src/net/mail/message.go - go - Git at Google

 // Copyright 2011 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 mail implements parsing of mail messages.

 For the most part, this package follows the syntax as specified by RFC 5322.
 Notable divergences:
 	* Obsolete address formats are not parsed, including addresses with
 	  embedded route information.
 	* Group addresses are not parsed.
 	* The full range of spacing (the CFWS syntax element) is not supported,
 	  such as breaking addresses across lines.
 */
 package mail

 import (
 	"bufio"
 	"bytes"
 	"errors"
 	"fmt"
 	"io"
 	"log"
 	"mime"
 	"net/textproto"
 	"strings"
 	"time"
 )

 var debug = debugT(false)

 type debugT bool

 func (d debugT) Printf(format string, args ...interface{}) {
 	if d {
 		log.Printf(format, args...)
 	}
 }

 // A Message represents a parsed mail message.
 type Message struct {
 	Header Header
 	Body   io.Reader
 }

 // ReadMessage reads a message from r.
 // The headers are parsed, and the body of the message will be available
 // for reading from r.
 func ReadMessage(r io.Reader) (msg *Message, err error) {
 	tp := textproto.NewReader(bufio.NewReader(r))

 	hdr, err := tp.ReadMIMEHeader()
 	if err != nil {
 		return nil, err
 	}

 	return &Message{
 		Header: Header(hdr),
 		Body:   tp.R,
 	}, nil
 }

 // Layouts suitable for passing to time.Parse.
 // These are tried in order.
 var dateLayouts []string

 func init() {
 	// Generate layouts based on RFC 5322, section 3.3.

 	dows := [...]string{"", "Mon, "}   // day-of-week
 	days := [...]string{"2", "02"}     // day = 1*2DIGIT
 	years := [...]string{"2006", "06"} // year = 4*DIGIT / 2*DIGIT
 	seconds := [...]string{":05", ""}  // second
 	// "-0700 (MST)" is not in RFC 5322, but is common.
 	zones := [...]string{"-0700", "MST", "-0700 (MST)"} // zone = (("+" / "-") 4DIGIT) / "GMT" / ...

 	for _, dow := range dows {
 		for _, day := range days {
 			for _, year := range years {
 				for _, second := range seconds {
 					for _, zone := range zones {
 						s := dow + day + " Jan " + year + " 15:04" + second + " " + zone
 						dateLayouts = append(dateLayouts, s)
 					}
 				}
 			}
 		}
 	}
 }

 func parseDate(date string) (time.Time, error) {
 	for _, layout := range dateLayouts {
 		t, err := time.Parse(layout, date)
 		if err == nil {
 			return t, nil
 		}
 	}
 	return time.Time{}, errors.New("mail: header could not be parsed")
 }

 // A Header represents the key-value pairs in a mail message header.
 type Header map[string][]string

 // Get gets the first value associated with the given key.
 // If there are no values associated with the key, Get returns "".
 func (h Header) Get(key string) string {
 	return textproto.MIMEHeader(h).Get(key)
 }

 var ErrHeaderNotPresent = errors.New("mail: header not in message")

 // Date parses the Date header field.
 func (h Header) Date() (time.Time, error) {
 	hdr := h.Get("Date")
 	if hdr == "" {
 		return time.Time{}, ErrHeaderNotPresent
 	}
 	return parseDate(hdr)
 }

 // AddressList parses the named header field as a list of addresses.
 func (h Header) AddressList(key string) ([]*Address, error) {
 	hdr := h.Get(key)
 	if hdr == "" {
 		return nil, ErrHeaderNotPresent
 	}
 	return ParseAddressList(hdr)
 }

 // Address represents a single mail address.
 // An address such as "Barry Gibbs <bg@example.com>" is represented
 // as Address{Name: "Barry Gibbs", Address: "bg@example.com"}.
 type Address struct {
 	Name    string // Proper name; may be empty.
 	Address string // user@domain
 }

 // Parses a single RFC 5322 address, e.g. "Barry Gibbs <bg@example.com>"
 func ParseAddress(address string) (*Address, error) {
 	return (&addrParser{s: address}).parseAddress()
 }

 // ParseAddressList parses the given string as a list of addresses.
 func ParseAddressList(list string) ([]*Address, error) {
 	return (&addrParser{s: list}).parseAddressList()
 }

