add vendoring

vendor/github.com/jhillyerd/enmime/internal/stringutil/wrap.go

@@ -0,0 +1,36 @@
+package stringutil
+
+// Wrap builds a byte slice from strs, wrapping on word boundaries before max chars
+func Wrap(max int, strs ...string) []byte {
+	input := make([]byte, 0)
+	output := make([]byte, 0)
+	for _, s := range strs {
+		input = append(input, []byte(s)...)
+	}
+	if len(input) < max {
+		// Doesn't need to be wrapped
+		return input
+	}
+	ls := -1 // Last seen space index
+	lw := -1 // Last written byte index
+	ll := 0  // Length of current line
+	for i := 0; i < len(input); i++ {
+		ll++
+		switch input[i] {
+		case ' ', '\t':
+			ls = i
+		}
+		if ll >= max {
+			if ls >= 0 {
+				output = append(output, input[lw+1:ls]...)
+				output = append(output, '\r', '\n', ' ')
+				lw = ls // Jump over the space we broke on
+				ll = 1  // Count leading space above
+				// Rewind
+				i = lw + 1
+				ls = -1
+			}
+		}
+	}
+	return append(output, input[lw+1:]...)
+}