142 lines
3.7 KiB
Go
142 lines
3.7 KiB
Go
package bbolt
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import (
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"fmt"
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"os"
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"syscall"
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"time"
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"unsafe"
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)
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// LockFileEx code derived from golang build filemutex_windows.go @ v1.5.1
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var (
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modkernel32 = syscall.NewLazyDLL("kernel32.dll")
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procLockFileEx = modkernel32.NewProc("LockFileEx")
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procUnlockFileEx = modkernel32.NewProc("UnlockFileEx")
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)
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const (
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// see https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
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flagLockExclusive = 2
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flagLockFailImmediately = 1
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// see https://msdn.microsoft.com/en-us/library/windows/desktop/ms681382(v=vs.85).aspx
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errLockViolation syscall.Errno = 0x21
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)
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func lockFileEx(h syscall.Handle, flags, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
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r, _, err := procLockFileEx.Call(uintptr(h), uintptr(flags), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)))
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if r == 0 {
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return err
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}
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return nil
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}
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func unlockFileEx(h syscall.Handle, reserved, locklow, lockhigh uint32, ol *syscall.Overlapped) (err error) {
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r, _, err := procUnlockFileEx.Call(uintptr(h), uintptr(reserved), uintptr(locklow), uintptr(lockhigh), uintptr(unsafe.Pointer(ol)), 0)
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if r == 0 {
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return err
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}
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return nil
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}
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// fdatasync flushes written data to a file descriptor.
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func fdatasync(db *DB) error {
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return db.file.Sync()
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}
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// flock acquires an advisory lock on a file descriptor.
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func flock(db *DB, exclusive bool, timeout time.Duration) error {
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var t time.Time
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if timeout != 0 {
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t = time.Now()
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}
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var flag uint32 = flagLockFailImmediately
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if exclusive {
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flag |= flagLockExclusive
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}
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for {
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// Fix for https://github.com/etcd-io/bbolt/issues/121. Use byte-range
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// -1..0 as the lock on the database file.
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var m1 uint32 = (1 << 32) - 1 // -1 in a uint32
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err := lockFileEx(syscall.Handle(db.file.Fd()), flag, 0, 1, 0, &syscall.Overlapped{
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Offset: m1,
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OffsetHigh: m1,
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})
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if err == nil {
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return nil
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} else if err != errLockViolation {
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return err
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}
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// If we timed oumercit then return an error.
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if timeout != 0 && time.Since(t) > timeout-flockRetryTimeout {
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return ErrTimeout
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}
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// Wait for a bit and try again.
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time.Sleep(flockRetryTimeout)
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}
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}
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// funlock releases an advisory lock on a file descriptor.
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func funlock(db *DB) error {
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var m1 uint32 = (1 << 32) - 1 // -1 in a uint32
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err := unlockFileEx(syscall.Handle(db.file.Fd()), 0, 1, 0, &syscall.Overlapped{
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Offset: m1,
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OffsetHigh: m1,
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})
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return err
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}
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// mmap memory maps a DB's data file.
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// Based on: https://github.com/edsrzf/mmap-go
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func mmap(db *DB, sz int) error {
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if !db.readOnly {
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// Truncate the database to the size of the mmap.
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if err := db.file.Truncate(int64(sz)); err != nil {
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return fmt.Errorf("truncate: %s", err)
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}
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}
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// Open a file mapping handle.
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sizelo := uint32(sz >> 32)
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sizehi := uint32(sz) & 0xffffffff
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h, errno := syscall.CreateFileMapping(syscall.Handle(db.file.Fd()), nil, syscall.PAGE_READONLY, sizelo, sizehi, nil)
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if h == 0 {
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return os.NewSyscallError("CreateFileMapping", errno)
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}
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// Create the memory map.
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addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, uintptr(sz))
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if addr == 0 {
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return os.NewSyscallError("MapViewOfFile", errno)
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}
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// Close mapping handle.
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if err := syscall.CloseHandle(syscall.Handle(h)); err != nil {
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return os.NewSyscallError("CloseHandle", err)
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}
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// Convert to a byte array.
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db.data = ((*[maxMapSize]byte)(unsafe.Pointer(addr)))
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db.datasz = sz
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return nil
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}
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// munmap unmaps a pointer from a file.
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// Based on: https://github.com/edsrzf/mmap-go
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func munmap(db *DB) error {
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if db.data == nil {
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return nil
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}
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addr := (uintptr)(unsafe.Pointer(&db.data[0]))
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if err := syscall.UnmapViewOfFile(addr); err != nil {
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return os.NewSyscallError("UnmapViewOfFile", err)
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}
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return nil
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}
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