 // An AddressParser is an RFC 5322 address parser.
 type AddressParser struct {
 	// WordDecoder optionally specifies a decoder for RFC 2047 encoded-words.
 	WordDecoder *mime.WordDecoder
 }

 // Parse parses a single RFC 5322 address of the
 // form "Gogh Fir <gf@example.com>" or "foo@example.com".
 func (p *AddressParser) Parse(address string) (*Address, error) {
 	return (&addrParser{s: address, dec: p.WordDecoder}).parseAddress()
 }

 // ParseList parses the given string as a list of comma-separated addresses
 // of the form "Gogh Fir <gf@example.com>" or "foo@example.com".
 func (p *AddressParser) ParseList(list string) ([]*Address, error) {
 	return (&addrParser{s: list, dec: p.WordDecoder}).parseAddressList()
 }

 // String formats the address as a valid RFC 5322 address.
 // If the address's name contains non-ASCII characters
 // the name will be rendered according to RFC 2047.
 func (a *Address) String() string {

 	// Format address local@domain
 	at := strings.LastIndex(a.Address, "@")
 	var local, domain string
 	if at < 0 {
 		// This is a malformed address ("@" is required in addr-spec);
 		// treat the whole address as local-part.
 		local = a.Address
 	} else {
 		local, domain = a.Address[:at], a.Address[at+1:]
 	}

 	// Add quotes if needed
 	// TODO: rendering quoted local part and rendering printable name
 	//       should be merged in helper function.
 	quoteLocal := false
 	for i := 0; i < len(local); i++ {
 		ch := local[i]
 		if isAtext(ch, false) {
 			continue
 		}
 		if ch == '.' {
 			// Dots are okay if they are surrounded by atext.
 			// We only need to check that the previous byte is
 			// not a dot, and this isn't the end of the string.
 			if i > 0 && local[i-1] != '.' && i < len(local)-1 {
 				continue
 			}
 		}
 		quoteLocal = true
 		break
 	}
 	if quoteLocal {
 		local = quoteString(local)

 	}

 	s := "<" + local + "@" + domain + ">"

 	if a.Name == "" {
 		return s
 	}

 	// If every character is printable ASCII, quoting is simple.
 	allPrintable := true
 	for i := 0; i < len(a.Name); i++ {
 		// isWSP here should actually be isFWS,
 		// but we don't support folding yet.
 		if !isVchar(a.Name[i]) && !isWSP(a.Name[i]) {
 			allPrintable = false
 			break
 		}
 	}
 	if allPrintable {
 		b := bytes.NewBufferString(`"`)
 		for i := 0; i < len(a.Name); i++ {
 			if !isQtext(a.Name[i]) && !isWSP(a.Name[i]) {
 				b.WriteByte('\\')
 			}
 			b.WriteByte(a.Name[i])
 		}
 		b.WriteString(`" `)
 		b.WriteString(s)
 		return b.String()
 	}

 	// Text in an encoded-word in a display-name must not contain certain
 	// characters like quotes or parentheses (see RFC 2047 section 5.3).
 	// When this is the case encode the name using base64 encoding.
 	if strings.ContainsAny(a.Name, "\"#$%&'(),.:;<>@[]^`{|}~") {
 		return mime.BEncoding.Encode("utf-8", a.Name) + " " + s
 	}
 	return mime.QEncoding.Encode("utf-8", a.Name) + " " + s
 }

 type addrParser struct {
 	s   string
 	dec *mime.WordDecoder // may be nil
 }

 func (p *addrParser) parseAddressList() ([]*Address, error) {
 	var list []*Address
 	for {
 		p.skipSpace()
 		addr, err := p.parseAddress()
 		if err != nil {
 			return nil, err
 		}
 		list = append(list, addr)

 		p.skipSpace()
 		if p.empty() {
 			break
 		}
 		if !p.consume(',') {
 			return nil, errors.New("mail: expected comma")
 		}
 	}
 	return list, nil
 }

 // parseAddress parses a single RFC 5322 address at the start of p.
 func (p *addrParser) parseAddress() (addr *Address, err error) {
 	debug.Printf("parseAddress: %q", p.s)
 	p.skipSpace()
 	if p.empty() {
 		return nil, errors.New("mail: no address")
 	}

 	// address = name-addr / addr-spec
 	// TODO(dsymonds): Support parsing group address.

