
Implementations of hash
should ensure that the data they
pass to the Hasher
are prefix-free. That is,
unequal values should cause two different sequences of values to be written,
and neither of the two sequences should be a prefix of the other.
For example, the standard implementation of Hash
for &str
passes an extra
0xFF
byte to the Hasher
so that the values ("ab", "c")
and ("a", "bc")
hash differently.
Portability
Due to differences in endianness and type sizes, data fed by Hash
to a Hasher
should not be considered portable across platforms. Additionally the data passed by most
standard library types should not be considered stable between compiler versions.
This means tests shouldn’t probe hard-coded hash values or data fed to a Hasher
and
instead should check consistency with Eq
.
Serialization formats intended to be portable between platforms or compiler versions should
either avoid encoding hashes or only rely on Hash
and Hasher
implementations that
provide additional guarantees.
Required Methods§
Provided Methods§
1.3.0 · sourcefn hash_slice<H>(data: &[Self], state: &mut H)where
H: Hasher,
Self: Sized,
fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,
Feeds a slice of this type into the given Hasher
.
This method is meant as a convenience, but its implementation is
also explicitly left unspecified. It isn’t guaranteed to be
equivalent to repeated calls of hash
and implementations of
Hash
should keep that in mind and call hash
themselves
if the slice isn’t treated as a whole unit in the PartialEq
implementation.
For example, a VecDeque
implementation might naïvely call
as_slices
and then hash_slice
on each slice, but this
is wrong since the two slices can change with a call to
make_contiguous
without affecting the PartialEq
result. Since these slices aren’t treated as singular
units, and instead part of a larger deque, this method cannot
be used.
Examples
use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};
let mut hasher = DefaultHasher::new();
let numbers = [6, 28, 496, 8128];
Hash::hash_slice(&numbers, &mut hasher);
println!("Hash is {:x}!", hasher.finish());
Implementors§
impl Hash for core::cmp::Ordering
impl Hash for Infallible
impl Hash for Which
impl Hash for core::sync::atomic::Ordering
impl Hash for ErrorKind
impl Hash for IpAddr
impl Hash for Ipv6MulticastScope
impl Hash for SocketAddr
impl Hash for TAffine
impl Hash for TGeneral
impl Hash for TProjective
impl Hash for SliceInfoElem
impl Hash for Sign
impl Hash for Direction
impl Hash for bool
impl Hash for char
impl Hash for i8
impl Hash for i16
impl Hash for i32
impl Hash for i64
impl Hash for i128
impl Hash for isize
impl Hash for !
impl Hash for str
impl Hash for u8
impl Hash for u16
impl Hash for u32
impl Hash for u64
impl Hash for u128
impl Hash for ()
impl Hash for usize
impl Hash for CString
impl Hash for String
impl Hash for Layout
impl Hash for TypeId
impl Hash for CStr
impl Hash for core::fmt::Error
impl Hash for PhantomPinned
impl Hash for NonZeroI8
impl Hash for NonZeroI16
impl Hash for NonZeroI32
impl Hash for NonZeroI64
impl Hash for NonZeroI128
impl Hash for NonZeroIsize
impl Hash for NonZeroU8
impl Hash for NonZeroU16
impl Hash for NonZeroU32
impl Hash for NonZeroU64
impl Hash for NonZeroU128
impl Hash for NonZeroUsize
