1 files changed, 266 insertions, 0 deletions
diff --git a/Godeps/_workspace/src/github.com/microsoft/go-winio/backup.go b/Godeps/_workspace/src/github.com/microsoft/go-winio/backup.go
new file mode 100644
index 000000000..864935175
--- /dev/null
+++ b/Godeps/_workspace/src/github.com/microsoft/go-winio/backup.go
@@ -0,0 +1,266 @@
+package winio
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"runtime"
+	"syscall"
+	"unicode/utf16"
+)
+
+//sys backupRead(h syscall.Handle, b []byte, bytesRead *uint32, abort bool, processSecurity bool, context *uintptr) (err error) = BackupRead
+//sys backupWrite(h syscall.Handle, b []byte, bytesWritten *uint32, abort bool, processSecurity bool, context *uintptr) (err error) = BackupWrite
+
+const (
+	BackupData = uint32(iota + 1)
+	BackupEaData
+	BackupSecurity
+	BackupAlternateData
+	BackupLink
+	BackupPropertyData
+	BackupObjectId
+	BackupReparseData
+	BackupSparseBlock
+	BackupTxfsData
+)
+
+const (
+	StreamSparseAttributes = uint32(8)
+)
+
+const (
+	WRITE_DAC              = 0x40000
+	WRITE_OWNER            = 0x80000
+	ACCESS_SYSTEM_SECURITY = 0x1000000
+)
+
+// BackupHeader represents a backup stream of a file.
+type BackupHeader struct {
+	Id         uint32 // The backup stream ID
+	Attributes uint32 // Stream attributes
+	Size       int64  // The size of the stream in bytes
+	Name       string // The name of the stream (for BackupAlternateData only).
+	Offset     int64  // The offset of the stream in the file (for BackupSparseBlock only).
+}
+
+type win32StreamId struct {
+	StreamId   uint32
+	Attributes uint32
+	Size       uint64
+	NameSize   uint32
+}
+
+// BackupStreamReader reads from a stream produced by the BackupRead Win32 API and produces a series
+// of BackupHeader values.
+type BackupStreamReader struct {
+	r         io.Reader
+	bytesLeft int64
+}
+
+// NewBackupStreamReader produces a BackupStreamReader from any io.Reader.
+func NewBackupStreamReader(r io.Reader) *BackupStreamReader {
+	return &BackupStreamReader{r, 0}
+}
+
+// Next returns the next backup stream and prepares for calls to Write(). It skips the remainder of the current stream if
+// it was not completely read.
+func (r *BackupStreamReader) Next() (*BackupHeader, error) {
+	if r.bytesLeft > 0 {
+		if _, err := io.Copy(ioutil.Discard, r); err != nil {
+			return nil, err
+		}
+	}
+	var wsi win32StreamId
+	if err := binary.Read(r.r, binary.LittleEndian, &wsi); err != nil {
+		return nil, err
+	}
+	hdr := &BackupHeader{
+		Id:         wsi.StreamId,
+		Attributes: wsi.Attributes,
+		Size:       int64(wsi.Size),
+	}
+	if wsi.NameSize != 0 {
+		name := make([]uint16, int(wsi.NameSize/2))
+		if err := binary.Read(r.r, binary.LittleEndian, name); err != nil {
+			return nil, err
+		}
+		hdr.Name = syscall.UTF16ToString(name)
+	}
+	if wsi.StreamId == BackupSparseBlock {
+		if err := binary.Read(r.r, binary.LittleEndian, &hdr.Offset); err != nil {
+			return nil, err
+		}
+		hdr.Size -= 8
+	}
+	r.bytesLeft = hdr.Size
+	return hdr, nil
+}
+
+// Read reads from the current backup stream.
+func (r *BackupStreamReader) Read(b []byte) (int, error) {
+	if r.bytesLeft == 0 {
+		return 0, io.EOF
+	}
+	if int64(len(b)) > r.bytesLeft {
+		b = b[:r.bytesLeft]
+	}
+	n, err := r.r.Read(b)
+	r.bytesLeft -= int64(n)
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	} else if r.bytesLeft == 0 && err == nil {
+		err = io.EOF
+	}
+	return n, err
+}
+
+// BackupStreamWriter writes a stream compatible with the BackupWrite Win32 API.
+type BackupStreamWriter struct {
+	w         io.Writer
+	bytesLeft int64
+}
+
+// NewBackupStreamWriter produces a BackupStreamWriter on top of an io.Writer.
+func NewBackupStreamWriter(w io.Writer) *BackupStreamWriter {
+	return &BackupStreamWriter{w, 0}
+}
+
+// WriteHeader writes the next backup stream header and prepares for calls to Write().
