1//go:build (linux || darwin) && !(sqlite3_flock || sqlite3_dotlk)
 2
 3package vfs
 4
 5import (
 6	"os"
 7	"time"
 8
 9	"golang.org/x/sys/unix"
10)
11
12func osGetSharedLock(file *os.File) _ErrorCode {
13	// Test the PENDING lock before acquiring a new SHARED lock.
14	if lock, _ := osTestLock(file, _PENDING_BYTE, 1); lock == unix.F_WRLCK {
15		return _BUSY
16	}
17	// Acquire the SHARED lock.
18	return osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0)
19}
20
21func osGetReservedLock(file *os.File) _ErrorCode {
22	// Acquire the RESERVED lock.
23	return osWriteLock(file, _RESERVED_BYTE, 1, 0)
24}
25
26func osGetExclusiveLock(file *os.File, state *LockLevel) _ErrorCode {
27	if *state == LOCK_RESERVED {
28		// A PENDING lock is needed before acquiring an EXCLUSIVE lock.
29		if rc := osWriteLock(file, _PENDING_BYTE, 1, -1); rc != _OK {
30			return rc
31		}
32		*state = LOCK_PENDING
33	}
34	// Acquire the EXCLUSIVE lock.
35	return osWriteLock(file, _SHARED_FIRST, _SHARED_SIZE, time.Millisecond)
36}
37
38func osDowngradeLock(file *os.File, state LockLevel) _ErrorCode {
39	if state >= LOCK_EXCLUSIVE {
40		// Downgrade to a SHARED lock.
41		if rc := osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0); rc != _OK {
42			// notest // this should never happen
43			return _IOERR_RDLOCK
44		}
45	}
46	// Release the PENDING and RESERVED locks.
47	return osUnlock(file, _PENDING_BYTE, 2)
48}
49
50func osReleaseLock(file *os.File, _ LockLevel) _ErrorCode {
51	// Release all locks.
52	return osUnlock(file, 0, 0)
53}
54
55func osCheckReservedLock(file *os.File) (bool, _ErrorCode) {
56	// Test the RESERVED lock.
57	lock, rc := osTestLock(file, _RESERVED_BYTE, 1)
58	return lock == unix.F_WRLCK, rc
59}