impl Hash for RangeFull
impl Hash for core::ptr::alignment::Alignment
impl Hash for Duration
impl Hash for OsStr
impl Hash for OsString
impl Hash for FileType
impl Hash for Ipv4Addr
impl Hash for Ipv6Addr
impl Hash for SocketAddrV4
impl Hash for SocketAddrV6
impl Hash for PathBuf
impl Hash for PrefixComponent<'_>
impl Hash for ThreadId
impl Hash for Instant
impl Hash for SystemTime
impl Hash for FixedBitSet
impl Hash for IxDynImpl
impl Hash for Slice
impl Hash for BigInt
impl Hash for BigUint
impl Hash for Time
impl Hash for ATerm
impl Hash for B0
impl Hash for B1
impl Hash for Z0
impl Hash for Equal
impl Hash for Greater
impl Hash for Less
impl Hash for UTerm
impl Hash for Axis
impl Hash for Path
impl Hash for consalign::Record
impl Hash for Sequence
impl Hash for Alignment
impl Hash for AlignmentOperation
impl Hash for AlignmentOperation
impl Hash for Alphabet
impl Hash for BNDM
impl Hash for BOM
impl Hash for BackwardSearchResult
impl Hash for BiInterval
impl Hash for BigEndian
impl Hash for BitEnc
impl Hash for CheckedCastError
impl Hash for Error
impl Hash for Error
impl Hash for ExactMatch
impl Hash for Finder
impl Hash for GffType
impl Hash for Interval
impl Hash for Interval
impl Hash for Interval
impl Hash for Kind
impl Hash for LittleEndian
impl Hash for Locus
impl Hash for Match
impl Hash for Match
impl Hash for MatchParams
impl Hash for MaxOp
impl Hash for NoStrand
impl Hash for Occ
impl Hash for Orf
impl Hash for ParseError
impl Hash for PodCastError
impl Hash for QGramIndex
impl Hash for RankSelect
impl Hash for RankTransform
impl Hash for Record
impl Hash for Record
impl Hash for ReqStrand
impl Hash for ShiftAnd
impl Hash for SparseAlignmentResult
impl Hash for State
impl Hash for StateIter
impl Hash for StateTransition
impl Hash for StateTransitionIter
impl Hash for SumOp
impl Hash for SuperblockRank
impl Hash for TracebackCell
impl Hash for WaveletMatrix
impl<'a> Hash for Component<'a>
impl<'a> Hash for Prefix<'a>
impl<'a> Hash for Location<'a>
impl<'a> Hash for BitEncIter<'a>
impl<'a> Hash for Horspool<'a>
impl<'a> Hash for KMP<'a>
impl<'a> Hash for Matches<'a>
impl<'a> Hash for Matches<'a>
impl<'a> Hash for Matches<'a>
impl<'a, Block> Hash for BitSlice<'a, Block>where Block: BlockType + Hash,
impl<'a, Block> Hash for BitSliceMut<'a, Block>where Block: BlockType + Hash,
impl<'a, C, T> Hash for QGrams<'a, C, T>where C: Hash + Borrow<u8>, T: Hash + Iterator<Item = C>,
impl<'a, N, D> Hash for Entry<'a, N, D>where N: Hash + Ord + Clone, D: Hash,
impl<'a, N, D> Hash for EntryMut<'a, N, D>where N: Hash + Ord + Clone, D: Hash,
impl<'a, N, D> Hash for IntervalTreeIterator<'a, N, D>where N: Hash + Ord + Clone, D: Hash,
impl<'a, N, D> Hash for IntervalTreeIteratorMut<'a, N, D>where N: Hash + Ord + Clone, D: Hash,
impl<'a, R, T> Hash for AnnotMapIterator<'a, R, T>where R: Hash + Eq, T: Hash,
impl<'a, R, T> Hash for Entry<'a, R, T>where R: Hash + Eq, T: Hash,
impl<'b, T> Hash for Ptr<'b, T>
impl<A, B> Hash for EitherOrBoth<A, B>where A: Hash, B: Hash,
impl<B> Hash for Cow<'_, B>where B: Hash + ToOwned + ?Sized,
impl<B> Hash for bit_vec::BitVec<B>where B: BitBlock,
impl<B> Hash for consalign::Reader<B>where B: Hash,
impl<B> Hash for consalign::Records<B>where B: Hash + BufRead,
impl<B> Hash for BitSet<B>where B: BitBlock,
