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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfsitem
import (
"fmt"
"hash/crc32"
"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"
)
const MaxNameLen = 255
func NameHash(dat []byte) uint64 {
return uint64(^crc32.Update(1, crc32.MakeTable(crc32.Castagnoli), dat))
}
// key.objectid = inode of directory containing this entry
// key.offset =
// - for DIR_ITEM and XATTR_ITEM = NameHash(name)
// - for DIR_INDEX = index id in the directory (starting at 2, because "." and "..")
type DirEntry struct { // DIR_ITEM=84 DIR_INDEX=96 XATTR_ITEM=24
Location btrfsprim.Key `bin:"off=0x0, siz=0x11"`
TransID int64 `bin:"off=0x11, siz=8"`
DataLen uint16 `bin:"off=0x19, siz=2"` // [ignored-when-writing]
NameLen uint16 `bin:"off=0x1b, siz=2"` // [ignored-when-writing]
Type FileType `bin:"off=0x1d, siz=1"`
binstruct.End `bin:"off=0x1e"`
Data []byte `bin:"-"` // xattr value (only for XATTR_ITEM)
Name []byte `bin:"-"`
}
func (o *DirEntry) UnmarshalBinary(dat []byte) (int, error) {
if err := binutil.NeedNBytes(dat, 0x1e); 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, 0x1e+int(o.DataLen)+int(o.NameLen)); err != nil {
return 0, err
}
o.Data = dat[n : n+int(o.DataLen)]
n += int(o.DataLen)
o.Name = dat[n : n+int(o.NameLen)]
n += int(o.NameLen)
return n, nil
}
func (o DirEntry) MarshalBinary() ([]byte, error) {
o.DataLen = uint16(len(o.Data))
o.NameLen = uint16(len(o.Name))
dat, err := binstruct.MarshalWithoutInterface(o)
if err != nil {
return dat, err
}
dat = append(dat, o.Data...)
dat = append(dat, o.Name...)
return dat, nil
}
type FileType uint8
const (
FT_UNKNOWN = FileType(0)
FT_REG_FILE = FileType(1)
FT_DIR = FileType(2)
FT_CHRDEV = FileType(3)
FT_BLKDEV = FileType(4)
FT_FIFO = FileType(5)
FT_SOCK = FileType(6)
FT_SYMLINK = FileType(7)
FT_XATTR = FileType(8)
FT_MAX = FileType(9)
)
func (ft FileType) String() string {
names := map[FileType]string{
FT_UNKNOWN: "UNKNOWN",
FT_REG_FILE: "FILE", // XXX
FT_DIR: "DIR",
FT_CHRDEV: "CHRDEV",
FT_BLKDEV: "BLKDEV",
FT_FIFO: "FIFO",
FT_SOCK: "SOCK",
FT_SYMLINK: "SYMLINK",
FT_XATTR: "XATTR",
}
if name, ok := names[ft]; ok {
return name
}
return fmt.Sprintf("DIR_ITEM.%d", uint8(ft))
}
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