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|
package btrfs
import (
"bytes"
"os"
"syscall"
)
const (
xattrPrefix = "btrfs."
xattrCompression = xattrPrefix + "compression"
)
type Compression string
const (
CompressionNone = Compression("")
LZO = Compression("lzo")
ZLIB = Compression("zlib")
)
func SetCompression(path string, v Compression) error {
var value []byte
if v != CompressionNone {
var err error
value, err = syscall.ByteSliceFromString(string(v))
if err != nil {
return err
}
}
err := syscall.Setxattr(path, xattrCompression, value, 0)
if err != nil {
return &os.PathError{Op: "setxattr", Path: path, Err: err}
}
return nil
}
func GetCompression(path string) (Compression, error) {
var buf []byte
for {
sz, err := syscall.Getxattr(path, xattrCompression, nil)
if err == syscall.ENODATA || sz == 0 {
return CompressionNone, nil
} else if err != nil {
return CompressionNone, &os.PathError{Op: "getxattr", Path: path, Err: err}
}
if cap(buf) < sz {
buf = make([]byte, sz)
} else {
buf = buf[:sz]
}
sz, err = syscall.Getxattr(path, xattrCompression, buf)
if err == syscall.ENODATA {
return CompressionNone, nil
} else if err == syscall.ERANGE {
// xattr changed by someone else, and is larger than our current buffer
continue
} else if err != nil {
return CompressionNone, &os.PathError{Op: "getxattr", Path: path, Err: err}
}
buf = buf[:sz]
break
}
buf = bytes.TrimSuffix(buf, []byte{0})
return Compression(buf), nil
}
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