net/textproto: Handle multi-line responses

This is required for FTP and SMTP; maybe others.

R=rsc
CC=golang-dev
https://golang.org/cl/1892052

src/pkg/net/textproto/reader.go

@@ -155,28 +155,16 @@ func (r *Reader) ReadContinuedLineBytes() ([]byte, os.Error) {
 	return line, err
 }
 
-// ReadCodeLine reads a response code line of the form
-//	code message
-// where code is a 3-digit status code and the message
-// extends to the rest of the line.  An example of such a line is:
-//	220 plan9.bell-labs.com ESMTP
-//
-// If the prefix of the status does not match the digits in expectCode,
-// ReadCodeLine returns with err set to &Error{code, message}.
-// For example, if expectCode is 31, an error will be returned if
-// the status is not in the range [310,319].
-//
-// An expectCode <= 0 disables the check of the status code.
-//
-func (r *Reader) ReadCodeLine(expectCode int) (code int, message string, err os.Error) {
+func (r *Reader) readCodeLine(expectCode int) (code int, continued bool, message string, err os.Error) {
 	line, err := r.ReadLine()
 	if err != nil {
 		return
 	}
-	if len(line) < 4 || line[3] != ' ' {
+	if len(line) < 4 || line[3] != ' ' && line[3] != '-' {
 		err = ProtocolError("short response: " + line)
 		return
 	}
+	continued = line[3] == '-'
 	code, err = strconv.Atoi(line[0:3])
 	if err != nil || code < 100 {
 		err = ProtocolError("invalid response code: " + line)
@@ -191,6 +179,60 @@ func (r *Reader) ReadCodeLine(expectCode int) (code int, message string, err os.
 	return
 }
 
+// ReadCodeLine reads a response code line of the form
+//	code message
+// where code is a 3-digit status code and the message
+// extends to the rest of the line.  An example of such a line is:
+//	220 plan9.bell-labs.com ESMTP
+//
+// If the prefix of the status does not match the digits in expectCode,
+// ReadCodeLine returns with err set to &Error{code, message}.
+// For example, if expectCode is 31, an error will be returned if
+// the status is not in the range [310,319].
+//
+// If the response is multi-line, ReadCodeLine returns an error.
+//
+// An expectCode <= 0 disables the check of the status code.
+//
+func (r *Reader) ReadCodeLine(expectCode int) (code int, message string, err os.Error) {
+	code, continued, message, err := r.readCodeLine(expectCode)
+	if err == nil && continued {
+		err = ProtocolError("unexpected multi-line response: " + message)
+	}
+	return
+}
+
+// ReadResponse reads a multi-line response of the form
+//	code-message line 1
+//	code-message line 2
+//	...
+//	code message line n
+// where code is a 3-digit status code. Each line should have the same code.
+// The response is terminated by a line that uses a space between the code and
+// the message line rather than a dash. Each line in message is separated by
+// a newline (\n).
+//
+// If the prefix of the status does not match the digits in expectCode,
+// ReadResponse returns with err set to &Error{code, message}.
+// For example, if expectCode is 31, an error will be returned if
+// the status is not in the range [310,319].
+//
+// An expectCode <= 0 disables the check of the status code.
+//
+func (r *Reader) ReadResponse(expectCode int) (code int, message string, err os.Error) {
+	code, continued, message, err := r.readCodeLine(expectCode)
+	for err == nil && continued {
+		var code2 int
+		var moreMessage string
+		code2, continued, moreMessage, err = r.readCodeLine(expectCode)
+		if code != code2 {
+			err = ProtocolError("status code mismatch: " + strconv.Itoa(code) + ", " + strconv.Itoa(code2))
+		}
+		message += "\n" + moreMessage
+	}
+	return
+}
+
 // DotReader returns a new Reader that satisfies Reads using the
 // decoded text of a dot-encoded block read from r.
 // The returned Reader is only valid until the next call