impl<B> Hash for Reader<B>where B: Hash,
impl<B, C> Hash for ControlFlow<B, C>where B: Hash, C: Hash,
impl<Block> Hash for bv::bit_vec::BitVec<Block>where Block: BlockType + Hash,
impl<DBWT, DLess, DOcc> Hash for FMDIndex<DBWT, DLess, DOcc>where DBWT: Hash + Borrow<Vec<u8, Global>>, DLess: Hash + Borrow<Vec<usize, Global>>, DOcc: Hash + Borrow<Occ>,
impl<DBWT, DLess, DOcc> Hash for FMIndex<DBWT, DLess, DOcc>where DBWT: Hash + Borrow<Vec<u8, Global>>, DLess: Hash + Borrow<Vec<usize, Global>>, DOcc: Hash + Borrow<Occ>,
impl<Dyn> Hash for DynMetadata<Dyn>where Dyn: ?Sized,
impl<F> Hash for Aligner<F>where F: Hash + MatchFunc,
impl<F> Hash for Aligner<F>where F: Hash + MatchFunc,
impl<F> Hash for Scoring<F>where F: Hash + MatchFunc,
impl<F> Hash for Ukkonen<F>where F: Hash + Fn(u8, u8) -> u32,
impl<F, B> Hash for SmallInts<F, B>where F: Hash + Integer + Bounded + NumCast + Copy, B: Hash + Integer + NumCast + Copy,
impl<I> Hash for Dim<I>where I: Hash + ?Sized,
impl<Idx> Hash for Range<Idx>where Idx: Hash,
impl<Idx> Hash for RangeFrom<Idx>where Idx: Hash,
impl<Idx> Hash for RangeInclusive<Idx>where Idx: Hash,
impl<Idx> Hash for RangeTo<Idx>where Idx: Hash,
impl<Idx> Hash for RangeToInclusive<Idx>where Idx: Hash,
impl<Ix> Hash for petgraph::adj::EdgeIndex<Ix>where Ix: Hash + IndexType,
impl<Ix> Hash for petgraph::graph_impl::EdgeIndex<Ix>where Ix: Hash,
impl<Ix> Hash for NodeIndex<Ix>where Ix: Hash,
impl<K, V> Hash for EnumMap<K, V>where K: Enum<V>, V: Hash,
impl<K, V, A> Hash for BTreeMap<K, V, A>where K: Hash, V: Hash, A: Allocator + Clone,
impl<L, Pr, Po, Payload> Hash for Model<L, Pr, Po, Payload>where L: Hash + Likelihood<Payload>, Pr: Hash + Prior, Po: Hash + Posterior, Payload: Hash + Default,
impl<L, R> Hash for Either<L, R>where L: Hash, R: Hash,
impl<N> Hash for consalign::Interval<N>where N: Hash + Ord + Clone,
impl<N, D> Hash for ArrayBackedIntervalTree<N, D>where N: Hash + Ord + Clone + Copy, D: Hash,
impl<N, D> Hash for IntervalTree<N, D>where N: Hash + Ord + Clone, D: Hash,
impl<P> Hash for Pin<P>where P: Deref, <P as Deref>::Target: Hash,
impl<R> Hash for Records<R>where R: Hash + Read,
impl<R, S> Hash for Contig<R, S>where R: Hash, S: Hash,
impl<R, S> Hash for Pos<R, S>where R: Hash, S: Hash,
impl<R, S> Hash for Spliced<R, S>where R: Hash, S: Hash,
impl<Ret, T> Hash for fn (T₁, T₂, …, Tₙ) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for extern "C" fn (T₁, T₂, …, Tₙ) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for extern "C" fn (T₁, T₂, …, Tₙ, ...) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for extern "C-unwind" fn (T₁, T₂, …, Tₙ) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for extern "C-unwind" fn (T₁, T₂, …, Tₙ, ...) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for unsafe fn (T₁, T₂, …, Tₙ) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for unsafe extern "C" fn (T₁, T₂, …, Tₙ) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for unsafe extern "C" fn (T₁, T₂, …, Tₙ, ...) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for unsafe extern "C-unwind" fn (T₁, T₂, …, Tₙ) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<Ret, T> Hash for unsafe extern "C-unwind" fn (T₁, T₂, …, Tₙ, ...) -> Ret
This trait is implemented for function pointers with up to twelve arguments.
