Struct exonum_merkledb::indexes::ProofEntry

pub struct ProofEntry<T: RawAccess, V> { /* fields omitted */ }

A hashed index that may only contain one element.

You can add an element to this index and check whether it exists. A value should implement BinaryValue and ObjectHash traits. Unlike Entry, hashed entries are eagerly hashed and may participate in state aggregation.

Methods

impl<T, V> ProofEntry<T, V> where
    T: RawAccess,
    V: BinaryValue, 

pub fn get(&self) -> Option<V>

Returns a value of the entry or None if does not exist.

Examples

use exonum_merkledb::{access::CopyAccessExt, TemporaryDB, Database, Entry};

let db = TemporaryDB::new();
let fork = db.fork();
let mut index = fork.get_proof_entry("name");
assert_eq!(None, index.get());

index.set(10);
assert_eq!(Some(10), index.get());

pub fn exists(&self) -> bool

Returns true if a value of the entry exists.

Examples

use exonum_merkledb::{access::CopyAccessExt, TemporaryDB, Database, Entry};

let db = TemporaryDB::new();
let fork = db.fork();
let mut index = fork.get_proof_entry("name");
assert!(!index.exists());

index.set(10);
assert!(index.exists());

impl<T, V> ProofEntry<T, V> where
    T: RawAccessMut,
    V: BinaryValue + ObjectHash, 

pub fn set(&mut self, value: V)

Changes a value of the entry.

Examples

use exonum_merkledb::{access::CopyAccessExt, TemporaryDB, Database, Entry};

let db = TemporaryDB::new();
let fork = db.fork();
let mut index = fork.get_proof_entry("name");

index.set(10);
assert_eq!(Some(10), index.get());

pub fn remove(&mut self)

Removes a value of the entry.

Examples

use exonum_merkledb::{access::CopyAccessExt, TemporaryDB, Database, Entry};

let db = TemporaryDB::new();
let fork = db.fork();
let mut index = fork.get_proof_entry("name");

index.set(10);
assert_eq!(Some(10), index.get());

index.remove();
assert_eq!(None, index.get());

pub fn take(&mut self) -> Option<V>

Takes the value out of the entry, leaving a None in its place.

Examples

use exonum_merkledb::{access::CopyAccessExt, TemporaryDB, Database, Entry};

let db = TemporaryDB::new();
let fork = db.fork();
let mut index = fork.get_proof_entry("name");

index.set(10);
assert_eq!(Some(10), index.get());

let value = index.take();
assert_eq!(Some(10), value);
assert_eq!(None, index.get());

pub fn swap(&mut self, value: V) -> Option<V>

Replaces the value in the entry with the given one, returning the previously stored value.

Examples

use exonum_merkledb::{access::CopyAccessExt, TemporaryDB, Database, Entry};

let db = TemporaryDB::new();
let fork = db.fork();
let mut index = fork.get_proof_entry("name");

index.set(10);
assert_eq!(Some(10), index.get());

let value = index.swap(20);
assert_eq!(Some(10), value);
assert_eq!(Some(20), index.get());

Trait Implementations

impl<T: Debug + RawAccess, V: Debug> Debug for ProofEntry<T, V>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<T, V> FromAccess<T> for ProofEntry<T::Base, V> where
    T: Access,
    V: BinaryValue + ObjectHash, 

fn from_access(access: T, addr: IndexAddress) -> Result<Self, AccessError>

Constructs the object at the given address.

fn from_root(access: T) -> Result<Self, AccessError>

Constructs the object from the root of the access.

impl<T, V> ObjectHash for ProofEntry<T, V> where
    T: RawAccess,
    V: BinaryValue + ObjectHash, 

object_hash is computed as SHA-256 of the entry serialization, or Hash::zero() if the entry is not set.

Examples

let db = TemporaryDB::new();
let fork = db.fork();
let mut index = fork.get_proof_entry("name");
assert_eq!(Hash::default(), index.object_hash());

let value = 10;
index.set(value);
assert_eq!(exonum_crypto::hash(&[value]), index.object_hash());

fn object_hash(&self) -> Hash

Returns a hash of the value.