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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 ext
import (
"io"
)
// fileReader is used to abstact away the complexity of how the file data is
// stored under the hood. Provides a method to get a file reader which can be
// used to read file data without worrying about how it is organized on disk.
type fileReader interface {
// getFileReader returns a Reader implementation which can be used to read a
// file. It abstracts away the complexity of how the file is actually
// organized on disk. The reader is initialized with the passed offset.
//
// This reader is not meant to be retained across Read operations as it needs
// to be reinitialized with the correct offset for every Read.
//
// Precondition: Must hold the mutex of the filesystem containing dev while
// using the Reader.
getFileReader(dev io.ReadSeeker, blkSize uint64, offset uint64) io.Reader
}
// regularFile represents a regular file's inode. This too follows the
// inheritance pattern prevelant in the vfs layer described in
// pkg/sentry/vfs/README.md.
type regularFile struct {
inode inode
// This is immutable. The first field of fileReader implementations must be
// regularFile to ensure temporality.
impl fileReader
}
// newRegularFile is the regularFile constructor. It figures out what kind of
// file this is and initializes the fileReader.
//
// Preconditions: Must hold the mutex of the filesystem containing dev.
func newRegularFile(dev io.ReadSeeker, blkSize uint64, inode inode) (*regularFile, error) {
regFile := regularFile{
inode: inode,
}
inodeFlags := inode.diskInode.Flags()
if inodeFlags.Extents {
file, err := newExtentFile(dev, blkSize, regFile)
if err != nil {
return nil, err
}
file.regFile.inode.impl = &file.regFile
return &file.regFile, nil
}
if inodeFlags.Inline {
if inode.diskInode.Size() > 60 {
panic("ext fs: inline file larger than 60 bytes")
}
file := newInlineFile(regFile)
file.regFile.inode.impl = &file.regFile
return &file.regFile, nil
}
file, err := newBlockMapFile(blkSize, regFile)
if err != nil {
return nil, err
}
file.regFile.inode.impl = &file.regFile
return &file.regFile, nil
}
func (f *regularFile) blksUsed(blkSize uint64) uint64 {
return (f.inode.diskInode.Size() + blkSize - 1) / blkSize
}
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