ephemeral.go

package wal

import (
	"bytes"
)

type ephemeralWAL struct {
	ch  chan Entry
	idx uint64
}

// NewEphemeral returns a memory-backed WriteAheadLogger
func NewEphemeral() WriteAheadLogger {
	return &ephemeralWAL{
		ch: make(chan Entry, 1000),
	}
}

func (e *ephemeralWAL) Index() uint64 {
	return e.idx
}

func (e *ephemeralWAL) AppendBytes(entries [][]byte, crc []uint32) (uint64, uint64, error) {
	idxStart := e.idx
	for _, entry := range entries {
		e.ch <- Entry{
			Body: entry,
			ID:   e.idx,
		}
		e.idx++
	}
	return idxStart, e.idx - 1, nil
}

func (e *ephemeralWAL) Append(entries []EntryWriterTo) (uint64, uint64, error) {
	var entriesBytes [][]byte
	for _, entry := range entries {
		var b bytes.Buffer
		entry.WriteTo(&b)
		entriesBytes = append(entriesBytes, b.Bytes())
	}
	return e.AppendBytes(entriesBytes, nil)
}

func (e *ephemeralWAL) GetCursor(idx uint64) (Cursor, error) {
	return ephemeralCursor{
		readCh: e.ch,
	}, nil
}

func (e *ephemeralWAL) Close() error {
	close(e.ch)
	return nil
}

func (e *ephemeralWAL) Delete() error {
	return e.Empty()
}

func (e *ephemeralWAL) Empty() error {
	for {
		select {
		case <-e.ch:
		default:
			return nil
		}
	}
}

type ephemeralCursor struct {
	readCh chan Entry
}

func (c ephemeralCursor) ReadCh() <-chan Entry {
	return c.readCh
}

func (c ephemeralCursor) Reset() (uint64, error) {
	return 0, nil
}

func (c ephemeralCursor) Close() error {
	return nil
}