build: move package sources from src/pkg to src

Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.

20 files changed, 3008 insertions, 0 deletions

diff --git a/src/mime/grammar.go b/src/mime/grammar.go
new file mode 100644
index 000000000..2347324aa
--- /dev/null
+++ b/src/mime/grammar.go
@@ -0,0 +1,32 @@
+// 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 mime
+
+import (
+	"strings"
+)
+
+// isTSpecial returns true if rune is in 'tspecials' as defined by RFC
+// 1521 and RFC 2045.
+func isTSpecial(r rune) bool {
+	return strings.IndexRune(`()<>@,;:\"/[]?=`, r) != -1
+}
+
+// isTokenChar returns true if rune is in 'token' as defined by RFC
+// 1521 and RFC 2045.
+func isTokenChar(r rune) bool {
+	// token := 1*<any (US-ASCII) CHAR except SPACE, CTLs,
+	//             or tspecials>
+	return r > 0x20 && r < 0x7f && !isTSpecial(r)
+}
+
+// isToken returns true if s is a 'token' as defined by RFC 1521
+// and RFC 2045.
+func isToken(s string) bool {
+	if s == "" {
+		return false
+	}
+	return strings.IndexFunc(s, isNotTokenChar) < 0
+}
diff --git a/src/mime/mediatype.go b/src/mime/mediatype.go
new file mode 100644
index 000000000..ad63f9bb9
--- /dev/null
+++ b/src/mime/mediatype.go
@@ -0,0 +1,358 @@
+// 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 mime
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+	"unicode"
+)
+
+// FormatMediaType serializes mediatype t and the parameters
+// param as a media type conforming to RFC 2045 and RFC 2616.
+// The type and parameter names are written in lower-case.
+// When any of the arguments result in a standard violation then
+// FormatMediaType returns the empty string.
+func FormatMediaType(t string, param map[string]string) string {
+	slash := strings.Index(t, "/")
+	if slash == -1 {
+		return ""
+	}
+	major, sub := t[:slash], t[slash+1:]
+	if !isToken(major) || !isToken(sub) {
+		return ""
+	}
+	var b bytes.Buffer
+	b.WriteString(strings.ToLower(major))
+	b.WriteByte('/')
+	b.WriteString(strings.ToLower(sub))
+
+	attrs := make([]string, 0, len(param))
+	for a := range param {
+		attrs = append(attrs, a)
+	}
+	sort.Strings(attrs)
+
+	for _, attribute := range attrs {
+		value := param[attribute]
+		b.WriteByte(';')
+		b.WriteByte(' ')
+		if !isToken(attribute) {
+			return ""
+		}
+		b.WriteString(strings.ToLower(attribute))
+		b.WriteByte('=')
+		if isToken(value) {
+			b.WriteString(value)
+			continue
+		}
+
+		b.WriteByte('"')
+		offset := 0
+		for index, character := range value {
+			if character == '"' || character == '\\' {
+				b.WriteString(value[offset:index])
+				offset = index
+				b.WriteByte('\\')
+			}
+			if character&0x80 != 0 {
+				return ""
+			}
+		}
+		b.WriteString(value[offset:])
+		b.WriteByte('"')
+	}
+	return b.String()
+}
+
+func checkMediaTypeDisposition(s string) error {
+	typ, rest := consumeToken(s)
+	if typ == "" {
+		return errors.New("mime: no media type")
+	}
+	if rest == "" {
+		return nil
+	}
+	if !strings.HasPrefix(rest, "/") {
+		return errors.New("mime: expected slash after first token")
+	}
+	subtype, rest := consumeToken(rest[1:])
+	if subtype == "" {
+		return errors.New("mime: expected token after slash")
+	}
+	if rest != "" {
+		return errors.New("mime: unexpected content after media subtype")
+	}
+	return nil
+}
+
+// ParseMediaType parses a media type value and any optional
+// parameters, per RFC 1521.  Media types are the values in
+// Content-Type and Content-Disposition headers (RFC 2183).
+// On success, ParseMediaType returns the media type converted
+// to lowercase and trimmed of white space and a non-nil map.
+// The returned map, params, maps from the lowercase
+// attribute to the attribute value with its case preserved.
+func ParseMediaType(v string) (mediatype string, params map[string]string, err error) {
+	i := strings.Index(v, ";")
+	if i == -1 {
+		i = len(v)
+	}
+	mediatype = strings.TrimSpace(strings.ToLower(v[0:i]))
+
+	err = checkMediaTypeDisposition(mediatype)
+	if err != nil {
+		return "", nil, err
+	}
+
+	params = make(map[string]string)
+
+	// Map of base parameter name -> parameter name -> value
+	// for parameters containing a '*' character.
+	// Lazily initialized.
+	var continuation map[string]map[string]string
+
+	v = v[i:]
+	for len(v) > 0 {
+		v = strings.TrimLeftFunc(v, unicode.IsSpace)
+		if len(v) == 0 {
+			break
+		}
+		key, value, rest := consumeMediaParam(v)
+		if key == "" {
+			if strings.TrimSpace(rest) == ";" {
+				// Ignore trailing semicolons.
+				// Not an error.
+				return
+			}
+			// Parse error.
+			return "", nil, errors.New("mime: invalid media parameter")
+		}
+
+		pmap := params
+		if idx := strings.Index(key, "*"); idx != -1 {
+			baseName := key[:idx]
+			if continuation == nil {
+				continuation = make(map[string]map[string]string)
+			}
+			var ok bool
+			if pmap, ok = continuation[baseName]; !ok {
+				continuation[baseName] = make(map[string]string)
+				pmap = continuation[baseName]
+			}
+		}
+		if _, exists := pmap[key]; exists {
+			// Duplicate parameter name is bogus.
+			return "", nil, errors.New("mime: duplicate parameter name")
+		}
+		pmap[key] = value
+		v = rest
+	}
+
+	// Stitch together any continuations or things with stars
+	// (i.e. RFC 2231 things with stars: "foo*0" or "foo*")
+	var buf bytes.Buffer
+	for key, pieceMap := range continuation {
+		singlePartKey := key + "*"
+		if v, ok := pieceMap[singlePartKey]; ok {
+			decv := decode2231Enc(v)
+			params[key] = decv
+			continue
+		}
+
+		buf.Reset()
+		valid := false
+		for n := 0; ; n++ {
+			simplePart := fmt.Sprintf("%s*%d", key, n)
+			if v, ok := pieceMap[simplePart]; ok {
+				valid = true
+				buf.WriteString(v)
+				continue
+			}
+			encodedPart := simplePart + "*"
+			if v, ok := pieceMap[encodedPart]; ok {
+				valid = true
+				if n == 0 {
+					buf.WriteString(decode2231Enc(v))
+				} else {
+					decv, _ := percentHexUnescape(v)
+					buf.WriteString(decv)
+				}
+			} else {
+				break
+			}
+		}
+		if valid {
+			params[key] = buf.String()
+		}
+	}
+
+	return
+}
+
+func decode2231Enc(v string) string {
+	sv := strings.SplitN(v, "'", 3)
+	if len(sv) != 3 {
+		return ""
+	}
+	// TODO: ignoring lang in sv[1] for now. If anybody needs it we'll
+	// need to decide how to expose it in the API. But I'm not sure
+	// anybody uses it in practice.
+	charset := strings.ToLower(sv[0])
+	if charset != "us-ascii" && charset != "utf-8" {
+		// TODO: unsupported encoding
+		return ""
+	}
+	encv, _ := percentHexUnescape(sv[2])
+	return encv
+}
+
+func isNotTokenChar(r rune) bool {
+	return !isTokenChar(r)
+}
+
+// consumeToken consumes a token from the beginning of provided
+// string, per RFC 2045 section 5.1 (referenced from 2183), and return
+// the token consumed and the rest of the string.  Returns ("", v) on
+// failure to consume at least one character.
+func consumeToken(v string) (token, rest string) {
+	notPos := strings.IndexFunc(v, isNotTokenChar)
+	if notPos == -1 {
+		return v, ""
+	}
+	if notPos == 0 {
+		return "", v
+	}
+	return v[0:notPos], v[notPos:]
+}
+
+// consumeValue consumes a "value" per RFC 2045, where a value is
+// either a 'token' or a 'quoted-string'.  On success, consumeValue
+// returns the value consumed (and de-quoted/escaped, if a
+// quoted-string) and the rest of the string.  On failure, returns
+// ("", v).
+func consumeValue(v string) (value, rest string) {
+	if !strings.HasPrefix(v, `"`) && !strings.HasPrefix(v, `'`) {
+		return consumeToken(v)
+	}
+
+	leadQuote := rune(v[0])
+
+	// parse a quoted-string
+	rest = v[1:] // consume the leading quote
+	buffer := new(bytes.Buffer)
+	var idx int
+	var r rune
+	var nextIsLiteral bool
+	for idx, r = range rest {
+		switch {
+		case nextIsLiteral:
+			buffer.WriteRune(r)
+			nextIsLiteral = false
+		case r == leadQuote:
+			return buffer.String(), rest[idx+1:]
+		case r == '\\':
+			nextIsLiteral = true
+		case r != '\r' && r != '\n':
+			buffer.WriteRune(r)
+		default:
+			return "", v
+		}
+	}
+	return "", v
+}
+
+func consumeMediaParam(v string) (param, value, rest string) {
+	rest = strings.TrimLeftFunc(v, unicode.IsSpace)
+	if !strings.HasPrefix(rest, ";") {
+		return "", "", v
+	}
+
+	rest = rest[1:] // consume semicolon
+	rest = strings.TrimLeftFunc(rest, unicode.IsSpace)
+	param, rest = consumeToken(rest)
+	param = strings.ToLower(param)
+	if param == "" {
+		return "", "", v
+	}
+
+	rest = strings.TrimLeftFunc(rest, unicode.IsSpace)
+	if !strings.HasPrefix(rest, "=") {
+		return "", "", v
+	}
+	rest = rest[1:] // consume equals sign
+	rest = strings.TrimLeftFunc(rest, unicode.IsSpace)
+	value, rest = consumeValue(rest)
+	if value == "" {
+		return "", "", v
+	}
+	return param, value, rest
+}
+
+func percentHexUnescape(s string) (string, error) {
+	// Count %, check that they're well-formed.
+	percents := 0
+	for i := 0; i < len(s); {
+		if s[i] != '%' {
+			i++
+			continue
+		}
+		percents++
+		if i+2 >= len(s) || !ishex(s[i+1]) || !ishex(s[i+2]) {
+			s = s[i:]
+			if len(s) > 3 {
+				s = s[0:3]
+			}
+			return "", fmt.Errorf("mime: bogus characters after %%: %q", s)
+		}
+		i += 3
+	}
+	if percents == 0 {
+		return s, nil
+	}
+
+	t := make([]byte, len(s)-2*percents)
+	j := 0
+	for i := 0; i < len(s); {
+		switch s[i] {
+		case '%':
+			t[j] = unhex(s[i+1])<<4 | unhex(s[i+2])
+			j++
+			i += 3
+		default:
+			t[j] = s[i]
+			j++
+			i++
+		}
+	}
+	return string(t), nil
+}
+
+func ishex(c byte) bool {
+	switch {
+	case '0' <= c && c <= '9':
+		return true
+	case 'a' <= c && c <= 'f':
+		return true
