Decoder

spacetimedb_commitlog::payload

Trait Decoder 

Source 
pub trait Decoder {
    type Record: Encode;
    type Error: From<DecodeError>;

    // Required methods
    fn decode_record<'a, R: BufReader<'a>>(
        &self,
        version: u8,
        tx_offset: u64,
        reader: &mut R,
    ) -> Result<Self::Record, Self::Error>;
    fn skip_record<'a, R: BufReader<'a>>(
        &self,
        version: u8,
        tx_offset: u64,
        reader: &mut R,
    ) -> Result<(), Self::Error>;

    // Provided method
    fn consume_record<'a, R: BufReader<'a>>(
        &self,
        version: u8,
        tx_offset: u64,
        reader: &mut R,
    ) -> Result<(), Self::Error> { ... }
}
Expand description

A decoder which can decode the transaction (aka record) format of the log.

Unlike Encode, this is not a datatype: the canonical commitlog format requires to look up row types during log traversal in order to be able to decode.

Required Associated Types§

Source

type Record: Encode

The type of records this decoder can decode. This is also the type which can be appended to a commitlog, and so must satisfy Encode.

Source

type Error: From<DecodeError>

The type of decode errors, which must subsume DecodeError.

Required Methods§

Source

fn decode_record<'a, R: BufReader<'a>>( &self, version: u8, tx_offset: u64, reader: &mut R, ) -> Result<Self::Record, Self::Error>

Decode one Self::Record from the given buffer.

The version argument corresponds to the log format version of the current segment (see crate::segment::Header::log_format_version).

The tx_argument is the transaction offset of the current record relative to the start of the log.

Source

fn skip_record<'a, R: BufReader<'a>>( &self, version: u8, tx_offset: u64, reader: &mut R, ) -> Result<(), Self::Error>

Advance reader past the next Self::Record, without returning it or including it in a fold.

Provided Methods§

Source

fn consume_record<'a, R: BufReader<'a>>( &self, version: u8, tx_offset: u64, reader: &mut R, ) -> Result<(), Self::Error>

Variant of Self::decode_record which discards the decoded Self::Record.

Useful for folds which don’t need to yield or collect record values.

The default implementation just drops the record returned from Self::decode_record. Implementations may want to override this, such that the record is not allocated in the first place.

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.

Implementors§