Trait matterdb::BinaryKey

pub trait BinaryKey: ToOwned {
    fn size(&self) -> usize;
    fn write(&self, buffer: &mut [u8]) -> usize;
    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 matterdb::BinaryKey;

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

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

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

    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]) -> usize

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 returned via size(). Returns number of written bytes. The provided buffer may be uninitialized; an implementor must not read from it.

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

Deserializes the key from the specified buffer of bytes.

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Implementations on Foreign Types

impl BinaryKey for ()

No-op implementation.

fn size(&self) -> usize

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

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

impl BinaryKey for u8

fn size(&self) -> usize

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

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

impl BinaryKey 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]) -> usize

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

impl BinaryKey for u16

Uses big-endian encoding.

fn size(&self) -> usize

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

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

impl BinaryKey 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]) -> usize

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

impl BinaryKey for u32

Uses big-endian encoding.

fn size(&self) -> usize

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

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

impl BinaryKey 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]) -> usize

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

impl BinaryKey for u64

Uses big-endian encoding.

fn size(&self) -> usize

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

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

impl BinaryKey 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]) -> usize

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

impl BinaryKey for u128

Uses big-endian encoding.

fn size(&self) -> usize

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

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

impl BinaryKey for i128

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]) -> usize

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

impl BinaryKey for Vec<u8>

fn size(&self) -> usize

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

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

impl BinaryKey for [u8]

fn size(&self) -> usize

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

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

impl BinaryKey for [u8; 32]

fn size(&self) -> usize

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

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

impl BinaryKey for String

Uses UTF-8 string serialization.

fn size(&self) -> usize

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

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

impl BinaryKey for str

fn size(&self) -> usize

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

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

impl BinaryKey for DateTime<Utc>

chrono::DateTime uses only 12 bytes in the storage. It is represented by number of seconds since 1970-01-01 00:00:00 UTC, which are stored in the first 8 bytes as per the BinaryKey implementation for i64, and nanoseconds, which are stored in the remaining 4 bytes as per the BinaryKey implementation for u32.

fn size(&self) -> usize

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

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

impl BinaryKey for Uuid

fn size(&self) -> usize

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

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

impl BinaryKey for Decimal

fn size(&self) -> usize

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

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

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Implementors

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