refactoring

weed/storage/backend/memory_map/memory_map.go

@@ -0,0 +1,32 @@
+package memory_map
+
+import (
+	"os"
+	"strconv"
+)
+
+type MemoryBuffer struct {
+	aligned_length uint64
+	length         uint64
+	aligned_ptr    uintptr
+	ptr            uintptr
+	Buffer         []byte
+}
+
+type MemoryMap struct {
+	File                   *os.File
+	file_memory_map_handle uintptr
+	write_map_views        []MemoryBuffer
+	max_length             uint64
+	End_of_file            int64
+}
+
+var FileMemoryMap = make(map[string]*MemoryMap)
+
+func ReadMemoryMapMaxSizeMb(memoryMapMaxSizeMbString string) (uint32, error) {
+	if memoryMapMaxSizeMbString == "" {
+		return 0, nil
+	}
+	memoryMapMaxSize64, err := strconv.ParseUint(memoryMapMaxSizeMbString, 10, 32)
+	return uint32(memoryMapMaxSize64), err
+}

weed/storage/backend/memory_map/memory_map_other.go

@@ -0,0 +1,24 @@
+// +build !windows
+
+package memory_map
+
+import (
+	"fmt"
+	"os"
+)
+
+func (mMap *MemoryMap) CreateMemoryMap(file *os.File, maxLength uint64) {
+}
+
+func (mMap *MemoryMap) WriteMemory(offset uint64, length uint64, data []byte) {
+
+}
+
+func (mMap *MemoryMap) ReadMemory(offset uint64, length uint64) ([]byte, error) {
+	dataSlice := []byte{}
+	return dataSlice, fmt.Errorf("Memory Map not implemented for this platform")
+}
+
+func (mBuffer *MemoryMap) DeleteFileAndMemoryMap() {
+
+}

weed/storage/backend/memory_map/memory_map_test.go

@@ -0,0 +1,10 @@
+package memory_map
+
+import "testing"
+
+func TestMemoryMapMaxSizeReadWrite(t *testing.T) {
+	memoryMapSize, _ := ReadMemoryMapMaxSizeMb("5000")
+	if memoryMapSize != 5000 {
+		t.Errorf("empty memoryMapSize:%v", memoryMapSize)
+	}
+}

