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 { ... }
}

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§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Trait HashCopy 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 ForwardKind

impl Hash for rama::futures::io::ErrorKind

impl Hash for PollNext

impl Hash for EmptyLineHandling

impl Hash for Encoding

impl Hash for ClientHint

impl Hash for PerMessageDeflateIdentifier

impl Hash for rama::http::layer::compression::CompressionLevel

impl Hash for ContentEncoding

impl Hash for HttpVersion

impl Hash for WriterMode

impl Hash for PseudoHeader

impl Hash for SettingId

impl Hash for ElementPatchMode

impl Hash for EventType

impl Hash for CrossOriginKind

impl Hash for rama::http::sse::datastar::execute_script::ReferrerPolicy

impl Hash for ScriptAttribute

impl Hash for ScriptType

impl Hash for rama::net::address::Host

impl Hash for ConnectIpMode

impl Hash for DnsResolveIpMode

impl Hash for IpAddrRange

impl Hash for IpSubnets

impl Hash for IpNet

impl Hash for ClientHelloExtension

impl Hash for ECHClientHello

impl Hash for ServerVerifyMode

impl Hash for ApplicationProtocol

impl Hash for CertificateCompressionAlgorithm

impl Hash for CipherSuite

impl Hash for CompressionAlgorithm

impl Hash for DataEncoding

impl Hash for ECPointFormat

impl Hash for ExtensionId

impl Hash for rama::net::tls::ProtocolVersion

impl Hash for SignatureScheme

impl Hash for SupportedGroup

impl Hash for ClientVerifyMode

impl Hash for TransportProtocol

impl Hash for UserId

impl Hash for MemoryProxyDBInsertErrorKind

impl Hash for MemoryProxyDBQueryErrorKind

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

impl Hash for AddressFamily

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

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

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

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

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

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

impl Hash for AddressType

impl Hash for rama::proxy::socks5::proto::Command

impl Hash for rama::proxy::socks5::proto::ProtocolVersion

impl Hash for ReplyKind

impl Hash for SocksMethod

impl Hash for UsernamePasswordSubnegotiationVersion

impl Hash for RelayDirection

impl Hash for InstrumentKind

impl Hash for Temporality

impl Hash for SslInfoCallbackValue

impl Hash for UserAgentSelectFallback

impl Hash for DeviceKind

impl Hash for HttpAgent

impl Hash for PlatformKind

impl Hash for TlsAgent

impl Hash for UserAgentKind

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,