 	// addr-spec has a more restricted grammar than name-addr,
 	// so try parsing it first, and fallback to name-addr.
 	// TODO(dsymonds): Is this really correct?
 	spec, err := p.consumeAddrSpec()
 	if err == nil {
 		return &Address{
 			Address: spec,
 		}, err
 	}
 	debug.Printf("parseAddress: not an addr-spec: %v", err)
 	debug.Printf("parseAddress: state is now %q", p.s)

 	// display-name
 	var displayName string
 	if p.peek() != '<' {
 		displayName, err = p.consumePhrase()
 		if err != nil {
 			return nil, err
 		}
 	}
 	debug.Printf("parseAddress: displayName=%q", displayName)

 	// angle-addr = "<" addr-spec ">"
 	p.skipSpace()
 	if !p.consume('<') {
 		return nil, errors.New("mail: no angle-addr")
 	}
 	spec, err = p.consumeAddrSpec()
 	if err != nil {
 		return nil, err
 	}
 	if !p.consume('>') {
 		return nil, errors.New("mail: unclosed angle-addr")
 	}
 	debug.Printf("parseAddress: spec=%q", spec)

 	return &Address{
 		Name:    displayName,
 		Address: spec,
 	}, nil
 }

 // consumeAddrSpec parses a single RFC 5322 addr-spec at the start of p.
 func (p *addrParser) consumeAddrSpec() (spec string, err error) {
 	debug.Printf("consumeAddrSpec: %q", p.s)

 	orig := *p
 	defer func() {
 		if err != nil {
 			*p = orig
 		}
 	}()

 	// local-part = dot-atom / quoted-string
 	var localPart string
 	p.skipSpace()
 	if p.empty() {
 		return "", errors.New("mail: no addr-spec")
 	}
 	if p.peek() == '"' {
 		// quoted-string
 		debug.Printf("consumeAddrSpec: parsing quoted-string")
 		localPart, err = p.consumeQuotedString()
 	} else {
 		// dot-atom
 		debug.Printf("consumeAddrSpec: parsing dot-atom")
 		localPart, err = p.consumeAtom(true, false)
 	}
 	if err != nil {
 		debug.Printf("consumeAddrSpec: failed: %v", err)
 		return "", err
 	}

 	if !p.consume('@') {
 		return "", errors.New("mail: missing @ in addr-spec")
 	}

 	// domain = dot-atom / domain-literal
 	var domain string
 	p.skipSpace()
 	if p.empty() {
 		return "", errors.New("mail: no domain in addr-spec")
 	}
 	// TODO(dsymonds): Handle domain-literal
 	domain, err = p.consumeAtom(true, false)
 	if err != nil {
 		return "", err
 	}

 	return localPart + "@" + domain, nil
 }

 // consumePhrase parses the RFC 5322 phrase at the start of p.
 func (p *addrParser) consumePhrase() (phrase string, err error) {
 	debug.Printf("consumePhrase: [%s]", p.s)
 	// phrase = 1*word
 	var words []string
 	for {
 		// word = atom / quoted-string
 		var word string
 		p.skipSpace()
 		if p.empty() {
 			return "", errors.New("mail: missing phrase")
 		}
 		if p.peek() == '"' {
 			// quoted-string
 			word, err = p.consumeQuotedString()
 		} else {
 			// atom
 			// We actually parse dot-atom here to be more permissive
 			// than what RFC 5322 specifies.
 			word, err = p.consumeAtom(true, true)
 			if err == nil {
 				word, err = p.decodeRFC2047Word(word)
 			}
 		}

 		if err != nil {
 			break
 		}
 		debug.Printf("consumePhrase: consumed %q", word)
 		words = append(words, word)
 	}
 	// Ignore any error if we got at least one word.
 	if err != nil && len(words) == 0 {
 		debug.Printf("consumePhrase: hit err: %v", err)
 		return "", fmt.Errorf("mail: missing word in phrase: %v", err)
 	}
 	phrase = strings.Join(words, " ")
 	return phrase, nil
 }