weed/storage/backend/memory_map/memory_map_windows.go

@@ -0,0 +1,325 @@
+// +build windows
+
+package memory_map
+
+import (
+	"os"
+	"reflect"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+type DWORDLONG = uint64
+type DWORD = uint32
+type WORD = uint16
+
+var (
+	modkernel32 = syscall.NewLazyDLL("kernel32.dll")
+
+	procGetSystemInfo            = modkernel32.NewProc("GetSystemInfo")
+	procGlobalMemoryStatusEx     = modkernel32.NewProc("GlobalMemoryStatusEx")
+	procGetProcessWorkingSetSize = modkernel32.NewProc("GetProcessWorkingSetSize")
+	procSetProcessWorkingSetSize = modkernel32.NewProc("SetProcessWorkingSetSize")
+)
+
+var currentProcess, _ = windows.GetCurrentProcess()
+var currentMinWorkingSet uint64 = 0
+var currentMaxWorkingSet uint64 = 0
+var _ = getProcessWorkingSetSize(uintptr(currentProcess), &currentMinWorkingSet, &currentMaxWorkingSet)
+
+var systemInfo, _ = getSystemInfo()
+var chunkSize = uint64(systemInfo.dwAllocationGranularity) * 128
+
+var memoryStatusEx, _ = globalMemoryStatusEx()
+var maxMemoryLimitBytes = uint64(float64(memoryStatusEx.ullTotalPhys) * 0.8)
+
+func (mMap *MemoryMap) CreateMemoryMap(file *os.File, maxLength uint64) {
+
+	chunks := (maxLength / chunkSize)
+	if chunks*chunkSize < maxLength {
+		chunks = chunks + 1
+	}
+
+	alignedMaxLength := chunks * chunkSize
+
+	maxLength_high := uint32(alignedMaxLength >> 32)
+	maxLength_low := uint32(alignedMaxLength & 0xFFFFFFFF)
+	file_memory_map_handle, err := windows.CreateFileMapping(windows.Handle(file.Fd()), nil, windows.PAGE_READWRITE, maxLength_high, maxLength_low, nil)
+
+	if err == nil {
+		mMap.File = file
+		mMap.file_memory_map_handle = uintptr(file_memory_map_handle)
+		mMap.write_map_views = make([]MemoryBuffer, 0, alignedMaxLength/chunkSize)
+		mMap.max_length = alignedMaxLength
+		mMap.End_of_file = -1
+	}
+}
+
+func (mMap *MemoryMap) DeleteFileAndMemoryMap() {
+	//First we close the file handles first to delete the file,
+	//Then we unmap the memory to ensure the unmapping process doesn't write the data to disk
+	windows.CloseHandle(windows.Handle(mMap.file_memory_map_handle))
+	windows.CloseHandle(windows.Handle(mMap.File.Fd()))
+
+	for _, view := range mMap.write_map_views {
+		view.releaseMemory()
+	}
+
+	mMap.write_map_views = nil
+	mMap.max_length = 0
+}
+
+func min(x, y uint64) uint64 {
+	if x < y {
+		return x
+	}
+	return y
+}
+
+func (mMap *MemoryMap) WriteMemory(offset uint64, length uint64, data []byte) {
+
+	for {
+		if ((offset+length)/chunkSize)+1 > uint64(len(mMap.write_map_views)) {
+			allocateChunk(mMap)
+		} else {
+			break
+		}
+	}
+
+	remaining_length := length
+	sliceIndex := offset / chunkSize
+	sliceOffset := offset - (sliceIndex * chunkSize)
+	dataOffset := uint64(0)
+
+	for {
+		writeEnd := min((remaining_length + sliceOffset), chunkSize)
+		copy(mMap.write_map_views[sliceIndex].Buffer[sliceOffset:writeEnd], data[dataOffset:])
+		remaining_length -= (writeEnd - sliceOffset)
+		dataOffset += (writeEnd - sliceOffset)
+
+		if remaining_length > 0 {
+			sliceIndex += 1
+			sliceOffset = 0
+		} else {
+			break
+		}
+	}
+
+	if mMap.End_of_file < int64(offset+length-1) {
+		mMap.End_of_file = int64(offset + length - 1)
+	}
+}
+
+func (mMap *MemoryMap) ReadMemory(offset uint64, length uint64) (dataSlice []byte, err error) {
