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package fusefrontend_reverse
import (
"bytes"
"context"
"os"
"syscall"
"github.com/hanwen/go-fuse/v2/fs"
"github.com/hanwen/go-fuse/v2/fuse"
"github.com/rfjakob/gocryptfs/internal/contentenc"
)
type File struct {
// Backing FD
fd *os.File
// File header (contains the IV)
header contentenc.FileHeader
// IV for block 0
block0IV []byte
// Content encryption helper
contentEnc *contentenc.ContentEnc
}
// Read - FUSE call
func (f *File) Read(ctx context.Context, buf []byte, ioff int64) (resultData fuse.ReadResult, errno syscall.Errno) {
length := uint64(len(buf))
off := uint64(ioff)
out := bytes.NewBuffer(buf[:0])
var header []byte
// Synthesize file header
if off < contentenc.HeaderLen {
header = f.header.Pack()
// Truncate to requested part
end := int(off) + len(buf)
if end > len(header) {
end = len(header)
}
header = header[off:end]
// Write into output buffer and adjust offsets
out.Write(header)
hLen := uint64(len(header))
off += hLen
length -= hLen
}
// Read actual file data
if length > 0 {
fileData, err := f.readBackingFile(off, length)
if err != nil {
return nil, fs.ToErrno(err)
}
if len(fileData) == 0 {
// If we could not read any actual data, we also don't want to
// return the file header. An empty file stays empty in encrypted
// form.
return nil, 0
}
out.Write(fileData)
}
return fuse.ReadResultData(out.Bytes()), 0
}
// Release - FUSE call, close file
func (f *File) Release(context.Context) syscall.Errno {
return fs.ToErrno(f.fd.Close())
}
// Lseek - FUSE call.
func (f *File) Lseek(ctx context.Context, off uint64, whence uint32) (uint64, syscall.Errno) {
plainOff := f.contentEnc.CipherSizeToPlainSize(off)
newPlainOff, err := syscall.Seek(int(f.fd.Fd()), int64(plainOff), int(whence))
if err != nil {
return 0, fs.ToErrno(err)
}
newOff := f.contentEnc.PlainSizeToCipherSize(uint64(newPlainOff))
return newOff, 0
}
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