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//go:build !windows
package lockfile
import (
"time"
"github.com/containers/storage/pkg/system"
"golang.org/x/sys/unix"
)
// GetLastWrite returns a LastWrite value corresponding to current state of the lock.
// This is typically called before (_not after_) loading the state when initializing a consumer
// of the data protected by the lock.
// During the lifetime of the consumer, the consumer should usually call ModifiedSince instead.
//
// The caller must hold the lock (for reading or writing).
func (l *LockFile) GetLastWrite() (LastWrite, error) {
l.AssertLocked()
contents := make([]byte, lastWriterIDSize)
n, err := unix.Pread(int(l.fd), contents, 0)
if err != nil {
return LastWrite{}, err
}
// It is important to handle the partial read case, because
// the initial size of the lock file is zero, which is a valid
// state (no writes yet)
contents = contents[:n]
return newLastWriteFromData(contents), nil
}
// RecordWrite updates the lock with a new LastWrite value, and returns the new value.
//
// If this function fails, the LastWriter value of the lock is indeterminate;
// the caller should keep using the previously-recorded LastWrite value,
// and possibly detecting its own modification as an external one:
//
// lw, err := state.lock.RecordWrite()
// if err != nil { /* fail */ }
// state.lastWrite = lw
//
// The caller must hold the lock for writing.
func (l *LockFile) RecordWrite() (LastWrite, error) {
l.AssertLockedForWriting()
lw := newLastWrite()
lockContents := lw.serialize()
n, err := unix.Pwrite(int(l.fd), lockContents, 0)
if err != nil {
return LastWrite{}, err
}
if n != len(lockContents) {
return LastWrite{}, unix.ENOSPC
}
return lw, nil
}
// TouchedSince indicates if the lock file has been touched since the specified time
func (l *LockFile) TouchedSince(when time.Time) bool {
st, err := system.Fstat(int(l.fd))
if err != nil {
return true
}
mtim := st.Mtim()
touched := time.Unix(mtim.Unix())
return when.Before(touched)
}
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