+	dataSlice = make([]byte, length)
+	mBuffer, err := allocate(windows.Handle(mMap.file_memory_map_handle), offset, length, false)
+	copy(dataSlice, mBuffer.Buffer)
+	mBuffer.releaseMemory()
+	return dataSlice, err
+}
+
+func (mBuffer *MemoryBuffer) releaseMemory() {
+
+	windows.VirtualUnlock(mBuffer.aligned_ptr, uintptr(mBuffer.aligned_length))
+	windows.UnmapViewOfFile(mBuffer.aligned_ptr)
+
+	currentMinWorkingSet -= mBuffer.aligned_length
+	currentMaxWorkingSet -= mBuffer.aligned_length
+
+	if currentMinWorkingSet < maxMemoryLimitBytes {
+		var _ = setProcessWorkingSetSize(uintptr(currentProcess), currentMinWorkingSet, currentMaxWorkingSet)
+	}
+
+	mBuffer.ptr = 0
+	mBuffer.aligned_ptr = 0
+	mBuffer.length = 0
+	mBuffer.aligned_length = 0
+	mBuffer.Buffer = nil
+}
+
+func allocateChunk(mMap *MemoryMap) {
+	start := uint64(len(mMap.write_map_views)) * chunkSize
+	mBuffer, err := allocate(windows.Handle(mMap.file_memory_map_handle), start, chunkSize, true)
+
+	if err == nil {
+		mMap.write_map_views = append(mMap.write_map_views, mBuffer)
+	}
+}
+
+func allocate(hMapFile windows.Handle, offset uint64, length uint64, write bool) (MemoryBuffer, error) {
+
+	mBuffer := MemoryBuffer{}
+
+	//align memory allocations to the minium virtal memory allocation size
+	dwSysGran := systemInfo.dwAllocationGranularity
+
+	start := (offset / uint64(dwSysGran)) * uint64(dwSysGran)
+	diff := offset - start
+	aligned_length := diff + length
+
+	offset_high := uint32(start >> 32)
+	offset_low := uint32(start & 0xFFFFFFFF)
+
+	access := windows.FILE_MAP_READ
+
+	if write {
+		access = windows.FILE_MAP_WRITE
+	}
+
+	currentMinWorkingSet += aligned_length
+	currentMaxWorkingSet += aligned_length
+
+	if currentMinWorkingSet < maxMemoryLimitBytes {
+		// increase the process working set size to hint to windows memory manager to
+		// prioritise keeping this memory mapped in physical memory over other standby memory
+		var _ = setProcessWorkingSetSize(uintptr(currentProcess), currentMinWorkingSet, currentMaxWorkingSet)
+	}
+
+	addr_ptr, errno := windows.MapViewOfFile(hMapFile,
+		uint32(access), // read/write permission
+		offset_high,
+		offset_low,
+		uintptr(aligned_length))
+
+	if addr_ptr == 0 {
+		return mBuffer, errno
+	}
+
+	if currentMinWorkingSet < maxMemoryLimitBytes {
+		windows.VirtualLock(mBuffer.aligned_ptr, uintptr(mBuffer.aligned_length))
+	}
+
+	mBuffer.aligned_ptr = addr_ptr
+	mBuffer.aligned_length = aligned_length
+	mBuffer.ptr = addr_ptr + uintptr(diff)
+	mBuffer.length = length
+
+	slice_header := (*reflect.SliceHeader)(unsafe.Pointer(&mBuffer.Buffer))
+	slice_header.Data = addr_ptr + uintptr(diff)
+	slice_header.Len = int(length)
+	slice_header.Cap = int(length)
+
+	return mBuffer, nil
+}
+
+//typedef struct _MEMORYSTATUSEX {
+//	DWORD     dwLength;
+//	DWORD     dwMemoryLoad;
+//	DWORDLONG ullTotalPhys;
+//	DWORDLONG ullAvailPhys;
+//	DWORDLONG ullTotalPageFile;
+//	DWORDLONG ullAvailPageFile;
+//	DWORDLONG ullTotalVirtual;
+//	DWORDLONG ullAvailVirtual;
+//	DWORDLONG ullAvailExtendedVirtual;
+//  } MEMORYSTATUSEX, *LPMEMORYSTATUSEX;
+//https://docs.microsoft.com/en-gb/windows/win32/api/sysinfoapi/ns-sysinfoapi-memorystatusex
+
+type _MEMORYSTATUSEX struct {
+	dwLength                DWORD
+	dwMemoryLoad            DWORD
