github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/fsimpl/ext/disklayout/dirent_new.go (about)

     1  // Copyright 2019 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package disklayout
    16  
    17  import (
    18  	"fmt"
    19  
    20  	"github.com/SagerNet/gvisor/pkg/sentry/fs"
    21  )
    22  
    23  // DirentNew represents the ext4 directory entry struct. This emulates Linux's
    24  // ext4_dir_entry_2 struct. The FileName can not be more than 255 bytes so we
    25  // only need 8 bits to store the NameLength. As a result, NameLength has been
    26  // shortened and the other 8 bits are used to encode the file type. Use the
    27  // FileTypeRaw field only if the SbDirentFileType feature is set.
    28  //
    29  // Note: This struct can be of variable size on disk. The one described below
    30  // is of maximum size and the FileName beyond NameLength bytes might contain
    31  // garbage.
    32  //
    33  // +marshal
    34  type DirentNew struct {
    35  	InodeNumber  uint32
    36  	RecordLength uint16
    37  	NameLength   uint8
    38  	FileTypeRaw  uint8
    39  	FileNameRaw  [MaxFileName]byte `marshal:"unaligned"`
    40  }
    41  
    42  // Compiles only if DirentNew implements Dirent.
    43  var _ Dirent = (*DirentNew)(nil)
    44  
    45  // Inode implements Dirent.Inode.
    46  func (d *DirentNew) Inode() uint32 { return d.InodeNumber }
    47  
    48  // RecordSize implements Dirent.RecordSize.
    49  func (d *DirentNew) RecordSize() uint16 { return d.RecordLength }
    50  
    51  // FileName implements Dirent.FileName.
    52  func (d *DirentNew) FileName() string {
    53  	return string(d.FileNameRaw[:d.NameLength])
    54  }
    55  
    56  // FileType implements Dirent.FileType.
    57  func (d *DirentNew) FileType() (fs.InodeType, bool) {
    58  	if inodeType, ok := inodeTypeByFileType[d.FileTypeRaw]; ok {
    59  		return inodeType, true
    60  	}
    61  
    62  	panic(fmt.Sprintf("unknown file type %v", d.FileTypeRaw))
    63  }