Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

8 files changed, 1753 insertions, 0 deletions

diff --git a/src/net/textproto/header.go b/src/net/textproto/header.go
new file mode 100644
index 0000000..a58df7a
--- /dev/null
+++ b/src/net/textproto/header.go
@@ -0,0 +1,56 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+// A MIMEHeader represents a MIME-style header mapping
+// keys to sets of values.
+type MIMEHeader map[string][]string
+
+// Add adds the key, value pair to the header.
+// It appends to any existing values associated with key.
+func (h MIMEHeader) Add(key, value string) {
+	key = CanonicalMIMEHeaderKey(key)
+	h[key] = append(h[key], value)
+}
+
+// Set sets the header entries associated with key to
+// the single element value. It replaces any existing
+// values associated with key.
+func (h MIMEHeader) Set(key, value string) {
+	h[CanonicalMIMEHeaderKey(key)] = []string{value}
+}
+
+// Get gets the first value associated with the given key.
+// It is case insensitive; CanonicalMIMEHeaderKey is used
+// to canonicalize the provided key.
+// If there are no values associated with the key, Get returns "".
+// To use non-canonical keys, access the map directly.
+func (h MIMEHeader) Get(key string) string {
+	if h == nil {
+		return ""
+	}
+	v := h[CanonicalMIMEHeaderKey(key)]
+	if len(v) == 0 {
+		return ""
+	}
+	return v[0]
+}
+
+// Values returns all values associated with the given key.
+// It is case insensitive; CanonicalMIMEHeaderKey is
+// used to canonicalize the provided key. To use non-canonical
+// keys, access the map directly.
+// The returned slice is not a copy.
+func (h MIMEHeader) Values(key string) []string {
+	if h == nil {
+		return nil
+	}
+	return h[CanonicalMIMEHeaderKey(key)]
+}
+
+// Del deletes the values associated with key.
+func (h MIMEHeader) Del(key string) {
+	delete(h, CanonicalMIMEHeaderKey(key))
+}
diff --git a/src/net/textproto/header_test.go b/src/net/textproto/header_test.go
new file mode 100644
index 0000000..de9405c
--- /dev/null
+++ b/src/net/textproto/header_test.go
@@ -0,0 +1,54 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import "testing"
+
+type canonicalHeaderKeyTest struct {
+	in, out string
+}
+
+var canonicalHeaderKeyTests = []canonicalHeaderKeyTest{
+	{"a-b-c", "A-B-C"},
+	{"a-1-c", "A-1-C"},
+	{"User-Agent", "User-Agent"},
+	{"uSER-aGENT", "User-Agent"},
+	{"user-agent", "User-Agent"},
+	{"USER-AGENT", "User-Agent"},
+
+	// Other valid tchar bytes in tokens:
+	{"foo-bar_baz", "Foo-Bar_baz"},
+	{"foo-bar$baz", "Foo-Bar$baz"},
+	{"foo-bar~baz", "Foo-Bar~baz"},
+	{"foo-bar*baz", "Foo-Bar*baz"},
+
+	// Non-ASCII or anything with spaces or non-token chars is unchanged:
+	{"üser-agenT", "üser-agenT"},
+	{"a B", "a B"},
+
+	// This caused a panic due to mishandling of a space:
+	{"C Ontent-Transfer-Encoding", "C Ontent-Transfer-Encoding"},
+	{"foo bar", "foo bar"},
+}
+
+func TestCanonicalMIMEHeaderKey(t *testing.T) {
+	for _, tt := range canonicalHeaderKeyTests {
+		if s := CanonicalMIMEHeaderKey(tt.in); s != tt.out {
+			t.Errorf("CanonicalMIMEHeaderKey(%q) = %q, want %q", tt.in, s, tt.out)
+		}
+	}
+}
+
+// Issue #34799 add a Header method to get multiple values []string, with canonicalized key
+func TestMIMEHeaderMultipleValues(t *testing.T) {
+	testHeader := MIMEHeader{
+		"Set-Cookie": {"cookie 1", "cookie 2"},
+	}
+	values := testHeader.Values("set-cookie")
+	n := len(values)
+	if n != 2 {
+		t.Errorf("count: %d; want 2", n)
+	}
+}
diff --git a/src/net/textproto/pipeline.go b/src/net/textproto/pipeline.go
new file mode 100644
index 0000000..1928a30
--- /dev/null
+++ b/src/net/textproto/pipeline.go
@@ -0,0 +1,118 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"sync"
+)
+
+// A Pipeline manages a pipelined in-order request/response sequence.
+//
+// To use a Pipeline p to manage multiple clients on a connection,
+// each client should run:
+//
+//	id := p.Next()	// take a number
+//
+//	p.StartRequest(id)	// wait for turn to send request
+//	«send request»
+//	p.EndRequest(id)	// notify Pipeline that request is sent
+//
+//	p.StartResponse(id)	// wait for turn to read response
+//	«read response»
+//	p.EndResponse(id)	// notify Pipeline that response is read
+//
+// A pipelined server can use the same calls to ensure that
+// responses computed in parallel are written in the correct order.
+type Pipeline struct {
+	mu       sync.Mutex
+	id       uint
+	request  sequencer
+	response sequencer
+}
+
+// Next returns the next id for a request/response pair.
+func (p *Pipeline) Next() uint {
+	p.mu.Lock()
+	id := p.id
+	p.id++
+	p.mu.Unlock()
+	return id
+}
+
+// StartRequest blocks until it is time to send (or, if this is a server, receive)
+// the request with the given id.
+func (p *Pipeline) StartRequest(id uint) {
+	p.request.Start(id)
+}
+
+// EndRequest notifies p that the request with the given id has been sent
+// (or, if this is a server, received).
+func (p *Pipeline) EndRequest(id uint) {
+	p.request.End(id)
+}
+
+// StartResponse blocks until it is time to receive (or, if this is a server, send)
+// the request with the given id.
+func (p *Pipeline) StartResponse(id uint) {
+	p.response.Start(id)
+}
+
+// EndResponse notifies p that the response with the given id has been received
+// (or, if this is a server, sent).
+func (p *Pipeline) EndResponse(id uint) {
+	p.response.End(id)
+}
+
+// A sequencer schedules a sequence of numbered events that must
+// happen in order, one after the other. The event numbering must start
+// at 0 and increment without skipping. The event number wraps around
+// safely as long as there are not 2^32 simultaneous events pending.
+type sequencer struct {
+	mu   sync.Mutex
+	id   uint
+	wait map[uint]chan struct{}
+}
+
+// Start waits until it is time for the event numbered id to begin.
+// That is, except for the first event, it waits until End(id-1) has
+// been called.
