jldb/lib/flock/flock.go

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2023-10-13 09:43:27 +00:00
package flock
import (
"errors"
"os"
"golang.org/x/sys/unix"
)
// Lock gets an exclusive lock on the file at the given path. If the file
// doesn't exist, it's created.
func Lock(path string) (*os.File, error) {
return lock(path, unix.LOCK_EX)
}
// TryLock will return a nil file if the file is already locked.
func TryLock(path string) (*os.File, error) {
return lock(path, unix.LOCK_EX|unix.LOCK_NB)
}
func LockFile(f *os.File) error {
_, err := lockFile(f, unix.LOCK_EX)
return err
}
// Returns true if the lock was successfully acquired.
func TryLockFile(f *os.File) (bool, error) {
return lockFile(f, unix.LOCK_EX|unix.LOCK_NB)
}
func lockFile(f *os.File, flags int) (bool, error) {
if err := unix.Flock(int(f.Fd()), flags); err != nil {
if flags&unix.LOCK_NB != 0 && errors.Is(err, unix.EAGAIN) {
return false, nil
}
return false, err
}
return true, nil
}
func lock(path string, flags int) (*os.File, error) {
perm := os.O_CREATE | os.O_RDWR
f, err := os.OpenFile(path, perm, 0600)
if err != nil {
return nil, err
}
ok, err := lockFile(f, flags)
if err != nil || !ok {
f.Close()
f = nil
}
return f, err
}
// Unlock releases the lock acquired via the Lock function.
func Unlock(f *os.File) error {
return f.Close()
}