+	ullTotalPhys            DWORDLONG
+	ullAvailPhys            DWORDLONG
+	ullTotalPageFile        DWORDLONG
+	ullAvailPageFile        DWORDLONG
+	ullTotalVirtual         DWORDLONG
+	ullAvailVirtual         DWORDLONG
+	ullAvailExtendedVirtual DWORDLONG
+}
+
+// BOOL GlobalMemoryStatusEx(
+//  LPMEMORYSTATUSEX lpBuffer
+// );
+// https://docs.microsoft.com/en-gb/windows/win32/api/sysinfoapi/nf-sysinfoapi-globalmemorystatusex
+func globalMemoryStatusEx() (_MEMORYSTATUSEX, error) {
+	var mem_status _MEMORYSTATUSEX
+
+	mem_status.dwLength = uint32(unsafe.Sizeof(mem_status))
+	_, _, err := procGlobalMemoryStatusEx.Call(uintptr(unsafe.Pointer(&mem_status)))
+
+	if err != syscall.Errno(0) {
+		return mem_status, err
+	}
+	return mem_status, nil
+}
+
+// typedef struct _SYSTEM_INFO {
+//   union {
+//     DWORD  dwOemId;
+//     struct {
+//       WORD wProcessorArchitecture;
+//       WORD wReserved;
+//     };
+//   };
+//   DWORD     dwPageSize;
+//   LPVOID    lpMinimumApplicationAddress;
+//   LPVOID    lpMaximumApplicationAddress;
+//   DWORD_PTR dwActiveProcessorMask;
+//   DWORD     dwNumberOfProcessors;
+//   DWORD     dwProcessorType;
+//   DWORD     dwAllocationGranularity;
+//   WORD      wProcessorLevel;
+//   WORD      wProcessorRevision;
+// } SYSTEM_INFO;
+// https://docs.microsoft.com/en-gb/windows/win32/api/sysinfoapi/ns-sysinfoapi-system_info
+type _SYSTEM_INFO struct {
+	dwOemId                     DWORD
+	dwPageSize                  DWORD
+	lpMinimumApplicationAddress uintptr
+	lpMaximumApplicationAddress uintptr
+	dwActiveProcessorMask       uintptr
+	dwNumberOfProcessors        DWORD
+	dwProcessorType             DWORD
+	dwAllocationGranularity     DWORD
+	wProcessorLevel             WORD
+	wProcessorRevision          WORD
+}
+
+// void WINAPI GetSystemInfo(
+//   _Out_ LPSYSTEM_INFO lpSystemInfo
+// );
+// https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsysteminfo
+func getSystemInfo() (_SYSTEM_INFO, error) {
+	var si _SYSTEM_INFO
+	_, _, err := procGetSystemInfo.Call(uintptr(unsafe.Pointer(&si)))
+	if err != syscall.Errno(0) {
+		return si, err
+	}
+	return si, nil
+}
+
+// BOOL GetProcessWorkingSetSize(
+//   HANDLE  hProcess,
+//   PSIZE_T lpMinimumWorkingSetSize,
+//   PSIZE_T lpMaximumWorkingSetSize
+// );
+// https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getprocessworkingsetsize
+
+func getProcessWorkingSetSize(process uintptr, dwMinWorkingSet *uint64, dwMaxWorkingSet *uint64) error {
+	r1, _, err := syscall.Syscall(procGetProcessWorkingSetSize.Addr(), 3, process, uintptr(unsafe.Pointer(dwMinWorkingSet)), uintptr(unsafe.Pointer(dwMaxWorkingSet)))
+	if r1 == 0 {
+		if err != syscall.Errno(0) {
+			return err
+		}
+	}
+	return nil
+}
+
+// BOOL SetProcessWorkingSetSize(
+//   HANDLE hProcess,
+//   SIZE_T dwMinimumWorkingSetSize,
+//   SIZE_T dwMaximumWorkingSetSize
+// );
+// https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-setprocessworkingsetsize
+
+func setProcessWorkingSetSize(process uintptr, dwMinWorkingSet uint64, dwMaxWorkingSet uint64) error {
+	r1, _, err := syscall.Syscall(procSetProcessWorkingSetSize.Addr(), 3, process, uintptr(dwMinWorkingSet), uintptr(dwMaxWorkingSet))
+	if r1 == 0 {
+		if err != syscall.Errno(0) {
+			return err
+		}
+	}
+	return nil
+}