+func (s *sequencer) Start(id uint) {
+	s.mu.Lock()
+	if s.id == id {
+		s.mu.Unlock()
+		return
+	}
+	c := make(chan struct{})
+	if s.wait == nil {
+		s.wait = make(map[uint]chan struct{})
+	}
+	s.wait[id] = c
+	s.mu.Unlock()
+	<-c
+}
+
+// End notifies the sequencer that the event numbered id has completed,
+// allowing it to schedule the event numbered id+1.  It is a run-time error
+// to call End with an id that is not the number of the active event.
+func (s *sequencer) End(id uint) {
+	s.mu.Lock()
+	if s.id != id {
+		s.mu.Unlock()
+		panic("out of sync")
+	}
+	id++
+	s.id = id
+	if s.wait == nil {
+		s.wait = make(map[uint]chan struct{})
+	}
+	c, ok := s.wait[id]
+	if ok {
+		delete(s.wait, id)
+	}
+	s.mu.Unlock()
+	if ok {
+		close(c)
+	}
+}
diff --git a/src/net/textproto/reader.go b/src/net/textproto/reader.go
new file mode 100644
index 0000000..5c3084f
--- /dev/null
+++ b/src/net/textproto/reader.go
@@ -0,0 +1,800 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+// A Reader implements convenience methods for reading requests
+// or responses from a text protocol network connection.
+type Reader struct {
+	R   *bufio.Reader
+	dot *dotReader
+	buf []byte // a re-usable buffer for readContinuedLineSlice
+}
+
+// NewReader returns a new Reader reading from r.
+//
+// To avoid denial of service attacks, the provided bufio.Reader
+// should be reading from an io.LimitReader or similar Reader to bound
+// the size of responses.
+func NewReader(r *bufio.Reader) *Reader {
+	commonHeaderOnce.Do(initCommonHeader)
+	return &Reader{R: r}
+}
+
+// ReadLine reads a single line from r,
+// eliding the final \n or \r\n from the returned string.
+func (r *Reader) ReadLine() (string, error) {
+	line, err := r.readLineSlice()
+	return string(line), err
+}
+
+// ReadLineBytes is like ReadLine but returns a []byte instead of a string.
+func (r *Reader) ReadLineBytes() ([]byte, error) {
+	line, err := r.readLineSlice()
+	if line != nil {
+		buf := make([]byte, len(line))
+		copy(buf, line)
+		line = buf
+	}
+	return line, err
+}
+
+func (r *Reader) readLineSlice() ([]byte, error) {
+	r.closeDot()
+	var line []byte
+	for {
+		l, more, err := r.R.ReadLine()
+		if err != nil {
+			return nil, err
+		}
+		// Avoid the copy if the first call produced a full line.
+		if line == nil && !more {
+			return l, nil
+		}
+		line = append(line, l...)
+		if !more {
+			break
+		}
+	}
+	return line, nil
+}
+
+// ReadContinuedLine reads a possibly continued line from r,
+// eliding the final trailing ASCII white space.
+// Lines after the first are considered continuations if they
+// begin with a space or tab character. In the returned data,
+// continuation lines are separated from the previous line
+// only by a single space: the newline and leading white space
+// are removed.
+//
+// For example, consider this input:
+//
+//	Line 1
+//	  continued...
+//	Line 2
+//
+// The first call to ReadContinuedLine will return "Line 1 continued..."
+// and the second will return "Line 2".
+//
+// Empty lines are never continued.
+//
+func (r *Reader) ReadContinuedLine() (string, error) {
+	line, err := r.readContinuedLineSlice(noValidation)
+	return string(line), err
+}
+
+// trim returns s with leading and trailing spaces and tabs removed.
+// It does not assume Unicode or UTF-8.
+func trim(s []byte) []byte {
+	i := 0
+	for i < len(s) && (s[i] == ' ' || s[i] == '\t') {
+		i++
+	}
+	n := len(s)
+	for n > i && (s[n-1] == ' ' || s[n-1] == '\t') {
+		n--
+	}
+	return s[i:n]
+}
+
+// ReadContinuedLineBytes is like ReadContinuedLine but
+// returns a []byte instead of a string.
+func (r *Reader) ReadContinuedLineBytes() ([]byte, error) {
+	line, err := r.readContinuedLineSlice(noValidation)
+	if line != nil {
+		buf := make([]byte, len(line))
+		copy(buf, line)
+		line = buf
+	}
+	return line, err
+}
+
+// readContinuedLineSlice reads continued lines from the reader buffer,
+// returning a byte slice with all lines. The validateFirstLine function
+// is run on the first read line, and if it returns an error then this
+// error is returned from readContinuedLineSlice.
+func (r *Reader) readContinuedLineSlice(validateFirstLine func([]byte) error) ([]byte, error) {
+	if validateFirstLine == nil {
+		return nil, fmt.Errorf("missing validateFirstLine func")
+	}
+
+	// Read the first line.
+	line, err := r.readLineSlice()
+	if err != nil {
+		return nil, err
+	}
+	if len(line) == 0 { // blank line - no continuation
+		return line, nil
+	}
+
+	if err := validateFirstLine(line); err != nil {
+		return nil, err
+	}
+
+	// Optimistically assume that we have started to buffer the next line
+	// and it starts with an ASCII letter (the next header key), or a blank
+	// line, so we can avoid copying that buffered data around in memory
+	// and skipping over non-existent whitespace.
+	if r.R.Buffered() > 1 {
+		peek, _ := r.R.Peek(2)
+		if len(peek) > 0 && (isASCIILetter(peek[0]) || peek[0] == '\n') ||
+			len(peek) == 2 && peek[0] == '\r' && peek[1] == '\n' {
+			return trim(line), nil
+		}
+	}
+
+	// ReadByte or the next readLineSlice will flush the read buffer;
+	// copy the slice into buf.
+	r.buf = append(r.buf[:0], trim(line)...)
+
+	// Read continuation lines.
+	for r.skipSpace() > 0 {
+		line, err := r.readLineSlice()
+		if err != nil {
+			break
+		}
+		r.buf = append(r.buf, ' ')
+		r.buf = append(r.buf, trim(line)...)
+	}
+	return r.buf, nil
+}
+
+// skipSpace skips R over all spaces and returns the number of bytes skipped.
+func (r *Reader) skipSpace() int {
+	n := 0
+	for {
+		c, err := r.R.ReadByte()
+		if err != nil {
+			// Bufio will keep err until next read.
+			break
+		}
+		if c != ' ' && c != '\t' {
+			r.R.UnreadByte()
+			break
+		}
+		n++
+	}
+	return n
+}
+
+func (r *Reader) readCodeLine(expectCode int) (code int, continued bool, message string, err error) {
+	line, err := r.ReadLine()
+	if err != nil {
+		return
+	}
+	return parseCodeLine(line, expectCode)
+}
+
+func parseCodeLine(line string, expectCode int) (code int, continued bool, message string, err error) {
+	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)
+		return
+	}
+	message = line[4:]
+	if 1 <= expectCode && expectCode < 10 && code/100 != expectCode ||
+		10 <= expectCode && expectCode < 100 && code/10 != expectCode ||
+		100 <= expectCode && expectCode < 1000 && code != expectCode {
+		err = &Error{code, message}
+	}
+	return
+}
+
+// ReadCodeLine reads a response code line of the form
+//	code message
+// where code is a three-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 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 three-digit status code. The first line starts with the
+// code and a hyphen. The response is terminated by a line that starts
+// with the same code followed by a space. Each line in message is
+// separated by a newline (\n).