 // consumeQuotedString parses the quoted string at the start of p.
 func (p *addrParser) consumeQuotedString() (qs string, err error) {
 	// Assume first byte is '"'.
 	i := 1
 	qsb := make([]byte, 0, 10)
 Loop:
 	for {
 		if i >= p.len() {
 			return "", errors.New("mail: unclosed quoted-string")
 		}
 		switch c := p.s[i]; {
 		case c == '"':
 			break Loop
 		case c == '\\':
 			if i+1 == p.len() {
 				return "", errors.New("mail: unclosed quoted-string")
 			}
 			qsb = append(qsb, p.s[i+1])
 			i += 2
 		case isQtext(c), c == ' ':
 			// qtext (printable US-ASCII excluding " and \), or
 			// FWS (almost; we're ignoring CRLF)
 			qsb = append(qsb, c)
 			i++
 		default:
 			return "", fmt.Errorf("mail: bad character in quoted-string: %q", c)
 		}
 	}
 	p.s = p.s[i+1:]
 	if len(qsb) == 0 {
 		return "", errors.New("mail: empty quoted-string")
 	}
 	return string(qsb), nil
 }

 var errNonASCII = errors.New("mail: unencoded non-ASCII text in address")

 // consumeAtom parses an RFC 5322 atom at the start of p.
 // If dot is true, consumeAtom parses an RFC 5322 dot-atom instead.
 // If permissive is true, consumeAtom will not fail on
 // leading/trailing/double dots in the atom (see golang.org/issue/4938).
 func (p *addrParser) consumeAtom(dot bool, permissive bool) (atom string, err error) {
 	if c := p.peek(); !isAtext(c, false) {
 		if c > 127 {
 			return "", errNonASCII
 		}
 		return "", errors.New("mail: invalid string")
 	}
 	i := 1
 	for ; i < p.len() && isAtext(p.s[i], dot); i++ {
 	}
 	if i < p.len() && p.s[i] > 127 {
 		return "", errNonASCII
 	}
 	atom, p.s = string(p.s[:i]), p.s[i:]
 	if !permissive {
 		if strings.HasPrefix(atom, ".") {
 			return "", errors.New("mail: leading dot in atom")
 		}
 		if strings.Contains(atom, "..") {
 			return "", errors.New("mail: double dot in atom")
 		}
 		if strings.HasSuffix(atom, ".") {
 			return "", errors.New("mail: trailing dot in atom")
 		}
 	}
 	return atom, nil
 }

 func (p *addrParser) consume(c byte) bool {
 	if p.empty() || p.peek() != c {
 		return false
 	}
 	p.s = p.s[1:]
 	return true
 }

 // skipSpace skips the leading space and tab characters.
 func (p *addrParser) skipSpace() {
 	p.s = strings.TrimLeft(p.s, " \t")
 }

 func (p *addrParser) peek() byte {
 	return p.s[0]
 }

 func (p *addrParser) empty() bool {
 	return p.len() == 0
 }

 func (p *addrParser) len() int {
 	return len(p.s)
 }

 func (p *addrParser) decodeRFC2047Word(s string) (string, error) {
 	if p.dec != nil {
 		return p.dec.DecodeHeader(s)
 	}

 	dec, err := rfc2047Decoder.Decode(s)
 	if err == nil {
 		return dec, nil
 	}

 	if _, ok := err.(charsetError); ok {
 		return s, err
 	}

 	// Ignore invalid RFC 2047 encoded-word errors.
 	return s, nil
 }

 var rfc2047Decoder = mime.WordDecoder{
 	CharsetReader: func(charset string, input io.Reader) (io.Reader, error) {
 		return nil, charsetError(charset)
 	},
 }

 type charsetError string

 func (e charsetError) Error() string {
 	return fmt.Sprintf("charset not supported: %q", string(e))
 }

 var atextChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
 	"abcdefghijklmnopqrstuvwxyz" +
 	"0123456789" +
 	"!#$%&'*+-/=?^_`{|}~")

 // isAtext reports whether c is an RFC 5322 atext character.
 // If dot is true, period is included.
 func isAtext(c byte, dot bool) bool {
 	if dot && c == '.' {
 		return true
 	}
 	return bytes.IndexByte(atextChars, c) >= 0
 }

 // isQtext reports whether c is an RFC 5322 qtext character.
 func isQtext(c byte) bool {
 	// Printable US-ASCII, excluding backslash or quote.
 	if c == '\\' || c == '"' {
 		return false
 	}
 	return '!' <= c && c <= '~'
 }

 // quoteString renders a string as a RFC5322 quoted-string.
 func quoteString(s string) string {
 	var buf bytes.Buffer
 	buf.WriteByte('"')
 	for _, c := range s {
 		ch := byte(c)
 		if isQtext(ch) || isWSP(ch) {
 			buf.WriteByte(ch)
 		} else if isVchar(ch) {
 			buf.WriteByte('\\')
 			buf.WriteByte(ch)
 		}
 	}
 	buf.WriteByte('"')
 	return buf.String()
 }

 // isVchar reports whether c is an RFC 5322 VCHAR character.
 func isVchar(c byte) bool {
 	// Visible (printing) characters.
 	return '!' <= c && c <= '~'
 }

 // isWSP reports whether c is a WSP (white space).
 // WSP is a space or horizontal tab (RFC5234 Appendix B).
 func isWSP(c byte) bool {
 	return c == ' ' || c == '\t'
 }
	// Copyright 2011 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 mail implements parsing of mail messages.

