forked from zserge/kveer
/
append.go
100 lines (87 loc) · 1.5 KB
/
append.go
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package kveer
import (
"encoding/csv"
"io"
"os"
)
type record struct {
Key string
Value []byte
Err chan error
}
type kvAppend struct {
*kvMem
w io.WriteCloser
queue chan *record
}
func NewAppend(path string) *kvAppend {
kv := &kvAppend{
kvMem: NewMemory(),
queue: make(chan *record),
}
var lastErr error
f, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0644)
if err != nil {
lastErr = err
} else {
r := csv.NewReader(f)
for {
rec, err := r.Read()
if err != nil {
if err != io.EOF {
lastErr = err
}
break
}
kv.kvMem.m[rec[0]] = []byte(rec[1])
}
}
var w *csv.Writer
if lastErr == nil {
w = csv.NewWriter(f)
}
go func() {
for r := range kv.queue {
if lastErr == nil {
var rec []string
if r.Value != nil {
rec = []string{r.Key, string(r.Value)}
} else {
rec = []string{r.Key}
}
if err = w.Write(rec); err != nil {
lastErr = err
}
if r != nil && r.Err != nil {
w.Flush()
f.Sync()
r.Err <- nil
close(r.Err)
}
} else if r.Err != nil {
r.Err <- lastErr
}
}
if f != nil {
f.Close()
}
}()
return kv
}
func (kv *kvAppend) Set(k string, v []byte) {
kv.kvMem.Set(k, v)
kv.queue <- &record{k, v, nil}
}
func (kv *kvAppend) Get(k string) []byte {
return kv.kvMem.Get(k)
}
func (kv *kvAppend) Sync() <-chan error {
c := make(chan error, 1)
kv.queue <- &record{Err: c}
return c
}
func (kv *kvAppend) Close() error {
err := <-kv.Sync()
close(kv.queue)
return err
}