+//
+// See page 36 of RFC 959 (https://www.ietf.org/rfc/rfc959.txt) for
+// details of another form of response accepted:
+//
+//  code-message line 1
+//  message line 2
+//  ...
+//  code message line 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 error) {
+	code, continued, message, err := r.readCodeLine(expectCode)
+	multi := continued
+	for continued {
+		line, err := r.ReadLine()
+		if err != nil {
+			return 0, "", err
+		}
+
+		var code2 int
+		var moreMessage string
+		code2, continued, moreMessage, err = parseCodeLine(line, 0)
+		if err != nil || code2 != code {
+			message += "\n" + strings.TrimRight(line, "\r\n")
+			continued = true
+			continue
+		}
+		message += "\n" + moreMessage
+	}
+	if err != nil && multi && message != "" {
+		// replace one line error message with all lines (full message)
+		err = &Error{code, message}
+	}
+	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
+// to a method on r.
+//
+// Dot encoding is a common framing used for data blocks
+// in text protocols such as SMTP.  The data consists of a sequence
+// of lines, each of which ends in "\r\n".  The sequence itself
+// ends at a line containing just a dot: ".\r\n".  Lines beginning
+// with a dot are escaped with an additional dot to avoid
+// looking like the end of the sequence.
+//
+// The decoded form returned by the Reader's Read method
+// rewrites the "\r\n" line endings into the simpler "\n",
+// removes leading dot escapes if present, and stops with error io.EOF
+// after consuming (and discarding) the end-of-sequence line.
+func (r *Reader) DotReader() io.Reader {
+	r.closeDot()
+	r.dot = &dotReader{r: r}
+	return r.dot
+}
+
+type dotReader struct {
+	r     *Reader
+	state int
+}
+
+// Read satisfies reads by decoding dot-encoded data read from d.r.
+func (d *dotReader) Read(b []byte) (n int, err error) {
+	// Run data through a simple state machine to
+	// elide leading dots, rewrite trailing \r\n into \n,
+	// and detect ending .\r\n line.
+	const (
+		stateBeginLine = iota // beginning of line; initial state; must be zero
+		stateDot              // read . at beginning of line
+		stateDotCR            // read .\r at beginning of line
+		stateCR               // read \r (possibly at end of line)
+		stateData             // reading data in middle of line
+		stateEOF              // reached .\r\n end marker line
+	)
+	br := d.r.R
+	for n < len(b) && d.state != stateEOF {
+		var c byte
+		c, err = br.ReadByte()
+		if err != nil {
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
+			break
+		}
+		switch d.state {
+		case stateBeginLine:
+			if c == '.' {
+				d.state = stateDot
+				continue
+			}
+			if c == '\r' {
+				d.state = stateCR
+				continue
+			}
+			d.state = stateData
+
+		case stateDot:
+			if c == '\r' {
+				d.state = stateDotCR
+				continue
+			}
+			if c == '\n' {
+				d.state = stateEOF
+				continue
+			}
+			d.state = stateData
+
+		case stateDotCR:
+			if c == '\n' {
+				d.state = stateEOF
+				continue
+			}
+			// Not part of .\r\n.
+			// Consume leading dot and emit saved \r.
+			br.UnreadByte()
+			c = '\r'
+			d.state = stateData
+
+		case stateCR:
+			if c == '\n' {
+				d.state = stateBeginLine
+				break
+			}
+			// Not part of \r\n. Emit saved \r
+			br.UnreadByte()
+			c = '\r'
+			d.state = stateData
+
+		case stateData:
+			if c == '\r' {
+				d.state = stateCR
+				continue
+			}
+			if c == '\n' {
+				d.state = stateBeginLine
+			}
+		}
+		b[n] = c
+		n++
+	}
+	if err == nil && d.state == stateEOF {
+		err = io.EOF
+	}
+	if err != nil && d.r.dot == d {
+		d.r.dot = nil
+	}
+	return
+}
+
+// closeDot drains the current DotReader if any,
+// making sure that it reads until the ending dot line.
+func (r *Reader) closeDot() {
+	if r.dot == nil {
+		return
+	}
+	buf := make([]byte, 128)
+	for r.dot != nil {
+		// When Read reaches EOF or an error,
+		// it will set r.dot == nil.
+		r.dot.Read(buf)
+	}
+}
+
+// ReadDotBytes reads a dot-encoding and returns the decoded data.
+//
+// See the documentation for the DotReader method for details about dot-encoding.
+func (r *Reader) ReadDotBytes() ([]byte, error) {
+	return io.ReadAll(r.DotReader())
+}
+
+// ReadDotLines reads a dot-encoding and returns a slice
+// containing the decoded lines, with the final \r\n or \n elided from each.
+//
+// See the documentation for the DotReader method for details about dot-encoding.
+func (r *Reader) ReadDotLines() ([]string, error) {
+	// We could use ReadDotBytes and then Split it,
+	// but reading a line at a time avoids needing a
+	// large contiguous block of memory and is simpler.
+	var v []string
+	var err error
+	for {
+		var line string
+		line, err = r.ReadLine()
+		if err != nil {
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
+			break
+		}
+
+		// Dot by itself marks end; otherwise cut one dot.
+		if len(line) > 0 && line[0] == '.' {
+			if len(line) == 1 {
+				break
+			}
+			line = line[1:]
+		}
+		v = append(v, line)
+	}
+	return v, err
+}
+
+// ReadMIMEHeader reads a MIME-style header from r.
+// The header is a sequence of possibly continued Key: Value lines
+// ending in a blank line.
+// The returned map m maps CanonicalMIMEHeaderKey(key) to a
+// sequence of values in the same order encountered in the input.
+//
+// For example, consider this input:
+//
+//	My-Key: Value 1
+//	Long-Key: Even
+//	       Longer Value
+//	My-Key: Value 2
+//
+// Given that input, ReadMIMEHeader returns the map:
+//
+//	map[string][]string{
+//		"My-Key": {"Value 1", "Value 2"},
+//		"Long-Key": {"Even Longer Value"},
+//	}
+//
+func (r *Reader) ReadMIMEHeader() (MIMEHeader, error) {
+	// Avoid lots of small slice allocations later by allocating one
+	// large one ahead of time which we'll cut up into smaller
+	// slices. If this isn't big enough later, we allocate small ones.
+	var strs []string
+	hint := r.upcomingHeaderNewlines()
+	if hint > 0 {
+		strs = make([]string, hint)
+	}
+
+	m := make(MIMEHeader, hint)
+
+	// The first line cannot start with a leading space.
