/
const.go
171 lines (146 loc) · 4.88 KB
/
const.go
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package okstore
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"os"
)
const (
fileFormat = "%020d%s"
segmentSuffix = ".log"
indexSuffix = ".index"
streamSuffix = ".stream"
streamMetaSuffix = ".stream.meta"
)
// FileDefaultMode FileDefaultMode
const FileDefaultMode os.FileMode = 0755
type SegmentMode int
const (
SegmentModeAll SegmentMode = iota
SegmentModeRead
)
var (
// Encoding Encoding
Encoding = binary.BigEndian
// ErrorNotData ErrorNotData
ErrorNotData = errors.New("no data")
// MagicNumber MagicNumber
MagicNumber = [2]byte{0x15, 0x16} // lm
// EndMagicNumber EndMagicNumber
EndMagicNumber = [1]byte{0x3}
// MessageVersion log version
MessageVersion = [1]byte{0x01}
// SnapshotMagicNumber SnapshotMagicNumber
SnapshotMagicNumber = [2]byte{0xb, 0xa} // ba
// EndSnapshotMagicNumber EndSnapshotMagicNumber
EndSnapshotMagicNumber = [1]byte{0xf}
// BackupSlotMagicNumber BackupSlotMagicNumber
BackupSlotMagicNumber = [2]byte{0xc, 0xd}
// BackupMagicNumber BackupMagicNumber
BackupMagicNumber = []byte("---backup start ---")
// BackupMagicEndNumber BackupMagicEndNumber
// MessageSeqSize MessageSeqSize
MessageSeqSize = 8
// LogDataLenSize LogDataLenSize
MessageDataLenSize = 4
// AppliIndexSize AppliIndexSize
AppliIndexSize = 8
IndexMaxSizeOfByte int64 = 2 * 1024 * 1024 // 索引文件的最大大小 2M
)
// a message min len
func getMinMessageLen() int {
return len(MagicNumber) + len(MessageVersion) + MessageDataLenSize + MessageSeqSize + AppliIndexSize + len(EndMagicNumber)
}
// next message is vaild if return next message start position
func nextMessageIsVail(reader io.ReaderAt, startOffset int64) (int, error) {
offset := startOffset
startMagic := make([]byte, len(MagicNumber))
// min
minN, err := reader.ReadAt(startMagic, offset)
if err != nil {
return minN, err
}
offset += int64(len(MagicNumber))
// start magic
if !bytes.Equal(startMagic, MagicNumber[:]) {
return minN, fmt.Errorf("start MagicNumber不正确 expect:%s actual:%s", string(MagicNumber[:]), string(startMagic))
}
offset += int64(len(MessageVersion))
dataLenBytes := make([]byte, MessageDataLenSize)
dataLenN, err := reader.ReadAt(dataLenBytes, offset)
if err != nil {
return minN + dataLenN, err
}
dataLen := Encoding.Uint32(dataLenBytes)
offset = startOffset + int64(getMinMessageLen()+int(dataLen)-len(EndMagicNumber))
endMagic := make([]byte, len(EndMagicNumber))
endMagicN, err := reader.ReadAt(endMagic, offset)
if err != nil {
return minN + dataLenN + endMagicN, err
}
// start magic
if !bytes.Equal(endMagic, EndMagicNumber[:]) {
return minN + dataLenN + endMagicN, fmt.Errorf("end MagicNumber不正确 expect:%s actual:%s", string(EndMagicNumber[:]), string(endMagic))
}
return getMinMessageLen() + int(dataLen), nil
}
// 从文件解码日志
// 返回日志的整个字节长度
func decodeMessageAt(reader io.ReaderAt, offsetPosition int64, decodeMessageFnc func(msg []byte) (Message, error)) (Message, int, error) {
minLen := getMinMessageLen() - len(EndMagicNumber)
minBytes := make([]byte, minLen)
// min
_, err := reader.ReadAt(minBytes, offsetPosition)
if err != nil {
return nil, 0, err
}
off := 0
// start magic
magicNum := minBytes[off : len(MagicNumber)+off]
if !bytes.Equal(magicNum, MagicNumber[:]) {
return nil, 0, fmt.Errorf("start magicNumber不正确 expect:%s actual:%s", string(MagicNumber[:]), string(magicNum))
}
off += len(MagicNumber)
// version
off += len(MessageVersion)
// dataLen
dataLen := Encoding.Uint32(minBytes[off : MessageDataLenSize+off])
// end magic
endMagicNum := make([]byte, len(EndMagicNumber))
_, err = reader.ReadAt(endMagicNum, offsetPosition+int64(minLen)+int64(dataLen))
if err != nil {
return nil, 0, err
}
if !bytes.Equal(endMagicNum, EndMagicNumber[:]) {
return nil, 0, fmt.Errorf("end magicNumber不正确 expect:%s actual:%s", string(EndMagicNumber[:]), string(endMagicNum))
}
totalData := make([]byte, minLen+int(dataLen)+len(EndMagicNumber))
totalSize, err := reader.ReadAt(totalData, offsetPosition)
if err != nil {
return nil, 0, err
}
message, err := decodeMessageFnc(totalData)
if err != nil {
return nil, 0, err
}
return message, totalSize, nil
}
// 解码 message seq(序号)
func decodeMessageSeq(reader io.ReaderAt, position int64) (messageSeq uint32, dataLen int, err error) {
sizeByte := make([]byte, MessageDataLenSize)
if _, err = reader.ReadAt(sizeByte, position+int64(len(MagicNumber)+len(MessageVersion))); err != nil {
return
}
messageSeqByte := make([]byte, MessageSeqSize)
if _, err = reader.ReadAt(messageSeqByte, position+int64(len(MagicNumber)+len(MessageVersion)+MessageDataLenSize)); err != nil {
return
}
dataLen = int(Encoding.Uint32(sizeByte))
messageSeq = uint32(Encoding.Uint64(messageSeqByte)) // 实际编码中messageSeq是uint64的
return
}
func roundDown(total, factor int64) int64 {
return factor * (total / factor)
}