1package bbolt 2 3import ( 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 12var ( 13 modkernel32 = syscall.NewLazyDLL("kernel32.dll") 14 procLockFileEx = modkernel32.NewProc("LockFileEx") 15 procUnlockFileEx = modkernel32.NewProc("UnlockFileEx") 16) 17 18const ( 19 // see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx 20 flagLockExclusive = 2 21 flagLockFailImmediately = 1 22 23 // see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx 24 errLockViolation syscall.Errno = 0x21 25) 26 27func lockFileEx(h syscall.Handle, flags, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) { 28 r, _, err := procLockFileEx.Call(uintptr(h), uintptr(flags), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol))) 29 if r == 0 { 30 return err 31 } 32 return nil 33} 34 35func unlockFileEx(h syscall.Handle, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) { 36 r, _, err := procUnlockFileEx.Call(uintptr(h), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)), 0) 37 if r == 0 { 38 return err 39 } 40 return nil 41} 42 43// fdatasync flushes written data to a file descriptor. 44func fdatasync(db *DB) error { 45 return db.file.Sync() 46} 47 48// flock acquires an advisory lock on a file descriptor. 49func flock(db *DB, exclusive bool, timeout time.Duration) error { 50 var t time.Time 51 if timeout != 0 { 52 t = time.Now() 53 } 54 var flag uint32 = flagLockFailImmediately 55 if exclusive { 56 flag |= flagLockExclusive 57 } 58 for { 59 // Fix for https://github.com/etcd-io/bbolt/issues/121. Use byte-range 60 // -1..0 as the lock on the database file. 61 var m1 uint32 = (1 << 32) - 1 // -1 in a uint32 62 err := lockFileEx(syscall.Handle(db.file.Fd()), flag, 0, 1, 0, &syscall.Overlapped{ 63 Offset: m1, 64 OffsetHigh: m1, 65 }) 66 67 if err == nil { 68 return nil 69 } else if err != errLockViolation { 70 return err 71 } 72 73 // If we timed oumercit then return an error. 74 if timeout != 0 && time.Since(t) > timeout-flockRetryTimeout { 75 return ErrTimeout 76 } 77 78 // Wait for a bit and try again. 79 time.Sleep(flockRetryTimeout) 80 } 81} 82 83// funlock releases an advisory lock on a file descriptor. 84func funlock(db *DB) error { 85 var m1 uint32 = (1 << 32) - 1 // -1 in a uint32 86 err := unlockFileEx(syscall.Handle(db.file.Fd()), 0, 1, 0, &syscall.Overlapped{ 87 Offset: m1, 88 OffsetHigh: m1, 89 }) 90 return err 91} 92 93// mmap memory maps a DB's data file. 94// Based on: https://github.com/edsrzf/mmap-go 95func mmap(db *DB, sz int) error { 96 if !db.readOnly { 97 // Truncate the database to the size of the mmap. 98 if err := db.file.Truncate(int64(sz)); err != nil { 99 return fmt.Errorf("truncate: %s", err) 100 } 101 } 102 103 // Open a file mapping handle. 104 sizelo := uint32(sz >> 32) 105 sizehi := uint32(sz) & 0xffffffff 106 h, errno := syscall.CreateFileMapping(syscall.Handle(db.file.Fd()), nil, syscall.PAGE_READONLY, sizelo, sizehi, nil) 107 if h == 0 { 108 return os.NewSyscallError("CreateFileMapping", errno) 109 } 110 111 // Create the memory map. 112 addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, uintptr(sz)) 113 if addr == 0 { 114 return os.NewSyscallError("MapViewOfFile", errno) 115 } 116 117 // Close mapping handle. 118 if err := syscall.CloseHandle(syscall.Handle(h)); err != nil { 119 return os.NewSyscallError("CloseHandle", err) 120 } 121 122 // Convert to a byte array. 123 db.data = ((*[maxMapSize]byte)(unsafe.Pointer(addr))) 124 db.datasz = sz 125 126 return nil 127} 128 129// munmap unmaps a pointer from a file. 130// Based on: https://github.com/edsrzf/mmap-go 131func munmap(db *DB) error { 132 if db.data == nil { 133 return nil 134 } 135 136 addr := (uintptr)(unsafe.Pointer(&db.data[0])) 137 if err := syscall.UnmapViewOfFile(addr); err != nil { 138 return os.NewSyscallError("UnmapViewOfFile", err) 139 } 140 return nil 141} 142