11 // LockFileEx code derived from golang build filemutex_windows.go @ v1.5.1
13 modkernel32 = syscall.NewLazyDLL("kernel32.dll")
14 procLockFileEx = modkernel32.NewProc("LockFileEx")
15 procUnlockFileEx = modkernel32.NewProc("UnlockFileEx")
21 // see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
23 flagLockFailImmediately = 1
25 // see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx
26 errLockViolation syscall.Errno = 0x21
29 func lockFileEx(h syscall.Handle, flags, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
30 r, _, err := procLockFileEx.Call(uintptr(h), uintptr(flags), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)))
37 func unlockFileEx(h syscall.Handle, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
38 r, _, err := procUnlockFileEx.Call(uintptr(h), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)), 0)
45 // fdatasync flushes written data to a file descriptor.
46 func fdatasync(db *DB) error {
50 // flock acquires an advisory lock on a file descriptor.
51 func flock(db *DB, mode os.FileMode, exclusive bool, timeout time.Duration) error {
52 // Create a separate lock file on windows because a process
53 // cannot share an exclusive lock on the same file. This is
54 // needed during Tx.WriteTo().
55 f, err := os.OpenFile(db.path+lockExt, os.O_CREATE, mode)
63 // If we're beyond our timeout then return an error.
64 // This can only occur after we've attempted a flock once.
67 } else if timeout > 0 && time.Since(t) > timeout {
71 var flag uint32 = flagLockFailImmediately
73 flag |= flagLockExclusive
76 err := lockFileEx(syscall.Handle(db.lockfile.Fd()), flag, 0, 1, 0, &syscall.Overlapped{})
79 } else if err != errLockViolation {
83 // Wait for a bit and try again.
84 time.Sleep(50 * time.Millisecond)
88 // funlock releases an advisory lock on a file descriptor.
89 func funlock(db *DB) error {
90 err := unlockFileEx(syscall.Handle(db.lockfile.Fd()), 0, 1, 0, &syscall.Overlapped{})
92 os.Remove(db.path+lockExt)
96 // mmap memory maps a DB's data file.
97 // Based on: https://github.com/edsrzf/mmap-go
98 func mmap(db *DB, sz int) error {
100 // Truncate the database to the size of the mmap.
101 if err := db.file.Truncate(int64(sz)); err != nil {
102 return fmt.Errorf("truncate: %s", err)
106 // Open a file mapping handle.
107 sizelo := uint32(sz >> 32)
108 sizehi := uint32(sz) & 0xffffffff
109 h, errno := syscall.CreateFileMapping(syscall.Handle(db.file.Fd()), nil, syscall.PAGE_READONLY, sizelo, sizehi, nil)
111 return os.NewSyscallError("CreateFileMapping", errno)
114 // Create the memory map.
115 addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, uintptr(sz))
117 return os.NewSyscallError("MapViewOfFile", errno)
120 // Close mapping handle.
121 if err := syscall.CloseHandle(syscall.Handle(h)); err != nil {
122 return os.NewSyscallError("CloseHandle", err)
125 // Convert to a byte array.
126 db.data = ((*[maxMapSize]byte)(unsafe.Pointer(addr)))
132 // munmap unmaps a pointer from a file.
133 // Based on: https://github.com/edsrzf/mmap-go
134 func munmap(db *DB) error {
139 addr := (uintptr)(unsafe.Pointer(&db.data[0]))
140 if err := syscall.UnmapViewOfFile(addr); err != nil {
141 return os.NewSyscallError("UnmapViewOfFile", err)