Trait exonum::storage::StorageKey

pub trait StorageKey: ToOwned {
    fn size(&self) -> usize;
    fn write(&self, buffer: &mut [u8]);
    fn read(buffer: &[u8]) -> Self::Owned;
}

A type that can be (de)serialized as a key in the blockchain storage.

Since keys are sorted in the serialized form, the big-endian encoding should be used with unsigned integer types. Note however that the big-endian encoding will not sort signed integer types in the natural order; therefore, they are mapped to the corresponding unsigned type by adding a constant to the source value.

Examples

use std::mem;
use exonum::storage::StorageKey;

#[derive(Clone)]
struct Key {
    a: i16,
    b: u32,
}

impl StorageKey for Key {
    fn size(&self) -> usize {
        mem::size_of_val(&self.a) + mem::size_of_val(&self.b)
    }

    fn write(&self, buffer: &mut [u8]) {
        self.a.write(&mut buffer[0..2]);
        self.b.write(&mut buffer[2..6]);
    }

    fn read(buffer: &[u8]) -> Self {
        let a = i16::read(&buffer[0..2]);
        let b = u32::read(&buffer[2..6]);
        Key { a, b }
    }
}

Required Methods

fn size(&self) -> usize

Returns the size of the serialized key in bytes.

fn write(&self, buffer: &mut [u8])

Serializes the key into the specified buffer of bytes.

The caller must guarantee that the size of the buffer is equal to the precalculated size of the serialized key.

fn read(buffer: &[u8]) -> Self::Owned

Deserializes the key from the specified buffer of bytes.

Implementations on Foreign Types

impl StorageKey for ()

No-op implementation.

fn size(&self) -> usize

fn write(&self, _buffer: &mut [u8])

fn read(_buffer: &[u8]) -> Self::Owned

impl StorageKey for u8

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self::Owned

impl StorageKey for i8

Uses encoding with the values mapped to u8 by adding the corresponding constant (128) to the value.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self::Owned

impl StorageKey for u16

Uses big-endian encoding.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self

impl StorageKey for i16

Uses big-endian encoding with the values mapped to the unsigned format by adding the corresponding constant to the value.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self

impl StorageKey for u32

Uses big-endian encoding.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self

impl StorageKey for i32

Uses big-endian encoding with the values mapped to the unsigned format by adding the corresponding constant to the value.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self

impl StorageKey for u64

Uses big-endian encoding.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self

impl StorageKey for i64

Uses big-endian encoding with the values mapped to the unsigned format by adding the corresponding constant to the value.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self

impl StorageKey for Vec<u8>

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self

impl StorageKey for [u8]

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self::Owned

impl StorageKey for String

Uses UTF-8 string serialization.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self::Owned

impl StorageKey for str

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self::Owned

impl StorageKey for SystemTime

The SystemTime (de)serialization is only possible for the values greater than 1970-01-01 00:00:00 UTC. Since the SystemTime type saves time in the form (seconds: u64, nanoseconds: u32), the total occupied size of SystemTime in the storage is 12 bytes. The seconds are stored in the first 8 bytes as per the StorageKey implementation for u64, and nanoseconds in the remaining 4 bytes as per the StorageKey implementation for u32.

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self::Owned

impl StorageKey for [u8; 32]

fn size(&self) -> usize

fn write(&self, buffer: &mut [u8])

fn read(buffer: &[u8]) -> Self

Implementors

• impl StorageKey for Hash
• impl StorageKey for PublicKey
• impl StorageKey for ProofPath