+	case 'A' <= c && c <= 'F':
+		return true
+	}
+	return false
+}
+
+func unhex(c byte) byte {
+	switch {
+	case '0' <= c && c <= '9':
+		return c - '0'
+	case 'a' <= c && c <= 'f':
+		return c - 'a' + 10
+	case 'A' <= c && c <= 'F':
+		return c - 'A' + 10
+	}
+	return 0
+}
diff --git a/src/mime/mediatype_test.go b/src/mime/mediatype_test.go
new file mode 100644
index 000000000..026bfa4d7
--- /dev/null
+++ b/src/mime/mediatype_test.go
@@ -0,0 +1,306 @@
+// 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 mime
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestConsumeToken(t *testing.T) {
+	tests := [...][3]string{
+		{"foo bar", "foo", " bar"},
+		{"bar", "bar", ""},
+		{"", "", ""},
+		{" foo", "", " foo"},
+	}
+	for _, test := range tests {
+		token, rest := consumeToken(test[0])
+		expectedToken := test[1]
+		expectedRest := test[2]
+		if token != expectedToken {
+			t.Errorf("expected to consume token '%s', not '%s' from '%s'",
+				expectedToken, token, test[0])
+		} else if rest != expectedRest {
+			t.Errorf("expected to have left '%s', not '%s' after reading token '%s' from '%s'",
+				expectedRest, rest, token, test[0])
+		}
+	}
+}
+
+func TestConsumeValue(t *testing.T) {
+	tests := [...][3]string{
+		{"foo bar", "foo", " bar"},
+		{"bar", "bar", ""},
+		{" bar ", "", " bar "},
+		{`"My value"end`, "My value", "end"},
+		{`"My value" end`, "My value", " end"},
+		{`"\\" rest`, "\\", " rest"},
+		{`"My \" value"end`, "My \" value", "end"},
+		{`"\" rest`, "", `"\" rest`},
+	}
+	for _, test := range tests {
+		value, rest := consumeValue(test[0])
+		expectedValue := test[1]
+		expectedRest := test[2]
+		if value != expectedValue {
+			t.Errorf("expected to consume value [%s], not [%s] from [%s]",
+				expectedValue, value, test[0])
+		} else if rest != expectedRest {
+			t.Errorf("expected to have left [%s], not [%s] after reading value [%s] from [%s]",
+				expectedRest, rest, value, test[0])
+		}
+	}
+}
+
+func TestConsumeMediaParam(t *testing.T) {
+	tests := [...][4]string{
+		{" ; foo=bar", "foo", "bar", ""},
+		{"; foo=bar", "foo", "bar", ""},
+		{";foo=bar", "foo", "bar", ""},
+		{";FOO=bar", "foo", "bar", ""},
+		{`;foo="bar"`, "foo", "bar", ""},
+		{`;foo="bar"; `, "foo", "bar", "; "},
+		{`;foo="bar"; foo=baz`, "foo", "bar", "; foo=baz"},
+		{` ; boundary=----CUT;`, "boundary", "----CUT", ";"},
+		{` ; key=value;  blah="value";name="foo" `, "key", "value", `;  blah="value";name="foo" `},
+		{`;  blah="value";name="foo" `, "blah", "value", `;name="foo" `},
+		{`;name="foo" `, "name", "foo", ` `},
+	}
+	for _, test := range tests {
+		param, value, rest := consumeMediaParam(test[0])
+		expectedParam := test[1]
+		expectedValue := test[2]
+		expectedRest := test[3]
+		if param != expectedParam {
+			t.Errorf("expected to consume param [%s], not [%s] from [%s]",
+				expectedParam, param, test[0])
+		} else if value != expectedValue {
+			t.Errorf("expected to consume value [%s], not [%s] from [%s]",
+				expectedValue, value, test[0])
+		} else if rest != expectedRest {
+			t.Errorf("expected to have left [%s], not [%s] after reading [%s/%s] from [%s]",
+				expectedRest, rest, param, value, test[0])
+		}
+	}
+}
+
+type mediaTypeTest struct {
+	in string
+	t  string
+	p  map[string]string
+}
+
+func TestParseMediaType(t *testing.T) {
+	// Convenience map initializer
+	m := func(s ...string) map[string]string {
+		sm := make(map[string]string)
+		for i := 0; i < len(s); i += 2 {
+			sm[s[i]] = s[i+1]
+		}
+		return sm
+	}
+
+	nameFoo := map[string]string{"name": "foo"}
+	tests := []mediaTypeTest{
+		{`form-data; name="foo"`, "form-data", nameFoo},
+		{` form-data ; name=foo`, "form-data", nameFoo},
+		{`FORM-DATA;name="foo"`, "form-data", nameFoo},
+		{` FORM-DATA ; name="foo"`, "form-data", nameFoo},
+		{` FORM-DATA ; name="foo"`, "form-data", nameFoo},
+
+		{`form-data; key=value;  blah="value";name="foo" `,
+			"form-data",
+			m("key", "value", "blah", "value", "name", "foo")},
+
+		{`foo; key=val1; key=the-key-appears-again-which-is-bogus`,
+			"", m()},
+
+		// From RFC 2231:
+		{`application/x-stuff; title*=us-ascii'en-us'This%20is%20%2A%2A%2Afun%2A%2A%2A`,
+			"application/x-stuff",
+			m("title", "This is ***fun***")},
+
+		{`message/external-body; access-type=URL; ` +
+			`URL*0="ftp://";` +
+			`URL*1="cs.utk.edu/pub/moore/bulk-mailer/bulk-mailer.tar"`,
+			"message/external-body",
+			m("access-type", "URL",
+				"url", "ftp://cs.utk.edu/pub/moore/bulk-mailer/bulk-mailer.tar")},
+
+		{`application/x-stuff; ` +
+			`title*0*=us-ascii'en'This%20is%20even%20more%20; ` +
+			`title*1*=%2A%2A%2Afun%2A%2A%2A%20; ` +
+			`title*2="isn't it!"`,
+			"application/x-stuff",
+			m("title", "This is even more ***fun*** isn't it!")},
+
+		// Tests from http://greenbytes.de/tech/tc2231/
+		// TODO(bradfitz): add the rest of the tests from that site.
+		{`attachment; filename="f\oo.html"`,
+			"attachment",
+			m("filename", "foo.html")},
+		{`attachment; filename="\"quoting\" tested.html"`,
+			"attachment",
+			m("filename", `"quoting" tested.html`)},
+		{`attachment; filename="Here's a semicolon;.html"`,
+			"attachment",
+			m("filename", "Here's a semicolon;.html")},
+		{`attachment; foo="\"\\";filename="foo.html"`,
+			"attachment",
+			m("foo", "\"\\", "filename", "foo.html")},
+		{`attachment; filename=foo.html`,
+			"attachment",
+			m("filename", "foo.html")},
+		{`attachment; filename=foo.html ;`,
+			"attachment",
+			m("filename", "foo.html")},
+		{`attachment; filename='foo.html'`,
+			"attachment",
+			m("filename", "foo.html")},
+		{`attachment; filename="foo-%41.html"`,
+			"attachment",
+			m("filename", "foo-%41.html")},
+		{`attachment; filename="foo-%\41.html"`,
+			"attachment",
+			m("filename", "foo-%41.html")},
+		{`filename=foo.html`,
+			"", m()},
+		{`x=y; filename=foo.html`,
+			"", m()},
+		{`"foo; filename=bar;baz"; filename=qux`,
+			"", m()},
+		{`inline; attachment; filename=foo.html`,
+			"", m()},
+		{`attachment; filename="foo.html".txt`,
+			"", m()},
+		{`attachment; filename="bar`,
+			"", m()},
+		{`attachment; creation-date="Wed, 12 Feb 1997 16:29:51 -0500"`,
+			"attachment",
+			m("creation-date", "Wed, 12 Feb 1997 16:29:51 -0500")},
+		{`foobar`, "foobar", m()},
+		{`attachment; filename* =UTF-8''foo-%c3%a4.html`,
+			"attachment",
+			m("filename", "foo-ä.html")},
+		{`attachment; filename*=UTF-8''A-%2541.html`,
+			"attachment",
+			m("filename", "A-%41.html")},
+		{`attachment; filename*0="foo."; filename*1="html"`,
+			"attachment",
+			m("filename", "foo.html")},
+		{`attachment; filename*0*=UTF-8''foo-%c3%a4; filename*1=".html"`,
+			"attachment",
+			m("filename", "foo-ä.html")},
+		{`attachment; filename*0="foo"; filename*01="bar"`,
+			"attachment",
+			m("filename", "foo")},
+		{`attachment; filename*0="foo"; filename*2="bar"`,
+			"attachment",
+			m("filename", "foo")},
+		{`attachment; filename*1="foo"; filename*2="bar"`,
+			"attachment", m()},
+		{`attachment; filename*1="bar"; filename*0="foo"`,
+			"attachment",
+			m("filename", "foobar")},
+		{`attachment; filename="foo-ae.html"; filename*=UTF-8''foo-%c3%a4.html`,
+			"attachment",
+			m("filename", "foo-ä.html")},
+		{`attachment; filename*=UTF-8''foo-%c3%a4.html; filename="foo-ae.html"`,
+			"attachment",
+			m("filename", "foo-ä.html")},
+
+		// Browsers also just send UTF-8 directly without RFC 2231,
+		// at least when the source page is served with UTF-8.
+		{`form-data; firstname="Брэд"; lastname="Фицпатрик"`,
+			"form-data",
+			m("firstname", "Брэд", "lastname", "Фицпатрик")},
+	}
+	for _, test := range tests {
+		mt, params, err := ParseMediaType(test.in)
+		if err != nil {
+			if test.t != "" {
+				t.Errorf("for input %q, unexpected error: %v", test.in, err)
+				continue
+			}
+			continue
+		}
+		if g, e := mt, test.t; g != e {
+			t.Errorf("for input %q, expected type %q, got %q",
+				test.in, e, g)
+			continue
+		}
+		if len(params) == 0 && len(test.p) == 0 {
+			continue
+		}
+		if !reflect.DeepEqual(params, test.p) {
+			t.Errorf("for input %q, wrong params.\n"+
+				"expected: %#v\n"+
+				"     got: %#v",
+				test.in, test.p, params)
+		}
+	}
+}
+
+type badMediaTypeTest struct {
+	in  string
+	err string
+}
+
+var badMediaTypeTests = []badMediaTypeTest{
+	{"bogus ;=========", "mime: invalid media parameter"},
+	{"bogus/<script>alert</script>", "mime: expected token after slash"},
+	{"bogus/bogus<script>alert</script>", "mime: unexpected content after media subtype"},
+}
+
+func TestParseMediaTypeBogus(t *testing.T) {
+	for _, tt := range badMediaTypeTests {
+		mt, params, err := ParseMediaType(tt.in)
+		if err == nil {
+			t.Errorf("ParseMediaType(%q) = nil error; want parse error", tt.in)
+			continue
+		}
+		if err.Error() != tt.err {
+			t.Errorf("ParseMediaType(%q) = err %q; want %q", tt.in, err.Error(), tt.err)
+		}
+		if params != nil {
+			t.Errorf("ParseMediaType(%q): got non-nil params on error", tt.in)
+		}
+		if mt != "" {
+			t.Errorf("ParseMediaType(%q): got non-empty media type string on error", tt.in)
+		}
+	}
+}
+
+type formatTest struct {
+	typ    string
+	params map[string]string
+	want   string
+}
+
+var formatTests = []formatTest{
+	{"noslash", nil, ""},
+	{"foo bar/baz", nil, ""},
+	{"foo/bar baz", nil, ""},
+	{"foo/BAR", nil, "foo/bar"},
+	{"foo/BAR", map[string]string{"X": "Y"}, "foo/bar; x=Y"},
+	{"foo/BAR", map[string]string{"space": "With space"}, `foo/bar; space="With space"`},
+	{"foo/BAR", map[string]string{"quote": `With "quote`}, `foo/bar; quote="With \"quote"`},
