vendor: add buildkit

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/github.com/gofrs/flock/flock_winapi.go

@@ -0,0 +1,76 @@
+// Copyright 2015 Tim Heckman. All rights reserved.
+// Use of this source code is governed by the BSD 3-Clause
+// license that can be found in the LICENSE file.
+
+// +build windows
+
+package flock
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var (
+	kernel32, _         = syscall.LoadLibrary("kernel32.dll")
+	procLockFileEx, _   = syscall.GetProcAddress(kernel32, "LockFileEx")
+	procUnlockFileEx, _ = syscall.GetProcAddress(kernel32, "UnlockFileEx")
+)
+
+const (
+	winLockfileFailImmediately = 0x00000001
+	winLockfileExclusiveLock   = 0x00000002
+	winLockfileSharedLock      = 0x00000000
+)
+
+// Use of 0x00000000 for the shared lock is a guess based on some the MS Windows
+// `LockFileEX` docs, which document the `LOCKFILE_EXCLUSIVE_LOCK` flag as:
+//
+// > The function requests an exclusive lock. Otherwise, it requests a shared
+// > lock.
+//
+// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365203(v=vs.85).aspx
+
+func lockFileEx(handle syscall.Handle, flags uint32, reserved uint32, numberOfBytesToLockLow uint32, numberOfBytesToLockHigh uint32, offset *syscall.Overlapped) (bool, syscall.Errno) {
+	r1, _, errNo := syscall.Syscall6(
+		uintptr(procLockFileEx),
+		6,
+		uintptr(handle),
+		uintptr(flags),
+		uintptr(reserved),
+		uintptr(numberOfBytesToLockLow),
+		uintptr(numberOfBytesToLockHigh),
+		uintptr(unsafe.Pointer(offset)))
+
+	if r1 != 1 {
+		if errNo == 0 {
+			return false, syscall.EINVAL
+		}
+
+		return false, errNo
+	}
+
+	return true, 0
+}
+
+func unlockFileEx(handle syscall.Handle, reserved uint32, numberOfBytesToLockLow uint32, numberOfBytesToLockHigh uint32, offset *syscall.Overlapped) (bool, syscall.Errno) {
+	r1, _, errNo := syscall.Syscall6(
+		uintptr(procUnlockFileEx),
+		5,
+		uintptr(handle),
+		uintptr(reserved),
+		uintptr(numberOfBytesToLockLow),
+		uintptr(numberOfBytesToLockHigh),
+		uintptr(unsafe.Pointer(offset)),
+		0)
+
+	if r1 != 1 {
+		if errNo == 0 {
+			return false, syscall.EINVAL
+		}
+
+		return false, errNo
+	}
+
+	return true, 0
+}