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// Copyright 2019 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package disklayout
import (
"gvisor.dev/gvisor/pkg/sentry/fs"
)
const (
// MaxFileName is the maximum length of an ext fs file's name.
MaxFileName = 255
// DirentSize is the size of ext dirent structures.
DirentSize = 263
)
var (
// inodeTypeByFileType maps ext4 file types to vfs inode types.
//
// See https://www.kernel.org/doc/html/latest/filesystems/ext4/dynamic.html#ftype.
inodeTypeByFileType = map[uint8]fs.InodeType{
0: fs.Anonymous,
1: fs.RegularFile,
2: fs.Directory,
3: fs.CharacterDevice,
4: fs.BlockDevice,
5: fs.Pipe,
6: fs.Socket,
7: fs.Symlink,
}
)
// The Dirent interface should be implemented by structs representing ext
// directory entries. These are for the linear classical directories which
// just store a list of dirent structs. A directory is a series of data blocks
// where is each data block contains a linear array of dirents. The last entry
// of the block has a record size that takes it to the end of the block. The
// end of the directory is when you read dirInode.Size() bytes from the blocks.
//
// See https://www.kernel.org/doc/html/latest/filesystems/ext4/dynamic.html#linear-classic-directories.
type Dirent interface {
// Inode returns the absolute inode number of the underlying inode.
// Inode number 0 signifies an unused dirent.
Inode() uint32
// RecordSize returns the record length of this dirent on disk. The next
// dirent in the dirent list should be read after these many bytes from
// the current dirent. Must be a multiple of 4.
RecordSize() uint16
// FileName returns the name of the file. Can be at most 255 is length.
FileName() string
// FileType returns the inode type of the underlying inode. This is a
// performance hack so that we do not have to read the underlying inode struct
// to know the type of inode. This will only work when the SbDirentFileType
// feature is set. If not, the second returned value will be false indicating
// that user code has to use the inode mode to extract the file type.
FileType() (fs.InodeType, bool)
}
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