go-mmkv/metadata.go

57 lines
1.1 KiB
Go
Raw Permalink Normal View History

2022-12-04 22:27:41 +00:00
package mmkv
import (
"encoding/binary"
"fmt"
"io"
)
type metadata struct {
// added in version 0
crc32 uint32
// added in version 1
version uint32
sequence uint32 // full write back count
// added in version 2
aesVector []byte // random iv for encryption, aes.BlockSize (16 bytes)
// added in version 3, try to reduce file corruption
actualSize uint32
lastActualSize uint32
lastCRC32 uint32
//_reversed []byte // 64 bytes
}
func loadMetadata(rd io.Reader) (*metadata, error) {
buf := make([]byte, 0x68)
_, err := io.ReadFull(rd, buf)
if err != nil {
return nil, fmt.Errorf("failed to read metadata: %w", err)
}
m := &metadata{}
m.crc32 = binary.LittleEndian.Uint32(buf[0:4])
m.version = binary.LittleEndian.Uint32(buf[4:8])
if m.version >= 1 {
m.sequence = binary.LittleEndian.Uint32(buf[8:12])
}
if m.version >= 2 {
m.aesVector = buf[12:28]
}
if m.version >= 3 {
m.actualSize = binary.LittleEndian.Uint32(buf[28:32])
m.lastActualSize = binary.LittleEndian.Uint32(buf[32:36])
m.lastCRC32 = binary.LittleEndian.Uint32(buf[36:40])
}
//m._reversed = buf[40:104]
return m, nil
}