impl<S, D> Hash for ArrayBase<S, D>where D: Dimension, S: Data, <S as RawData>::Elem: Hash,
impl<T> Hash for Bound<T>where T: Hash,
impl<T> Hash for Option<T>where T: Hash,
impl<T> Hash for Poll<T>where T: Hash,
impl<T> Hash for *const Twhere T: ?Sized,
impl<T> Hash for *mut Twhere T: ?Sized,
impl<T> Hash for &Twhere T: Hash + ?Sized,
impl<T> Hash for &mut Twhere T: Hash + ?Sized,
impl<T> Hash for [T]where T: Hash,
impl<T> Hash for (T₁, T₂, …, Tₙ)where T: Hash + ?Sized,
This trait is implemented for tuples up to twelve items long.
impl<T> Hash for LinkedList<T>where T: Hash,
impl<T> Hash for Rc<T>where T: Hash + ?Sized,
impl<T> Hash for Arc<T>where T: Hash + ?Sized,
impl<T> Hash for Reverse<T>where T: Hash,
impl<T> Hash for PhantomData<T>where T: ?Sized,
impl<T> Hash for ManuallyDrop<T>where T: Hash + ?Sized,
impl<T> Hash for Discriminant<T>
impl<T> Hash for Saturating<T>where T: Hash,
impl<T> Hash for Wrapping<T>where T: Hash,
impl<T> Hash for NonNull<T>where T: ?Sized,
impl<T> Hash for IJKW<T>where T: Hash + Scalar,
impl<T> Hash for M2x2<T>where T: Hash + Scalar,
impl<T> Hash for M2x3<T>where T: Hash + Scalar,
impl<T> Hash for M2x4<T>where T: Hash + Scalar,
impl<T> Hash for M2x5<T>where T: Hash + Scalar,
impl<T> Hash for M2x6<T>where T: Hash + Scalar,
impl<T> Hash for M3x2<T>where T: Hash + Scalar,
impl<T> Hash for M3x3<T>where T: Hash + Scalar,
impl<T> Hash for M3x4<T>where T: Hash + Scalar,
impl<T> Hash for M3x5<T>where T: Hash + Scalar,
impl<T> Hash for M3x6<T>where T: Hash + Scalar,
impl<T> Hash for M4x2<T>where T: Hash + Scalar,
impl<T> Hash for M4x3<T>where T: Hash + Scalar,
impl<T> Hash for M4x4<T>where T: Hash + Scalar,
impl<T> Hash for M4x5<T>where T: Hash + Scalar,
impl<T> Hash for M4x6<T>where T: Hash + Scalar,
impl<T> Hash for M5x2<T>where T: Hash + Scalar,
impl<T> Hash for M5x3<T>where T: Hash + Scalar,
impl<T> Hash for M5x4<T>where T: Hash + Scalar,
impl<T> Hash for M5x5<T>where T: Hash + Scalar,
impl<T> Hash for M5x6<T>where T: Hash + Scalar,
impl<T> Hash for M6x2<T>where T: Hash + Scalar,
impl<T> Hash for M6x3<T>where T: Hash + Scalar,
impl<T> Hash for M6x4<T>where T: Hash + Scalar,
impl<T> Hash for M6x5<T>where T: Hash + Scalar,
impl<T> Hash for M6x6<T>where T: Hash + Scalar,
impl<T> Hash for X<T>where T: Hash + Scalar,
impl<T> Hash for XY<T>where T: Hash + Scalar,
impl<T> Hash for XYZ<T>where T: Hash + Scalar,
impl<T> Hash for XYZW<T>where T: Hash + Scalar,
impl<T> Hash for XYZWA<T>where T: Hash + Scalar,
impl<T> Hash for XYZWAB<T>where T: Hash + Scalar,
impl<T> Hash for Unit<T>where T: Hash,
impl<T> Hash for Quaternion<T>where T: Scalar + Hash,
impl<T> Hash for num_complex::Complex<T>where T: Hash,
impl<T> Hash for num_complex::Complex<T>where T: Hash,
impl<T> Hash for num_rational::Ratio<T>where T: Clone + Integer + Hash,
impl<T> Hash for num_rational::Ratio<T>where T: Clone + Integer + Hash,
impl<T> Hash for Myers<T>where T: Hash + BitVec, <T as BitVec>::DistType: Hash,
impl<T> Hash for Myers<T>where T: Hash + BitVec,
impl<T> Hash for NotNan<T>where T: Float,
impl<T> Hash for OrderedFloat<T>where T: Float,
impl<T, A> Hash for Box<T, A>where T: Hash + ?Sized, A: Allocator,
impl<T, A> Hash for BTreeSet<T, A>where T: Hash, A: Allocator + Clone,
impl<T, A> Hash for VecDeque<T, A>where T: Hash, A: Allocator,
impl<T, A> Hash for Vec<T, A>where T: Hash, A: Allocator,
The hash of a vector is the same as that of the corresponding slice,
as required by the core::borrow::Borrow
implementation.