+	if buf, err := r.R.Peek(1); err == nil && (buf[0] == ' ' || buf[0] == '\t') {
+		line, err := r.readLineSlice()
+		if err != nil {
+			return m, err
+		}
+		return m, ProtocolError("malformed MIME header initial line: " + string(line))
+	}
+
+	for {
+		kv, err := r.readContinuedLineSlice(mustHaveFieldNameColon)
+		if len(kv) == 0 {
+			return m, err
+		}
+
+		// Key ends at first colon.
+		i := bytes.IndexByte(kv, ':')
+		if i < 0 {
+			return m, ProtocolError("malformed MIME header line: " + string(kv))
+		}
+		key := canonicalMIMEHeaderKey(kv[:i])
+
+		// As per RFC 7230 field-name is a token, tokens consist of one or more chars.
+		// We could return a ProtocolError here, but better to be liberal in what we
+		// accept, so if we get an empty key, skip it.
+		if key == "" {
+			continue
+		}
+
+		// Skip initial spaces in value.
+		i++ // skip colon
+		for i < len(kv) && (kv[i] == ' ' || kv[i] == '\t') {
+			i++
+		}
+		value := string(kv[i:])
+
+		vv := m[key]
+		if vv == nil && len(strs) > 0 {
+			// More than likely this will be a single-element key.
+			// Most headers aren't multi-valued.
+			// Set the capacity on strs[0] to 1, so any future append
+			// won't extend the slice into the other strings.
+			vv, strs = strs[:1:1], strs[1:]
+			vv[0] = value
+			m[key] = vv
+		} else {
+			m[key] = append(vv, value)
+		}
+
+		if err != nil {
+			return m, err
+		}
+	}
+}
+
+// noValidation is a no-op validation func for readContinuedLineSlice
+// that permits any lines.
+func noValidation(_ []byte) error { return nil }
+
+// mustHaveFieldNameColon ensures that, per RFC 7230, the
+// field-name is on a single line, so the first line must
+// contain a colon.
+func mustHaveFieldNameColon(line []byte) error {
+	if bytes.IndexByte(line, ':') < 0 {
+		return ProtocolError(fmt.Sprintf("malformed MIME header: missing colon: %q", line))
+	}
+	return nil
+}
+
+// upcomingHeaderNewlines returns an approximation of the number of newlines
+// that will be in this header. If it gets confused, it returns 0.
+func (r *Reader) upcomingHeaderNewlines() (n int) {
+	// Try to determine the 'hint' size.
+	r.R.Peek(1) // force a buffer load if empty
+	s := r.R.Buffered()
+	if s == 0 {
+		return
+	}
+	peek, _ := r.R.Peek(s)
+	for len(peek) > 0 {
+		i := bytes.IndexByte(peek, '\n')
+		if i < 3 {
+			// Not present (-1) or found within the next few bytes,
+			// implying we're at the end ("\r\n\r\n" or "\n\n")
+			return
+		}
+		n++
+		peek = peek[i+1:]
+	}
+	return
+}
+
+// CanonicalMIMEHeaderKey returns the canonical format of the
+// MIME header key s. The canonicalization converts the first
+// letter and any letter following a hyphen to upper case;
+// the rest are converted to lowercase. For example, the
+// canonical key for "accept-encoding" is "Accept-Encoding".
+// MIME header keys are assumed to be ASCII only.
+// If s contains a space or invalid header field bytes, it is
+// returned without modifications.
+func CanonicalMIMEHeaderKey(s string) string {
+	commonHeaderOnce.Do(initCommonHeader)
+
+	// Quick check for canonical encoding.
+	upper := true
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if !validHeaderFieldByte(c) {
+			return s
+		}
+		if upper && 'a' <= c && c <= 'z' {
+			return canonicalMIMEHeaderKey([]byte(s))
+		}
+		if !upper && 'A' <= c && c <= 'Z' {
+			return canonicalMIMEHeaderKey([]byte(s))
+		}
+		upper = c == '-'
+	}
+	return s
+}
+
+const toLower = 'a' - 'A'
+
+// validHeaderFieldByte reports whether b is a valid byte in a header
+// field name. RFC 7230 says:
+//   header-field   = field-name ":" OWS field-value OWS
+//   field-name     = token
+//   tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
+//           "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
+//   token = 1*tchar
+func validHeaderFieldByte(b byte) bool {
+	return int(b) < len(isTokenTable) && isTokenTable[b]
+}
+
+// canonicalMIMEHeaderKey is like CanonicalMIMEHeaderKey but is
+// allowed to mutate the provided byte slice before returning the
+// string.
+//
+// For invalid inputs (if a contains spaces or non-token bytes), a
+// is unchanged and a string copy is returned.
+func canonicalMIMEHeaderKey(a []byte) string {
+	// See if a looks like a header key. If not, return it unchanged.
+	for _, c := range a {
+		if validHeaderFieldByte(c) {
+			continue
+		}
+		// Don't canonicalize.
+		return string(a)
+	}
+
+	upper := true
+	for i, c := range a {
+		// Canonicalize: first letter upper case
+		// and upper case after each dash.
+		// (Host, User-Agent, If-Modified-Since).
+		// MIME headers are ASCII only, so no Unicode issues.
+		if upper && 'a' <= c && c <= 'z' {
+			c -= toLower
+		} else if !upper && 'A' <= c && c <= 'Z' {
+			c += toLower
+		}
+		a[i] = c
+		upper = c == '-' // for next time
+	}
+	// The compiler recognizes m[string(byteSlice)] as a special
+	// case, so a copy of a's bytes into a new string does not
+	// happen in this map lookup:
+	if v := commonHeader[string(a)]; v != "" {
+		return v
+	}
+	return string(a)
+}
+
+// commonHeader interns common header strings.
+var commonHeader map[string]string
+
+var commonHeaderOnce sync.Once
+
+func initCommonHeader() {
+	commonHeader = make(map[string]string)
+	for _, v := range []string{
+		"Accept",
+		"Accept-Charset",
+		"Accept-Encoding",
+		"Accept-Language",
+		"Accept-Ranges",
+		"Cache-Control",
+		"Cc",
+		"Connection",
+		"Content-Id",
+		"Content-Language",
+		"Content-Length",
+		"Content-Transfer-Encoding",
+		"Content-Type",
+		"Cookie",
+		"Date",
+		"Dkim-Signature",
+		"Etag",
+		"Expires",
+		"From",
+		"Host",
+		"If-Modified-Since",
+		"If-None-Match",
+		"In-Reply-To",
+		"Last-Modified",
+		"Location",
+		"Message-Id",
+		"Mime-Version",
+		"Pragma",
+		"Received",
+		"Return-Path",
+		"Server",
+		"Set-Cookie",
+		"Subject",
+		"To",
+		"User-Agent",
+		"Via",
+		"X-Forwarded-For",
+		"X-Imforwards",
+		"X-Powered-By",
+	} {
+		commonHeader[v] = v
+	}
+}
+
+// isTokenTable is a copy of net/http/lex.go's isTokenTable.
