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/*
* Copyright (c) 2022. Nydus Developers. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*/
package layout
import (
"encoding/binary"
"errors"
"unsafe"
)
// RafsV6 layout: 1k + SuperBlock(128) + SuperBlockExtended(256)
// RafsV5 layout: 8K superblock
// So we only need to read the MaxSuperBlockSize size to include both v5 and v6 superblocks
const MaxSuperBlockSize = 8 * 1024
const (
RafsV5 string = "v5"
RafsV6 string = "v6"
RafsV5SuperVersion uint32 = 0x500
RafsV5SuperMagic uint32 = 0x5241_4653
RafsV6SuperMagic uint32 = 0xE0F5_E1E2
RafsV6SuperBlockSize uint32 = 1024 + 128 + 256
RafsV6SuperBlockOffset uint32 = 1024
RafsV6ChunkInfoOffset uint32 = 1024 + 128 + 24
BootstrapFile string = "image/image.boot"
LegacyBootstrapFile string = "image.boot"
DummyMountpoint string = "/dummy"
)
var nativeEndian binary.ByteOrder
type ImageMode int
const (
OnDemand ImageMode = iota
PreLoad
)
func init() {
buf := [2]byte{}
*(*uint16)(unsafe.Pointer(&buf[0])) = uint16(0xABCD)
switch buf {
case [2]byte{0xCD, 0xAB}:
nativeEndian = binary.LittleEndian
case [2]byte{0xAB, 0xCD}:
nativeEndian = binary.BigEndian
default:
panic("Could not determine native endianness.")
}
}
func isRafsV6(buf []byte) bool {
return nativeEndian.Uint32(buf[RafsV6SuperBlockOffset:]) == RafsV6SuperMagic
}
func DetectFsVersion(header []byte) (string, error) {
if len(header) < 8 {
return "", errors.New("header buffer to DetectFsVersion is too small")
}
magic := binary.LittleEndian.Uint32(header[0:4])
fsVersion := binary.LittleEndian.Uint32(header[4:8])
if magic == RafsV5SuperMagic && fsVersion == RafsV5SuperVersion {
return RafsV5, nil
}
// FIXME: detect more magic numbers to reduce collision
if len(header) >= int(RafsV6SuperBlockSize) && isRafsV6(header) {
return RafsV6, nil
}
return "", errors.New("unknown file system header")
}
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