#![feature(build_hasher_simple_hash_one)]
use std::hash::BuildHasher;
let b = std::collections::hash_map::RandomState::new();
let v: Vec<u8> = vec![0xa8, 0x3c, 0x09];
let s: &[u8] = &[0xa8, 0x3c, 0x09];
assert_eq!(b.hash_one(v), b.hash_one(s));
impl<T, C, const D: usize> Hash for Transform<T, C, D>where T: RealField + Hash, C: TCategory, Const<D>: DimNameAdd<Const<1>>, DefaultAllocator: Allocator<T, <Const<D> as DimNameAdd<Const<1>>>::Output, <Const<D> as DimNameAdd<Const<1>>>::Output>, <DefaultAllocator as Allocator<T, <Const<D> as DimNameAdd<Const<1>>>::Output, <Const<D> as DimNameAdd<Const<1>>>::Output>>::Buffer: Hash,
impl<T, D> Hash for OPoint<T, D>where T: Scalar + Hash, D: DimName, DefaultAllocator: Allocator<T, D, Const<1>>,
impl<T, E> Hash for Result<T, E>where T: Hash, E: Hash,
impl<T, Op> Hash for FenwickTree<T, Op>where T: Hash + Default + Ord, Op: Hash + PrefixOp<T>,
impl<T, R, C, S> Hash for Matrix<T, R, C, S>where T: Scalar + Hash, R: Dim, C: Dim, S: RawStorage<T, R, C>,
impl<T, R, const D: usize> Hash for Isometry<T, R, D>where T: Scalar + Hash, R: Hash, <DefaultAllocator as Allocator<T, Const<D>, Const<1>>>::Buffer: Hash,
impl<T, R, const D: usize> Hash for Similarity<T, R, D>where T: Scalar + Hash, R: Hash, <DefaultAllocator as Allocator<T, Const<D>, Const<1>>>::Buffer: Hash,
impl<T, const D: usize> Hash for Rotation<T, D>where T: Scalar + Hash, <DefaultAllocator as Allocator<T, Const<D>, Const<D>>>::Buffer: Hash,
impl<T, const D: usize> Hash for Translation<T, D>where T: Scalar + Hash, <DefaultAllocator as Allocator<T, Const<D>, Const<1>>>::Buffer: Hash,
impl<T, const LANES: usize> Hash for Simd<T, LANES>where LaneCount<LANES>: SupportedLaneCount, T: SimdElement + Hash,
impl<T, const N: usize> Hash for [T; N]where T: Hash,
The hash of an array is the same as that of the corresponding slice,
as required by the Borrow
implementation.
#![feature(build_hasher_simple_hash_one)]
use std::hash::BuildHasher;
let b = std::collections::hash_map::RandomState::new();
let a: [u8; 3] = [0xa8, 0x3c, 0x09];
let s: &[u8] = &[0xa8, 0x3c, 0x09];
assert_eq!(b.hash_one(a), b.hash_one(s));