	For the most part, this package follows the syntax as specified by RFC 5322.
	Notable divergences:
	* Obsolete address formats are not parsed, including addresses with
	embedded route information.
	* Group addresses are not parsed.
	* The full range of spacing (the CFWS syntax element) is not supported,
	such as breaking addresses across lines.
	*/
	package mail

	import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"log"
	"mime"
	"net/textproto"
	"strings"
	"time"
	)

	var debug = debugT(false)

	type debugT bool

	func (d debugT) Printf(format string, args ...interface{}) {
	if d {
	log.Printf(format, args...)
	}
	}

	// A Message represents a parsed mail message.
	type Message struct {
	Header Header
	Body io.Reader
	}

	// ReadMessage reads a message from r.
	// The headers are parsed, and the body of the message will be available
	// for reading from r.
	func ReadMessage(r io.Reader) (msg *Message, err error) {
	tp := textproto.NewReader(bufio.NewReader(r))

	hdr, err := tp.ReadMIMEHeader()
	if err != nil {
	return nil, err
	}

	return &Message{
	Header: Header(hdr),
	Body: tp.R,
	}, nil
	}

	// Layouts suitable for passing to time.Parse.
	// These are tried in order.
	var dateLayouts []string

	func init() {
	// Generate layouts based on RFC 5322, section 3.3.

	dows := [...]string{"", "Mon, "} // day-of-week
	days := [...]string{"2", "02"} // day = 1*2DIGIT
	years := [...]string{"2006", "06"} // year = 4DIGIT / 2DIGIT
	seconds := [...]string{":05", ""} // second
	// "-0700 (MST)" is not in RFC 5322, but is common.
	zones := [...]string{"-0700", "MST", "-0700 (MST)"} // zone = (("+" / "-") 4DIGIT) / "GMT" / ...

	for _, dow := range dows {
	for _, day := range days {
	for _, year := range years {
	for _, second := range seconds {
	for _, zone := range zones {
	s := dow + day + " Jan " + year + " 15:04" + second + " " + zone
	dateLayouts = append(dateLayouts, s)
	}
	}
	}
	}
	}
	}

	func parseDate(date string) (time.Time, error) {
	for _, layout := range dateLayouts {
	t, err := time.Parse(layout, date)
	if err == nil {
	return t, nil
	}
	}
	return time.Time{}, errors.New("mail: header could not be parsed")
	}

	// A Header represents the key-value pairs in a mail message header.
	type Header map[string][]string

	// Get gets the first value associated with the given key.
	// If there are no values associated with the key, Get returns "".
	func (h Header) Get(key string) string {
	return textproto.MIMEHeader(h).Get(key)
	}

	var ErrHeaderNotPresent = errors.New("mail: header not in message")

	// Date parses the Date header field.
	func (h Header) Date() (time.Time, error) {
	hdr := h.Get("Date")
	if hdr == "" {
	return time.Time{}, ErrHeaderNotPresent
	}
	return parseDate(hdr)
	}

	// AddressList parses the named header field as a list of addresses.
	func (h Header) AddressList(key string) ([]*Address, error) {
	hdr := h.Get(key)
	if hdr == "" {
	return nil, ErrHeaderNotPresent
	}
	return ParseAddressList(hdr)
	}

	// Address represents a single mail address.
	// An address such as "Barry Gibbs <bg@example.com>" is represented
	// as Address{Name: "Barry Gibbs", Address: "bg@example.com"}.
	type Address struct {
	Name string // Proper name; may be empty.
	Address string // user@domain
	}

	// Parses a single RFC 5322 address, e.g. "Barry Gibbs <bg@example.com>"
	func ParseAddress(address string) (*Address, error) {
	return (&addrParser{s: address}).parseAddress()
	}

