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// +build linux
package fsutils
import (
"fmt"
"io/ioutil"
"os"
"unsafe"
"golang.org/x/sys/unix"
)
func locateDummyIfEmpty(path string) (string, error) {
children, err := ioutil.ReadDir(path)
if err != nil {
return "", err
}
if len(children) != 0 {
return "", nil
}
dummyFile, err := ioutil.TempFile(path, "fsutils-dummy")
if err != nil {
return "", err
}
name := dummyFile.Name()
err = dummyFile.Close()
return name, err
}
// SupportsDType returns whether the filesystem mounted on path supports d_type
func SupportsDType(path string) (bool, error) {
// locate dummy so that we have at least one dirent
dummy, err := locateDummyIfEmpty(path)
if err != nil {
return false, err
}
if dummy != "" {
defer os.Remove(dummy)
}
visited := 0
supportsDType := true
fn := func(ent *unix.Dirent) bool {
visited++
if ent.Type == unix.DT_UNKNOWN {
supportsDType = false
// stop iteration
return true
}
// continue iteration
return false
}
if err = iterateReadDir(path, fn); err != nil {
return false, err
}
if visited == 0 {
return false, fmt.Errorf("did not hit any dirent during iteration %s", path)
}
return supportsDType, nil
}
func iterateReadDir(path string, fn func(*unix.Dirent) bool) error {
d, err := os.Open(path)
if err != nil {
return err
}
defer d.Close()
fd := int(d.Fd())
buf := make([]byte, 4096)
for {
nbytes, err := unix.ReadDirent(fd, buf)
if err != nil {
return err
}
if nbytes == 0 {
break
}
for off := 0; off < nbytes; {
ent := (*unix.Dirent)(unsafe.Pointer(&buf[off]))
if stop := fn(ent); stop {
return nil
}
off += int(ent.Reclen)
}
}
return nil
}
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