+	{"foo/BAR", map[string]string{"bslash": `With \backslash`}, `foo/bar; bslash="With \\backslash"`},
+	{"foo/BAR", map[string]string{"both": `With \backslash and "quote`}, `foo/bar; both="With \\backslash and \"quote"`},
+	{"foo/BAR", map[string]string{"": "empty attribute"}, ""},
+	{"foo/BAR", map[string]string{"bad attribute": "baz"}, ""},
+	{"foo/BAR", map[string]string{"nonascii": "not an ascii character: ä"}, ""},
+	{"foo/bar", map[string]string{"a": "av", "b": "bv", "c": "cv"}, "foo/bar; a=av; b=bv; c=cv"},
+}
+
+func TestFormatMediaType(t *testing.T) {
+	for i, tt := range formatTests {
+		got := FormatMediaType(tt.typ, tt.params)
+		if got != tt.want {
+			t.Errorf("%d. FormatMediaType(%q, %v) = %q; want %q", i, tt.typ, tt.params, got, tt.want)
+		}
+	}
+}
diff --git a/src/mime/multipart/example_test.go b/src/mime/multipart/example_test.go
new file mode 100644
index 000000000..6d6ba81d5
--- /dev/null
+++ b/src/mime/multipart/example_test.go
@@ -0,0 +1,53 @@
+// Copyright 2014 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 multipart_test
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"mime"
+	"mime/multipart"
+	"net/mail"
+	"strings"
+)
+
+func ExampleNewReader() {
+	msg := &mail.Message{
+		Header: map[string][]string{
+			"Content-Type": {"multipart/mixed; boundary=foo"},
+		},
+		Body: strings.NewReader(
+			"--foo\r\nFoo: one\r\n\r\nA section\r\n" +
+				"--foo\r\nFoo: two\r\n\r\nAnd another\r\n" +
+				"--foo--\r\n"),
+	}
+	mediaType, params, err := mime.ParseMediaType(msg.Header.Get("Content-Type"))
+	if err != nil {
+		log.Fatal(err)
+	}
+	if strings.HasPrefix(mediaType, "multipart/") {
+		mr := multipart.NewReader(msg.Body, params["boundary"])
+		for {
+			p, err := mr.NextPart()
+			if err == io.EOF {
+				return
+			}
+			if err != nil {
+				log.Fatal(err)
+			}
+			slurp, err := ioutil.ReadAll(p)
+			if err != nil {
+				log.Fatal(err)
+			}
+			fmt.Printf("Part %q: %q\n", p.Header.Get("Foo"), slurp)
+		}
+	}
+
+	// Output:
+	// Part "one": "A section"
+	// Part "two": "And another"
+}
diff --git a/src/mime/multipart/formdata.go b/src/mime/multipart/formdata.go
new file mode 100644
index 000000000..eee53fc8d
--- /dev/null
+++ b/src/mime/multipart/formdata.go
@@ -0,0 +1,157 @@
+// 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 multipart
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"io/ioutil"
+	"net/textproto"
+	"os"
+)
+
+// TODO(adg,bradfitz): find a way to unify the DoS-prevention strategy here
+// with that of the http package's ParseForm.
+
+// ReadForm parses an entire multipart message whose parts have
+// a Content-Disposition of "form-data".
+// It stores up to maxMemory bytes of the file parts in memory
+// and the remainder on disk in temporary files.
+func (r *Reader) ReadForm(maxMemory int64) (f *Form, err error) {
+	form := &Form{make(map[string][]string), make(map[string][]*FileHeader)}
+	defer func() {
+		if err != nil {
+			form.RemoveAll()
+		}
+	}()
+
+	maxValueBytes := int64(10 << 20) // 10 MB is a lot of text.
+	for {
+		p, err := r.NextPart()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		name := p.FormName()
+		if name == "" {
+			continue
+		}
+		filename := p.FileName()
+
+		var b bytes.Buffer
+
+		if filename == "" {
+			// value, store as string in memory
+			n, err := io.CopyN(&b, p, maxValueBytes)
+			if err != nil && err != io.EOF {
+				return nil, err
+			}
+			maxValueBytes -= n
+			if maxValueBytes == 0 {
+				return nil, errors.New("multipart: message too large")
+			}
+			form.Value[name] = append(form.Value[name], b.String())
+			continue
+		}
+
+		// file, store in memory or on disk
+		fh := &FileHeader{
+			Filename: filename,
+			Header:   p.Header,
+		}
+		n, err := io.CopyN(&b, p, maxMemory+1)
+		if err != nil && err != io.EOF {
+			return nil, err
+		}
+		if n > maxMemory {
+			// too big, write to disk and flush buffer
+			file, err := ioutil.TempFile("", "multipart-")
+			if err != nil {
+				return nil, err
+			}
+			defer file.Close()
+			_, err = io.Copy(file, io.MultiReader(&b, p))
+			if err != nil {
+				os.Remove(file.Name())
+				return nil, err
+			}
+			fh.tmpfile = file.Name()
+		} else {
+			fh.content = b.Bytes()
+			maxMemory -= n
+		}
+		form.File[name] = append(form.File[name], fh)
+	}
+
+	return form, nil
+}
+
+// Form is a parsed multipart form.
+// Its File parts are stored either in memory or on disk,
+// and are accessible via the *FileHeader's Open method.
+// Its Value parts are stored as strings.
+// Both are keyed by field name.
+type Form struct {
+	Value map[string][]string
+	File  map[string][]*FileHeader
+}
+
+// RemoveAll removes any temporary files associated with a Form.
+func (f *Form) RemoveAll() error {
+	var err error
+	for _, fhs := range f.File {
+		for _, fh := range fhs {
+			if fh.tmpfile != "" {
+				e := os.Remove(fh.tmpfile)
+				if e != nil && err == nil {
+					err = e
+				}
+			}
+		}
+	}
+	return err
+}
+
+// A FileHeader describes a file part of a multipart request.
+type FileHeader struct {
+	Filename string
+	Header   textproto.MIMEHeader
+
+	content []byte
+	tmpfile string
+}
+
+// Open opens and returns the FileHeader's associated File.
+func (fh *FileHeader) Open() (File, error) {
+	if b := fh.content; b != nil {
+		r := io.NewSectionReader(bytes.NewReader(b), 0, int64(len(b)))
+		return sectionReadCloser{r}, nil
+	}
+	return os.Open(fh.tmpfile)
+}
+
+// File is an interface to access the file part of a multipart message.
+// Its contents may be either stored in memory or on disk.
+// If stored on disk, the File's underlying concrete type will be an *os.File.
+type File interface {
+	io.Reader
+	io.ReaderAt
+	io.Seeker
+	io.Closer
+}
+
+// helper types to turn a []byte into a File
+
+type sectionReadCloser struct {
+	*io.SectionReader
+}
+
+func (rc sectionReadCloser) Close() error {
+	return nil
+}
diff --git a/src/mime/multipart/formdata_test.go b/src/mime/multipart/formdata_test.go
new file mode 100644
index 000000000..6e2388baf
--- /dev/null
+++ b/src/mime/multipart/formdata_test.go
@@ -0,0 +1,90 @@
+// 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 multipart
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"regexp"
+	"strings"
+	"testing"
+)
+
+func TestReadForm(t *testing.T) {
+	testBody := regexp.MustCompile("\n").ReplaceAllString(message, "\r\n")
+	b := strings.NewReader(testBody)
+	r := NewReader(b, boundary)
+	f, err := r.ReadForm(25)
+	if err != nil {
+		t.Fatal("ReadForm:", err)
+	}
+	defer f.RemoveAll()
+	if g, e := f.Value["texta"][0], textaValue; g != e {
+		t.Errorf("texta value = %q, want %q", g, e)
+	}
+	if g, e := f.Value["textb"][0], textbValue; g != e {
+		t.Errorf("texta value = %q, want %q", g, e)
+	}
+	fd := testFile(t, f.File["filea"][0], "filea.txt", fileaContents)
+	if _, ok := fd.(*os.File); ok {
+		t.Error("file is *os.File, should not be")
+	}
+	fd.Close()
+	fd = testFile(t, f.File["fileb"][0], "fileb.txt", filebContents)
+	if _, ok := fd.(*os.File); !ok {
+		t.Errorf("file has unexpected underlying type %T", fd)
+	}
+	fd.Close()
+}
+
+func testFile(t *testing.T, fh *FileHeader, efn, econtent string) File {
+	if fh.Filename != efn {
+		t.Errorf("filename = %q, want %q", fh.Filename, efn)
+	}
+	f, err := fh.Open()
+	if err != nil {
+		t.Fatal("opening file:", err)
+	}
+	b := new(bytes.Buffer)
+	_, err = io.Copy(b, f)
+	if err != nil {
+		t.Fatal("copying contents:", err)
+	}
+	if g := b.String(); g != econtent {
+		t.Errorf("contents = %q, want %q", g, econtent)
+	}
+	return f
+}
+
+const (
+	fileaContents = "This is a test file."
+	filebContents = "Another test file."
+	textaValue    = "foo"
+	textbValue    = "bar"
+	boundary      = `MyBoundary`
+)
+
+const message = `
+--MyBoundary
+Content-Disposition: form-data; name="filea"; filename="filea.txt"
+Content-Type: text/plain
+
+` + fileaContents + `
+--MyBoundary
+Content-Disposition: form-data; name="fileb"; filename="fileb.txt"
+Content-Type: text/plain
+
+` + filebContents + `
+--MyBoundary
+Content-Disposition: form-data; name="texta"
+
+` + textaValue + `
+--MyBoundary
+Content-Disposition: form-data; name="textb"
+
+` + textbValue + `
+--MyBoundary--
+`
diff --git a/src/mime/multipart/multipart.go b/src/mime/multipart/multipart.go
new file mode 100644
index 000000000..01a667d93
--- /dev/null
+++ b/src/mime/multipart/multipart.go
@@ -0,0 +1,348 @@
+// 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 multipart implements MIME multipart parsing, as defined in RFC
+2046.
+
+The implementation is sufficient for HTTP (RFC 2388) and the multipart
+bodies generated by popular browsers.
+*/
+package multipart
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"mime"
+	"net/textproto"
+)
+
+var emptyParams = make(map[string]string)
+
+// A Part represents a single part in a multipart body.
+type Part struct {
+	// The headers of the body, if any, with the keys canonicalized
+	// in the same fashion that the Go http.Request headers are.
+	// For example, "foo-bar" changes case to "Foo-Bar"
+	//
+	// As a special case, if the "Content-Transfer-Encoding" header
+	// has a value of "quoted-printable", that header is instead
+	// hidden from this map and the body is transparently decoded
+	// during Read calls.
+	Header textproto.MIMEHeader
+
+	buffer    *bytes.Buffer
+	mr        *Reader
+	bytesRead int
+
+	disposition       string
+	dispositionParams map[string]string
+
+	// r is either a reader directly reading from mr, or it's a
+	// wrapper around such a reader, decoding the
+	// Content-Transfer-Encoding