	// ParseAddressList parses the given string as a list of addresses.
	func ParseAddressList(list string) ([]*Address, error) {
	return (&addrParser{s: list}).parseAddressList()
	}

	// An AddressParser is an RFC 5322 address parser.
	type AddressParser struct {
	// WordDecoder optionally specifies a decoder for RFC 2047 encoded-words.
	WordDecoder *mime.WordDecoder
	}

	// Parse parses a single RFC 5322 address of the
	// form "Gogh Fir <gf@example.com>" or "foo@example.com".
	func (p AddressParser) Parse(address string) (Address, error) {
	return (&addrParser{s: address, dec: p.WordDecoder}).parseAddress()
	}

	// ParseList parses the given string as a list of comma-separated addresses
	// of the form "Gogh Fir <gf@example.com>" or "foo@example.com".
	func (p AddressParser) ParseList(list string) ([]Address, error) {
	return (&addrParser{s: list, dec: p.WordDecoder}).parseAddressList()
	}

	// String formats the address as a valid RFC 5322 address.
	// If the address's name contains non-ASCII characters
	// the name will be rendered according to RFC 2047.
	func (a *Address) String() string {

	// Format address local@domain
	at := strings.LastIndex(a.Address, "@")
	var local, domain string
	if at < 0 {
	// This is a malformed address ("@" is required in addr-spec);
	// treat the whole address as local-part.
	local = a.Address
	} else {
	local, domain = a.Address[:at], a.Address[at+1:]
	}

	// Add quotes if needed
	// TODO: rendering quoted local part and rendering printable name
	// should be merged in helper function.
	quoteLocal := false
	for i := 0; i < len(local); i++ {
	ch := local[i]
	if isAtext(ch, false) {
	continue
	}
	if ch == '.' {
	// Dots are okay if they are surrounded by atext.
	// We only need to check that the previous byte is
	// not a dot, and this isn't the end of the string.
	if i > 0 && local[i-1] != '.' && i < len(local)-1 {
	continue
	}
	}
	quoteLocal = true
	break
	}
	if quoteLocal {
	local = quoteString(local)

	}

	s := "<" + local + "@" + domain + ">"

	if a.Name == "" {
	return s
	}

	// If every character is printable ASCII, quoting is simple.
	allPrintable := true
	for i := 0; i < len(a.Name); i++ {
	// isWSP here should actually be isFWS,
	// but we don't support folding yet.
	if !isVchar(a.Name[i]) && !isWSP(a.Name[i]) {
	allPrintable = false
	break
	}
	}
	if allPrintable {
	b := bytes.NewBufferString(`"`)
	for i := 0; i < len(a.Name); i++ {
	if !isQtext(a.Name[i]) && !isWSP(a.Name[i]) {
	b.WriteByte('\\')
	}
	b.WriteByte(a.Name[i])
	}
	b.WriteString(`" `)
	b.WriteString(s)
	return b.String()
	}

	// Text in an encoded-word in a display-name must not contain certain
	// characters like quotes or parentheses (see RFC 2047 section 5.3).
	// When this is the case encode the name using base64 encoding.
	if strings.ContainsAny(a.Name, "\"#$%&'(),.:;<>@[]^`{\|}~") {
	return mime.BEncoding.Encode("utf-8", a.Name) + " " + s
	}
	return mime.QEncoding.Encode("utf-8", a.Name) + " " + s
	}

	type addrParser struct {
	s string
	dec *mime.WordDecoder // may be nil
	}

	func (p addrParser) parseAddressList() ([]Address, error) {
	var list []*Address
	for {
	p.skipSpace()
	addr, err := p.parseAddress()
	if err != nil {
	return nil, err
	}
	list = append(list, addr)

	p.skipSpace()
	if p.empty() {
	break
	}
	if !p.consume(',') {
	return nil, errors.New("mail: expected comma")
	}
	}
	return list, nil
	}

	// parseAddress parses a single RFC 5322 address at the start of p.
	func (p addrParser) parseAddress() (addr Address, err error) {
	debug.Printf("parseAddress: %q", p.s)
	p.skipSpace()
	if p.empty() {
	return nil, errors.New("mail: no address")
	}

	// address = name-addr / addr-spec
	// TODO(dsymonds): Support parsing group address.

