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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfsitem
import (
"fmt"
"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
"git.lukeshu.com/btrfs-progs-ng/lib/binstruct/binutil"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsprim"
)
// A RootRef links subvolumes parent→child for normal subvolumes and
// base→snapshot for snapshot subvolumes. BACKREF items go the other
// direction; child→parent and snapshot→base.
//
// Key:
//
// ROOT_REF | ROOT_BACKREF
// key.objectid = ID of the parent subvolume | ID of the child subvolume
// key.offset = ID of the child subvolume | ID of the parent subvolume
type RootRef struct { // complex ROOT_REF=156 ROOT_BACKREF=144
DirID btrfsprim.ObjID `bin:"off=0x00, siz=0x8"` // inode of the parent directory of the dir entry
Sequence int64 `bin:"off=0x08, siz=0x8"` // index of that dir entry within the parent
NameLen uint16 `bin:"off=0x10, siz=0x2"` // [ignored-when-writing]
binstruct.End `bin:"off=0x12"`
Name []byte `bin:"-"`
}
func (o *RootRef) Free() {
bytePool.Put(o.Name)
*o = RootRef{}
rootRefPool.Put(o)
}
func (o RootRef) Clone() RootRef {
o.Name = cloneBytes(o.Name)
return o
}
func (o *RootRef) UnmarshalBinary(dat []byte) (int, error) {
if err := binutil.NeedNBytes(dat, 0x12); err != nil {
return 0, err
}
n, err := binstruct.UnmarshalWithoutInterface(dat, o)
if err != nil {
return n, err
}
if o.NameLen > MaxNameLen {
return 0, fmt.Errorf("maximum name len is %v, but .NameLen=%v",
MaxNameLen, o.NameLen)
}
if err := binutil.NeedNBytes(dat, 0x12+int(o.NameLen)); err != nil {
return 0, err
}
o.Name = cloneBytes(dat[n : n+int(o.NameLen)])
n += int(o.NameLen)
return n, nil
}
func (o RootRef) MarshalBinary() ([]byte, error) {
o.NameLen = uint16(len(o.Name))
dat, err := binstruct.MarshalWithoutInterface(o)
if err != nil {
return dat, err
}
dat = append(dat, o.Name...)
return dat, nil
}
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