Add base64 encoding for S/MIME

b64/b64.go

@@ -0,0 +1,78 @@
+//Package b64 encodes base64 and does formating for S/MIME
+package b64
+
+import (
+	"bytes"
+	"encoding/base64"
+	"io"
+)
+
+// From https://golang.org/src/encoding/pem/pem.go
+
+//Takes an byteslice and outputs the base64 encoded version with linebreaks. The constant PemLineLength defines the lenght of the lines.
+func EncodeBase64(in []byte) ([]byte, error) {
+
+	var buf bytes.Buffer
+	var breaker lineBreaker
+	breaker.out = &buf
+
+	b64 := base64.NewEncoder(base64.StdEncoding, &breaker)
+	if _, err := b64.Write(in); err != nil {
+		return nil, err
+	}
+	b64.Close()
+	breaker.Close()
+
+	return buf.Bytes(), nil
+
+}
+
+//Lenght of the lines in the output of the function EncodeBase64.
+const PemLineLength = 64
+
+type lineBreaker struct {
+	line [PemLineLength]byte
+	used int
+	out  io.Writer
+}
+
+var nl = []byte{'\n'}
+
+func (l *lineBreaker) Write(b []byte) (n int, err error) {
+	if l.used+len(b) < PemLineLength {
+		copy(l.line[l.used:], b)
+		l.used += len(b)
+		return len(b), nil
+	}
+
+	n, err = l.out.Write(l.line[0:l.used])
+	if err != nil {
+		return
+	}
+	excess := PemLineLength - l.used
+	l.used = 0
+
+	n, err = l.out.Write(b[0:excess])
+	if err != nil {
+		return
+	}
+
+	n, err = l.out.Write(nl)
+	if err != nil {
+		return
+	}
+
+	return l.Write(b[excess:])
+}
+
+func (l *lineBreaker) Close() (err error) {
+	if l.used > 0 {
+		_, err = l.out.Write(l.line[0:l.used])
+		if err != nil {
+			return
+		}
+		_, err = l.out.Write(nl)
+	}
+
+	return
+}