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 { ... }
}
miri-test-libstd
only.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,
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§
1.3.0 · 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 CachePreferenceError
impl Hash for ClientCachePreference
impl Hash for CompressPreference
impl Hash for ServerCachePreference
impl Hash for UriKey
impl Hash for kvarn::prelude::io::ErrorKind
impl Hash for kvarn::prelude::net::IpAddr
impl Hash for Ipv6MulticastScope
impl Hash for SocketAddr
impl Hash for kvarn::prelude::compact_str::core::cmp::Ordering
impl Hash for Infallible
impl Hash for Which
impl Hash for kvarn::prelude::compact_str::core::sync::atomic::Ordering
impl Hash for webpki::subject_name::ip_address::IpAddr
impl Hash for log::Level
impl Hash for log::LevelFilter
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 PathQuery
impl Hash for Bytes
impl Hash for BytesMut
impl Hash for OffsetDateTime
impl Hash for kvarn::prelude::fmt::Error
impl Hash for HeaderName
impl Hash for HeaderValue
impl Hash for Mime
impl Hash for Ipv4Addr
impl Hash for Ipv6Addr
impl Hash for SocketAddrV4
impl Hash for SocketAddrV6
impl Hash for kvarn::prelude::Instant
impl Hash for Method
impl Hash for Path
impl Hash for PathBuf
impl Hash for StatusCode
impl Hash for Version
impl Hash for Authority
Case-insensitive hashing
Examples
let a: Authority = "HELLO.com".parse().unwrap();
let b: Authority = "hello.coM".parse().unwrap();
let mut s = DefaultHasher::new();
a.hash(&mut s);
let a = s.finish();
let mut s = DefaultHasher::new();
b.hash(&mut s);
let b = s.finish();
assert_eq!(a, b);
impl Hash for PathAndQuery
impl Hash for Scheme
Case-insensitive hashing
impl Hash for Uri
impl Hash for CompactString
impl Hash for Layout
impl Hash for TypeId
impl Hash for CStr
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 Alignment
impl Hash for kvarn::prelude::compact_str::core::time::Duration
impl Hash for DnsName
impl Hash for CString
impl Hash for String
impl Hash for OsStr
impl Hash for OsString
impl Hash for FileType
impl Hash for std::os::unix::ucred::UCred
impl Hash for PrefixComponent<'_>
impl Hash for ThreadId
impl Hash for SystemTime
impl Hash for FixedBitSet
impl Hash for StreamId
impl Hash for BigInt
impl Hash for BigUint
impl Hash for petgraph::visit::dfsvisit::Time
impl Hash for Identifier
impl Hash for Field
impl Hash for tracing_core::metadata::Level
impl Hash for tracing_core::metadata::LevelFilter
impl Hash for Id
impl Hash for Span
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 uuid::error::Error
impl Hash for Braced
impl Hash for Hyphenated
impl Hash for Simple
impl Hash for Urn
impl Hash for Uuid
impl Hash for Timestamp
impl Hash for ASN1Time
impl Hash for AccessKind
impl Hash for AccessMode
impl Hash for AnyDelimiterCodec
impl Hash for BigEndian
impl Hash for BytesCodec
impl Hash for Certificate
impl Hash for ComponentRange
impl Hash for CompressionLevel
impl Hash for CompressionStrategy
impl Hash for Config
impl Hash for CreateKind
impl Hash for DataChange
impl Hash for DataFormat
impl Hash for Date
impl Hash for Dl_info
impl Hash for Duration
impl Hash for Elf32_Chdr
impl Hash for Elf32_Ehdr
impl Hash for Elf32_Phdr
impl Hash for Elf32_Shdr
impl Hash for Elf32_Sym
impl Hash for Elf64_Chdr
impl Hash for Elf64_Ehdr
impl Hash for Elf64_Phdr
impl Hash for Elf64_Shdr
impl Hash for Elf64_Sym
impl Hash for ErrorKind
impl Hash for Event
impl Hash for EventKind
impl Hash for EventMask
impl Hash for FileTime
impl Hash for Flag
impl Hash for Flags
impl Hash for FsyncFlags
impl Hash for Handle
impl Hash for Instant
impl Hash for Instant
