73 lines
2.2 KiB
Go
73 lines
2.2 KiB
Go
//go:build ((freebsd || openbsd || netbsd || dragonfly || illumos) && !(sqlite3_dotlk || sqlite3_nosys)) || sqlite3_flock
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package vfs
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import (
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"os"
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"golang.org/x/sys/unix"
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)
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func osGetSharedLock(file *os.File) _ErrorCode {
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return osLock(file, unix.LOCK_SH|unix.LOCK_NB, _IOERR_RDLOCK)
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}
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func osGetReservedLock(file *os.File) _ErrorCode {
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rc := osLock(file, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK)
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if rc == _BUSY {
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// The documentation states that a lock is upgraded by
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// releasing the previous lock, then acquiring the new lock.
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// Going over the source code of various BSDs, though,
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// with LOCK_NB, the lock is not released,
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// and EAGAIN is returned holding the shared lock.
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// Still, if we're already in a transaction, we want to abort it,
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// so return BUSY_SNAPSHOT here. If there's no transaction active,
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// SQLite will change this back to SQLITE_BUSY,
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// and invoke the busy handler if appropriate.
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return _BUSY_SNAPSHOT
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}
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return rc
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}
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func osGetExclusiveLock(file *os.File, state *LockLevel) _ErrorCode {
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if *state >= LOCK_RESERVED {
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return _OK
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}
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return osGetReservedLock(file)
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}
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func osDowngradeLock(file *os.File, _ LockLevel) _ErrorCode {
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rc := osLock(file, unix.LOCK_SH|unix.LOCK_NB, _IOERR_RDLOCK)
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if rc == _BUSY {
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// The documentation states that a lock is downgraded by
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// releasing the previous lock then acquiring the new lock.
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// Going over the source code of various BSDs, though,
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// with LOCK_SH|LOCK_NB this should never happen.
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// Return IOERR_RDLOCK, as BUSY would cause an assert to fail.
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return _IOERR_RDLOCK
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}
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return _OK
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}
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func osReleaseLock(file *os.File, _ LockLevel) _ErrorCode {
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err := unix.Flock(int(file.Fd()), unix.LOCK_UN)
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if err != nil {
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return _IOERR_UNLOCK
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}
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return _OK
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}
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func osCheckReservedLock(file *os.File) (bool, _ErrorCode) {
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// Test the RESERVED lock with fcntl(F_GETLK).
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// This only works on systems where fcntl and flock are compatible.
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// However, SQLite only calls this while holding a shared lock,
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// so the difference is immaterial.
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lock, rc := osTestLock(file, _RESERVED_BYTE, 1)
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return lock == unix.F_WRLCK, rc
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}
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func osLock(file *os.File, how int, def _ErrorCode) _ErrorCode {
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err := unix.Flock(int(file.Fd()), how)
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return osLockErrorCode(err, def)
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}
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