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package bolt
import (
"fmt"
"os"
"syscall"
"time"
"unsafe"
)
// LockFileEx code derived from golang build filemutex_windows.go @ v1.5.1
var (
modkernel32 = syscall.NewLazyDLL("kernel32.dll")
procLockFileEx = modkernel32.NewProc("LockFileEx")
procUnlockFileEx = modkernel32.NewProc("UnlockFileEx")
)
const (
lockExt = ".lock"
// see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
flagLockExclusive = 2
flagLockFailImmediately = 1
// see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx
errLockViolation syscall.Errno = 0x21
)
func lockFileEx(h syscall.Handle, flags, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
r, _, err := procLockFileEx.Call(uintptr(h), uintptr(flags), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)))
if r == 0 {
return err
}
return nil
}
func unlockFileEx(h syscall.Handle, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
r, _, err := procUnlockFileEx.Call(uintptr(h), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)), 0)
if r == 0 {
return err
}
return nil
}
// fdatasync flushes written data to a file descriptor.
func fdatasync(db *DB) error {
return db.file.Sync()
}
// flock acquires an advisory lock on a file descriptor.
func flock(db *DB, mode os.FileMode, exclusive bool, timeout time.Duration) error {
// Create a separate lock file on windows because a process
// cannot share an exclusive lock on the same file. This is
// needed during Tx.WriteTo().
f, err := os.OpenFile(db.path+lockExt, os.O_CREATE, mode)
if err != nil {
return err
}
db.lockfile = f
var t time.Time
for {
// If we're beyond our timeout then return an error.
// This can only occur after we've attempted a flock once.
if t.IsZero() {
t = time.Now()
} else if timeout > 0 && time.Since(t) > timeout {
return ErrTimeout
}
var flag uint32 = flagLockFailImmediately
if exclusive {
flag |= flagLockExclusive
}
err := lockFileEx(syscall.Handle(db.lockfile.Fd()), flag, 0, 1, 0, &syscall.Overlapped{})
if err == nil {
return nil
} else if err != errLockViolation {
return err
}
// Wait for a bit and try again.
time.Sleep(50 * time.Millisecond)
}
}
// funlock releases an advisory lock on a file descriptor.
func funlock(db *DB) error {
err := unlockFileEx(syscall.Handle(db.lockfile.Fd()), 0, 1, 0, &syscall.Overlapped{})
db.lockfile.Close()
os.Remove(db.path + lockExt)
return err
}
// mmap memory maps a DB's data file.
// Based on: https://github.com/edsrzf/mmap-go
func mmap(db *DB, sz int) error {
if !db.readOnly {
// Truncate the database to the size of the mmap.
if err := db.file.Truncate(int64(sz)); err != nil {
return fmt.Errorf("truncate: %s", err)
}
}
// Open a file mapping handle.
sizelo := uint32(sz >> 32)
sizehi := uint32(sz) & 0xffffffff
h, errno := syscall.CreateFileMapping(syscall.Handle(db.file.Fd()), nil, syscall.PAGE_READONLY, sizelo, sizehi, nil)
if h == 0 {
return os.NewSyscallError("CreateFileMapping", errno)
}
// Create the memory map.
addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, uintptr(sz))
if addr == 0 {
return os.NewSyscallError("MapViewOfFile", errno)
}
// Close mapping handle.
if err := syscall.CloseHandle(syscall.Handle(h)); err != nil {
return os.NewSyscallError("CloseHandle", err)
}
// Convert to a byte array.
db.data = ((*[maxMapSize]byte)(unsafe.Pointer(addr)))
db.datasz = sz
return nil
}
// munmap unmaps a pointer from a file.
// Based on: https://github.com/edsrzf/mmap-go
func munmap(db *DB) error {
if db.data == nil {
return nil
}
addr := (uintptr)(unsafe.Pointer(&db.data[0]))
if err := syscall.UnmapViewOfFile(addr); err != nil {
return os.NewSyscallError("UnmapViewOfFile", err)
}
return nil
}
|