+	r io.Reader
+}
+
+// FormName returns the name parameter if p has a Content-Disposition
+// of type "form-data".  Otherwise it returns the empty string.
+func (p *Part) FormName() string {
+	// See http://tools.ietf.org/html/rfc2183 section 2 for EBNF
+	// of Content-Disposition value format.
+	if p.dispositionParams == nil {
+		p.parseContentDisposition()
+	}
+	if p.disposition != "form-data" {
+		return ""
+	}
+	return p.dispositionParams["name"]
+}
+
+// FileName returns the filename parameter of the Part's
+// Content-Disposition header.
+func (p *Part) FileName() string {
+	if p.dispositionParams == nil {
+		p.parseContentDisposition()
+	}
+	return p.dispositionParams["filename"]
+}
+
+func (p *Part) parseContentDisposition() {
+	v := p.Header.Get("Content-Disposition")
+	var err error
+	p.disposition, p.dispositionParams, err = mime.ParseMediaType(v)
+	if err != nil {
+		p.dispositionParams = emptyParams
+	}
+}
+
+// NewReader creates a new multipart Reader reading from r using the
+// given MIME boundary.
+//
+// The boundary is usually obtained from the "boundary" parameter of
+// the message's "Content-Type" header. Use mime.ParseMediaType to
+// parse such headers.
+func NewReader(r io.Reader, boundary string) *Reader {
+	b := []byte("\r\n--" + boundary + "--")
+	return &Reader{
+		bufReader:        bufio.NewReader(r),
+		nl:               b[:2],
+		nlDashBoundary:   b[:len(b)-2],
+		dashBoundaryDash: b[2:],
+		dashBoundary:     b[2 : len(b)-2],
+	}
+}
+
+func newPart(mr *Reader) (*Part, error) {
+	bp := &Part{
+		Header: make(map[string][]string),
+		mr:     mr,
+		buffer: new(bytes.Buffer),
+	}
+	if err := bp.populateHeaders(); err != nil {
+		return nil, err
+	}
+	bp.r = partReader{bp}
+	const cte = "Content-Transfer-Encoding"
+	if bp.Header.Get(cte) == "quoted-printable" {
+		bp.Header.Del(cte)
+		bp.r = newQuotedPrintableReader(bp.r)
+	}
+	return bp, nil
+}
+
+func (bp *Part) populateHeaders() error {
+	r := textproto.NewReader(bp.mr.bufReader)
+	header, err := r.ReadMIMEHeader()
+	if err == nil {
+		bp.Header = header
+	}
+	return err
+}
+
+// Read reads the body of a part, after its headers and before the
+// next part (if any) begins.
+func (p *Part) Read(d []byte) (n int, err error) {
+	return p.r.Read(d)
+}
+
+// partReader implements io.Reader by reading raw bytes directly from the
+// wrapped *Part, without doing any Transfer-Encoding decoding.
+type partReader struct {
+	p *Part
+}
+
+func (pr partReader) Read(d []byte) (n int, err error) {
+	p := pr.p
+	defer func() {
+		p.bytesRead += n
+	}()
+	if p.buffer.Len() >= len(d) {
+		// Internal buffer of unconsumed data is large enough for
+		// the read request.  No need to parse more at the moment.
+		return p.buffer.Read(d)
+	}
+	peek, err := p.mr.bufReader.Peek(4096) // TODO(bradfitz): add buffer size accessor
+
+	// Look for an immediate empty part without a leading \r\n
+	// before the boundary separator.  Some MIME code makes empty
+	// parts like this. Most browsers, however, write the \r\n
+	// before the subsequent boundary even for empty parts and
+	// won't hit this path.
+	if p.bytesRead == 0 && p.mr.peekBufferIsEmptyPart(peek) {
+		return 0, io.EOF
+	}
+	unexpectedEOF := err == io.EOF
+	if err != nil && !unexpectedEOF {
+		return 0, fmt.Errorf("multipart: Part Read: %v", err)
+	}
+	if peek == nil {
+		panic("nil peek buf")
+	}
+
+	// Search the peek buffer for "\r\n--boundary". If found,
+	// consume everything up to the boundary. If not, consume only
+	// as much of the peek buffer as cannot hold the boundary
+	// string.
+	nCopy := 0
+	foundBoundary := false
+	if idx := bytes.Index(peek, p.mr.nlDashBoundary); idx != -1 {
+		nCopy = idx
+		foundBoundary = true
+	} else if safeCount := len(peek) - len(p.mr.nlDashBoundary); safeCount > 0 {
+		nCopy = safeCount
+	} else if unexpectedEOF {
+		// If we've run out of peek buffer and the boundary
+		// wasn't found (and can't possibly fit), we must have
+		// hit the end of the file unexpectedly.
+		return 0, io.ErrUnexpectedEOF
+	}
+	if nCopy > 0 {
+		if _, err := io.CopyN(p.buffer, p.mr.bufReader, int64(nCopy)); err != nil {
+			return 0, err
+		}
+	}
+	n, err = p.buffer.Read(d)
+	if err == io.EOF && !foundBoundary {
+		// If the boundary hasn't been reached there's more to
+		// read, so don't pass through an EOF from the buffer
+		err = nil
+	}
+	return
+}
+
+func (p *Part) Close() error {
+	io.Copy(ioutil.Discard, p)
+	return nil
+}
+
+// Reader is an iterator over parts in a MIME multipart body.
+// Reader's underlying parser consumes its input as needed.  Seeking
+// isn't supported.
+type Reader struct {
+	bufReader *bufio.Reader
+
+	currentPart *Part
+	partsRead   int
+
+	nl               []byte // "\r\n" or "\n" (set after seeing first boundary line)
+	nlDashBoundary   []byte // nl + "--boundary"
+	dashBoundaryDash []byte // "--boundary--"
+	dashBoundary     []byte // "--boundary"
+}
+
+// NextPart returns the next part in the multipart or an error.
+// When there are no more parts, the error io.EOF is returned.
+func (r *Reader) NextPart() (*Part, error) {
+	if r.currentPart != nil {
+		r.currentPart.Close()
+	}
+
+	expectNewPart := false
+	for {
+		line, err := r.bufReader.ReadSlice('\n')
+		if err == io.EOF && r.isFinalBoundary(line) {
+			// If the buffer ends in "--boundary--" without the
+			// trailing "\r\n", ReadSlice will return an error
+			// (since it's missing the '\n'), but this is a valid
+			// multipart EOF so we need to return io.EOF instead of
+			// a fmt-wrapped one.
+			return nil, io.EOF
+		}
+		if err != nil {
+			return nil, fmt.Errorf("multipart: NextPart: %v", err)
+		}
+
+		if r.isBoundaryDelimiterLine(line) {
+			r.partsRead++
+			bp, err := newPart(r)
+			if err != nil {
+				return nil, err
+			}
+			r.currentPart = bp
+			return bp, nil
+		}
+
+		if r.isFinalBoundary(line) {
+			// Expected EOF
+			return nil, io.EOF
+		}
+
+		if expectNewPart {
+			return nil, fmt.Errorf("multipart: expecting a new Part; got line %q", string(line))
+		}
+
+		if r.partsRead == 0 {
+			// skip line
+			continue
+		}
+
+		// Consume the "\n" or "\r\n" separator between the
+		// body of the previous part and the boundary line we
+		// now expect will follow. (either a new part or the
+		// end boundary)
+		if bytes.Equal(line, r.nl) {
+			expectNewPart = true
+			continue
+		}
+
+		return nil, fmt.Errorf("multipart: unexpected line in Next(): %q", line)
+	}
+}
+
+// isFinalBoundary reports whether line is the final boundary line
+// indicating that all parts are over.
+// It matches `^--boundary--[ \t]*(\r\n)?$`
+func (mr *Reader) isFinalBoundary(line []byte) bool {
+	if !bytes.HasPrefix(line, mr.dashBoundaryDash) {
+		return false
+	}
+	rest := line[len(mr.dashBoundaryDash):]
+	rest = skipLWSPChar(rest)
+	return len(rest) == 0 || bytes.Equal(rest, mr.nl)
+}
+
+func (mr *Reader) isBoundaryDelimiterLine(line []byte) (ret bool) {
+	// http://tools.ietf.org/html/rfc2046#section-5.1
+	//   The boundary delimiter line is then defined as a line
+	//   consisting entirely of two hyphen characters ("-",
+	//   decimal value 45) followed by the boundary parameter
+	//   value from the Content-Type header field, optional linear
+	//   whitespace, and a terminating CRLF.
+	if !bytes.HasPrefix(line, mr.dashBoundary) {
+		return false
+	}
+	rest := line[len(mr.dashBoundary):]
+	rest = skipLWSPChar(rest)
+
+	// On the first part, see our lines are ending in \n instead of \r\n
+	// and switch into that mode if so.  This is a violation of the spec,
+	// but occurs in practice.
+	if mr.partsRead == 0 && len(rest) == 1 && rest[0] == '\n' {
+		mr.nl = mr.nl[1:]
+		mr.nlDashBoundary = mr.nlDashBoundary[1:]
+	}
+	return bytes.Equal(rest, mr.nl)
+}
+
+// peekBufferIsEmptyPart reports whether the provided peek-ahead
+// buffer represents an empty part. It is called only if we've not
+// already read any bytes in this part and checks for the case of MIME
+// software not writing the \r\n on empty parts. Some does, some
+// doesn't.
+//
+// This checks that what follows the "--boundary" is actually the end
+// ("--boundary--" with optional whitespace) or optional whitespace
+// and then a newline, so we don't catch "--boundaryFAKE", in which
+// case the whole line is part of the data.
+func (mr *Reader) peekBufferIsEmptyPart(peek []byte) bool {
+	// End of parts case.
+	// Test whether peek matches `^--boundary--[ \t]*(?:\r\n|$)`
+	if bytes.HasPrefix(peek, mr.dashBoundaryDash) {
+		rest := peek[len(mr.dashBoundaryDash):]
+		rest = skipLWSPChar(rest)
+		return bytes.HasPrefix(rest, mr.nl) || len(rest) == 0
+	}
+	if !bytes.HasPrefix(peek, mr.dashBoundary) {
+		return false
+	}
+	// Test whether rest matches `^[ \t]*\r\n`)
+	rest := peek[len(mr.dashBoundary):]
+	rest = skipLWSPChar(rest)
+	return bytes.HasPrefix(rest, mr.nl)
+}
+
+// skipLWSPChar returns b with leading spaces and tabs removed.
+// RFC 822 defines:
+//    LWSP-char = SPACE / HTAB
+func skipLWSPChar(b []byte) []byte {
+	for len(b) > 0 && (b[0] == ' ' || b[0] == '\t') {
+		b = b[1:]
+	}
+	return b
+}
diff --git a/src/mime/multipart/multipart_test.go b/src/mime/multipart/multipart_test.go
new file mode 100644
index 000000000..d662e8340
--- /dev/null
+++ b/src/mime/multipart/multipart_test.go
@@ -0,0 +1,634 @@
+// 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 multipart
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/textproto"
+	"os"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestBoundaryLine(t *testing.T) {
+	mr := NewReader(strings.NewReader(""), "myBoundary")
