172 lines
4.2 KiB
Go
172 lines
4.2 KiB
Go
//go:build !(sqlite3_dotlk || sqlite3_nosys)
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package vfs
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import (
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"math/rand"
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"os"
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"time"
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"golang.org/x/sys/windows"
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)
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func osGetSharedLock(file *os.File) _ErrorCode {
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// Acquire the PENDING lock temporarily before acquiring a new SHARED lock.
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rc := osReadLock(file, _PENDING_BYTE, 1, 0)
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if rc == _OK {
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// Acquire the SHARED lock.
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rc = osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0)
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// Release the PENDING lock.
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osUnlock(file, _PENDING_BYTE, 1)
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}
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return rc
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}
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func osGetReservedLock(file *os.File) _ErrorCode {
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// Acquire the RESERVED lock.
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return osWriteLock(file, _RESERVED_BYTE, 1, 0)
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}
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func osGetExclusiveLock(file *os.File, state *LockLevel) _ErrorCode {
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// A PENDING lock is needed before releasing the SHARED lock.
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if *state < LOCK_PENDING {
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// If we were RESERVED, we can block indefinitely.
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var timeout time.Duration
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if *state == LOCK_RESERVED {
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timeout = -1
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}
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if rc := osWriteLock(file, _PENDING_BYTE, 1, timeout); rc != _OK {
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return rc
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}
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*state = LOCK_PENDING
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}
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// Release the SHARED lock.
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osUnlock(file, _SHARED_FIRST, _SHARED_SIZE)
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// Acquire the EXCLUSIVE lock.
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rc := osWriteLock(file, _SHARED_FIRST, _SHARED_SIZE, time.Millisecond)
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if rc != _OK {
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// Reacquire the SHARED lock.
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osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0)
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}
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return rc
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}
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func osDowngradeLock(file *os.File, state LockLevel) _ErrorCode {
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if state >= LOCK_EXCLUSIVE {
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// Release the EXCLUSIVE lock.
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osUnlock(file, _SHARED_FIRST, _SHARED_SIZE)
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// Reacquire the SHARED lock.
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if rc := osReadLock(file, _SHARED_FIRST, _SHARED_SIZE, 0); rc != _OK {
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// notest // this should never happen
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return _IOERR_RDLOCK
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}
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}
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// Release the PENDING and RESERVED locks.
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if state >= LOCK_RESERVED {
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osUnlock(file, _RESERVED_BYTE, 1)
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}
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if state >= LOCK_PENDING {
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osUnlock(file, _PENDING_BYTE, 1)
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}
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return _OK
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}
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func osReleaseLock(file *os.File, state LockLevel) _ErrorCode {
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// Release all locks.
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if state >= LOCK_RESERVED {
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osUnlock(file, _RESERVED_BYTE, 1)
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}
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if state >= LOCK_SHARED {
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osUnlock(file, _SHARED_FIRST, _SHARED_SIZE)
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}
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if state >= LOCK_PENDING {
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osUnlock(file, _PENDING_BYTE, 1)
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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.
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rc := osLock(file, 0, _RESERVED_BYTE, 1, 0, _IOERR_CHECKRESERVEDLOCK)
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if rc == _BUSY {
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return true, _OK
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}
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if rc == _OK {
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// Release the RESERVED lock.
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osUnlock(file, _RESERVED_BYTE, 1)
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}
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return false, rc
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}
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func osUnlock(file *os.File, start, len uint32) _ErrorCode {
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err := windows.UnlockFileEx(windows.Handle(file.Fd()),
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0, len, 0, &windows.Overlapped{Offset: start})
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if err == windows.ERROR_NOT_LOCKED {
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return _OK
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}
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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 osLock(file *os.File, flags, start, len uint32, timeout time.Duration, def _ErrorCode) _ErrorCode {
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var err error
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switch {
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case timeout == 0:
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err = osLockEx(file, flags|windows.LOCKFILE_FAIL_IMMEDIATELY, start, len)
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case timeout < 0:
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err = osLockEx(file, flags, start, len)
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default:
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before := time.Now()
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for {
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err = osLockEx(file, flags|windows.LOCKFILE_FAIL_IMMEDIATELY, start, len)
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if errno, _ := err.(windows.Errno); errno != windows.ERROR_LOCK_VIOLATION {
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break
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}
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if time.Since(before) > timeout {
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break
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}
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const sleepIncrement = 1024*1024 - 1 // power of two, ~1ms
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time.Sleep(time.Duration(rand.Int63() & sleepIncrement))
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}
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}
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return osLockErrorCode(err, def)
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}
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func osLockEx(file *os.File, flags, start, len uint32) error {
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return windows.LockFileEx(windows.Handle(file.Fd()), flags,
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0, len, 0, &windows.Overlapped{Offset: start})
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}
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func osReadLock(file *os.File, start, len uint32, timeout time.Duration) _ErrorCode {
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return osLock(file, 0, start, len, timeout, _IOERR_RDLOCK)
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}
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func osWriteLock(file *os.File, start, len uint32, timeout time.Duration) _ErrorCode {
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return osLock(file, windows.LOCKFILE_EXCLUSIVE_LOCK, start, len, timeout, _IOERR_LOCK)
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}
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func osLockErrorCode(err error, def _ErrorCode) _ErrorCode {
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if err == nil {
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return _OK
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}
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if errno, ok := err.(windows.Errno); ok {
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// https://devblogs.microsoft.com/oldnewthing/20140905-00/?p=63
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switch errno {
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case
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windows.ERROR_LOCK_VIOLATION,
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windows.ERROR_IO_PENDING,
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windows.ERROR_OPERATION_ABORTED:
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return _BUSY
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}
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}
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return def
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}
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