+// See https://httpwg.github.io/specs/rfc7230.html#rule.token.separators
+var isTokenTable = [127]bool{
+	'!':  true,
+	'#':  true,
+	'$':  true,
+	'%':  true,
+	'&':  true,
+	'\'': true,
+	'*':  true,
+	'+':  true,
+	'-':  true,
+	'.':  true,
+	'0':  true,
+	'1':  true,
+	'2':  true,
+	'3':  true,
+	'4':  true,
+	'5':  true,
+	'6':  true,
+	'7':  true,
+	'8':  true,
+	'9':  true,
+	'A':  true,
+	'B':  true,
+	'C':  true,
+	'D':  true,
+	'E':  true,
+	'F':  true,
+	'G':  true,
+	'H':  true,
+	'I':  true,
+	'J':  true,
+	'K':  true,
+	'L':  true,
+	'M':  true,
+	'N':  true,
+	'O':  true,
+	'P':  true,
+	'Q':  true,
+	'R':  true,
+	'S':  true,
+	'T':  true,
+	'U':  true,
+	'W':  true,
+	'V':  true,
+	'X':  true,
+	'Y':  true,
+	'Z':  true,
+	'^':  true,
+	'_':  true,
+	'`':  true,
+	'a':  true,
+	'b':  true,
+	'c':  true,
+	'd':  true,
+	'e':  true,
+	'f':  true,
+	'g':  true,
+	'h':  true,
+	'i':  true,
+	'j':  true,
+	'k':  true,
+	'l':  true,
+	'm':  true,
+	'n':  true,
+	'o':  true,
+	'p':  true,
+	'q':  true,
+	'r':  true,
+	's':  true,
+	't':  true,
+	'u':  true,
+	'v':  true,
+	'w':  true,
+	'x':  true,
+	'y':  true,
+	'z':  true,
+	'|':  true,
+	'~':  true,
+}
diff --git a/src/net/textproto/reader_test.go b/src/net/textproto/reader_test.go
new file mode 100644
index 0000000..3124d43
--- /dev/null
+++ b/src/net/textproto/reader_test.go
@@ -0,0 +1,391 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func reader(s string) *Reader {
+	return NewReader(bufio.NewReader(strings.NewReader(s)))
+}
+
+func TestReadLine(t *testing.T) {
+	r := reader("line1\nline2\n")
+	s, err := r.ReadLine()
+	if s != "line1" || err != nil {
+		t.Fatalf("Line 1: %s, %v", s, err)
+	}
+	s, err = r.ReadLine()
+	if s != "line2" || err != nil {
+		t.Fatalf("Line 2: %s, %v", s, err)
+	}
+	s, err = r.ReadLine()
+	if s != "" || err != io.EOF {
+		t.Fatalf("EOF: %s, %v", s, err)
+	}
+}
+
+func TestReadContinuedLine(t *testing.T) {
+	r := reader("line1\nline\n 2\nline3\n")
+	s, err := r.ReadContinuedLine()
+	if s != "line1" || err != nil {
+		t.Fatalf("Line 1: %s, %v", s, err)
+	}
+	s, err = r.ReadContinuedLine()
+	if s != "line 2" || err != nil {
+		t.Fatalf("Line 2: %s, %v", s, err)
+	}
+	s, err = r.ReadContinuedLine()
+	if s != "line3" || err != nil {
+		t.Fatalf("Line 3: %s, %v", s, err)
+	}
+	s, err = r.ReadContinuedLine()
+	if s != "" || err != io.EOF {
+		t.Fatalf("EOF: %s, %v", s, err)
+	}
+}
+
+func TestReadCodeLine(t *testing.T) {
+	r := reader("123 hi\n234 bye\n345 no way\n")
+	code, msg, err := r.ReadCodeLine(0)
+	if code != 123 || msg != "hi" || err != nil {
+		t.Fatalf("Line 1: %d, %s, %v", code, msg, err)
+	}
+	code, msg, err = r.ReadCodeLine(23)
+	if code != 234 || msg != "bye" || err != nil {
+		t.Fatalf("Line 2: %d, %s, %v", code, msg, err)
+	}
+	code, msg, err = r.ReadCodeLine(346)
+	if code != 345 || msg != "no way" || err == nil {
+		t.Fatalf("Line 3: %d, %s, %v", code, msg, err)
+	}
+	if e, ok := err.(*Error); !ok || e.Code != code || e.Msg != msg {
+		t.Fatalf("Line 3: wrong error %v\n", err)
+	}
+	code, msg, err = r.ReadCodeLine(1)
+	if code != 0 || msg != "" || err != io.EOF {
+		t.Fatalf("EOF: %d, %s, %v", code, msg, err)
+	}
+}
+
+func TestReadDotLines(t *testing.T) {
+	r := reader("dotlines\r\n.foo\r\n..bar\n...baz\nquux\r\n\r\n.\r\nanother\n")
+	s, err := r.ReadDotLines()
+	want := []string{"dotlines", "foo", ".bar", "..baz", "quux", ""}
+	if !reflect.DeepEqual(s, want) || err != nil {
+		t.Fatalf("ReadDotLines: %v, %v", s, err)
+	}
+
+	s, err = r.ReadDotLines()
+	want = []string{"another"}
+	if !reflect.DeepEqual(s, want) || err != io.ErrUnexpectedEOF {
+		t.Fatalf("ReadDotLines2: %v, %v", s, err)
+	}
+}
+
+func TestReadDotBytes(t *testing.T) {
+	r := reader("dotlines\r\n.foo\r\n..bar\n...baz\nquux\r\n\r\n.\r\nanot.her\r\n")
+	b, err := r.ReadDotBytes()
+	want := []byte("dotlines\nfoo\n.bar\n..baz\nquux\n\n")
+	if !reflect.DeepEqual(b, want) || err != nil {
+		t.Fatalf("ReadDotBytes: %q, %v", b, err)
+	}
+
+	b, err = r.ReadDotBytes()
+	want = []byte("anot.her\n")
+	if !reflect.DeepEqual(b, want) || err != io.ErrUnexpectedEOF {
+		t.Fatalf("ReadDotBytes2: %q, %v", b, err)
+	}
+}
+
+func TestReadMIMEHeader(t *testing.T) {
+	r := reader("my-key: Value 1  \r\nLong-key: Even \n Longer Value\r\nmy-Key: Value 2\r\n\n")
+	m, err := r.ReadMIMEHeader()
+	want := MIMEHeader{
+		"My-Key":   {"Value 1", "Value 2"},
+		"Long-Key": {"Even Longer Value"},
+	}
+	if !reflect.DeepEqual(m, want) || err != nil {
+		t.Fatalf("ReadMIMEHeader: %v, %v; want %v", m, err, want)
+	}
+}
+
+func TestReadMIMEHeaderSingle(t *testing.T) {
+	r := reader("Foo: bar\n\n")
+	m, err := r.ReadMIMEHeader()
+	want := MIMEHeader{"Foo": {"bar"}}
+	if !reflect.DeepEqual(m, want) || err != nil {
+		t.Fatalf("ReadMIMEHeader: %v, %v; want %v", m, err, want)
+	}
+}
+
+func TestReadMIMEHeaderNoKey(t *testing.T) {
+	r := reader(": bar\ntest-1: 1\n\n")
+	m, err := r.ReadMIMEHeader()
+	want := MIMEHeader{"Test-1": {"1"}}
+	if !reflect.DeepEqual(m, want) || err != nil {
+		t.Fatalf("ReadMIMEHeader: %v, %v; want %v", m, err, want)
+	}
+}
+
+func TestLargeReadMIMEHeader(t *testing.T) {
+	data := make([]byte, 16*1024)
+	for i := 0; i < len(data); i++ {
+		data[i] = 'x'
+	}
+	sdata := string(data)
+	r := reader("Cookie: " + sdata + "\r\n\n")
+	m, err := r.ReadMIMEHeader()
+	if err != nil {
+		t.Fatalf("ReadMIMEHeader: %v", err)
+	}
+	cookie := m.Get("Cookie")
+	if cookie != sdata {
+		t.Fatalf("ReadMIMEHeader: %v bytes, want %v bytes", len(cookie), len(sdata))
+	}
+}
+
+// TestReadMIMEHeaderNonCompliant checks that we don't normalize headers
+// with spaces before colons, and accept spaces in keys.