+	if !mr.isBoundaryDelimiterLine([]byte("--myBoundary\r\n")) {
+		t.Error("expected")
+	}
+	if !mr.isBoundaryDelimiterLine([]byte("--myBoundary \r\n")) {
+		t.Error("expected")
+	}
+	if !mr.isBoundaryDelimiterLine([]byte("--myBoundary \n")) {
+		t.Error("expected")
+	}
+	if mr.isBoundaryDelimiterLine([]byte("--myBoundary bogus \n")) {
+		t.Error("expected fail")
+	}
+	if mr.isBoundaryDelimiterLine([]byte("--myBoundary bogus--")) {
+		t.Error("expected fail")
+	}
+}
+
+func escapeString(v string) string {
+	bytes, _ := json.Marshal(v)
+	return string(bytes)
+}
+
+func expectEq(t *testing.T, expected, actual, what string) {
+	if expected == actual {
+		return
+	}
+	t.Errorf("Unexpected value for %s; got %s (len %d) but expected: %s (len %d)",
+		what, escapeString(actual), len(actual), escapeString(expected), len(expected))
+}
+
+func TestNameAccessors(t *testing.T) {
+	tests := [...][3]string{
+		{`form-data; name="foo"`, "foo", ""},
+		{` form-data ; name=foo`, "foo", ""},
+		{`FORM-DATA;name="foo"`, "foo", ""},
+		{` FORM-DATA ; name="foo"`, "foo", ""},
+		{` FORM-DATA ; name="foo"`, "foo", ""},
+		{` FORM-DATA ; name=foo`, "foo", ""},
+		{` FORM-DATA ; filename="foo.txt"; name=foo; baz=quux`, "foo", "foo.txt"},
+		{` not-form-data ; filename="bar.txt"; name=foo; baz=quux`, "", "bar.txt"},
+	}
+	for i, test := range tests {
+		p := &Part{Header: make(map[string][]string)}
+		p.Header.Set("Content-Disposition", test[0])
+		if g, e := p.FormName(), test[1]; g != e {
+			t.Errorf("test %d: FormName() = %q; want %q", i, g, e)
+		}
+		if g, e := p.FileName(), test[2]; g != e {
+			t.Errorf("test %d: FileName() = %q; want %q", i, g, e)
+		}
+	}
+}
+
+var longLine = strings.Repeat("\n\n\r\r\r\n\r\000", (1<<20)/8)
+
+func testMultipartBody(sep string) string {
+	testBody := `
+This is a multi-part message.  This line is ignored.
+--MyBoundary
+Header1: value1
+HEADER2: value2
+foo-bar: baz
+
+My value
+The end.
+--MyBoundary
+name: bigsection
+
+[longline]
+--MyBoundary
+Header1: value1b
+HEADER2: value2b
+foo-bar: bazb
+
+Line 1
+Line 2
+Line 3 ends in a newline, but just one.
+
+--MyBoundary
+
+never read data
+--MyBoundary--
+
+
+useless trailer
+`
+	testBody = strings.Replace(testBody, "\n", sep, -1)
+	return strings.Replace(testBody, "[longline]", longLine, 1)
+}
+
+func TestMultipart(t *testing.T) {
+	bodyReader := strings.NewReader(testMultipartBody("\r\n"))
+	testMultipart(t, bodyReader, false)
+}
+
+func TestMultipartOnlyNewlines(t *testing.T) {
+	bodyReader := strings.NewReader(testMultipartBody("\n"))
+	testMultipart(t, bodyReader, true)
+}
+
+func TestMultipartSlowInput(t *testing.T) {
+	bodyReader := strings.NewReader(testMultipartBody("\r\n"))
+	testMultipart(t, &slowReader{bodyReader}, false)
+}
+
+func testMultipart(t *testing.T, r io.Reader, onlyNewlines bool) {
+	reader := NewReader(r, "MyBoundary")
+	buf := new(bytes.Buffer)
+
+	// Part1
+	part, err := reader.NextPart()
+	if part == nil || err != nil {
+		t.Error("Expected part1")
+		return
+	}
+	if x := part.Header.Get("Header1"); x != "value1" {
+		t.Errorf("part.Header.Get(%q) = %q, want %q", "Header1", x, "value1")
+	}
+	if x := part.Header.Get("foo-bar"); x != "baz" {
+		t.Errorf("part.Header.Get(%q) = %q, want %q", "foo-bar", x, "baz")
+	}
+	if x := part.Header.Get("Foo-Bar"); x != "baz" {
+		t.Errorf("part.Header.Get(%q) = %q, want %q", "Foo-Bar", x, "baz")
+	}
+	buf.Reset()
+	if _, err := io.Copy(buf, part); err != nil {
+		t.Errorf("part 1 copy: %v", err)
+	}
+
+	adjustNewlines := func(s string) string {
+		if onlyNewlines {
+			return strings.Replace(s, "\r\n", "\n", -1)
+		}
+		return s
+	}
+
+	expectEq(t, adjustNewlines("My value\r\nThe end."), buf.String(), "Value of first part")
+
+	// Part2
+	part, err = reader.NextPart()
+	if err != nil {
+		t.Fatalf("Expected part2; got: %v", err)
+		return
+	}
+	if e, g := "bigsection", part.Header.Get("name"); e != g {
+		t.Errorf("part2's name header: expected %q, got %q", e, g)
+	}
+	buf.Reset()
+	if _, err := io.Copy(buf, part); err != nil {
+		t.Errorf("part 2 copy: %v", err)
+	}
+	s := buf.String()
+	if len(s) != len(longLine) {
+		t.Errorf("part2 body expected long line of length %d; got length %d",
+			len(longLine), len(s))
+	}
+	if s != longLine {
+		t.Errorf("part2 long body didn't match")
+	}
+
+	// Part3
+	part, err = reader.NextPart()
+	if part == nil || err != nil {
+		t.Error("Expected part3")
+		return
+	}
+	if part.Header.Get("foo-bar") != "bazb" {
+		t.Error("Expected foo-bar: bazb")
+	}
+	buf.Reset()
+	if _, err := io.Copy(buf, part); err != nil {
+		t.Errorf("part 3 copy: %v", err)
+	}
+	expectEq(t, adjustNewlines("Line 1\r\nLine 2\r\nLine 3 ends in a newline, but just one.\r\n"),
+		buf.String(), "body of part 3")
+
+	// Part4
+	part, err = reader.NextPart()
+	if part == nil || err != nil {
+		t.Error("Expected part 4 without errors")
+		return
+	}
+
+	// Non-existent part5
+	part, err = reader.NextPart()
+	if part != nil {
+		t.Error("Didn't expect a fifth part.")
+	}
+	if err != io.EOF {
+		t.Errorf("On fifth part expected io.EOF; got %v", err)
+	}
+}
+
+func TestVariousTextLineEndings(t *testing.T) {
+	tests := [...]string{
+		"Foo\nBar",
+		"Foo\nBar\n",
+		"Foo\r\nBar",
+		"Foo\r\nBar\r\n",
+		"Foo\rBar",
+		"Foo\rBar\r",
+		"\x00\x01\x02\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10",
+	}
+
+	for testNum, expectedBody := range tests {
+		body := "--BOUNDARY\r\n" +
+			"Content-Disposition: form-data; name=\"value\"\r\n" +
+			"\r\n" +
+			expectedBody +
+			"\r\n--BOUNDARY--\r\n"
+		bodyReader := strings.NewReader(body)
+
+		reader := NewReader(bodyReader, "BOUNDARY")
+		buf := new(bytes.Buffer)
+		part, err := reader.NextPart()
+		if part == nil {
+			t.Errorf("Expected a body part on text %d", testNum)
+			continue
+		}
+		if err != nil {
+			t.Errorf("Unexpected error on text %d: %v", testNum, err)
+			continue
+		}
+		written, err := io.Copy(buf, part)
+		expectEq(t, expectedBody, buf.String(), fmt.Sprintf("test %d", testNum))
+		if err != nil {
+			t.Errorf("Error copying multipart; bytes=%v, error=%v", written, err)
+		}
+
+		part, err = reader.NextPart()
+		if part != nil {
+			t.Errorf("Unexpected part in test %d", testNum)
+		}
+		if err != io.EOF {
+			t.Errorf("On test %d expected io.EOF; got %v", testNum, err)
+		}
+
+	}
+}
+
+type maliciousReader struct {
+	t *testing.T
+	n int
+}
+
+const maxReadThreshold = 1 << 20
+
+func (mr *maliciousReader) Read(b []byte) (n int, err error) {
+	mr.n += len(b)
+	if mr.n >= maxReadThreshold {
+		mr.t.Fatal("too much was read")
+		return 0, io.EOF
+	}
+	return len(b), nil
+}
+
+func TestLineLimit(t *testing.T) {
+	mr := &maliciousReader{t: t}
+	r := NewReader(mr, "fooBoundary")
+	part, err := r.NextPart()
+	if part != nil {
+		t.Errorf("unexpected part read")
+	}
+	if err == nil {
+		t.Errorf("expected an error")
+	}
+	if mr.n >= maxReadThreshold {
+		t.Errorf("expected to read < %d bytes; read %d", maxReadThreshold, mr.n)
+	}
+}
+
+func TestMultipartTruncated(t *testing.T) {
+	testBody := `
+This is a multi-part message.  This line is ignored.
+--MyBoundary
+foo-bar: baz
+
+Oh no, premature EOF!
+`
+	body := strings.Replace(testBody, "\n", "\r\n", -1)
+	bodyReader := strings.NewReader(body)
+	r := NewReader(bodyReader, "MyBoundary")
+
+	part, err := r.NextPart()
+	if err != nil {
+		t.Fatalf("didn't get a part")
+	}
+	_, err = io.Copy(ioutil.Discard, part)
+	if err != io.ErrUnexpectedEOF {
+		t.Fatalf("expected error io.ErrUnexpectedEOF; got %v", err)
+	}
+}
+
+type slowReader struct {
+	r io.Reader
+}
+
+func (s *slowReader) Read(p []byte) (int, error) {
+	if len(p) == 0 {
+		return s.r.Read(p)
+	}
+	return s.r.Read(p[:1])
+}
+
+func TestLineContinuation(t *testing.T) {
+	// This body, extracted from an email, contains headers that span multiple
+	// lines.
+
+	// TODO: The original mail ended with a double-newline before the
+	// final delimiter; this was manually edited to use a CRLF.
+	testBody :=
+		"\n--Apple-Mail-2-292336769\nContent-Transfer-Encoding: 7bit\nContent-Type: text/plain;\n\tcharset=US-ASCII;\n\tdelsp=yes;\n\tformat=flowed\n\nI'm finding the same thing happening on my system (10.4.1).\n\n\n--Apple-Mail-2-292336769\nContent-Transfer-Encoding: quoted-printable\nContent-Type: text/html;\n\tcharset=ISO-8859-1\n\n<HTML><BODY>I'm finding the same thing =\nhappening on my system (10.4.1).=A0 But I built it with XCode =\n2.0.</BODY></=\nHTML>=\n\r\n--Apple-Mail-2-292336769--\n"
+
+	r := NewReader(strings.NewReader(testBody), "Apple-Mail-2-292336769")
+
+	for i := 0; i < 2; i++ {
+		part, err := r.NextPart()
+		if err != nil {
+			t.Fatalf("didn't get a part")
+		}
+		var buf bytes.Buffer
+		n, err := io.Copy(&buf, part)
+		if err != nil {
+			t.Errorf("error reading part: %v\nread so far: %q", err, buf.String())
+		}
+		if n <= 0 {
+			t.Errorf("read %d bytes; expected >0", n)
+		}
+	}
+}
+
+func TestQuotedPrintableEncoding(t *testing.T) {
+	// From http://golang.org/issue/4411
+	body := "--0016e68ee29c5d515f04cedf6733\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=text\r\nContent-Transfer-Encoding: quoted-printable\r\n\r\nwords words words words words words words words words words words words wor=\r\nds words words words words words words words words words words words words =\r\nwords words words words words words words words words words words words wor=\r\nds words words words words words words words words words words words words =\r\nwords words words words words words words words words\r\n--0016e68ee29c5d515f04cedf6733\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=submit\r\n\r\nSubmit\r\n--0016e68ee29c5d515f04cedf6733--"
