Windows USN Journal sample in Go based on Jeffrey Richter's superb MSDN Journal article. A work in progress, intended to provide similar API to go.fsevents.

fsevents_windows.go

// 
// File:   fsevents_windows.go
// Date:   October 29, 2013
// Author: Peter Krnjevic <pkrnjevic@gmail.com>, on the shoulders of many others
// 
// This code sample is released into the Public Domain.
//
package fsevents

import (
	// "bytes"
	// "encoding/binary"
	"fmt"
	"reflect"
	"syscall"
	"unsafe"
)

import (
	// "github.com/lxn/go-winapi"
	"github.com/lxn/walk"
)

type (
	WCHAR         uint16
	WORD          uint16
	DWORD         uint32
	DWORDLONG     uint64
	LONGLONG      int64
	USN           int64
	LARGE_INTEGER LONGLONG
)

type USN_JOURNAL_DATA struct {
	UsnJournalID    DWORDLONG
	FirstUsn        USN
	NextUsn         USN
	LowestValidUsn  USN
	MaxUsn          USN
	MaximumSize     DWORDLONG
	AllocationDelta DWORDLONG
}

type READ_USN_JOURNAL_DATA struct {
	StartUsn          USN
	ReasonMask        DWORD
	ReturnOnlyOnClose DWORD
	Timeout           DWORDLONG
	BytesToWaitFor    DWORDLONG
	UsnJournalID      DWORDLONG
}

type USN_RECORD struct {
	RecordLength              DWORD
	MajorVersion              WORD
	MinorVersion              WORD
	FileReferenceNumber       DWORDLONG
	ParentFileReferenceNumber DWORDLONG
	Usn                       USN
	TimeStamp                 LARGE_INTEGER
	Reason                    DWORD
	SourceInfo                DWORD
	SecurityId                DWORD
	FileAttributes            DWORD
	FileNameLength            WORD
	FileNameOffset            WORD
	FileName                  [1]WCHAR
}

type MFT_ENUM_DATA struct {
	StartFileReferenceNumber DWORDLONG
	LowUsn                   USN
	HighUsn                  USN
}

const (
	FSCTL_ENUM_USN_DATA        = 0x900B3
	FSCTL_QUERY_USN_JOURNAL    = 0x900F4
	FSCTL_READ_USN_JOURNAL     = 0x900BB
	O_RDONLY                   = syscall.O_RDONLY
	O_RDWR                     = syscall.O_RDWR
	O_CREAT                    = syscall.O_CREAT
	O_WRONLY                   = syscall.O_WRONLY
	GENERIC_READ               = syscall.GENERIC_READ
	GENERIC_WRITE              = syscall.GENERIC_WRITE
	FILE_APPEND_DATA           = syscall.FILE_APPEND_DATA
	FILE_SHARE_READ            = syscall.FILE_SHARE_READ
	FILE_SHARE_WRITE           = syscall.FILE_SHARE_WRITE
	ERROR_FILE_NOT_FOUND       = syscall.ERROR_FILE_NOT_FOUND
	O_APPEND                   = syscall.O_APPEND
	O_CLOEXEC                  = syscall.O_CLOEXEC
	O_EXCL                     = syscall.O_EXCL
	O_TRUNC                    = syscall.O_TRUNC
	CREATE_ALWAYS              = syscall.CREATE_ALWAYS
	CREATE_NEW                 = syscall.CREATE_NEW
	OPEN_ALWAYS                = syscall.OPEN_ALWAYS
	TRUNCATE_EXISTING          = syscall.TRUNCATE_EXISTING
	OPEN_EXISTING              = syscall.OPEN_EXISTING
	FILE_ATTRIBUTE_NORMAL      = syscall.FILE_ATTRIBUTE_NORMAL
	FILE_FLAG_BACKUP_SEMANTICS = syscall.FILE_FLAG_BACKUP_SEMANTICS
	FILE_ATTRIBUTE_DIRECTORY   = syscall.FILE_ATTRIBUTE_DIRECTORY
	MAX_LONG_PATH              = syscall.MAX_LONG_PATH
)

