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package raft
import (
"bytes"
"encoding/json"
"fmt"
"io"
"code.google.com/p/gogoprotobuf/proto"
"github.com/coreos/raft/protobuf"
)
// A log entry stores a single item in the log.
type LogEntry struct {
pb *protobuf.LogEntry
Position int64 // position in the log file
log *Log
event *ev
}
// Creates a new log entry associated with a log.
func newLogEntry(log *Log, event *ev, index uint64, term uint64, command Command) (*LogEntry, error) {
var buf bytes.Buffer
var commandName string
if command != nil {
commandName = command.CommandName()
if encoder, ok := command.(CommandEncoder); ok {
if err := encoder.Encode(&buf); err != nil {
return nil, err
}
} else {
json.NewEncoder(&buf).Encode(command)
}
}
pb := &protobuf.LogEntry{
Index: proto.Uint64(index),
Term: proto.Uint64(term),
CommandName: proto.String(commandName),
Command: buf.Bytes(),
}
e := &LogEntry{
pb: pb,
log: log,
event: event,
}
return e, nil
}
func (e *LogEntry) Index() uint64 {
return e.pb.GetIndex()
}
func (e *LogEntry) Term() uint64 {
return e.pb.GetTerm()
}
func (e *LogEntry) CommandName() string {
return e.pb.GetCommandName()
}
func (e *LogEntry) Command() []byte {
return e.pb.GetCommand()
}
// Encodes the log entry to a buffer. Returns the number of bytes
// written and any error that may have occurred.
func (e *LogEntry) Encode(w io.Writer) (int, error) {
b, err := proto.Marshal(e.pb)
if err != nil {
return -1, err
}
if _, err = fmt.Fprintf(w, "%8x\n", len(b)); err != nil {
return -1, err
}
return w.Write(b)
}
// Decodes the log entry from a buffer. Returns the number of bytes read and
// any error that occurs.
func (e *LogEntry) Decode(r io.Reader) (int, error) {
var length int
_, err := fmt.Fscanf(r, "%8x\n", &length)
if err != nil {
return -1, err
}
data := make([]byte, length)
_, err = io.ReadFull(r, data)
if err != nil {
return -1, err
}
if err = proto.Unmarshal(data, e.pb); err != nil {
return -1, err
}
return length + 8 + 1, nil
}