impl Hash for LinesCodec
impl Hash for LiteralPredictionModeNibble
impl Hash for LittleEndian
impl Hash for MZError
impl Hash for MZFlush
impl Hash for MZStatus
impl Hash for MetadataKind
impl Hash for ModifyKind
impl Hash for Month
impl Hash for Null
impl Hash for PollNext
impl Hash for PrimitiveDateTime
impl Hash for RecursiveMode
impl Hash for RemoveKind
impl Hash for RenameMode
impl Hash for ServerName
impl Hash for StreamResult
impl Hash for TDEFLFlush
impl Hash for TDEFLStatus
impl Hash for TINFLStatus
impl Hash for Time
impl Hash for TimeoutFlags
impl Hash for Token
impl Hash for UCred
impl Hash for UtcOffset
impl Hash for WatchDescriptor
impl Hash for WatchMask
impl Hash for WatcherKind
impl Hash for Weekday
impl Hash for __c_anonymous_ifru_map
impl Hash for __c_anonymous_ptrace_syscall_info_data
extra_traits
and libc_union
only.impl Hash for __c_anonymous_ptrace_syscall_info_entry
impl Hash for __c_anonymous_ptrace_syscall_info_exit
impl Hash for __c_anonymous_ptrace_syscall_info_seccomp
impl Hash for __c_anonymous_sockaddr_can_j1939
impl Hash for __c_anonymous_sockaddr_can_tp
impl Hash for __exit_status
impl Hash for __timeval
impl Hash for _libc_fpstate
impl Hash for _libc_fpxreg
impl Hash for _libc_xmmreg
impl Hash for addrinfo
impl Hash for af_alg_iv
extra_traits
only.impl Hash for aiocb
impl Hash for arpd_request
impl Hash for arphdr
impl Hash for arpreq
impl Hash for arpreq_old
impl Hash for can_filter
impl Hash for clone_args
impl Hash for cmsghdr
impl Hash for cpu_set_t
impl Hash for dirent
extra_traits
only.impl Hash for dirent64
extra_traits
only.impl Hash for dl_phdr_info
impl Hash for dqblk
impl Hash for epoll_event
extra_traits
only.impl Hash for fanotify_event_metadata
impl Hash for fanotify_response
impl Hash for fd_set
impl Hash for ff_condition_effect
impl Hash for ff_constant_effect
impl Hash for ff_effect
impl Hash for ff_envelope
impl Hash for ff_periodic_effect
impl Hash for ff_ramp_effect
impl Hash for ff_replay
impl Hash for ff_rumble_effect
impl Hash for ff_trigger
impl Hash for file_clone_range
impl Hash for flock
impl Hash for flock64
impl Hash for fsid_t
impl Hash for genlmsghdr
impl Hash for glob64_t
impl Hash for glob_t
impl Hash for group
impl Hash for hostent
impl Hash for if_nameindex
impl Hash for ifaddrs
impl Hash for in6_addr
impl Hash for in6_ifreq
impl Hash for in6_pktinfo
impl Hash for in6_rtmsg
impl Hash for in_addr
impl Hash for in_pktinfo
impl Hash for inotify_event
impl Hash for input_absinfo
impl Hash for input_event
impl Hash for input_id
impl Hash for input_keymap_entry
impl Hash for input_mask
impl Hash for iovec
impl Hash for ip_mreq
impl Hash for ip_mreq_source
impl Hash for ip_mreqn
impl Hash for ipc_perm
impl Hash for ipv6_mreq
impl Hash for itimerspec
impl Hash for itimerval
impl Hash for j1939_filter
impl Hash for lconv
impl Hash for linger
impl Hash for mallinfo
impl Hash for mallinfo2
impl Hash for mcontext_t
impl Hash for mmsghdr
impl Hash for mntent
impl Hash for mq_attr
extra_traits
only.impl Hash for msghdr
impl Hash for msginfo
impl Hash for msqid_ds
impl Hash for nl_mmap_hdr
impl Hash for nl_mmap_req
impl Hash for nl_pktinfo
impl Hash for nlattr
impl Hash for nlmsgerr
impl Hash for nlmsghdr
impl Hash for ntptimeval
impl Hash for open_how
impl Hash for option
impl Hash for packet_mreq
impl Hash for passwd
impl Hash for pollfd
impl Hash for posix_spawn_file_actions_t
impl Hash for posix_spawnattr_t
impl Hash for protoent
impl Hash for pthread_attr_t
impl Hash for pthread_cond_t
extra_traits
only.impl Hash for pthread_condattr_t
impl Hash for pthread_mutex_t
extra_traits
only.impl Hash for pthread_mutexattr_t