var (
	modkernel32         = syscall.NewLazyDLL("kernel32.dll")
	procDeviceIoControl = modkernel32.NewProc("DeviceIoControl")
	usnJournalData      USN_JOURNAL_DATA
	readUsnJournalData  READ_USN_JOURNAL_DATA
	cb                  int
)

func getPointer(i interface{}) (pointer, size uintptr) {
	v := reflect.ValueOf(i)
	switch k := v.Kind(); k {
	case reflect.Ptr:
		t := v.Elem().Type()
		size = t.Size()
		pointer = v.Pointer()
	case reflect.Slice:
		size = uintptr(v.Cap())
		pointer = v.Pointer()
	default:
		fmt.Println("oops")
	}
	return
}

func DeviceIoControl(handle syscall.Handle, controlCode uint32, in interface{}, out interface{}, done *uint32) (err error) {
	inPtr, inSize := getPointer(in)
	outPtr, outSize := getPointer(out)
	r1, _, e1 := syscall.Syscall9(procDeviceIoControl.Addr(), 8, uintptr(handle), uintptr(controlCode), inPtr, uintptr(inSize), outPtr, uintptr(outSize), uintptr(unsafe.Pointer(done)), uintptr(0), 0)
	if r1 == 0 {
		if e1 != 0 {
			err = error(e1)
		} else {
			err = syscall.EINVAL
		}
	}
	return
}

func makeInheritSa() *syscall.SecurityAttributes {
	var sa syscall.SecurityAttributes
	sa.Length = uint32(unsafe.Sizeof(sa))
	sa.InheritHandle = 1
	return &sa
}

// Need a custom Open to work with backup_semantics
func open(path string, mode int, attrs uint32) (fd syscall.Handle, err error) {
	if len(path) == 0 {
		return syscall.InvalidHandle, ERROR_FILE_NOT_FOUND
	}
	pathp, err := syscall.UTF16PtrFromString(path)
	if err != nil {
		return syscall.InvalidHandle, err
	}
	var access uint32
	switch mode & (O_RDONLY | O_WRONLY | O_RDWR) {
	case O_RDONLY:
		access = GENERIC_READ
	case O_WRONLY:
		access = GENERIC_WRITE
	case O_RDWR:
		access = GENERIC_READ | GENERIC_WRITE
	}
	if mode&O_CREAT != 0 {
		access |= GENERIC_WRITE
	}
	if mode&O_APPEND != 0 {
		access &^= GENERIC_WRITE
		access |= FILE_APPEND_DATA
	}
	sharemode := uint32(FILE_SHARE_READ | FILE_SHARE_WRITE)
	var sa *syscall.SecurityAttributes
	if mode&O_CLOEXEC == 0 {
		sa = makeInheritSa()
	}
	var createmode uint32
	switch {
	case mode&(O_CREAT|O_EXCL) == (O_CREAT | O_EXCL):
		createmode = CREATE_NEW
	case mode&(O_CREAT|O_TRUNC) == (O_CREAT | O_TRUNC):
		createmode = CREATE_ALWAYS
	case mode&O_CREAT == O_CREAT:
		createmode = OPEN_ALWAYS
	case mode&O_TRUNC == O_TRUNC:
		createmode = TRUNCATE_EXISTING
	default:
		createmode = OPEN_EXISTING
	}
	h, e := syscall.CreateFile(pathp, access, sharemode, sa, createmode, attrs, 0)
	return h, e
}