weed/storage/backend/memory_map/os_overloads/file_windows.go

@@ -0,0 +1,168 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os_overloads
+
+import (
+	"os"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+func isAbs(path string) (b bool) {
+	v := volumeName(path)
+	if v == "" {
+		return false
+	}
+	path = path[len(v):]
+	if path == "" {
+		return false
+	}
+	return os.IsPathSeparator(path[0])
+}
+
+func volumeName(path string) (v string) {
+	if len(path) < 2 {
+		return ""
+	}
+	// with drive letter
+	c := path[0]
+	if path[1] == ':' &&
+		('0' <= c && c <= '9' || 'a' <= c && c <= 'z' ||
+			'A' <= c && c <= 'Z') {
+		return path[:2]
+	}
+	// is it UNC
+	if l := len(path); l >= 5 && os.IsPathSeparator(path[0]) && os.IsPathSeparator(path[1]) &&
+		!os.IsPathSeparator(path[2]) && path[2] != '.' {
+		// first, leading `\\` and next shouldn't be `\`. its server name.
+		for n := 3; n < l-1; n++ {
+			// second, next '\' shouldn't be repeated.
+			if os.IsPathSeparator(path[n]) {
+				n++
+				// third, following something characters. its share name.
+				if !os.IsPathSeparator(path[n]) {
+					if path[n] == '.' {
+						break
+					}
+					for ; n < l; n++ {
+						if os.IsPathSeparator(path[n]) {
+							break
+						}
+					}
+					return path[:n]
+				}
+				break
+			}
+		}
+	}
+	return ""
+}
+
+// fixLongPath returns the extended-length (\\?\-prefixed) form of
+// path when needed, in order to avoid the default 260 character file
+// path limit imposed by Windows. If path is not easily converted to
+// the extended-length form (for example, if path is a relative path
+// or contains .. elements), or is short enough, fixLongPath returns
+// path unmodified.
+//
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
+func fixLongPath(path string) string {
+	// Do nothing (and don't allocate) if the path is "short".
+	// Empirically (at least on the Windows Server 2013 builder),
+	// the kernel is arbitrarily okay with < 248 bytes. That
+	// matches what the docs above say:
+	// "When using an API to create a directory, the specified
+	// path cannot be so long that you cannot append an 8.3 file
+	// name (that is, the directory name cannot exceed MAX_PATH
+	// minus 12)." Since MAX_PATH is 260, 260 - 12 = 248.
+	//
+	// The MSDN docs appear to say that a normal path that is 248 bytes long
+	// will work; empirically the path must be less then 248 bytes long.
+	if len(path) < 248 {
+		// Don't fix. (This is how Go 1.7 and earlier worked,
+		// not automatically generating the \\?\ form)
+		return path
+	}
+
+	// The extended form begins with \\?\, as in
+	// \\?\c:\windows\foo.txt or \\?\UNC\server\share\foo.txt.
+	// The extended form disables evaluation of . and .. path
+	// elements and disables the interpretation of / as equivalent
+	// to \. The conversion here rewrites / to \ and elides
+	// . elements as well as trailing or duplicate separators. For
+	// simplicity it avoids the conversion entirely for relative
+	// paths or paths containing .. elements. For now,
+	// \\server\share paths are not converted to
+	// \\?\UNC\server\share paths because the rules for doing so
+	// are less well-specified.
+	if len(path) >= 2 && path[:2] == `\\` {
+		// Don't canonicalize UNC paths.
+		return path
+	}
+	if !isAbs(path) {
+		// Relative path
+		return path
+	}
+
+	const prefix = `\\?`
+
+	pathbuf := make([]byte, len(prefix)+len(path)+len(`\`))
+	copy(pathbuf, prefix)
+	n := len(path)
+	r, w := 0, len(prefix)
+	for r < n {
+		switch {
+		case os.IsPathSeparator(path[r]):
+			// empty block
+			r++
+		case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
+			// /./
+			r++
+		case r+1 < n && path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
+			// /../ is currently unhandled
+			return path
+		default:
+			pathbuf[w] = '\\'
+			w++
+			for ; r < n && !os.IsPathSeparator(path[r]); r++ {
+				pathbuf[w] = path[r]
+				w++
+			}
+		}
+	}
+	// A drive's root directory needs a trailing \
+	if w == len(`\\?\c:`) {
+		pathbuf[w] = '\\'
+		w++
+	}
+	return string(pathbuf[:w])
+}
+
+// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
+func syscallMode(i os.FileMode) (o uint32) {
+	o |= uint32(i.Perm())
+	if i&os.ModeSetuid != 0 {
+		o |= syscall.S_ISUID
+	}
+	if i&os.ModeSetgid != 0 {
+		o |= syscall.S_ISGID
+	}
+	if i&os.ModeSticky != 0 {
+		o |= syscall.S_ISVTX
+	}
+	// No mapping for Go's ModeTemporary (plan9 only).
+	return
+}
+
+//If the bool is set to true then the file is opened with the parameters FILE_ATTRIBUTE_TEMPORARY and
+// FILE_FLAG_DELETE_ON_CLOSE
+func OpenFile(name string, flag int, perm os.FileMode, setToTempAndDelete bool) (file *os.File, err error) {
+	r, e := Open(fixLongPath(name), flag|windows.O_CLOEXEC, syscallMode(perm), setToTempAndDelete)
+	if e != nil {
+		return nil, e
+	}
+	return os.NewFile(uintptr(r), name), nil
+}

