Struct reed_solomon_erasure::ShardByShard

pub struct ShardByShard<'a, F: 'a + Field> { /* fields omitted */ }

Bookkeeper for shard by shard encoding.

This is useful for avoiding incorrect use of encode_single and encode_single_sep

Use cases

Shard by shard encoding is useful for streamed data encoding where you do not have all the needed data shards immediately, but you want to spread out the encoding workload rather than doing the encoding after everything is ready.

A concrete example would be network packets encoding, where encoding packet by packet as you receive them may be more efficient than waiting for N packets then encode them all at once.

Example

use reed_solomon_erasure::galois_8::Field;
let r: ReedSolomon<Field> = ReedSolomon::new(3, 2).unwrap();

let mut sbs = ShardByShard::new(&r);

let mut shards = shards!([0u8,  1,  2,  3,  4],
                         [5,  6,  7,  8,  9],
                         // say we don't have the 3rd data shard yet
                         // and we want to fill it in later
                         [0,  0,  0,  0,  0],
                         [0,  0,  0,  0,  0],
                         [0,  0,  0,  0,  0]);

// encode 1st and 2nd data shard
sbs.encode(&mut shards).unwrap();
sbs.encode(&mut shards).unwrap();

// fill in 3rd data shard
shards[2][0] = 10.into();
shards[2][1] = 11.into();
shards[2][2] = 12.into();
shards[2][3] = 13.into();
shards[2][4] = 14.into();

// now do the encoding
sbs.encode(&mut shards).unwrap();

assert!(r.verify(&shards).unwrap());

Methods

impl<'a, F: 'a + Field> ShardByShard<'a, F>

pub fn new(codec: &'a ReedSolomon<F>) -> ShardByShard<'a, F>

Creates a new instance of the bookkeeping struct.

pub fn parity_ready(&self) -> bool

Checks if the parity shards are ready to use.

pub fn reset(&mut self) -> Result<(), SBSError>

Resets the bookkeeping data.

You should call this when you have added and encoded all data shards, and have finished using the parity shards.

Returns SBSError::LeftoverShards when there are shards encoded but parity shards are not ready to use.

pub fn reset_force(&mut self)

Resets the bookkeeping data without checking.

pub fn cur_input_index(&self) -> usize

Returns the current input shard index.

pub fn encode<T, U>(&mut self, shards: T) -> Result<(), SBSError> where
    T: AsRef<[U]> + AsMut<[U]>,
    U: AsRef<[F::Elem]> + AsMut<[F::Elem]>, 

Constructs the parity shards partially using the current input data shard.

Returns SBSError::TooManyCalls when all input data shards have already been filled in via encode

pub fn encode_sep<T: AsRef<[F::Elem]>, U: AsRef<[F::Elem]> + AsMut<[F::Elem]>>(
    &mut self,
    data: &[T],
    parity: &mut [U]
) -> Result<(), SBSError>

Constructs the parity shards partially using the current input data shard.

Returns SBSError::TooManyCalls when all input data shards have already been filled in via encode

Trait Implementations

impl<'a, F: Debug + 'a + Field> Debug for ShardByShard<'a, F>

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

Formats the value using the given formatter.

impl<'a, F: PartialEq + 'a + Field> PartialEq<ShardByShard<'a, F>> for ShardByShard<'a, F>

fn eq(&self, other: &ShardByShard<'a, F>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &ShardByShard<'a, F>) -> bool

This method tests for !=.

impl<'a, F: 'a + Field> StructuralPartialEq for ShardByShard<'a, F>