impl Hash for pthread_rwlock_t
extra_traits
only.impl Hash for pthread_rwlockattr_t
impl Hash for ptrace_peeksiginfo_args
impl Hash for ptrace_rseq_configuration
impl Hash for ptrace_syscall_info
impl Hash for regex_t
impl Hash for regmatch_t
impl Hash for rlimit
impl Hash for rlimit64
impl Hash for rtentry
impl Hash for rusage
impl Hash for sched_param
impl Hash for seccomp_data
impl Hash for seccomp_notif_sizes
impl Hash for sem_t
impl Hash for sembuf
impl Hash for semid_ds
impl Hash for seminfo
impl Hash for servent
impl Hash for shmid_ds
impl Hash for sigaction
impl Hash for sigevent
extra_traits
only.impl Hash for siginfo_t
impl Hash for signalfd_siginfo
impl Hash for sigset_t
impl Hash for sigval
impl Hash for sock_extended_err
impl Hash for sock_filter
impl Hash for sock_fprog
impl Hash for sockaddr
impl Hash for sockaddr_alg
extra_traits
only.impl Hash for sockaddr_in
impl Hash for sockaddr_in6
impl Hash for sockaddr_ll
impl Hash for sockaddr_nl
extra_traits
only.impl Hash for sockaddr_storage
extra_traits
only.impl Hash for sockaddr_un
extra_traits
only.impl Hash for sockaddr_vm
impl Hash for spwd
impl Hash for stack_t
impl Hash for stat
impl Hash for stat64
impl Hash for statfs
impl Hash for statfs64
impl Hash for statvfs
impl Hash for statvfs64
impl Hash for statx
impl Hash for statx_timestamp
impl Hash for sysinfo
impl Hash for termios
impl Hash for termios2
impl Hash for timespec
impl Hash for timeval
impl Hash for timex
impl Hash for tm
impl Hash for tms
impl Hash for ucontext_t
extra_traits
only.impl Hash for ucred
impl Hash for uinput_abs_setup
impl Hash for uinput_ff_erase
impl Hash for uinput_ff_upload
impl Hash for uinput_setup
extra_traits
only.impl Hash for uinput_user_dev
extra_traits
only.impl Hash for user
impl Hash for user_fpregs_struct
extra_traits
only.impl Hash for user_regs_struct
impl Hash for utimbuf
impl Hash for utmpx
extra_traits
only.impl Hash for utsname
extra_traits
only.impl Hash for winsize
impl<'a> Hash for Component<'a>
impl<'a> Hash for Prefix<'a>
impl<'a> Hash for Location<'a>
impl<'a> Hash for Metadata<'a>
impl<'a> Hash for MetadataBuilder<'a>
impl<'a> Hash for Name<'a>
impl<'a> Hash for Oid<'a>
impl<'b, T> Hash for Ptr<'b, T>
impl<A> Hash for SmallVec<A>where A: Array, <A as Array>::Item: Hash,
impl<B> Hash for Cow<'_, B>where B: Hash + ToOwned + ?Sized,
impl<B, C> Hash for ControlFlow<B, C>where B: Hash, C: Hash,
impl<Dyn> Hash for DynMetadata<Dyn>where Dyn: ?Sized,
impl<H> Hash for HeaderWithLength<H>where H: Hash,
impl<H, T> Hash for HeaderSlice<H, T>where H: Hash, T: Hash + ?Sized,
impl<H, T> Hash for ThinArc<H, T>where H: Hash, T: Hash,
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, A> Hash for BTreeMap<K, V, A>where K: Hash, V: Hash, A: Allocator + Clone,
impl<P> Hash for Pin<P>where P: Deref, <P as Deref>::Target: 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> Hash for Ascii<S>where S: AsRef<str>,
impl<S> Hash for UniCase<S>where S: AsRef<str>,
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 kvarn::prelude::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 Discriminant<T>
impl<T> Hash for ManuallyDrop<T>where T: Hash + ?Sized,
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 LinkedList<T>where T: Hash,
impl<T> Hash for Rc<T>where T: Hash + ?Sized,
impl<T> Hash for AllowStdIo<T>where T: Hash,
impl<T> Hash for Arc<T>where T: Hash + ?Sized,
impl<T> Hash for CachePadded<T>where T: Hash,
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, E> Hash for Result<T, E>where T: Hash, E: Hash,
impl<T, N> Hash for GenericArray<T, N>where T: Hash, N: ArrayLength<T>,
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));