weed/storage/backend/memory_map/os_overloads/syscall_windows.go

@@ -0,0 +1,80 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Windows system calls.
+
+package os_overloads
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// windows api calls
+
+//sys	CreateFile(name *uint16, access uint32, mode uint32, sa *SecurityAttributes, createmode uint32, attrs uint32, templatefile int32) (handle Handle, err error) [failretval==InvalidHandle] = CreateFileW
+
+func makeInheritSa() *syscall.SecurityAttributes {
+	var sa syscall.SecurityAttributes
+	sa.Length = uint32(unsafe.Sizeof(sa))
+	sa.InheritHandle = 1
+	return &sa
+}
+
+// opens the
+func Open(path string, mode int, perm uint32, setToTempAndDelete bool) (fd syscall.Handle, err error) {
+	if len(path) == 0 {
+		return syscall.InvalidHandle, windows.ERROR_FILE_NOT_FOUND
+	}
+	pathp, err := syscall.UTF16PtrFromString(path)
+	if err != nil {
+		return syscall.InvalidHandle, err
+	}
+	var access uint32
+	switch mode & (windows.O_RDONLY | windows.O_WRONLY | windows.O_RDWR) {
+	case windows.O_RDONLY:
+		access = windows.GENERIC_READ
+	case windows.O_WRONLY:
+		access = windows.GENERIC_WRITE
+	case windows.O_RDWR:
+		access = windows.GENERIC_READ | windows.GENERIC_WRITE
+	}
+	if mode&windows.O_CREAT != 0 {
+		access |= windows.GENERIC_WRITE
+	}
+	if mode&windows.O_APPEND != 0 {
+		access &^= windows.GENERIC_WRITE
+		access |= windows.FILE_APPEND_DATA
+	}
+	sharemode := uint32(windows.FILE_SHARE_READ | windows.FILE_SHARE_WRITE)
+	var sa *syscall.SecurityAttributes
+	if mode&windows.O_CLOEXEC == 0 {
+		sa = makeInheritSa()
+	}
+	var createmode uint32
+	switch {
+	case mode&(windows.O_CREAT|windows.O_EXCL) == (windows.O_CREAT | windows.O_EXCL):
+		createmode = windows.CREATE_NEW
+	case mode&(windows.O_CREAT|windows.O_TRUNC) == (windows.O_CREAT | windows.O_TRUNC):
+		createmode = windows.CREATE_ALWAYS
+	case mode&windows.O_CREAT == windows.O_CREAT:
+		createmode = windows.OPEN_ALWAYS
+	case mode&windows.O_TRUNC == windows.O_TRUNC:
+		createmode = windows.TRUNCATE_EXISTING
+	default:
+		createmode = windows.OPEN_EXISTING
+	}
+
+	var h syscall.Handle
+	var e error
+
+	if setToTempAndDelete {
+		h, e = syscall.CreateFile(pathp, access, sharemode, sa, createmode, (windows.FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE), 0)
+	} else {
+		h, e = syscall.CreateFile(pathp, access, sharemode, sa, createmode, windows.FILE_ATTRIBUTE_NORMAL, 0)
+	}
+	return h, e
+}

weed/storage/backend/memory_map/os_overloads/types_windows.go

@@ -0,0 +1,9 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os_overloads
+
+const (
+	FILE_FLAG_DELETE_ON_CLOSE = 0x04000000
+)