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)]
.
Violating this property is a logic error. The behavior resulting from a logic error is not
specified, but users of the trait must ensure that such logic errors do not result in
undefined behavior. This means that unsafe
code must not rely on the correctness of these
methods.
§Prefix collisions
Implementations of hash
should ensure that the data they
pass to the Hasher
are prefix-free. That is,
values which are not equal 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§
1.6.0 · sourcefn hash_slice<H>(data: &[Self], state: &mut H)
fn hash_slice<H>(data: &[Self], state: &mut H)
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::hash::{DefaultHasher, 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());
Dyn Compatibility§
This trait is not dyn compatible.
In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.
Implementors§
impl Hash for wasmtime_environ::component::dfg::CoreDef
impl Hash for Trampoline
impl Hash for wasmtime_environ::component::CoreDef
impl Hash for FixedEncoding
impl Hash for InterfaceType
impl Hash for StringEncoding
impl Hash for Transcode
impl Hash for Collector
impl Hash for ConstOp
impl Hash for EngineOrModuleTypeIndex
impl Hash for EntityIndex
impl Hash for IndexType
impl Hash for MemoryStyle
impl Hash for Trap
impl Hash for WasmCompositeInnerType
impl Hash for WasmHeapType
impl Hash for WasmStorageType
impl Hash for WasmValType
impl Hash for LibCall
impl Hash for AsciiChar
impl Hash for wasmtime_environ::__core::cmp::Ordering
impl Hash for Infallible
impl Hash for IpAddr
impl Hash for Ipv6MulticastScope
impl Hash for SocketAddr
impl Hash for wasmtime_environ::__core::sync::atomic::Ordering
impl Hash for ErrorKind
impl Hash for Level
impl Hash for LevelFilter
impl Hash for Op
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 AdapterId
impl Hash for AdapterModuleId
impl Hash for CanonicalOptions
impl Hash for InstanceId
impl Hash for MemoryId
impl Hash for PostReturnId
impl Hash for ReallocId
impl Hash for Adapter
impl Hash for AdapterOptions
impl Hash for CanonicalAbiInfo
impl Hash for ComponentFuncIndex
impl Hash for ComponentIndex
impl Hash for ComponentInstanceIndex
impl Hash for ComponentTypeIndex
impl Hash for ComponentUpvarIndex
impl Hash for DefinedResourceIndex
impl Hash for ExportIndex
impl Hash for ImportIndex
impl Hash for LoweredIndex
impl Hash for ModuleIndex
impl Hash for ModuleInstanceIndex
impl Hash for ModuleUpvarIndex
impl Hash for RecordField
impl Hash for ResourceIndex
impl Hash for RuntimeComponentInstanceIndex
impl Hash for RuntimeImportIndex
impl Hash for RuntimeInstanceIndex
impl Hash for RuntimeMemoryIndex
impl Hash for RuntimePostReturnIndex
impl Hash for RuntimeReallocIndex
impl Hash for StaticComponentIndex
impl Hash for TrampolineIndex
impl Hash for TypeComponentIndex
impl Hash for TypeComponentInstanceIndex
impl Hash for TypeEnum
impl Hash for TypeEnumIndex
impl Hash for TypeFlags
impl Hash for TypeFlagsIndex
impl Hash for TypeFunc
impl Hash for TypeFuncIndex
impl Hash for TypeList
impl Hash for TypeListIndex
impl Hash for TypeModuleIndex
impl Hash for TypeOption
impl Hash for TypeOptionIndex
impl Hash for TypeRecord
impl Hash for TypeRecordIndex
impl Hash for TypeResourceTable
impl Hash for TypeResourceTableIndex
impl Hash for TypeResult
impl Hash for TypeResultIndex
impl Hash for TypeTuple
impl Hash for TypeTupleIndex
impl Hash for TypeVariant
impl Hash for TypeVariantIndex
impl Hash for VariantInfo
impl Hash for String
impl Hash for BuiltinFunctionIndex
impl Hash for ConstExpr
impl Hash for DataIndex
impl Hash for DefinedFuncIndex