	// addr-spec has a more restricted grammar than name-addr,
	// so try parsing it first, and fallback to name-addr.
	// TODO(dsymonds): Is this really correct?
	spec, err := p.consumeAddrSpec()
	if err == nil {
	return &Address{
	Address: spec,
	}, err
	}
	debug.Printf("parseAddress: not an addr-spec: %v", err)
	debug.Printf("parseAddress: state is now %q", p.s)

	// display-name
	var displayName string
	if p.peek() != '<' {
	displayName, err = p.consumePhrase()
	if err != nil {
	return nil, err
	}
	}
	debug.Printf("parseAddress: displayName=%q", displayName)

	// angle-addr = "<" addr-spec ">"
	p.skipSpace()
	if !p.consume('<') {
	return nil, errors.New("mail: no angle-addr")
	}
	spec, err = p.consumeAddrSpec()
	if err != nil {
	return nil, err
	}
	if !p.consume('>') {
	return nil, errors.New("mail: unclosed angle-addr")
	}
	debug.Printf("parseAddress: spec=%q", spec)

	return &Address{
	Name: displayName,
	Address: spec,
	}, nil
	}

	// consumeAddrSpec parses a single RFC 5322 addr-spec at the start of p.
	func (p *addrParser) consumeAddrSpec() (spec string, err error) {
	debug.Printf("consumeAddrSpec: %q", p.s)

	orig := *p
	defer func() {
	if err != nil {
	*p = orig
	}
	}()

	// local-part = dot-atom / quoted-string
	var localPart string
	p.skipSpace()
	if p.empty() {
	return "", errors.New("mail: no addr-spec")
	}
	if p.peek() == '"' {
	// quoted-string
	debug.Printf("consumeAddrSpec: parsing quoted-string")
	localPart, err = p.consumeQuotedString()
	} else {
	// dot-atom
	debug.Printf("consumeAddrSpec: parsing dot-atom")
	localPart, err = p.consumeAtom(true, false)
	}
	if err != nil {
	debug.Printf("consumeAddrSpec: failed: %v", err)
	return "", err
	}

	if !p.consume('@') {
	return "", errors.New("mail: missing @ in addr-spec")
	}

	// domain = dot-atom / domain-literal
	var domain string
	p.skipSpace()
	if p.empty() {
	return "", errors.New("mail: no domain in addr-spec")
	}
	// TODO(dsymonds): Handle domain-literal
	domain, err = p.consumeAtom(true, false)
	if err != nil {
	return "", err
	}

	return localPart + "@" + domain, nil
	}

	// consumePhrase parses the RFC 5322 phrase at the start of p.
	func (p *addrParser) consumePhrase() (phrase string, err error) {
	debug.Printf("consumePhrase: [%s]", p.s)
	// phrase = 1*word
	var words []string
	for {
	// word = atom / quoted-string
	var word string
	p.skipSpace()
	if p.empty() {
	return "", errors.New("mail: missing phrase")
	}
	if p.peek() == '"' {
	// quoted-string
	word, err = p.consumeQuotedString()
	} else {
	// atom
	// We actually parse dot-atom here to be more permissive
	// than what RFC 5322 specifies.
	word, err = p.consumeAtom(true, true)
	if err == nil {
	word, err = p.decodeRFC2047Word(word)
	}
	}

	if err != nil {
	break
	}
	debug.Printf("consumePhrase: consumed %q", word)
	words = append(words, word)
	}
	// Ignore any error if we got at least one word.
	if err != nil && len(words) == 0 {
	debug.Printf("consumePhrase: hit err: %v", err)
	return "", fmt.Errorf("mail: missing word in phrase: %v", err)
	}
	phrase = strings.Join(words, " ")
	return phrase, nil
	}

	// consumeQuotedString parses the quoted string at the start of p.
	func (p *addrParser) consumeQuotedString() (qs string, err error) {
	// Assume first byte is '"'.
	i := 1
	qsb := make([]byte, 0, 10)
	Loop:
	for {
	if i >= p.len() {
	return "", errors.New("mail: unclosed quoted-string")
	}
	switch c := p.s[i]; {
	case c == '"':
	break Loop
	case c == '\\':
	if i+1 == p.len() {
	return "", errors.New("mail: unclosed quoted-string")
	}
	qsb = append(qsb, p.s[i+1])
	i += 2
	case isQtext(c), c == ' ':
	// qtext (printable US-ASCII excluding " and \), or
	// FWS (almost; we're ignoring CRLF)
	qsb = append(qsb, c)
	i++
	default:
	return "", fmt.Errorf("mail: bad character in quoted-string: %q", c)
	}
	}
	p.s = p.s[i+1:]
	if len(qsb) == 0 {
	return "", errors.New("mail: empty quoted-string")
	}
	return string(qsb), nil
	}

	var errNonASCII = errors.New("mail: unencoded non-ASCII text in address")