+func TestReadMIMEHeaderNonCompliant(t *testing.T) {
+	// These invalid headers will be rejected by net/http according to RFC 7230.
+	r := reader("Foo: bar\r\n" +
+		"Content-Language: en\r\n" +
+		"SID : 0\r\n" +
+		"Audio Mode : None\r\n" +
+		"Privilege : 127\r\n\r\n")
+	m, err := r.ReadMIMEHeader()
+	want := MIMEHeader{
+		"Foo":              {"bar"},
+		"Content-Language": {"en"},
+		"SID ":             {"0"},
+		"Audio Mode ":      {"None"},
+		"Privilege ":       {"127"},
+	}
+	if !reflect.DeepEqual(m, want) || err != nil {
+		t.Fatalf("ReadMIMEHeader =\n%v, %v; want:\n%v", m, err, want)
+	}
+}
+
+func TestReadMIMEHeaderMalformed(t *testing.T) {
+	inputs := []string{
+		"No colon first line\r\nFoo: foo\r\n\r\n",
+		" No colon first line with leading space\r\nFoo: foo\r\n\r\n",
+		"\tNo colon first line with leading tab\r\nFoo: foo\r\n\r\n",
+		" First: line with leading space\r\nFoo: foo\r\n\r\n",
+		"\tFirst: line with leading tab\r\nFoo: foo\r\n\r\n",
+		"Foo: foo\r\nNo colon second line\r\n\r\n",
+		"Foo-\n\tBar: foo\r\n\r\n",
+		"Foo-\r\n\tBar: foo\r\n\r\n",
+		"Foo\r\n\t: foo\r\n\r\n",
+		"Foo-\n\tBar",
+	}
+
+	for _, input := range inputs {
+		r := reader(input)
+		if m, err := r.ReadMIMEHeader(); err == nil {
+			t.Errorf("ReadMIMEHeader(%q) = %v, %v; want nil, err", input, m, err)
+		}
+	}
+}
+
+// Test that continued lines are properly trimmed. Issue 11204.
+func TestReadMIMEHeaderTrimContinued(t *testing.T) {
+	// In this header, \n and \r\n terminated lines are mixed on purpose.
+	// We expect each line to be trimmed (prefix and suffix) before being concatenated.
+	// Keep the spaces as they are.
+	r := reader("" + // for code formatting purpose.
+		"a:\n" +
+		" 0 \r\n" +
+		"b:1 \t\r\n" +
+		"c: 2\r\n" +
+		" 3\t\n" +
+		"  \t 4  \r\n\n")
+	m, err := r.ReadMIMEHeader()
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := MIMEHeader{
+		"A": {"0"},
+		"B": {"1"},
+		"C": {"2 3 4"},
+	}
+	if !reflect.DeepEqual(m, want) {
+		t.Fatalf("ReadMIMEHeader mismatch.\n got: %q\nwant: %q", m, want)
+	}
+}
+
+type readResponseTest struct {
+	in       string
+	inCode   int
+	wantCode int
+	wantMsg  string
+}
+
+var readResponseTests = []readResponseTest{
+	{"230-Anonymous access granted, restrictions apply\n" +
+		"Read the file README.txt,\n" +
+		"230  please",
+		23,
+		230,
+		"Anonymous access granted, restrictions apply\nRead the file README.txt,\n please",
+	},
+
+	{"230 Anonymous access granted, restrictions apply\n",
+		23,
+		230,
+		"Anonymous access granted, restrictions apply",
+	},
+
+	{"400-A\n400-B\n400 C",
+		4,
+		400,
+		"A\nB\nC",
+	},
+
+	{"400-A\r\n400-B\r\n400 C\r\n",
+		4,
+		400,
+		"A\nB\nC",
+	},
+}
+
+// See https://www.ietf.org/rfc/rfc959.txt page 36.
+func TestRFC959Lines(t *testing.T) {
+	for i, tt := range readResponseTests {
+		r := reader(tt.in + "\nFOLLOWING DATA")
+		code, msg, err := r.ReadResponse(tt.inCode)
+		if err != nil {
+			t.Errorf("#%d: ReadResponse: %v", i, err)
+			continue
+		}
+		if code != tt.wantCode {
+			t.Errorf("#%d: code=%d, want %d", i, code, tt.wantCode)
+		}
+		if msg != tt.wantMsg {
+			t.Errorf("#%d: msg=%q, want %q", i, msg, tt.wantMsg)
+		}
+	}
+}
+
+// Test that multi-line errors are appropriately and fully read. Issue 10230.