impl Hash for DefinedGlobalIndex
impl Hash for DefinedMemoryIndex
impl Hash for DefinedTableIndex
impl Hash for ElemIndex
impl Hash for EngineInternedRecGroupIndex
impl Hash for FuncIndex
impl Hash for FuncRefIndex
impl Hash for Global
impl Hash for GlobalIndex
impl Hash for Limits
impl Hash for Memory
impl Hash for MemoryIndex
impl Hash for ModuleInternedRecGroupIndex
impl Hash for ModuleInternedTypeIndex
impl Hash for OwnedMemoryIndex
impl Hash for RecGroupRelativeTypeIndex
impl Hash for StaticModuleIndex
impl Hash for Table
impl Hash for TableIndex
impl Hash for Tag
impl Hash for TagIndex
impl Hash for Tunables
impl Hash for TypeIndex
impl Hash for WasmArrayType
impl Hash for WasmCompositeType
impl Hash for WasmFieldType
impl Hash for WasmFuncType
impl Hash for WasmRecGroup
impl Hash for WasmRefType
impl Hash for WasmStructType
impl Hash for WasmSubType
impl Hash for Layout
impl Hash for TypeId
impl Hash for CStr
impl Hash for wasmtime_environ::__core::fmt::Error
impl Hash for PhantomPinned
impl Hash for Ipv4Addr
impl Hash for Ipv6Addr
impl Hash for SocketAddrV4
impl Hash for SocketAddrV6
impl Hash for Alignment
impl Hash for RangeFull
impl Hash for Duration
impl Hash for CString
impl Hash for OsStr
impl Hash for OsString
impl Hash for FileType
impl Hash for UCred
impl Hash for Path
impl Hash for PathBuf
impl Hash for PrefixComponent<'_>
impl Hash for ThreadId
impl Hash for Instant
impl Hash for SystemTime
impl Hash for BuildMetadata
impl Hash for Comparator
impl Hash for Prerelease
impl Hash for Version
impl Hash for VersionReq
impl Hash for Aarch64Architecture
impl Hash for AbstractHeapType
impl Hash for AbstractHeapType
impl Hash for Address
impl Hash for AddressSize
impl Hash for AliasableResourceId
impl Hash for AnyTypeId
impl Hash for Architecture
impl Hash for Architecture
impl Hash for ArmArchitecture
impl Hash for ArrayType
impl Hash for ArrayType
impl Hash for BigEndian
impl Hash for BigEndian
impl Hash for BinaryFormat
impl Hash for BinaryFormat
impl Hash for CDataModel
impl Hash for CallFrameInstruction
impl Hash for CallingConvention
impl Hash for CieId
impl Hash for ComdatId
impl Hash for ComdatKind
impl Hash for ComdatSymbolKind
impl Hash for CommonInformationEntry
impl Hash for ComponentAnyTypeId
impl Hash for ComponentCoreInstanceTypeId
impl Hash for ComponentCoreModuleTypeId
impl Hash for ComponentCoreTypeId
impl Hash for ComponentDefinedTypeId
impl Hash for ComponentFuncTypeId
impl Hash for ComponentInstanceTypeId
impl Hash for ComponentName
impl Hash for ComponentNameKind<'_>
impl Hash for ComponentTypeId
impl Hash for ComponentTypeRef
impl Hash for ComponentValType
impl Hash for ComponentValueTypeId
impl Hash for CompositeInnerType
impl Hash for CompositeType
impl Hash for CompressedFileRange
impl Hash for CompressionFormat
impl Hash for ContType
impl Hash for ContType
impl Hash for CoreTypeId
impl Hash for CustomVendor
impl Hash for CvQualifiers
impl Hash for DebugTypeSignature
impl Hash for DefaultToHost
impl Hash for DefaultToUnknown
impl Hash for DemangleNodeType
impl Hash for DirectoryId
impl Hash for DiscriminantSize
impl Hash for DwAccess
impl Hash for DwAddr
impl Hash for DwAt
impl Hash for DwAte
impl Hash for DwCc
impl Hash for DwCfa
impl Hash for DwChildren
impl Hash for DwDefaulted
impl Hash for DwDs
impl Hash for DwDsc
impl Hash for DwEhPe
impl Hash for DwEnd
impl Hash for DwForm
impl Hash for DwId
impl Hash for DwIdx
impl Hash for DwInl
impl Hash for DwLang
impl Hash for DwLle
impl Hash for DwLnct
impl Hash for DwLne
impl Hash for DwLns
impl Hash for DwMacro
impl Hash for DwOp
impl Hash for DwOrd
impl Hash for DwRle
impl Hash for DwSect
impl Hash for DwSectV2