+	r := NewReader(strings.NewReader(body), "0016e68ee29c5d515f04cedf6733")
+	part, err := r.NextPart()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if te, ok := part.Header["Content-Transfer-Encoding"]; ok {
+		t.Errorf("unexpected Content-Transfer-Encoding of %q", te)
+	}
+	var buf bytes.Buffer
+	_, err = io.Copy(&buf, part)
+	if err != nil {
+		t.Error(err)
+	}
+	got := buf.String()
+	want := "words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words words"
+	if got != want {
+		t.Errorf("wrong part value:\n got: %q\nwant: %q", got, want)
+	}
+}
+
+// Test parsing an image attachment from gmail, which previously failed.
+func TestNested(t *testing.T) {
+	// nested-mime is the body part of a multipart/mixed email
+	// with boundary e89a8ff1c1e83553e304be640612
+	f, err := os.Open("testdata/nested-mime")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	mr := NewReader(f, "e89a8ff1c1e83553e304be640612")
+	p, err := mr.NextPart()
+	if err != nil {
+		t.Fatalf("error reading first section (alternative): %v", err)
+	}
+
+	// Read the inner text/plain and text/html sections of the multipart/alternative.
+	mr2 := NewReader(p, "e89a8ff1c1e83553e004be640610")
+	p, err = mr2.NextPart()
+	if err != nil {
+		t.Fatalf("reading text/plain part: %v", err)
+	}
+	if b, err := ioutil.ReadAll(p); string(b) != "*body*\r\n" || err != nil {
+		t.Fatalf("reading text/plain part: got %q, %v", b, err)
+	}
+	p, err = mr2.NextPart()
+	if err != nil {
+		t.Fatalf("reading text/html part: %v", err)
+	}
+	if b, err := ioutil.ReadAll(p); string(b) != "<b>body</b>\r\n" || err != nil {
+		t.Fatalf("reading text/html part: got %q, %v", b, err)
+	}
+
+	p, err = mr2.NextPart()
+	if err != io.EOF {
+		t.Fatalf("final inner NextPart = %v; want io.EOF", err)
+	}
+
+	// Back to the outer multipart/mixed, reading the image attachment.
+	_, err = mr.NextPart()
+	if err != nil {
+		t.Fatalf("error reading the image attachment at the end: %v", err)
+	}
+
+	_, err = mr.NextPart()
+	if err != io.EOF {
+		t.Fatalf("final outer NextPart = %v; want io.EOF", err)
+	}
+}
+
+type headerBody struct {
+	header textproto.MIMEHeader
+	body   string
+}
+
+func formData(key, value string) headerBody {
+	return headerBody{
+		textproto.MIMEHeader{
+			"Content-Type":        {"text/plain; charset=ISO-8859-1"},
+			"Content-Disposition": {"form-data; name=" + key},
+		},
+		value,
+	}
+}
+
+type parseTest struct {
+	name    string
+	in, sep string
+	want    []headerBody
+}
+
+var parseTests = []parseTest{
+	// Actual body from App Engine on a blob upload. The final part (the
+	// Content-Type: message/external-body) is what App Engine replaces
+	// the uploaded file with.  The other form fields (prefixed with
+	// "other" in their form-data name) are unchanged.  A bug was
+	// reported with blob uploads failing when the other fields were
+	// empty. This was the MIME POST body that previously failed.
+	{
+		name: "App Engine post",
+		sep:  "00151757727e9583fd04bfbca4c6",
+		in:   "--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=otherEmpty1\r\n\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=otherFoo1\r\n\r\nfoo\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=otherFoo2\r\n\r\nfoo\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=otherEmpty2\r\n\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=otherRepeatFoo\r\n\r\nfoo\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=otherRepeatFoo\r\n\r\nfoo\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=otherRepeatEmpty\r\n\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=otherRepeatEmpty\r\n\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: text/plain; charset=ISO-8859-1\r\nContent-Disposition: form-data; name=submit\r\n\r\nSubmit\r\n--00151757727e9583fd04bfbca4c6\r\nContent-Type: message/external-body; charset=ISO-8859-1; blob-key=AHAZQqG84qllx7HUqO_oou5EvdYQNS3Mbbkb0RjjBoM_Kc1UqEN2ygDxWiyCPulIhpHRPx-VbpB6RX4MrsqhWAi_ZxJ48O9P2cTIACbvATHvg7IgbvZytyGMpL7xO1tlIvgwcM47JNfv_tGhy1XwyEUO8oldjPqg5Q\r\nContent-Disposition: form-data; name=file; filename=\"fall.png\"\r\n\r\nContent-Type: image/png\r\nContent-Length: 232303\r\nX-AppEngine-Upload-Creation: 2012-05-10 23:14:02.715173\r\nContent-MD5: MzRjODU1ZDZhZGU1NmRlOWEwZmMwMDdlODBmZTA0NzA=\r\nContent-Disposition: form-data; name=file; filename=\"fall.png\"\r\n\r\n\r\n--00151757727e9583fd04bfbca4c6--",
+		want: []headerBody{
+			formData("otherEmpty1", ""),
+			formData("otherFoo1", "foo"),
+			formData("otherFoo2", "foo"),
+			formData("otherEmpty2", ""),
+			formData("otherRepeatFoo", "foo"),
+			formData("otherRepeatFoo", "foo"),
+			formData("otherRepeatEmpty", ""),
+			formData("otherRepeatEmpty", ""),
+			formData("submit", "Submit"),
+			{textproto.MIMEHeader{
+				"Content-Type":        {"message/external-body; charset=ISO-8859-1; blob-key=AHAZQqG84qllx7HUqO_oou5EvdYQNS3Mbbkb0RjjBoM_Kc1UqEN2ygDxWiyCPulIhpHRPx-VbpB6RX4MrsqhWAi_ZxJ48O9P2cTIACbvATHvg7IgbvZytyGMpL7xO1tlIvgwcM47JNfv_tGhy1XwyEUO8oldjPqg5Q"},
+				"Content-Disposition": {"form-data; name=file; filename=\"fall.png\""},
+			}, "Content-Type: image/png\r\nContent-Length: 232303\r\nX-AppEngine-Upload-Creation: 2012-05-10 23:14:02.715173\r\nContent-MD5: MzRjODU1ZDZhZGU1NmRlOWEwZmMwMDdlODBmZTA0NzA=\r\nContent-Disposition: form-data; name=file; filename=\"fall.png\"\r\n\r\n"},
+		},
+	},
+
+	// Single empty part, ended with --boundary immediately after headers.
+	{
+		name: "single empty part, --boundary",
+		sep:  "abc",
+		in:   "--abc\r\nFoo: bar\r\n\r\n--abc--",
+		want: []headerBody{
+			{textproto.MIMEHeader{"Foo": {"bar"}}, ""},
+		},
+	},
+
+	// Single empty part, ended with \r\n--boundary immediately after headers.
+	{
+		name: "single empty part, \r\n--boundary",
+		sep:  "abc",
+		in:   "--abc\r\nFoo: bar\r\n\r\n\r\n--abc--",
+		want: []headerBody{
+			{textproto.MIMEHeader{"Foo": {"bar"}}, ""},
+		},
+	},
+
+	// Final part empty.
+	{
+		name: "final part empty",
+		sep:  "abc",
+		in:   "--abc\r\nFoo: bar\r\n\r\n--abc\r\nFoo2: bar2\r\n\r\n--abc--",
+		want: []headerBody{
+			{textproto.MIMEHeader{"Foo": {"bar"}}, ""},
+			{textproto.MIMEHeader{"Foo2": {"bar2"}}, ""},
+		},
+	},
+
+	// Final part empty with newlines after final separator.
+	{
+		name: "final part empty then crlf",
+		sep:  "abc",
+		in:   "--abc\r\nFoo: bar\r\n\r\n--abc--\r\n",
+		want: []headerBody{
+			{textproto.MIMEHeader{"Foo": {"bar"}}, ""},
+		},
+	},
+
+	// Final part empty with lwsp-chars after final separator.
+	{
+		name: "final part empty then lwsp",
+		sep:  "abc",
+		in:   "--abc\r\nFoo: bar\r\n\r\n--abc-- \t",
+		want: []headerBody{
+			{textproto.MIMEHeader{"Foo": {"bar"}}, ""},
+		},
+	},
+
+	// No parts (empty form as submitted by Chrome)
+	{
+		name: "no parts",
+		sep:  "----WebKitFormBoundaryQfEAfzFOiSemeHfA",
+		in:   "------WebKitFormBoundaryQfEAfzFOiSemeHfA--\r\n",
+		want: []headerBody{},
+	},
+
+	// Part containing data starting with the boundary, but with additional suffix.
+	{
+		name: "fake separator as data",
+		sep:  "sep",
+		in:   "--sep\r\nFoo: bar\r\n\r\n--sepFAKE\r\n--sep--",
+		want: []headerBody{
+			{textproto.MIMEHeader{"Foo": {"bar"}}, "--sepFAKE"},
+		},
+	},
+
+	// Part containing a boundary with whitespace following it.
+	{
+		name: "boundary with whitespace",
+		sep:  "sep",
+		in:   "--sep \r\nFoo: bar\r\n\r\ntext\r\n--sep--",
+		want: []headerBody{
+			{textproto.MIMEHeader{"Foo": {"bar"}}, "text"},
+		},
+	},
+
+	// With ignored leading line.
+	{
+		name: "leading line",
+		sep:  "MyBoundary",
+		in: strings.Replace(`This is a multi-part message.  This line is ignored.
+--MyBoundary
+foo: bar
+
+
+--MyBoundary--`, "\n", "\r\n", -1),
+		want: []headerBody{
+			{textproto.MIMEHeader{"Foo": {"bar"}}, ""},
+		},
+	},
+
+	roundTripParseTest(),
+}
+
+func TestParse(t *testing.T) {
+Cases:
+	for _, tt := range parseTests {
+		r := NewReader(strings.NewReader(tt.in), tt.sep)
+		got := []headerBody{}
+		for {
+			p, err := r.NextPart()
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				t.Errorf("in test %q, NextPart: %v", tt.name, err)
+				continue Cases
+			}
+			pbody, err := ioutil.ReadAll(p)
+			if err != nil {
+				t.Errorf("in test %q, error reading part: %v", tt.name, err)
+				continue Cases
+			}
+			got = append(got, headerBody{p.Header, string(pbody)})
+		}
+		if !reflect.DeepEqual(tt.want, got) {
+			t.Errorf("test %q:\n got: %v\nwant: %v", tt.name, got, tt.want)
+			if len(tt.want) != len(got) {
+				t.Errorf("test %q: got %d parts, want %d", tt.name, len(got), len(tt.want))
+			} else if len(got) > 1 {
+				for pi, wantPart := range tt.want {
+					if !reflect.DeepEqual(wantPart, got[pi]) {
+						t.Errorf("test %q, part %d:\n got: %v\nwant: %v", tt.name, pi, got[pi], wantPart)
+					}
+				}
+			}
+		}
+	}
+}
+
+func roundTripParseTest() parseTest {
+	t := parseTest{
+		name: "round trip",
+		want: []headerBody{
+			formData("empty", ""),
+			formData("lf", "\n"),
+			formData("cr", "\r"),
+			formData("crlf", "\r\n"),
+			formData("foo", "bar"),
+		},
+	}
+	var buf bytes.Buffer
+	w := NewWriter(&buf)
+	for _, p := range t.want {
+		pw, err := w.CreatePart(p.header)
+		if err != nil {
+			panic(err)
+		}
+		_, err = pw.Write([]byte(p.body))
+		if err != nil {
+			panic(err)
+		}
+	}
+	w.Close()
+	t.in = buf.String()
+	t.sep = w.Boundary()
+	return t
+}
diff --git a/src/mime/multipart/quotedprintable.go b/src/mime/multipart/quotedprintable.go