+func TestReadMultiLineError(t *testing.T) {
+	r := reader("550-5.1.1 The email account that you tried to reach does not exist. Please try\n" +
+		"550-5.1.1 double-checking the recipient's email address for typos or\n" +
+		"550-5.1.1 unnecessary spaces. Learn more at\n" +
+		"Unexpected but legal text!\n" +
+		"550 5.1.1 https://support.google.com/mail/answer/6596 h20si25154304pfd.166 - gsmtp\n")
+
+	wantMsg := "5.1.1 The email account that you tried to reach does not exist. Please try\n" +
+		"5.1.1 double-checking the recipient's email address for typos or\n" +
+		"5.1.1 unnecessary spaces. Learn more at\n" +
+		"Unexpected but legal text!\n" +
+		"5.1.1 https://support.google.com/mail/answer/6596 h20si25154304pfd.166 - gsmtp"
+
+	code, msg, err := r.ReadResponse(250)
+	if err == nil {
+		t.Errorf("ReadResponse: no error, want error")
+	}
+	if code != 550 {
+		t.Errorf("ReadResponse: code=%d, want %d", code, 550)
+	}
+	if msg != wantMsg {
+		t.Errorf("ReadResponse: msg=%q, want %q", msg, wantMsg)
+	}
+	if err != nil && err.Error() != "550 "+wantMsg {
+		t.Errorf("ReadResponse: error=%q, want %q", err.Error(), "550 "+wantMsg)
+	}
+}
+
+func TestCommonHeaders(t *testing.T) {
+	commonHeaderOnce.Do(initCommonHeader)
+	for h := range commonHeader {
+		if h != CanonicalMIMEHeaderKey(h) {
+			t.Errorf("Non-canonical header %q in commonHeader", h)
+		}
+	}
+	b := []byte("content-Length")
+	want := "Content-Length"
+	n := testing.AllocsPerRun(200, func() {
+		if x := canonicalMIMEHeaderKey(b); x != want {
+			t.Fatalf("canonicalMIMEHeaderKey(%q) = %q; want %q", b, x, want)
+		}
+	})
+	if n > 0 {
+		t.Errorf("canonicalMIMEHeaderKey allocs = %v; want 0", n)
+	}
+}
+
+var clientHeaders = strings.Replace(`Host: golang.org
+Connection: keep-alive
+Cache-Control: max-age=0
+Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
+User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US) AppleWebKit/534.3 (KHTML, like Gecko) Chrome/6.0.472.63 Safari/534.3
+Accept-Encoding: gzip,deflate,sdch
+Accept-Language: en-US,en;q=0.8,fr-CH;q=0.6
+Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
+COOKIE: __utma=000000000.0000000000.0000000000.0000000000.0000000000.00; __utmb=000000000.0.00.0000000000; __utmc=000000000; __utmz=000000000.0000000000.00.0.utmcsr=code.google.com|utmccn=(referral)|utmcmd=referral|utmcct=/p/go/issues/detail
+Non-Interned: test
+
+`, "\n", "\r\n", -1)
+
+var serverHeaders = strings.Replace(`Content-Type: text/html; charset=utf-8
+Content-Encoding: gzip
+Date: Thu, 27 Sep 2012 09:03:33 GMT
+Server: Google Frontend
+Cache-Control: private
+Content-Length: 2298
+VIA: 1.1 proxy.example.com:80 (XXX/n.n.n-nnn)
+Connection: Close
+Non-Interned: test
+
+`, "\n", "\r\n", -1)
+
+func BenchmarkReadMIMEHeader(b *testing.B) {
+	b.ReportAllocs()
+	for _, set := range []struct {
+		name    string
+		headers string
+	}{
+		{"client_headers", clientHeaders},
+		{"server_headers", serverHeaders},
+	} {
+		b.Run(set.name, func(b *testing.B) {
+			var buf bytes.Buffer
+			br := bufio.NewReader(&buf)
+			r := NewReader(br)
+
+			for i := 0; i < b.N; i++ {
+				buf.WriteString(set.headers)
+				if _, err := r.ReadMIMEHeader(); err != nil {
+					b.Fatal(err)
+				}
+			}
+		})
+	}
+}
+
+func BenchmarkUncommon(b *testing.B) {
+	b.ReportAllocs()
+	var buf bytes.Buffer
+	br := bufio.NewReader(&buf)
+	r := NewReader(br)
+	for i := 0; i < b.N; i++ {
+		buf.WriteString("uncommon-header-for-benchmark: foo\r\n\r\n")
+		h, err := r.ReadMIMEHeader()
+		if err != nil {
+			b.Fatal(err)
+		}
+		if _, ok := h["Uncommon-Header-For-Benchmark"]; !ok {
+			b.Fatal("Missing result header.")
+		}
+	}
+}
diff --git a/src/net/textproto/textproto.go b/src/net/textproto/textproto.go
new file mode 100644
index 0000000..8fd781e
--- /dev/null
+++ b/src/net/textproto/textproto.go
@@ -0,0 +1,154 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package textproto implements generic support for text-based request/response
+// protocols in the style of HTTP, NNTP, and SMTP.
+//
+// The package provides:
+//
+// Error, which represents a numeric error response from
+// a server.
+//
+// Pipeline, to manage pipelined requests and responses
+// in a client.
+//
+// Reader, to read numeric response code lines,
+// key: value headers, lines wrapped with leading spaces
+// on continuation lines, and whole text blocks ending
+// with a dot on a line by itself.
+//
+// Writer, to write dot-encoded text blocks.
+//
+// Conn, a convenient packaging of Reader, Writer, and Pipeline for use
+// with a single network connection.
+//
+package textproto
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+)
+
+// An Error represents a numeric error response from a server.
+type Error struct {
+	Code int
+	Msg  string
+}
+
+func (e *Error) Error() string {
+	return fmt.Sprintf("%03d %s", e.Code, e.Msg)
+}
+
+// A ProtocolError describes a protocol violation such
+// as an invalid response or a hung-up connection.
+type ProtocolError string
+
+func (p ProtocolError) Error() string {
+	return string(p)
+}
+
+// A Conn represents a textual network protocol connection.
+// It consists of a Reader and Writer to manage I/O
+// and a Pipeline to sequence concurrent requests on the connection.
+// These embedded types carry methods with them;
+// see the documentation of those types for details.
+type Conn struct {
+	Reader
+	Writer
+	Pipeline
+	conn io.ReadWriteCloser
+}
+
+// NewConn returns a new Conn using conn for I/O.
+func NewConn(conn io.ReadWriteCloser) *Conn {
+	return &Conn{
+		Reader: Reader{R: bufio.NewReader(conn)},
+		Writer: Writer{W: bufio.NewWriter(conn)},
+		conn:   conn,
+	}
+}
+
+// Close closes the connection.
+func (c *Conn) Close() error {
+	return c.conn.Close()
+}
+
+// Dial connects to the given address on the given network using net.Dial
+// and then returns a new Conn for the connection.
+func Dial(network, addr string) (*Conn, error) {
+	c, err := net.Dial(network, addr)
+	if err != nil {
+		return nil, err
+	}
+	return NewConn(c), nil
+}
+
+// Cmd is a convenience method that sends a command after
+// waiting its turn in the pipeline. The command text is the
+// result of formatting format with args and appending \r\n.
+// Cmd returns the id of the command, for use with StartResponse and EndResponse.
