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//go:build windows
package lockfile
import (
"os"
"time"
"golang.org/x/sys/windows"
)
const (
reserved = 0
allBytes = ^uint32(0)
)
type fileHandle windows.Handle
// 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) before this function is called.
func (l *LockFile) GetLastWrite() (LastWrite, error) {
l.AssertLocked()
contents := make([]byte, lastWriterIDSize)
ol := new(windows.Overlapped)
var n uint32
err := windows.ReadFile(windows.Handle(l.fd), contents, &n, ol)
if err != nil && err != windows.ERROR_HANDLE_EOF {
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()
ol := new(windows.Overlapped)
var n uint32
err := windows.WriteFile(windows.Handle(l.fd), lockContents, &n, ol)
if err != nil {
return LastWrite{}, err
}
if int(n) != len(lockContents) {
return LastWrite{}, windows.ERROR_DISK_FULL
}
return lw, nil
}
// TouchedSince indicates if the lock file has been touched since the specified time
func (l *LockFile) TouchedSince(when time.Time) bool {
stat, err := os.Stat(l.file)
if err != nil {
return true
}
return when.Before(stat.ModTime())
}
func openHandle(path string, mode int) (fileHandle, error) {
mode |= windows.O_CLOEXEC
fd, err := windows.Open(path, mode, windows.S_IWRITE)
return fileHandle(fd), err
}
func lockHandle(fd fileHandle, lType lockType, nonblocking bool) error {
flags := 0
if lType != readLock {
flags = windows.LOCKFILE_EXCLUSIVE_LOCK
}
if nonblocking {
flags |= windows.LOCKFILE_FAIL_IMMEDIATELY
}
ol := new(windows.Overlapped)
if err := windows.LockFileEx(windows.Handle(fd), uint32(flags), reserved, allBytes, allBytes, ol); err != nil {
if nonblocking {
return err
}
panic(err)
}
return nil
}
func unlockAndCloseHandle(fd fileHandle) {
ol := new(windows.Overlapped)
windows.UnlockFileEx(windows.Handle(fd), reserved, allBytes, allBytes, ol)
closeHandle(fd)
}
func closeHandle(fd fileHandle) {
windows.Close(windows.Handle(fd))
}
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