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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"
"sync"
"gvisor.dev/gvisor/pkg/binary"
)
// blockMapFile is a type of regular file which uses direct/indirect block
// addressing to store file data. This was deprecated in ext4.
type blockMapFile struct {
regFile regularFile
// mu serializes changes to fileToPhysBlks.
mu sync.RWMutex
// fileToPhysBlks maps the file block numbers to the physical block numbers.
// the physical block number for the (i)th file block is stored in the (i)th
// index. This is initialized (at max) with the first 12 entries. The rest
// have to be read in from disk when required. Protected by mu.
fileToPhysBlks []uint32
}
// Compiles only if blockMapFile implements fileReader.
var _ fileReader = (*blockMapFile)(nil)
// Read implements fileReader.getFileReader.
func (f *blockMapFile) getFileReader(dev io.ReaderAt, blkSize uint64, offset uint64) io.Reader {
panic("unimplemented")
}
// newBlockMapFile is the blockMapFile constructor. It initializes the file to
// physical blocks map with (at most) the first 12 (direct) blocks.
func newBlockMapFile(blkSize uint64, regFile regularFile) (*blockMapFile, error) {
file := &blockMapFile{regFile: regFile}
file.regFile.impl = file
toFill := uint64(12)
blksUsed := regFile.blksUsed(blkSize)
if blksUsed < toFill {
toFill = blksUsed
}
blkMap := regFile.inode.diskInode.Data()
file.fileToPhysBlks = make([]uint32, toFill)
for i := uint64(0); i < toFill; i++ {
binary.Unmarshal(blkMap[i*4:(i+1)*4], binary.LittleEndian, &file.fileToPhysBlks[i])
}
return file, nil
}
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