new file mode 100644
index 000000000..9ff4ee703
--- /dev/null
+++ b/src/mime/multipart/quotedprintable.go
@@ -0,0 +1,118 @@
+// Copyright 2012 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.
+
+// The file define a quoted-printable decoder, as specified in RFC 2045.
+// Deviations:
+// 1. in addition to "=\r\n", "=\n" is also treated as soft line break.
+// 2. it will pass through a '\r' or '\n' not preceded by '=', consistent
+//    with other broken QP encoders & decoders.
+
+package multipart
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+)
+
+type qpReader struct {
+	br   *bufio.Reader
+	rerr error  // last read error
+	line []byte // to be consumed before more of br
+}
+
+func newQuotedPrintableReader(r io.Reader) io.Reader {
+	return &qpReader{
+		br: bufio.NewReader(r),
+	}
+}
+
+func fromHex(b byte) (byte, error) {
+	switch {
+	case b >= '0' && b <= '9':
+		return b - '0', nil
+	case b >= 'A' && b <= 'F':
+		return b - 'A' + 10, nil
+	}
+	return 0, fmt.Errorf("multipart: invalid quoted-printable hex byte 0x%02x", b)
+}
+
+func (q *qpReader) readHexByte(v []byte) (b byte, err error) {
+	if len(v) < 2 {
+		return 0, io.ErrUnexpectedEOF
+	}
+	var hb, lb byte
+	if hb, err = fromHex(v[0]); err != nil {
+		return 0, err
+	}
+	if lb, err = fromHex(v[1]); err != nil {
+		return 0, err
+	}
+	return hb<<4 | lb, nil
+}
+
+func isQPDiscardWhitespace(r rune) bool {
+	switch r {
+	case '\n', '\r', ' ', '\t':
+		return true
+	}
+	return false
+}
+
+var (
+	crlf       = []byte("\r\n")
+	lf         = []byte("\n")
+	softSuffix = []byte("=")
+)
+
+func (q *qpReader) Read(p []byte) (n int, err error) {
+	for len(p) > 0 {
+		if len(q.line) == 0 {
+			if q.rerr != nil {
+				return n, q.rerr
+			}
+			q.line, q.rerr = q.br.ReadSlice('\n')
+
+			// Does the line end in CRLF instead of just LF?
+			hasLF := bytes.HasSuffix(q.line, lf)
+			hasCR := bytes.HasSuffix(q.line, crlf)
+			wholeLine := q.line
+			q.line = bytes.TrimRightFunc(wholeLine, isQPDiscardWhitespace)
+			if bytes.HasSuffix(q.line, softSuffix) {
+				rightStripped := wholeLine[len(q.line):]
+				q.line = q.line[:len(q.line)-1]
+				if !bytes.HasPrefix(rightStripped, lf) && !bytes.HasPrefix(rightStripped, crlf) {
+					q.rerr = fmt.Errorf("multipart: invalid bytes after =: %q", rightStripped)
+				}
+			} else if hasLF {
+				if hasCR {
+					q.line = append(q.line, '\r', '\n')
+				} else {
+					q.line = append(q.line, '\n')
+				}
+			}
+			continue
+		}
+		b := q.line[0]
+
+		switch {
+		case b == '=':
+			b, err = q.readHexByte(q.line[1:])
+			if err != nil {
+				return n, err
+			}
+			q.line = q.line[2:] // 2 of the 3; other 1 is done below
+		case b == '\t' || b == '\r' || b == '\n':
+			break
+		case b < ' ' || b > '~':
+			return n, fmt.Errorf("multipart: invalid unescaped byte 0x%02x in quoted-printable body", b)
+		}
+		p[0] = b
+		p = p[1:]
+		q.line = q.line[1:]
+		n++
+	}
+	return n, nil
+}
diff --git a/src/mime/multipart/quotedprintable_test.go b/src/mime/multipart/quotedprintable_test.go
new file mode 100644
index 000000000..c4de3eb75
--- /dev/null
+++ b/src/mime/multipart/quotedprintable_test.go
@@ -0,0 +1,204 @@
+// Copyright 2012 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 multipart
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os/exec"
+	"regexp"
+	"sort"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestQuotedPrintable(t *testing.T) {
+	tests := []struct {
+		in, want string
+		err      interface{}
+	}{
+		{in: "", want: ""},
+		{in: "foo bar", want: "foo bar"},
+		{in: "foo bar=3D", want: "foo bar="},
+		{in: "foo bar=\n", want: "foo bar"},
+		{in: "foo bar\n", want: "foo bar\n"}, // somewhat lax.
+		{in: "foo bar=0", want: "foo bar", err: io.ErrUnexpectedEOF},
+		{in: "foo bar=ab", want: "foo bar", err: "multipart: invalid quoted-printable hex byte 0x61"},
+		{in: "foo bar=0D=0A", want: "foo bar\r\n"},
+		{in: " A B        \r\n C ", want: " A B\r\n C"},
+		{in: " A B =\r\n C ", want: " A B  C"},
+		{in: " A B =\n C ", want: " A B  C"}, // lax. treating LF as CRLF
+		{in: "foo=\nbar", want: "foobar"},
+		{in: "foo\x00bar", want: "foo", err: "multipart: invalid unescaped byte 0x00 in quoted-printable body"},
+		{in: "foo bar\xff", want: "foo bar", err: "multipart: invalid unescaped byte 0xff in quoted-printable body"},
+
+		// Equal sign.
+		{in: "=3D30\n", want: "=30\n"},
+		{in: "=00=FF0=\n", want: "\x00\xff0"},
+
+		// Trailing whitespace
+		{in: "foo  \n", want: "foo\n"},
+		{in: "foo  \n\nfoo =\n\nfoo=20\n\n", want: "foo\n\nfoo \nfoo \n\n"},
+
+		// Tests that we allow bare \n and \r through, despite it being strictly
+		// not permitted per RFC 2045, Section 6.7 Page 22 bullet (4).
+		{in: "foo\nbar", want: "foo\nbar"},
+		{in: "foo\rbar", want: "foo\rbar"},
+		{in: "foo\r\nbar", want: "foo\r\nbar"},
+
+		// Different types of soft line-breaks.
+		{in: "foo=\r\nbar", want: "foobar"},
+		{in: "foo=\nbar", want: "foobar"},
+		{in: "foo=\rbar", want: "foo", err: "multipart: invalid quoted-printable hex byte 0x0d"},
+		{in: "foo=\r\r\r \nbar", want: "foo", err: `multipart: invalid bytes after =: "\r\r\r \n"`},
+
+		// Example from RFC 2045:
+		{in: "Now's the time =\n" + "for all folk to come=\n" + " to the aid of their country.",
+			want: "Now's the time for all folk to come to the aid of their country."},
+	}
+	for _, tt := range tests {
+		var buf bytes.Buffer
+		_, err := io.Copy(&buf, newQuotedPrintableReader(strings.NewReader(tt.in)))
+		if got := buf.String(); got != tt.want {
+			t.Errorf("for %q, got %q; want %q", tt.in, got, tt.want)
+		}
+		switch verr := tt.err.(type) {
+		case nil:
+			if err != nil {
+				t.Errorf("for %q, got unexpected error: %v", tt.in, err)
+			}
+		case string:
+			if got := fmt.Sprint(err); got != verr {
+				t.Errorf("for %q, got error %q; want %q", tt.in, got, verr)
+			}
+		case error:
+			if err != verr {
+				t.Errorf("for %q, got error %q; want %q", tt.in, err, verr)
+			}
+		}
+	}
+
+}
+
+func everySequence(base, alpha string, length int, fn func(string)) {
+	if len(base) == length {
+		fn(base)
+		return
+	}
+	for i := 0; i < len(alpha); i++ {
+		everySequence(base+alpha[i:i+1], alpha, length, fn)
+	}
+}
+
+var useQprint = flag.Bool("qprint", false, "Compare against the 'qprint' program.")
+
+var badSoftRx = regexp.MustCompile(`=([^\r\n]+?\n)|([^\r\n]+$)|(\r$)|(\r[^\n]+\n)|( \r\n)`)
+
+func TestQPExhaustive(t *testing.T) {
+	if *useQprint {
+		_, err := exec.LookPath("qprint")
+		if err != nil {
+			t.Fatalf("Error looking for qprint: %v", err)
+		}
+	}
+
+	var buf bytes.Buffer
+	res := make(map[string]int)
+	everySequence("", "0A \r\n=", 6, func(s string) {
+		if strings.HasSuffix(s, "=") || strings.Contains(s, "==") {
+			return
+		}
+		buf.Reset()
+		_, err := io.Copy(&buf, newQuotedPrintableReader(strings.NewReader(s)))
+		if err != nil {
+			errStr := err.Error()
+			if strings.Contains(errStr, "invalid bytes after =:") {
+				errStr = "invalid bytes after ="
+			}
+			res[errStr]++
+			if strings.Contains(errStr, "invalid quoted-printable hex byte ") {
+				if strings.HasSuffix(errStr, "0x20") && (strings.Contains(s, "=0 ") || strings.Contains(s, "=A ") || strings.Contains(s, "= ")) {
+					return
+				}
+				if strings.HasSuffix(errStr, "0x3d") && (strings.Contains(s, "=0=") || strings.Contains(s, "=A=")) {
+					return
+				}
+				if strings.HasSuffix(errStr, "0x0a") || strings.HasSuffix(errStr, "0x0d") {
+					// bunch of cases; since whitespace at the end of a line before \n is removed.
+					return
+				}
+			}
+			if strings.Contains(errStr, "unexpected EOF") {
+				return
+			}
+			if errStr == "invalid bytes after =" && badSoftRx.MatchString(s) {
+				return
+			}
+			t.Errorf("decode(%q) = %v", s, err)
+			return
+		}
+		if *useQprint {
+			cmd := exec.Command("qprint", "-d")
+			cmd.Stdin = strings.NewReader(s)
+			stderr, err := cmd.StderrPipe()
+			if err != nil {
+				panic(err)
+			}
+			qpres := make(chan interface{}, 2)
+			go func() {
+				br := bufio.NewReader(stderr)
+				s, _ := br.ReadString('\n')
+				if s != "" {
+					qpres <- errors.New(s)
+					if cmd.Process != nil {
+						// It can get stuck on invalid input, like:
+						// echo -n "0000= " | qprint -d
+						cmd.Process.Kill()
+					}
+				}
+			}()
+			go func() {
+				want, err := cmd.Output()
+				if err == nil {
+					qpres <- want
+				}
+			}()
+			select {
+			case got := <-qpres:
+				if want, ok := got.([]byte); ok {
+					if string(want) != buf.String() {
+						t.Errorf("go decode(%q) = %q; qprint = %q", s, want, buf.String())
+					}
+				} else {
+					t.Logf("qprint -d(%q) = %v", s, got)
+				}
+			case <-time.After(5 * time.Second):
+				t.Logf("qprint timeout on %q", s)
+			}
+		}
+		res["OK"]++
+	})
+	var outcomes []string
+	for k, v := range res {
+		outcomes = append(outcomes, fmt.Sprintf("%v: %d", k, v))
+	}
+	sort.Strings(outcomes)
+	got := strings.Join(outcomes, "\n")
+	want := `OK: 21576
+invalid bytes after =: 3397
+multipart: invalid quoted-printable hex byte 0x0a: 1400
+multipart: invalid quoted-printable hex byte 0x0d: 2700
+multipart: invalid quoted-printable hex byte 0x20: 2490
+multipart: invalid quoted-printable hex byte 0x3d: 440
+unexpected EOF: 3122`
+	if got != want {
+		t.Errorf("Got:\n%s\nWant:\n%s", got, want)
+	}
+}
diff --git a/src/mime/multipart/testdata/nested-mime b/src/mime/multipart/testdata/nested-mime
new file mode 100644
index 000000000..71c238e38
--- /dev/null
+++ b/src/mime/multipart/testdata/nested-mime
@@ -0,0 +1,29 @@
+--e89a8ff1c1e83553e304be640612

