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// Package filelock provides advisory exclusive locks on open files.
package filelock
import (
"context"
"errors"
"os"
"time"
)
// ErrWouldBlock indicates a non-blocking lock attempt could not acquire the lock.
var ErrWouldBlock = errors.New("filelock: would block")
// TryExclusive attempts a non-blocking exclusive advisory lock on f.
func TryExclusive(f *os.File) error {
return tryLockExclusive(f.Fd())
}
// UnlockExclusive releases the advisory lock held on f.
func UnlockExclusive(f *os.File) error {
return unlockExclusive(f.Fd())
}
// AcquireExclusive spins with TryExclusive until the lock is acquired, ctx is done, or a non-would-block error occurs.
func AcquireExclusive(ctx context.Context, f *os.File) (func() error, error) {
fd := f.Fd()
retryTimer := time.NewTimer(5 * time.Millisecond)
defer retryTimer.Stop()
for {
err := tryLockExclusive(fd)
if err == nil {
return func() error { return unlockExclusive(fd) }, nil
}
if errors.Is(err, ErrWouldBlock) {
retryTimer.Reset(5 * time.Millisecond)
select {
case <-ctx.Done():
return nil, ctx.Err()
case <-retryTimer.C:
}
continue
}
return nil, err
}
}
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