func getUsnJournalReasonString(reason DWORD) (s string) {
	var reasons = []string{
		"DataOverwrite",       // 0x00000001
		"DataExtend",          // 0x00000002
		"DataTruncation",      // 0x00000004
		"0x00000008",          // 0x00000008
		"NamedDataOverwrite",  // 0x00000010
		"NamedDataExtend",     // 0x00000020
		"NamedDataTruncation", // 0x00000040
		"0x00000080",          // 0x00000080
		"FileCreate",          // 0x00000100
		"FileDelete",          // 0x00000200
		"PropertyChange",      // 0x00000400
		"SecurityChange",      // 0x00000800
		"RenameOldName",       // 0x00001000
		"RenameNewName",       // 0x00002000
		"IndexableChange",     // 0x00004000
		"BasicInfoChange",     // 0x00008000
		"HardLinkChange",      // 0x00010000
		"CompressionChange",   // 0x00020000
		"EncryptionChange",    // 0x00040000
		"ObjectIdChange",      // 0x00080000
		"ReparsePointChange",  // 0x00100000
		"StreamChange",        // 0x00200000
		"0x00400000",          // 0x00400000
		"0x00800000",          // 0x00800000
		"0x01000000",          // 0x01000000
		"0x02000000",          // 0x02000000
		"0x04000000",          // 0x04000000
		"0x08000000",          // 0x08000000
		"0x10000000",          // 0x10000000
		"0x20000000",          // 0x20000000
		"0x40000000",          // 0x40000000
		"*Close*",             // 0x80000000
	}
	for i := 0; reason != 0; {
		if reason&1 == 1 {
			s = s + ", " + reasons[i]
		}
		reason >>= 1
		i++
	}
	return
}

// Query usn journal data
func queryUsnJournal(fd syscall.Handle) (ujd USN_JOURNAL_DATA, done uint32, err error) {
	err = DeviceIoControl(fd, FSCTL_QUERY_USN_JOURNAL, []byte{}, &ujd, &done)
	return
}

func readUsnJournal(fd syscall.Handle, rujd *READ_USN_JOURNAL_DATA) (data []byte, done uint32, err error) {
	data = make([]byte, 0x1000)
	err = DeviceIoControl(fd, FSCTL_READ_USN_JOURNAL, rujd, data, &done)
	return
}

func enumUsnData(fd syscall.Handle, med *MFT_ENUM_DATA) (data []byte, done uint32, err error) {
	data = make([]byte, 0x10000)
	err = DeviceIoControl(fd, FSCTL_ENUM_USN_DATA, med, data, &done)
	return
}

type folderEntry struct {
	name   string
	parent DWORDLONG
}

// Build map of folder names using MFT (based on PopulateMethod2)
func buildFolderMap() (folders map[DWORDLONG]folderEntry) {
	folders = make(map[DWORDLONG]folderEntry)
	drives, _ := walk.DriveNames()
	fmt.Println(drives)

	fd, err := open("\\\\.\\C:", syscall.O_RDONLY, FILE_ATTRIBUTE_NORMAL)
	fmt.Println(fd, err)

	ujd, _, err := queryUsnJournal(fd)
	fmt.Printf("ujd = %v\n", ujd)

	// Open directory to read MFT and store off FRN (file reference numbers)
	dir, err := open("C:\\", syscall.O_RDONLY, FILE_FLAG_BACKUP_SEMANTICS)
	fmt.Println("dir,err", dir, err)

	var fi syscall.ByHandleFileInformation
	err = syscall.GetFileInformationByHandle(dir, &fi)
	err = syscall.CloseHandle(dir)
	fmt.Println("err, fi", err, fi)

	indexRoot := fi.FileSizeHigh<<32 | fi.FileSizeLow
	_ = indexRoot

	med := MFT_ENUM_DATA{0, 0, ujd.NextUsn}

	for {
		data, done, err := enumUsnData(fd, &med)
		if err != nil {
			fmt.Println(err)
		}
		if done == 0 {
			return
		}

		var usn USN = *(*USN)(unsafe.Pointer(&data[0]))
		// fmt.Println("usn", usn)