impl Hash for DwTag
impl Hash for DwUt
impl Hash for DwVirtuality
impl Hash for DwVis
impl Hash for DwoId
impl Hash for Encoding
impl Hash for Endianness
impl Hash for Endianness
impl Hash for Environment
impl Hash for Error
impl Hash for ExportKind
impl Hash for Expression
impl Hash for FieldType
impl Hash for FieldType
impl Hash for FileFlags
impl Hash for FileId
impl Hash for FileKind
impl Hash for Format
impl Hash for FuncType
impl Hash for FuncType
impl Hash for GlobalType
impl Hash for GlobalType
impl Hash for HeapType
impl Hash for HeapType
impl Hash for Ieee32
impl Hash for Ieee64
impl Hash for ImportType
impl Hash for KebabStr
impl Hash for KebabString
impl Hash for LineEncoding
impl Hash for LineString
impl Hash for LineStringId
impl Hash for LittleEndian
impl Hash for LittleEndian
impl Hash for Location
impl Hash for LocationList
impl Hash for LocationListId
impl Hash for Mangling
impl Hash for MemoryType
impl Hash for MemoryType
impl Hash for Mips32Architecture
impl Hash for Mips64Architecture
impl Hash for ObjectKind
impl Hash for OperatingSystem
impl Hash for Ordering
impl Hash for PackedIndex
impl Hash for PointerWidth
impl Hash for PrimitiveValType
impl Hash for Range
impl Hash for Range
impl Hash for RangeList
impl Hash for RangeListId
impl Hash for RecGroup
impl Hash for RecGroupId
impl Hash for RefType
impl Hash for RefType
impl Hash for Reference
impl Hash for Register
impl Hash for RelocAddendKind
impl Hash for RelocationEncoding
impl Hash for RelocationEntry
impl Hash for RelocationFlags
impl Hash for RelocationKind
impl Hash for RelocationTarget
impl Hash for RelocationType
impl Hash for ResourceId
impl Hash for Riscv32Architecture
impl Hash for Riscv64Architecture
impl Hash for RunTimeEndian
impl Hash for SectionFlags
impl Hash for SectionId
impl Hash for SectionId
impl Hash for SectionIndex
impl Hash for SectionIndex
impl Hash for SectionKind
impl Hash for SegmentFlags
impl Hash for SegmentFlags
impl Hash for Size
impl Hash for StandardSection
impl Hash for StandardSegment
impl Hash for StorageType
impl Hash for StorageType
impl Hash for StringId
impl Hash for StructType
impl Hash for StructType
impl Hash for SubArchitecture
impl Hash for SubType
impl Hash for SymbolFlags
impl Hash for SymbolId
impl Hash for SymbolIndex
impl Hash for SymbolIndex
impl Hash for SymbolKind
impl Hash for SymbolScope
impl Hash for SymbolSection
impl Hash for SymbolSection
impl Hash for TableType
impl Hash for TableType
impl Hash for Triple
impl Hash for TypeBounds
impl Hash for UnitEntryId
impl Hash for UnitId
impl Hash for UnpackedIndex
impl Hash for V128
impl Hash for ValType
impl Hash for ValType
impl Hash for ValidatorId
impl Hash for Vendor
impl Hash for WasmFeatures
impl Hash for X86_32Architecture
impl<'a> Hash for &'a TemplateParam
impl<'a> Hash for FlagValue<'a>
impl<'a> Hash for Component<'a>
impl<'a> Hash for Prefix<'a>
impl<'a> Hash for wasmtime_environ::__core::panic::Location<'a>
impl<'a> Hash for Metadata<'a>
impl<'a> Hash for MetadataBuilder<'a>
impl<'a> Hash for BinaryReader<'a>
impl<'a> Hash for DependencyName<'a>
impl<'a> Hash for HashName<'a>
impl<'a> Hash for InterfaceName<'a>
impl<'a> Hash for ResourceFunc<'a>
impl<'a> Hash for UrlName<'a>
impl<'data> Hash for CompressedData<'data>
impl<'data> Hash for ObjectMapEntry<'data>
impl<'data> Hash for ObjectMapFile<'data>
impl<'data> Hash for SymbolMapName<'data>
impl<'input, Endian> Hash for EndianSlice<'input, Endian>where
Endian: Hash + Endianity,
impl<A> Hash for SmallVec<A>where
A: Array,
<A as Array>::Item: Hash,
impl<B> Hash for Cow<'_, B>
impl<B, C> Hash for ControlFlow<B, C>
