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package cryptfs
// Per-file header
//
// Format: [ "Version" uint16 big endian ] [ "Id" 16 random bytes ]
import (
"encoding/binary"
"fmt"
)
const (
HEADER_CURRENT_VERSION = 1 // Current on-disk-format version
HEADER_VERSION_LEN = 2 // uint16
HEADER_ID_LEN = 16 // 128 bit random file id
HEADER_LEN = HEADER_VERSION_LEN + HEADER_ID_LEN // Total header length
)
type FileHeader struct {
Version uint16
Id []byte
}
// Pack - serialize fileHeader object
func (h *FileHeader) Pack() []byte {
if len(h.Id) != HEADER_ID_LEN || h.Version != HEADER_CURRENT_VERSION {
panic("FileHeader object not properly initialized")
}
buf := make([]byte, HEADER_LEN)
binary.BigEndian.PutUint16(buf[0:HEADER_VERSION_LEN], h.Version)
copy(buf[HEADER_VERSION_LEN:], h.Id)
return buf
}
// ParseHeader - parse "buf" into fileHeader object
func ParseHeader(buf []byte) (*FileHeader, error) {
if len(buf) != HEADER_LEN {
return nil, fmt.Errorf("ParseHeader: invalid length: got %d, want %d", len(buf), HEADER_LEN)
}
var h FileHeader
h.Version = binary.BigEndian.Uint16(buf[0:HEADER_VERSION_LEN])
if h.Version != HEADER_CURRENT_VERSION {
return nil, fmt.Errorf("ParseHeader: invalid version: got %d, want %d", h.Version, HEADER_CURRENT_VERSION)
}
h.Id = buf[HEADER_VERSION_LEN:]
return &h, nil
}
// RandomHeader - create new fileHeader object with random Id
func RandomHeader() *FileHeader {
var h FileHeader
h.Version = HEADER_CURRENT_VERSION
h.Id = RandBytes(HEADER_ID_LEN)
return &h
}
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