+func (w *BackupStreamWriter) WriteHeader(hdr *BackupHeader) error {
+	if w.bytesLeft != 0 {
+		return fmt.Errorf("missing %d bytes", w.bytesLeft)
+	}
+	name := utf16.Encode([]rune(hdr.Name))
+	wsi := win32StreamId{
+		StreamId:   hdr.Id,
+		Attributes: hdr.Attributes,
+		Size:       uint64(hdr.Size),
+		NameSize:   uint32(len(name) * 2),
+	}
+	if hdr.Id == BackupSparseBlock {
+		// Include space for the int64 block offset
+		wsi.Size += 8
+	}
+	if err := binary.Write(w.w, binary.LittleEndian, &wsi); err != nil {
+		return err
+	}
+	if len(name) != 0 {
+		if err := binary.Write(w.w, binary.LittleEndian, name); err != nil {
+			return err
+		}
+	}
+	if hdr.Id == BackupSparseBlock {
+		if err := binary.Write(w.w, binary.LittleEndian, hdr.Offset); err != nil {
+			return err
+		}
+	}
+	w.bytesLeft = hdr.Size
+	return nil
+}
+
+// Write writes to the current backup stream.
+func (w *BackupStreamWriter) Write(b []byte) (int, error) {
+	if w.bytesLeft < int64(len(b)) {
+		return 0, fmt.Errorf("too many bytes by %d", int64(len(b))-w.bytesLeft)
+	}
+	n, err := w.w.Write(b)
+	w.bytesLeft -= int64(n)
+	return n, err
+}
+
+// BackupFileReader provides an io.ReadCloser interface on top of the BackupRead Win32 API.
+type BackupFileReader struct {
+	f               *os.File
+	includeSecurity bool
+	ctx             uintptr
+}
+
+// NewBackupFileReader returns a new BackupFileReader from a file handle. If includeSecurity is true,
+// Read will attempt to read the security descriptor of the file.
+func NewBackupFileReader(f *os.File, includeSecurity bool) *BackupFileReader {
+	r := &BackupFileReader{f, includeSecurity, 0}
+	runtime.SetFinalizer(r, func(r *BackupFileReader) { r.Close() })
+	return r
+}
+
+// Read reads a backup stream from the file by calling the Win32 API BackupRead().
+func (r *BackupFileReader) Read(b []byte) (int, error) {
+	var bytesRead uint32
+	err := backupRead(syscall.Handle(r.f.Fd()), b, &bytesRead, false, r.includeSecurity, &r.ctx)
+	if err != nil {
+		return 0, &os.PathError{"BackupRead", r.f.Name(), err}
+	}
+	if bytesRead == 0 {
+		return 0, io.EOF
+	}
+	return int(bytesRead), nil
+}
+
+// Close frees Win32 resources associated with the BackupFileReader. It does not close
+// the underlying file.
+func (r *BackupFileReader) Close() error {
+	if r.ctx != 0 {
+		backupRead(syscall.Handle(r.f.Fd()), nil, nil, true, false, &r.ctx)
+		r.ctx = 0
+	}
+	return nil
+}
+
+// BackupFileWriter provides an io.WriteCloser interface on top of the BackupWrite Win32 API.
+type BackupFileWriter struct {
+	f               *os.File
+	includeSecurity bool
+	ctx             uintptr
+}
+
+// NewBackupFileWrtier returns a new BackupFileWriter from a file handle. If includeSecurity is true,
+// Write() will attempt to restore the security descriptor from the stream.
+func NewBackupFileWriter(f *os.File, includeSecurity bool) *BackupFileWriter {
+	w := &BackupFileWriter{f, includeSecurity, 0}
+	runtime.SetFinalizer(w, func(w *BackupFileWriter) { w.Close() })
+	return w
+}
+
+// Write restores a portion of the file using the provided backup stream.
+func (w *BackupFileWriter) Write(b []byte) (int, error) {
+	var bytesWritten uint32
+	err := backupWrite(syscall.Handle(w.f.Fd()), b, &bytesWritten, false, w.includeSecurity, &w.ctx)
+	if err != nil {
+		return 0, &os.PathError{"BackupWrite", w.f.Name(), err}
+	}
+	if int(bytesWritten) != len(b) {
+		return int(bytesWritten), errors.New("not all bytes could be written")
+	}
+	return len(b), nil
+}
+
+// Close frees Win32 resources associated with the BackupFileWriter. It does not
+// close the underlying file.
+func (w *BackupFileWriter) Close() error {
+	if w.ctx != 0 {
+		backupWrite(syscall.Handle(w.f.Fd()), nil, nil, true, false, &w.ctx)
+		w.ctx = 0
+	}
+	return nil
+}
+
+// OpenForBackup opens a file or directory, potentially skipping access checks if the backup
+// or restore privileges have been acquired.
+//
+// If the file opened was a directory, it cannot be used with Readdir().
+func OpenForBackup(path string, access uint32, share uint32, createmode uint32) (*os.File, error) {
+	winPath, err := syscall.UTF16FromString(path)
+	if err != nil {
+		return nil, err
+	}
+	h, err := syscall.CreateFile(&winPath[0], access, share, nil, createmode, syscall.FILE_FLAG_BACKUP_SEMANTICS, 0)
+	if err != nil {
+		err = &os.PathError{Op: "open", Path: path, Err: err}
+		return nil, err
+	}
+	return os.NewFile(uintptr(h), path), nil
+}