+//
+// For example, a client might run a HELP command that returns a dot-body
+// by using:
+//
+//	id, err := c.Cmd("HELP")
+//	if err != nil {
+//		return nil, err
+//	}
+//
+//	c.StartResponse(id)
+//	defer c.EndResponse(id)
+//
+//	if _, _, err = c.ReadCodeLine(110); err != nil {
+//		return nil, err
+//	}
+//	text, err := c.ReadDotBytes()
+//	if err != nil {
+//		return nil, err
+//	}
+//	return c.ReadCodeLine(250)
+//
+func (c *Conn) Cmd(format string, args ...interface{}) (id uint, err error) {
+	id = c.Next()
+	c.StartRequest(id)
+	err = c.PrintfLine(format, args...)
+	c.EndRequest(id)
+	if err != nil {
+		return 0, err
+	}
+	return id, nil
+}
+
+// TrimString returns s without leading and trailing ASCII space.
+func TrimString(s string) string {
+	for len(s) > 0 && isASCIISpace(s[0]) {
+		s = s[1:]
+	}
+	for len(s) > 0 && isASCIISpace(s[len(s)-1]) {
+		s = s[:len(s)-1]
+	}
+	return s
+}
+
+// TrimBytes returns b without leading and trailing ASCII space.
+func TrimBytes(b []byte) []byte {
+	for len(b) > 0 && isASCIISpace(b[0]) {
+		b = b[1:]
+	}
+	for len(b) > 0 && isASCIISpace(b[len(b)-1]) {
+		b = b[:len(b)-1]
+	}
+	return b
+}
+
+func isASCIISpace(b byte) bool {
+	return b == ' ' || b == '\t' || b == '\n' || b == '\r'
+}
+
+func isASCIILetter(b byte) bool {
+	b |= 0x20 // make lower case
+	return 'a' <= b && b <= 'z'
+}
diff --git a/src/net/textproto/writer.go b/src/net/textproto/writer.go
new file mode 100644
index 0000000..33c146c
--- /dev/null
+++ b/src/net/textproto/writer.go
@@ -0,0 +1,119 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+)
+
+// A Writer implements convenience methods for writing
+// requests or responses to a text protocol network connection.
+type Writer struct {
+	W   *bufio.Writer
+	dot *dotWriter
+}
+
+// NewWriter returns a new Writer writing to w.
+func NewWriter(w *bufio.Writer) *Writer {
+	return &Writer{W: w}
+}
+
+var crnl = []byte{'\r', '\n'}
+var dotcrnl = []byte{'.', '\r', '\n'}
+
+// PrintfLine writes the formatted output followed by \r\n.
+func (w *Writer) PrintfLine(format string, args ...interface{}) error {
+	w.closeDot()
+	fmt.Fprintf(w.W, format, args...)
+	w.W.Write(crnl)
+	return w.W.Flush()
+}
+
+// DotWriter returns a writer that can be used to write a dot-encoding to w.
+// It takes care of inserting leading dots when necessary,
+// translating line-ending \n into \r\n, and adding the final .\r\n line
+// when the DotWriter is closed. The caller should close the
+// DotWriter before the next call to a method on w.
+//
+// See the documentation for Reader's DotReader method for details about dot-encoding.
+func (w *Writer) DotWriter() io.WriteCloser {
+	w.closeDot()
+	w.dot = &dotWriter{w: w}
+	return w.dot
+}
+
+func (w *Writer) closeDot() {
+	if w.dot != nil {
+		w.dot.Close() // sets w.dot = nil
+	}
+}
+
+type dotWriter struct {
+	w     *Writer
+	state int
+}
+
+const (
+	wstateBegin     = iota // initial state; must be zero
+	wstateBeginLine        // beginning of line
+	wstateCR               // wrote \r (possibly at end of line)
+	wstateData             // writing data in middle of line
+)
+
+func (d *dotWriter) Write(b []byte) (n int, err error) {
+	bw := d.w.W
+	for n < len(b) {
+		c := b[n]
+		switch d.state {
+		case wstateBegin, wstateBeginLine:
+			d.state = wstateData
+			if c == '.' {
+				// escape leading dot
+				bw.WriteByte('.')
+			}
+			fallthrough
+
+		case wstateData:
+			if c == '\r' {
+				d.state = wstateCR
+			}
+			if c == '\n' {
+				bw.WriteByte('\r')
+				d.state = wstateBeginLine
+			}
+
+		case wstateCR:
+			d.state = wstateData
+			if c == '\n' {
+				d.state = wstateBeginLine
+			}
+		}
+		if err = bw.WriteByte(c); err != nil {
+			break
+		}
+		n++
+	}
+	return
+}
+
+func (d *dotWriter) Close() error {
+	if d.w.dot == d {
+		d.w.dot = nil
+	}
+	bw := d.w.W
+	switch d.state {
+	default:
+		bw.WriteByte('\r')
+		fallthrough
+	case wstateCR:
+		bw.WriteByte('\n')
+		fallthrough
+	case wstateBeginLine:
+		bw.Write(dotcrnl)
+	}
+	return bw.Flush()
+}
diff --git a/src/net/textproto/writer_test.go b/src/net/textproto/writer_test.go
new file mode 100644
index 0000000..2afef11
--- /dev/null
+++ b/src/net/textproto/writer_test.go
@@ -0,0 +1,61 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"bufio"
+	"bytes"
+	"testing"
+)
+
+func TestPrintfLine(t *testing.T) {
+	var buf bytes.Buffer
+	w := NewWriter(bufio.NewWriter(&buf))
+	err := w.PrintfLine("foo %d", 123)
+	if s := buf.String(); s != "foo 123\r\n" || err != nil {
+		t.Fatalf("s=%q; err=%s", s, err)
+	}
+}
+
+func TestDotWriter(t *testing.T) {
+	var buf bytes.Buffer
+	w := NewWriter(bufio.NewWriter(&buf))
+	d := w.DotWriter()
+	n, err := d.Write([]byte("abc\n.def\n..ghi\n.jkl\n."))
+	if n != 21 || err != nil {
+		t.Fatalf("Write: %d, %s", n, err)
+	}
+	d.Close()
+	want := "abc\r\n..def\r\n...ghi\r\n..jkl\r\n..\r\n.\r\n"
+	if s := buf.String(); s != want {
+		t.Fatalf("wrote %q", s)
+	}
+}
+
+func TestDotWriterCloseEmptyWrite(t *testing.T) {
+	var buf bytes.Buffer
+	w := NewWriter(bufio.NewWriter(&buf))
+	d := w.DotWriter()
+	n, err := d.Write([]byte{})
+	if n != 0 || err != nil {
+		t.Fatalf("Write: %d, %s", n, err)
+	}
+	d.Close()
+	want := "\r\n.\r\n"
+	if s := buf.String(); s != want {
+		t.Fatalf("wrote %q; want %q", s, want)
+	}
+}
+
+func TestDotWriterCloseNoWrite(t *testing.T) {
+	var buf bytes.Buffer
+	w := NewWriter(bufio.NewWriter(&buf))
+	d := w.DotWriter()
+	d.Close()
+	want := "\r\n.\r\n"
+	if s := buf.String(); s != want {
+		t.Fatalf("wrote %q; want %q", s, want)
+	}
+}