1package moxio

2

3import (

4 "encoding/base64"

5 "io"

6)

7

8// implement io.Closer

9type closerFunc func() error

10

11func (f closerFunc) Close() error {

12 return f()

13}

14

15// Base64Writer turns a writer for data into one that writes base64 content on

16// \r\n separated lines of max 76+2 characters length.

17func Base64Writer(w io.Writer) io.WriteCloser {

18 lw := &lineWrapper{w: w}

19 bw := base64.NewEncoder(base64.StdEncoding, lw)

20 return struct {

21 io.Writer

22 io.Closer

23 }{

24 Writer: bw,

25 Closer: closerFunc(func() error {

26 if err := bw.Close(); err != nil {

27 return err

28 }

29 return lw.Close()

30 }),

31 }

32}

33

34type lineWrapper struct {

35 w io.Writer

36 n int // Written on current line.

37}

38

39func (lw *lineWrapper) Write(buf []byte) (int, error) {

40 wrote := 0

41 for len(buf) > 0 {

42 // base64 has max 76 data bytes on per line. ../rfc/2045:1372

43 n := min(76-lw.n, len(buf))

44 nn, err := lw.w.Write(buf[:n])

45 if nn > 0 {

46 wrote += nn

47 buf = buf[nn:]

48 }

49 if err != nil {

50 return wrote, err

51 }

52 lw.n += nn

53 if lw.n == 76 {

54 _, err := lw.w.Write([]byte("\r\n"))

55 if err != nil {

56 return wrote, err

57 }

58 lw.n = 0

59 }

60 }

61 return wrote, nil

62}

63

64func (lw *lineWrapper) Close() error {

65 if lw.n > 0 {

66 lw.n = 0

67 _, err := lw.w.Write([]byte("\r\n"))

68 return err

69 }

70 return nil

71}

72