impl<Dyn> Hash for DynMetadata<Dyn>where
Dyn: ?Sized,
impl<E> Hash for I16<E>where
E: Hash + Endian,
impl<E> Hash for I16Bytes<E>where
E: Hash + Endian,
impl<E> Hash for I32<E>where
E: Hash + Endian,
impl<E> Hash for I32Bytes<E>where
E: Hash + Endian,
impl<E> Hash for I64<E>where
E: Hash + Endian,
impl<E> Hash for I64Bytes<E>where
E: Hash + Endian,
impl<E> Hash for U16<E>where
E: Hash + Endian,
impl<E> Hash for U16Bytes<E>where
E: Hash + Endian,
impl<E> Hash for U32<E>where
E: Hash + Endian,
impl<E> Hash for U32Bytes<E>where
E: Hash + Endian,
impl<E> Hash for U64<E>where
E: Hash + Endian,
impl<E> Hash for U64Bytes<E>where
E: Hash + Endian,
impl<F> Hash for Fwhere
F: FnPtr,
impl<Idx> Hash for wasmtime_environ::__core::range::legacy::Range<Idx>where
Idx: Hash,
impl<Idx> Hash for wasmtime_environ::__core::range::legacy::RangeFrom<Idx>where
Idx: Hash,
impl<Idx> Hash for wasmtime_environ::__core::range::legacy::RangeInclusive<Idx>where
Idx: Hash,
impl<Idx> Hash for wasmtime_environ::__core::range::Range<Idx>where
Idx: Hash,
impl<Idx> Hash for wasmtime_environ::__core::range::RangeFrom<Idx>where
Idx: Hash,
impl<Idx> Hash for wasmtime_environ::__core::range::RangeInclusive<Idx>where
Idx: Hash,
impl<Idx> Hash for RangeTo<Idx>where
Idx: Hash,
impl<Idx> Hash for RangeToInclusive<Idx>where
Idx: Hash,
impl<K, V> Hash for PrimaryMap<K, V>
impl<K, V> Hash for SecondaryMap<K, V>
impl<K, V> Hash for Slice<K, V>
impl<K, V, A> Hash for BTreeMap<K, V, A>
impl<Ptr> Hash for Pin<Ptr>
impl<R> Hash for Expression<R>where
R: Hash + Reader,
impl<R> Hash for LocationListEntry<R>where
R: Hash + Reader,
impl<Section, Symbol> Hash for SymbolFlags<Section, Symbol>
impl<T> Hash for Option<T>where
T: Hash,
impl<T> Hash for Bound<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 &T
impl<T> Hash for &mut T
impl<T> Hash for [T]where
T: Hash,
impl<T> Hash for (T₁, T₂, …, Tₙ)
This trait is implemented for tuples up to twelve items long.
impl<T> Hash for PackedOption<T>where
T: Hash + ReservedValue,
impl<T> Hash for EntityList<T>
impl<T> Hash for ListPool<T>
impl<T> Hash for Reverse<T>where
T: Hash,
impl<T> Hash for PhantomData<T>where
T: ?Sized,
impl<T> Hash for Discriminant<T>
impl<T> Hash for ManuallyDrop<T>
impl<T> Hash for NonZero<T>where
T: ZeroablePrimitive + Hash,
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 DebugAbbrevOffset<T>where
T: Hash,
impl<T> Hash for DebugFrameOffset<T>where
T: Hash,
impl<T> Hash for DebugInfoOffset<T>where
T: Hash,
impl<T> Hash for DebugMacinfoOffset<T>where
T: Hash,
impl<T> Hash for DebugMacroOffset<T>where
T: Hash,
impl<T> Hash for DebugTypesOffset<T>where
T: Hash,
impl<T> Hash for EhFrameOffset<T>where
T: Hash,
impl<T> Hash for LocationListsOffset<T>where
T: Hash,
impl<T> Hash for RangeListsOffset<T>where
T: Hash,
impl<T> Hash for RawRangeListsOffset<T>where
T: Hash,
impl<T> Hash for Slice<T>where
T: Hash,
impl<T> Hash for Unalign<T>where
T: Unaligned + Hash,
impl<T> Hash for UnitOffset<T>where
T: Hash,
impl<T> Hash for UnitSectionOffset<T>where
T: Hash,
impl<T, A> Hash for Box<T, A>
impl<T, A> Hash for Vec<T, A>
The hash of a vector is the same as that of the corresponding slice,
as required by the core::borrow::Borrow
implementation.
use std::hash::BuildHasher;
let b = std::hash::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, A> Hash for BTreeSet<T, A>
impl<T, A> Hash for LinkedList<T, A>
impl<T, A> Hash for VecDeque<T, A>
impl<T, A> Hash for Rc<T, A>
impl<T, A> Hash for Arc<T, A>
impl<T, E> Hash for Result<T, E>
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.
use std::hash::BuildHasher;
let b = std::hash::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));