khenaidoo | ffe076b | 2019-01-15 16:08:08 -0500 | [diff] [blame^] | 1 | package bolt |
| 2 | |
| 3 | import ( |
| 4 | "fmt" |
| 5 | "os" |
| 6 | "syscall" |
| 7 | "time" |
| 8 | "unsafe" |
| 9 | ) |
| 10 | |
| 11 | // LockFileEx code derived from golang build filemutex_windows.go @ v1.5.1 |
| 12 | var ( |
| 13 | modkernel32 = syscall.NewLazyDLL("kernel32.dll") |
| 14 | procLockFileEx = modkernel32.NewProc("LockFileEx") |
| 15 | procUnlockFileEx = modkernel32.NewProc("UnlockFileEx") |
| 16 | ) |
| 17 | |
| 18 | const ( |
| 19 | lockExt = ".lock" |
| 20 | |
| 21 | // see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx |
| 22 | flagLockExclusive = 2 |
| 23 | flagLockFailImmediately = 1 |
| 24 | |
| 25 | // see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx |
| 26 | errLockViolation syscall.Errno = 0x21 |
| 27 | ) |
| 28 | |
| 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))) |
| 31 | if r == 0 { |
| 32 | return err |
| 33 | } |
| 34 | return nil |
| 35 | } |
| 36 | |
| 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) |
| 39 | if r == 0 { |
| 40 | return err |
| 41 | } |
| 42 | return nil |
| 43 | } |
| 44 | |
| 45 | // fdatasync flushes written data to a file descriptor. |
| 46 | func fdatasync(db *DB) error { |
| 47 | return db.file.Sync() |
| 48 | } |
| 49 | |
| 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) |
| 56 | if err != nil { |
| 57 | return err |
| 58 | } |
| 59 | db.lockfile = f |
| 60 | |
| 61 | var t time.Time |
| 62 | for { |
| 63 | // If we're beyond our timeout then return an error. |
| 64 | // This can only occur after we've attempted a flock once. |
| 65 | if t.IsZero() { |
| 66 | t = time.Now() |
| 67 | } else if timeout > 0 && time.Since(t) > timeout { |
| 68 | return ErrTimeout |
| 69 | } |
| 70 | |
| 71 | var flag uint32 = flagLockFailImmediately |
| 72 | if exclusive { |
| 73 | flag |= flagLockExclusive |
| 74 | } |
| 75 | |
| 76 | err := lockFileEx(syscall.Handle(db.lockfile.Fd()), flag, 0, 1, 0, &syscall.Overlapped{}) |
| 77 | if err == nil { |
| 78 | return nil |
| 79 | } else if err != errLockViolation { |
| 80 | return err |
| 81 | } |
| 82 | |
| 83 | // Wait for a bit and try again. |
| 84 | time.Sleep(50 * time.Millisecond) |
| 85 | } |
| 86 | } |
| 87 | |
| 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{}) |
| 91 | db.lockfile.Close() |
| 92 | os.Remove(db.path+lockExt) |
| 93 | return err |
| 94 | } |
| 95 | |
| 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 { |
| 99 | if !db.readOnly { |
| 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) |
| 103 | } |
| 104 | } |
| 105 | |
| 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) |
| 110 | if h == 0 { |
| 111 | return os.NewSyscallError("CreateFileMapping", errno) |
| 112 | } |
| 113 | |
| 114 | // Create the memory map. |
| 115 | addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, uintptr(sz)) |
| 116 | if addr == 0 { |
| 117 | return os.NewSyscallError("MapViewOfFile", errno) |
| 118 | } |
| 119 | |
| 120 | // Close mapping handle. |
| 121 | if err := syscall.CloseHandle(syscall.Handle(h)); err != nil { |
| 122 | return os.NewSyscallError("CloseHandle", err) |
| 123 | } |
| 124 | |
| 125 | // Convert to a byte array. |
| 126 | db.data = ((*[maxMapSize]byte)(unsafe.Pointer(addr))) |
| 127 | db.datasz = sz |
| 128 | |
| 129 | return nil |
| 130 | } |
| 131 | |
| 132 | // munmap unmaps a pointer from a file. |
| 133 | // Based on: https://github.com/edsrzf/mmap-go |
| 134 | func munmap(db *DB) error { |
| 135 | if db.data == nil { |
| 136 | return nil |
| 137 | } |
| 138 | |
| 139 | addr := (uintptr)(unsafe.Pointer(&db.data[0])) |
| 140 | if err := syscall.UnmapViewOfFile(addr); err != nil { |
| 141 | return os.NewSyscallError("UnmapViewOfFile", err) |
| 142 | } |
| 143 | return nil |
| 144 | } |