sqlite3/vfs/os_ofd.go

//go:build (linux || illumos) && !sqlite3_nosys

package vfs

import (
	"os"
	"time"

	"golang.org/x/sys/unix"
)

func osUnlock(file *os.File, start, len int64) _ErrorCode {
	err := unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLK, &unix.Flock_t{
		Type:  unix.F_UNLCK,
		Start: start,
		Len:   len,
	})
	if err != nil {
		return _IOERR_UNLOCK
	}
	return _OK
}

func osLock(file *os.File, typ int16, start, len int64, timeout time.Duration, def _ErrorCode) _ErrorCode {
	lock := unix.Flock_t{
		Type:  typ,
		Start: start,
		Len:   len,
	}
	var err error
	switch {
	case timeout == 0:
		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLK, &lock)
	case timeout < 0:
		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLKW, &lock)
	default:
		before := time.Now()
		for {
			err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLK, &lock)
			if errno, _ := err.(unix.Errno); errno != unix.EAGAIN {
				break
			}
			if timeout <= 0 || timeout < time.Since(before) {
				break
			}
			osSleep(time.Millisecond)
		}
	}
	return osLockErrorCode(err, def)
}

func osReadLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
	return osLock(file, unix.F_RDLCK, start, len, timeout, _IOERR_RDLOCK)
}

func osWriteLock(file *os.File, start, len int64, timeout time.Duration) _ErrorCode {
	return osLock(file, unix.F_WRLCK, start, len, timeout, _IOERR_LOCK)
}

func osCheckLock(file *os.File, start, len int64) (bool, _ErrorCode) {
	lock := unix.Flock_t{
		Type:  unix.F_RDLCK,
		Start: start,
		Len:   len,
	}
	if unix.FcntlFlock(file.Fd(), unix.F_OFD_GETLK, &lock) != nil {
		return false, _IOERR_CHECKRESERVEDLOCK
	}
	return lock.Type != unix.F_UNLCK, _OK
}