	// consumeAtom parses an RFC 5322 atom at the start of p.
	// If dot is true, consumeAtom parses an RFC 5322 dot-atom instead.
	// If permissive is true, consumeAtom will not fail on
	// leading/trailing/double dots in the atom (see golang.org/issue/4938).
	func (p *addrParser) consumeAtom(dot bool, permissive bool) (atom string, err error) {
	if c := p.peek(); !isAtext(c, false) {
	if c > 127 {
	return "", errNonASCII
	}
	return "", errors.New("mail: invalid string")
	}
	i := 1
	for ; i < p.len() && isAtext(p.s[i], dot); i++ {
	}
	if i < p.len() && p.s[i] > 127 {
	return "", errNonASCII
	}
	atom, p.s = string(p.s[:i]), p.s[i:]
	if !permissive {
	if strings.HasPrefix(atom, ".") {
	return "", errors.New("mail: leading dot in atom")
	}
	if strings.Contains(atom, "..") {
	return "", errors.New("mail: double dot in atom")
	}
	if strings.HasSuffix(atom, ".") {
	return "", errors.New("mail: trailing dot in atom")
	}
	}
	return atom, nil
	}

	func (p *addrParser) consume(c byte) bool {
	if p.empty() \|\| p.peek() != c {
	return false
	}
	p.s = p.s[1:]
	return true
	}

	// skipSpace skips the leading space and tab characters.
	func (p *addrParser) skipSpace() {
	p.s = strings.TrimLeft(p.s, " \t")
	}

	func (p *addrParser) peek() byte {
	return p.s[0]
	}

	func (p *addrParser) empty() bool {
	return p.len() == 0
	}

	func (p *addrParser) len() int {
	return len(p.s)
	}

	func (p *addrParser) decodeRFC2047Word(s string) (string, error) {
	if p.dec != nil {
	return p.dec.DecodeHeader(s)
	}

	dec, err := rfc2047Decoder.Decode(s)
	if err == nil {
	return dec, nil
	}

	if _, ok := err.(charsetError); ok {
	return s, err
	}

	// Ignore invalid RFC 2047 encoded-word errors.
	return s, nil
	}

	var rfc2047Decoder = mime.WordDecoder{
	CharsetReader: func(charset string, input io.Reader) (io.Reader, error) {
	return nil, charsetError(charset)
	},
	}

	type charsetError string

	func (e charsetError) Error() string {
	return fmt.Sprintf("charset not supported: %q", string(e))
	}

	var atextChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
	"abcdefghijklmnopqrstuvwxyz" +
	"0123456789" +
	"!#$%&'*+-/=?^_`{\|}~")

	// isAtext reports whether c is an RFC 5322 atext character.
	// If dot is true, period is included.
	func isAtext(c byte, dot bool) bool {
	if dot && c == '.' {
	return true
	}
	return bytes.IndexByte(atextChars, c) >= 0
	}

	// isQtext reports whether c is an RFC 5322 qtext character.
	func isQtext(c byte) bool {
	// Printable US-ASCII, excluding backslash or quote.
	if c == '\\' \|\| c == '"' {
	return false
	}
	return '!' <= c && c <= '~'
	}

	// quoteString renders a string as a RFC5322 quoted-string.
	func quoteString(s string) string {
	var buf bytes.Buffer
	buf.WriteByte('"')
	for _, c := range s {
	ch := byte(c)
	if isQtext(ch) \|\| isWSP(ch) {
	buf.WriteByte(ch)
	} else if isVchar(ch) {
	buf.WriteByte('\\')
	buf.WriteByte(ch)
	}
	}
	buf.WriteByte('"')
	return buf.String()
	}

	// isVchar reports whether c is an RFC 5322 VCHAR character.
	func isVchar(c byte) bool {
	// Visible (printing) characters.
	return '!' <= c && c <= '~'
	}

	// isWSP reports whether c is a WSP (white space).
	// WSP is a space or horizontal tab (RFC5234 Appendix B).
	func isWSP(c byte) bool {
	return c == ' ' \|\| c == '\t'
	}