blob: fca178bd29082b3075736a90f44b9271d17d9fb6 [file] [log] [blame]
khenaidoo59ce9dd2019-11-11 13:05:32 -05001package 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}