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//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && !sqlite3_dotlk) || sqlite3_flock
package vfs
import (
"os"
"golang.org/x/sys/unix"
)
func osGetSharedLock(file *os.File) error {
return osFlock(file, unix.LOCK_SH|unix.LOCK_NB, _IOERR_RDLOCK)
}
func osGetReservedLock(file *os.File) error {
err := osFlock(file, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK)
if err == _BUSY {
// The documentation states that a lock is upgraded by
// releasing the previous lock, then acquiring the new lock.
// Going over the source code of various BSDs, though,
// with LOCK_NB, the lock is not released,
// and EAGAIN is returned holding the shared lock.
// Still, if we're already in a transaction, we want to abort it,
// so return BUSY_SNAPSHOT here. If there's no transaction active,
// SQLite will change this back to SQLITE_BUSY,
// and invoke the busy handler if appropriate.
return _BUSY_SNAPSHOT
}
return err
}
func osGetExclusiveLock(file *os.File, state *LockLevel) error {
if *state >= LOCK_RESERVED {
return nil
}
return osGetReservedLock(file)
}
func osDowngradeLock(file *os.File, _ LockLevel) error {
err := osFlock(file, unix.LOCK_SH|unix.LOCK_NB, _IOERR_RDLOCK)
if err == _BUSY {
// The documentation states that a lock is downgraded by
// releasing the previous lock then acquiring the new lock.
// Going over the source code of various BSDs, though,
// with LOCK_SH|LOCK_NB this should never happen.
// Return IOERR_RDLOCK, as BUSY would cause an assert to fail.
return _IOERR_RDLOCK
}
return err
}
func osReleaseLock(file *os.File, _ LockLevel) error {
for {
err := unix.Flock(int(file.Fd()), unix.LOCK_UN)
if err == nil {
return nil
}
if err != unix.EINTR {
return sysError{err, _IOERR_UNLOCK}
}
}
}
func osCheckReservedLock(file *os.File) (bool, error) {
// Test the RESERVED lock with fcntl(F_GETLK).
// This only works on systems where fcntl and flock are compatible.
// However, SQLite only calls this while holding a shared lock,
// so the difference is immaterial.
lock, err := osTestLock(file, _RESERVED_BYTE, 1, _IOERR_CHECKRESERVEDLOCK)
return lock == unix.F_WRLCK, err
}
func osFlock(file *os.File, how int, def _ErrorCode) error {
err := unix.Flock(int(file.Fd()), how)
return osLockErrorCode(err, def)
}
func osReadLock(file *os.File, start, len int64) error {
return osLock(file, unix.F_RDLCK, start, len, _IOERR_RDLOCK)
}
func osWriteLock(file *os.File, start, len int64) error {
return osLock(file, unix.F_WRLCK, start, len, _IOERR_LOCK)
}
func osLock(file *os.File, typ int16, start, len int64, def _ErrorCode) error {
err := unix.FcntlFlock(file.Fd(), unix.F_SETLK, &unix.Flock_t{
Type: typ,
Start: start,
Len: len,
})
return osLockErrorCode(err, def)
}
func osUnlock(file *os.File, start, len int64) error {
lock := unix.Flock_t{
Type: unix.F_UNLCK,
Start: start,
Len: len,
}
for {
err := unix.FcntlFlock(file.Fd(), unix.F_SETLK, &lock)
if err == nil {
return nil
}
if err != unix.EINTR {
return sysError{err, _IOERR_UNLOCK}
}
}
}
|
