rama::crypto::dep::x509_parser::prelude::asn1_rs::nom::lib::std::hash

Trait Hash

1.0.0 · Source

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 { ... }
}

Available on crate features crypto and std only.

Expand description

A hashable type.

Types implementing Hash are able to be hashed 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§

1.0.0 · Source

fn hash<H>(&self, state: &mut H)
where H: Hasher,

Feeds this value into the given Hasher.

§Examples

use std::hash::{DefaultHasher, Hash, Hasher};

let mut hasher = DefaultHasher::new();
7920.hash(&mut hasher);
println!("Hash is {:x}!", hasher.finish());

Provided Methods§

1.3.0 · Source

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::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§

Available on crate feature cli only.

§

Trait Hash Copy item path

§Implementing Hash

§Hash and Eq

§Prefix collisions

§Portability

Required Methods§

fn hash<H>(&self, state: &mut H)where H: Hasher,

§Examples

Provided Methods§

fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

§Examples

Dyn Compatibility§

Implementors§

impl Hash for !

impl Hash for ()

impl Hash for A

impl Hash for AAAA

impl Hash for ANAME

impl Hash for ASN1Time

impl Hash for ATerm

impl Hash for Aarch64Architecture

impl Hash for Abi

impl Hash for AbiParam

impl Hash for AbstractHeapType

impl Hash for AbstractHeapType

impl Hash for AbstractResourceIndex

impl Hash for Access

impl Hash for AccessControlAllowOrigin

impl Hash for AccessControlMaxAge

impl Hash for AccessControlRequestMethod

impl Hash for Adapter

impl Hash for AdapterId

impl Hash for AdapterModuleId

impl Hash for AdapterOptions

impl Hash for Address

impl Hash for AddressFamily

impl Hash for AddressSize

impl Hash for AddressType

impl Hash for rama::proxy::haproxy::protocol::v1::Addresses

impl Hash for rama::proxy::haproxy::protocol::v2::Addresses

impl Hash for Advice

impl Hash for Age

impl Hash for AggregationTemporality

impl Hash for rama::dns::client::hickory::resolver::net::proto::rr::rdata::cert::Algorithm

impl Hash for rama::dns::client::hickory::resolver::net::proto::rr::rdata::sshfp::Algorithm

impl Hash for AliasRegion

impl Hash for AliasRegionData

impl Hash for AliasRegionSet

impl Hash for AliasableResourceId

impl Hash for Alignment

impl Hash for Allocation

impl Hash for AllocationKind

impl Hash for AllowlistSource

impl Hash for Alpn

impl Hash for Annotation

impl Hash for Any

impl Hash for AnyDelimiterCodec

impl Hash for AnyEntity

impl Hash for AnyTypeId

impl Hash for ApplicationProtocol

impl Hash for ArcStr

impl Hash for Architecture

impl Hash for Architecture

impl Hash for ArgumentExtension

impl Hash for ArgumentPurpose

impl Hash for ArmArchitecture

impl Hash for ArrayType

impl Hash for ArrayType

impl Hash for ArrayType

impl Hash for rama::http::grpc::metadata::Ascii

impl Hash for AsciiChar

impl Hash for Asn

impl Hash for AtFlags

impl Hash for Atom

impl Hash for AtomicRmwOp

impl Hash for Attribute

impl Hash for rama::crypto::dep::rcgen::Attribute

impl Hash for Attributes

impl Hash for rama::net::address::Authority

impl Hash for Authority

Trait Hash

§Implementing `Hash`

§`Hash` and `Eq`

fn hash<H>(&self, state: &mut H)
where H: Hasher,

fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,