Trait ItemEncoder

Source

pub trait ItemEncoder<T> {
    // Required method
    fn encode(
        &mut self,
        item: &T,
        index: u64,
        buf: &mut BytesMut,
    ) -> Result<(), StreamError>;

    // Provided methods
    fn prologue(&mut self, buf: &mut BytesMut) -> Result<(), StreamError> { ... }
    fn epilogue(&mut self, buf: &mut BytesMut) -> Result<(), StreamError> { ... }
}

Expand description

Per-stream encoding state.

index is passed to encode rather than tracked internally because several formats key their framing off it: the JSON array writes a separator before every item but the first, CSV writes its header row only at index 0, and Arrow emits the schema message only at index 0. Implementations that do not care simply ignore it.

Required Methods§

Source

fn encode( &mut self, item: &T, index: u64, buf: &mut BytesMut, ) -> Result<(), StreamError>

Encode one item.

Provided Methods§

Source

fn prologue(&mut self, buf: &mut BytesMut) -> Result<(), StreamError>

Bytes emitted before the first item, if any.

Source

fn epilogue(&mut self, buf: &mut BytesMut) -> Result<(), StreamError>

Bytes emitted after the last item, if any.

Called on normal end of stream only, never after an error, and never if the stream is dropped, since in both cases the body is already truncated and a well-formed terminator would misrepresent it as complete.