		var ur *USN_RECORD
		for i := unsafe.Sizeof(usn); i < uintptr(done); i += uintptr(ur.RecordLength) {
			ur = (*USN_RECORD)(unsafe.Pointer(&data[i]))
			if ur.FileAttributes&FILE_ATTRIBUTE_DIRECTORY != 0 {
				nameLength := uintptr(ur.FileNameLength) / unsafe.Sizeof(ur.FileName[0])
				fnp := unsafe.Pointer(&data[i+uintptr(ur.FileNameOffset)])
				fnUtf := (*[10000]uint16)(fnp)[:nameLength]
				fn := syscall.UTF16ToString(fnUtf)
				(*reflect.SliceHeader)(unsafe.Pointer(&fn)).Cap = int(nameLength)
				// fmt.Println("len", ur.FileNameLength, ur.FileNameOffset, "fn", fn)
				folders[ur.FileReferenceNumber] = folderEntry{fn, ur.ParentFileReferenceNumber}
			}
		}
		med.StartFileReferenceNumber = DWORDLONG(usn)
	}
}

// Assemble the path by looking up parent pointers in the folders map
func getFullPath(folders map[DWORDLONG]folderEntry, parent DWORDLONG) (name string) {
	for parent != 0 {
		fe := folders[parent]
		name = fe.name + "/" + name
		parent = fe.parent
	}
	return
}

func processAvailableRecords(ch chan *USN_RECORD, folders map[DWORDLONG]folderEntry) {
	drives, _ := walk.DriveNames()
	fmt.Println(drives)

	fd, err := open("\\\\.\\C:", syscall.O_RDONLY, FILE_ATTRIBUTE_NORMAL)
	fmt.Println("fd, err", fd, err)

	ujd, _, err := queryUsnJournal(fd)
	fmt.Printf("ujd = %v\n", ujd)

	rujd := READ_USN_JOURNAL_DATA{ujd.FirstUsn, 0xFFFFFFFF, 0, 0, 1, ujd.UsnJournalID}

	for {
		var usn USN
		data, done, err := readUsnJournal(fd, &rujd)
		if err != nil || done <= uint32(unsafe.Sizeof(usn)) {
			return
		}

		usn = *(*USN)(unsafe.Pointer(&data[0]))
		fmt.Println("usn", usn)

		var ur *USN_RECORD
		for i := unsafe.Sizeof(usn); i < uintptr(done); i += uintptr(ur.RecordLength) {
			ur = (*USN_RECORD)(unsafe.Pointer(&data[i]))
			if ur.FileAttributes&FILE_ATTRIBUTE_DIRECTORY != 0 {
				nameLength := uintptr(ur.FileNameLength) / unsafe.Sizeof(ur.FileName[0])
				fnp := unsafe.Pointer(&data[i+uintptr(ur.FileNameOffset)])
				fn := (*[10000]uint16)(fnp)[:nameLength]
				(*reflect.SliceHeader)(unsafe.Pointer(&fn)).Cap = int(nameLength)
				// fmt.Println("len", ur.FileNameLength, ur.FileNameOffset, "fn", getFullPath(folders, ur.ParentFileReferenceNumber), syscall.UTF16ToString(fn), getUsnJournalReasonString(ur.Reason))
				ch <- ur
			}
		}
		rujd.StartUsn = usn
		if usn == 0 {
			return
		}
	}
}

// Main
func main() {
	folders := buildFolderMap()
	ch := make(chan *USN_RECORD)
	go processAvailableRecords(ch, folders)
	for {
		ur := <-ch
		fmt.Println("len", ur.FileNameLength, ur.FileNameOffset, "fn", getFullPath(folders, ur.ParentFileReferenceNumber), getUsnJournalReasonString(ur.Reason))
		// fmt.Println(r)
	}
}

type PathEvent struct {
	Path  string
	Flags uint32
	Eid   uint64
}

func WatchPaths(paths []string, eid int64) chan []PathEvent {
}

func Unwatch(ch chan []PathEvent) {
}