+Content-Type: multipart/alternative; boundary=e89a8ff1c1e83553e004be640610

+

+--e89a8ff1c1e83553e004be640610

+Content-Type: text/plain; charset=UTF-8

+

+*body*

+

+--e89a8ff1c1e83553e004be640610

+Content-Type: text/html; charset=UTF-8

+

+<b>body</b>

+

+--e89a8ff1c1e83553e004be640610--

+--e89a8ff1c1e83553e304be640612

+Content-Type: image/png; name="x.png"

+Content-Disposition: attachment; 

+	filename="x.png"

+Content-Transfer-Encoding: base64

+X-Attachment-Id: f_h1edgigu0

+

+iVBORw0KGgoAAAANSUhEUgAAAagAAADrCAIAAACza5XhAAAKMWlDQ1BJQ0MgUHJvZmlsZQAASImd

+lndUU9kWh8+9N71QkhCKlNBraFICSA29SJEuKjEJEErAkAAiNkRUcERRkaYIMijggKNDkbEiioUB

+8b2kqeGaj4aTNftesu5mob4pr07ecMywRwLBvDCJOksqlUyldAZD7g9fxIZRWWPMvXRNJROJRBIG

+Y7Vx0mva1HAwYqibdKONXye3dW4iUonhWFJnqK7OaanU1gGkErFYEgaj0cg8wK+zVPh2ziwnHy07

+U8lYTNapezSzOuevRwLB7CFkqQQCwaJDiBQIBIJFhwh8AoFg0SHUqQUCASRJKkwkhMy/JfODWPEJ

+BIJFhwh8AoFg0TFnQqQ55GtPFopcJsN97e1nYtNuIBYeGBgYCmYrmE3jZ05iaGAoMX0xzxkWz6Hv

+yO7WvrlwzA0uLzrD+VkKqViwl9IfTBVNFMyc/x9alloiPPlqhQAAAABJRU5ErkJggg==

+--e89a8ff1c1e83553e304be640612--

diff --git a/src/mime/multipart/writer.go b/src/mime/multipart/writer.go
new file mode 100644
index 000000000..e13a956af
--- /dev/null
+++ b/src/mime/multipart/writer.go
@@ -0,0 +1,184 @@
+// 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 multipart
+
+import (
+	"bytes"
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io"
+	"net/textproto"
+	"strings"
+)
+
+// A Writer generates multipart messages.
+type Writer struct {
+	w        io.Writer
+	boundary string
+	lastpart *part
+}
+
+// NewWriter returns a new multipart Writer with a random boundary,
+// writing to w.
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{
+		w:        w,
+		boundary: randomBoundary(),
+	}
+}
+
+// Boundary returns the Writer's boundary.
+func (w *Writer) Boundary() string {
+	return w.boundary
+}
+
+// SetBoundary overrides the Writer's default randomly-generated
+// boundary separator with an explicit value.
+//
+// SetBoundary must be called before any parts are created, may only
+// contain certain ASCII characters, and must be 1-69 bytes long.
+func (w *Writer) SetBoundary(boundary string) error {
+	if w.lastpart != nil {
+		return errors.New("mime: SetBoundary called after write")
+	}
+	// rfc2046#section-5.1.1
+	if len(boundary) < 1 || len(boundary) > 69 {
+		return errors.New("mime: invalid boundary length")
+	}
+	for _, b := range boundary {
+		if 'A' <= b && b <= 'Z' || 'a' <= b && b <= 'z' || '0' <= b && b <= '9' {
+			continue
+		}
+		switch b {
+		case '\'', '(', ')', '+', '_', ',', '-', '.', '/', ':', '=', '?':
+			continue
+		}
+		return errors.New("mime: invalid boundary character")
+	}
+	w.boundary = boundary
+	return nil
+}
+
+// FormDataContentType returns the Content-Type for an HTTP
+// multipart/form-data with this Writer's Boundary.
+func (w *Writer) FormDataContentType() string {
+	return "multipart/form-data; boundary=" + w.boundary
+}
+
+func randomBoundary() string {
+	var buf [30]byte
+	_, err := io.ReadFull(rand.Reader, buf[:])
+	if err != nil {
+		panic(err)
+	}
+	return fmt.Sprintf("%x", buf[:])
+}
+
+// CreatePart creates a new multipart section with the provided
+// header. The body of the part should be written to the returned
+// Writer. After calling CreatePart, any previous part may no longer
+// be written to.
+func (w *Writer) CreatePart(header textproto.MIMEHeader) (io.Writer, error) {
+	if w.lastpart != nil {
+		if err := w.lastpart.close(); err != nil {
+			return nil, err
+		}
+	}
+	var b bytes.Buffer
+	if w.lastpart != nil {
+		fmt.Fprintf(&b, "\r\n--%s\r\n", w.boundary)
+	} else {
+		fmt.Fprintf(&b, "--%s\r\n", w.boundary)
+	}
+	// TODO(bradfitz): move this to textproto.MimeHeader.Write(w), have it sort
+	// and clean, like http.Header.Write(w) does.
+	for k, vv := range header {
+		for _, v := range vv {
+			fmt.Fprintf(&b, "%s: %s\r\n", k, v)
+		}
+	}
+	fmt.Fprintf(&b, "\r\n")
+	_, err := io.Copy(w.w, &b)
+	if err != nil {
+		return nil, err
+	}
+	p := &part{
+		mw: w,
+	}
+	w.lastpart = p
+	return p, nil
+}
+
+var quoteEscaper = strings.NewReplacer("\\", "\\\\", `"`, "\\\"")
+
+func escapeQuotes(s string) string {
+	return quoteEscaper.Replace(s)
+}
+
+// CreateFormFile is a convenience wrapper around CreatePart. It creates
+// a new form-data header with the provided field name and file name.
+func (w *Writer) CreateFormFile(fieldname, filename string) (io.Writer, error) {
+	h := make(textproto.MIMEHeader)
+	h.Set("Content-Disposition",
+		fmt.Sprintf(`form-data; name="%s"; filename="%s"`,
+			escapeQuotes(fieldname), escapeQuotes(filename)))
+	h.Set("Content-Type", "application/octet-stream")
+	return w.CreatePart(h)
+}
+
+// CreateFormField calls CreatePart with a header using the
+// given field name.
+func (w *Writer) CreateFormField(fieldname string) (io.Writer, error) {
+	h := make(textproto.MIMEHeader)
+	h.Set("Content-Disposition",
+		fmt.Sprintf(`form-data; name="%s"`, escapeQuotes(fieldname)))
+	return w.CreatePart(h)
+}
+
+// WriteField calls CreateFormField and then writes the given value.
+func (w *Writer) WriteField(fieldname, value string) error {
+	p, err := w.CreateFormField(fieldname)
+	if err != nil {
+		return err
+	}
+	_, err = p.Write([]byte(value))
+	return err
+}
+
+// Close finishes the multipart message and writes the trailing
+// boundary end line to the output.
+func (w *Writer) Close() error {
+	if w.lastpart != nil {
+		if err := w.lastpart.close(); err != nil {
+			return err
+		}
+		w.lastpart = nil
+	}
+	_, err := fmt.Fprintf(w.w, "\r\n--%s--\r\n", w.boundary)
+	return err
+}
+
+type part struct {
+	mw     *Writer
+	closed bool
+	we     error // last error that occurred writing
+}
+
+func (p *part) close() error {
+	p.closed = true
+	return p.we
+}
+
+func (p *part) Write(d []byte) (n int, err error) {
+	if p.closed {
+		return 0, errors.New("multipart: can't write to finished part")
+	}
+	n, err = p.mw.w.Write(d)
+	if err != nil {
+		p.we = err
+	}
+	return
+}
diff --git a/src/mime/multipart/writer_test.go b/src/mime/multipart/writer_test.go
new file mode 100644
index 000000000..ba00c97ec
--- /dev/null
+++ b/src/mime/multipart/writer_test.go
@@ -0,0 +1,128 @@
+// 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 multipart
+
+import (
+	"bytes"
+	"io/ioutil"
+	"strings"
+	"testing"
+)
+
+func TestWriter(t *testing.T) {
+	fileContents := []byte("my file contents")
+
+	var b bytes.Buffer
+	w := NewWriter(&b)
+	{
+		part, err := w.CreateFormFile("myfile", "my-file.txt")
+		if err != nil {
+			t.Fatalf("CreateFormFile: %v", err)
+		}
+		part.Write(fileContents)
+		err = w.WriteField("key", "val")
+		if err != nil {
+			t.Fatalf("WriteField: %v", err)
+		}
+		part.Write([]byte("val"))
+		err = w.Close()
+		if err != nil {
+			t.Fatalf("Close: %v", err)
+		}
+		s := b.String()
+		if len(s) == 0 {
+			t.Fatal("String: unexpected empty result")
+		}
+		if s[0] == '\r' || s[0] == '\n' {
+			t.Fatal("String: unexpected newline")
+		}
+	}
+
+	r := NewReader(&b, w.Boundary())
+
+	part, err := r.NextPart()
+	if err != nil {
+		t.Fatalf("part 1: %v", err)
+	}
+	if g, e := part.FormName(), "myfile"; g != e {
+		t.Errorf("part 1: want form name %q, got %q", e, g)
+	}
+	slurp, err := ioutil.ReadAll(part)
+	if err != nil {
+		t.Fatalf("part 1: ReadAll: %v", err)
+	}
+	if e, g := string(fileContents), string(slurp); e != g {
+		t.Errorf("part 1: want contents %q, got %q", e, g)
+	}
+
+	part, err = r.NextPart()
+	if err != nil {
+		t.Fatalf("part 2: %v", err)
+	}
+	if g, e := part.FormName(), "key"; g != e {
+		t.Errorf("part 2: want form name %q, got %q", e, g)
+	}
+	slurp, err = ioutil.ReadAll(part)
+	if err != nil {
+		t.Fatalf("part 2: ReadAll: %v", err)
+	}
+	if e, g := "val", string(slurp); e != g {
+		t.Errorf("part 2: want contents %q, got %q", e, g)
+	}
+
+	part, err = r.NextPart()
+	if part != nil || err == nil {
+		t.Fatalf("expected end of parts; got %v, %v", part, err)
+	}
+}
+
+func TestWriterSetBoundary(t *testing.T) {
+	var b bytes.Buffer
+	w := NewWriter(&b)
+	tests := []struct {
+		b  string
+		ok bool
+	}{
+		{"abc", true},
+		{"", false},
+		{"ungültig", false},
+		{"!", false},
+		{strings.Repeat("x", 69), true},
+		{strings.Repeat("x", 70), false},
+		{"bad!ascii!", false},
+		{"my-separator", true},
+	}
+	for i, tt := range tests {
+		err := w.SetBoundary(tt.b)
+		got := err == nil
+		if got != tt.ok {
+			t.Errorf("%d. boundary %q = %v (%v); want %v", i, tt.b, got, err, tt.ok)
+		} else if tt.ok {
+			got := w.Boundary()
+			if got != tt.b {
+				t.Errorf("boundary = %q; want %q", got, tt.b)
+			}
+		}
+	}
+	w.Close()
+	if got := b.String(); !strings.Contains(got, "\r\n--my-separator--\r\n") {
+		t.Errorf("expected my-separator in output. got: %q", got)
+	}
+}
+
+func TestWriterBoundaryGoroutines(t *testing.T) {
+	// Verify there's no data race accessing any lazy boundary if it's used by
+	// different goroutines. This was previously broken by
+	// https://codereview.appspot.com/95760043/ and reverted in
+	// https://codereview.appspot.com/117600043/
+	w := NewWriter(ioutil.Discard)
+	done := make(chan int)
+	go func() {
+		w.CreateFormField("foo")
+		done <- 1
+	}()
+	w.Boundary()
+	<-done
+}
diff --git a/src/mime/testdata/test.types b/src/mime/testdata/test.types
new file mode 100644
index 000000000..9b040edd7
--- /dev/null
+++ b/src/mime/testdata/test.types
@@ -0,0 +1,8 @@
+# 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.
+
+
+ # mime package test
+application/test	t1	# Simple test
+text/test		t2	# Text test
diff --git a/src/mime/testdata/test.types.plan9 b/src/mime/testdata/test.types.plan9
new file mode 100644
index 000000000..19dbf41cc
--- /dev/null
+++ b/src/mime/testdata/test.types.plan9
@@ -0,0 +1,8 @@
+# Copyright 2013 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.
+
+
+ # mime package test
+.t1		application	test		-		y # Simple test	
+.t2		text		test		-		y # Text test	
diff --git a/src/mime/type.go b/src/mime/type.go
new file mode 100644
index 000000000..ffda1f0ce
--- /dev/null
+++ b/src/mime/type.go
@@ -0,0 +1,121 @@
+// 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 mime implements parts of the MIME spec.
+package mime
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+)
+
+var (
+	mimeLock       sync.RWMutex
+	mimeTypesLower = map[string]string{
+		".css":  "text/css; charset=utf-8",
+		".gif":  "image/gif",
+		".htm":  "text/html; charset=utf-8",
+		".html": "text/html; charset=utf-8",
+		".jpg":  "image/jpeg",
+		".js":   "application/x-javascript",
+		".pdf":  "application/pdf",
+		".png":  "image/png",
+		".xml":  "text/xml; charset=utf-8",
+	}
+	mimeTypes = clone(mimeTypesLower)
+)
+
+func clone(m map[string]string) map[string]string {
+	m2 := make(map[string]string, len(m))
+	for k, v := range m {
+		m2[k] = v
+		if strings.ToLower(k) != k {
+			panic("keys in mimeTypesLower must be lowercase")
+		}
+	}
+	return m2
+}
+
+var once sync.Once // guards initMime
+
+// TypeByExtension returns the MIME type associated with the file extension ext.
+// The extension ext should begin with a leading dot, as in ".html".
+// When ext has no associated type, TypeByExtension returns "".
+//
+// Extensions are looked up first case-sensitively, then case-insensitively.
+//
+// The built-in table is small but on unix it is augmented by the local
+// system's mime.types file(s) if available under one or more of these
+// names:
+//
+//   /etc/mime.types
+//   /etc/apache2/mime.types
+//   /etc/apache/mime.types
+//
+// On Windows, MIME types are extracted from the registry.
+//
+// Text types have the charset parameter set to "utf-8" by default.
+func TypeByExtension(ext string) string {
+	once.Do(initMime)
+	mimeLock.RLock()
+	defer mimeLock.RUnlock()
+
+	// Case-sensitive lookup.
+	v := mimeTypes[ext]
+	if v != "" {
+		return v
+	}
+
+	// Case-insensitive lookup.
+	// Optimistically assume a short ASCII extension and be
+	// allocation-free in that case.
+	var buf [10]byte
+	lower := buf[:0]
+	const utf8RuneSelf = 0x80 // from utf8 package, but not importing it.
+	for i := 0; i < len(ext); i++ {
+		c := ext[i]
+		if c >= utf8RuneSelf {
+			// Slow path.
+			return mimeTypesLower[strings.ToLower(ext)]
+		}
+		if 'A' <= c && c <= 'Z' {
+			lower = append(lower, c+('a'-'A'))
+		} else {
+			lower = append(lower, c)
+		}
+	}
+	// The conversion from []byte to string doesn't allocate in
+	// a map lookup.
+	return mimeTypesLower[string(lower)]
+}
+
+// AddExtensionType sets the MIME type associated with
+// the extension ext to typ. The extension should begin with
+// a leading dot, as in ".html".
+func AddExtensionType(ext, typ string) error {
+	if !strings.HasPrefix(ext, ".") {
+		return fmt.Errorf(`mime: extension %q misses dot`, ext)
+	}
+	once.Do(initMime)
+	return setExtensionType(ext, typ)
+}
+
+func setExtensionType(extension, mimeType string) error {
+	_, param, err := ParseMediaType(mimeType)
+	if err != nil {
+		return err
+	}
+	if strings.HasPrefix(mimeType, "text/") && param["charset"] == "" {
+		param["charset"] = "utf-8"
+		mimeType = FormatMediaType(mimeType, param)
+	}
+	extLower := strings.ToLower(extension)
+
+	mimeLock.Lock()
+	mimeTypes[extension] = mimeType
+	mimeTypesLower[extLower] = mimeType
+	mimeLock.Unlock()
+	return nil
+}
diff --git a/src/mime/type_plan9.go b/src/mime/type_plan9.go
new file mode 100644
index 000000000..8cbf6777f
--- /dev/null
+++ b/src/mime/type_plan9.go
@@ -0,0 +1,53 @@
+// Copyright 2013 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 mime
+
+import (
+	"bufio"
+	"os"
+	"strings"
+)
+
+var typeFiles = []string{
+	"/sys/lib/mimetypes",
+}
+
+func loadMimeFile(filename string) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) <= 2 || fields[0][0] != '.' {
+			continue
+		}
+		if fields[1] == "-" || fields[2] == "-" {
+			continue
+		}
+		setExtensionType(fields[0], fields[1]+"/"+fields[2])
+	}
+	if err := scanner.Err(); err != nil {
+		panic(err)
+	}
+}
+
+func initMime() {
+	for _, filename := range typeFiles {
+		loadMimeFile(filename)
+	}
+}
+
+func initMimeForTests() map[string]string {
+	typeFiles = []string{"testdata/test.types.plan9"}
+	return map[string]string{
+		".t1":  "application/test",
+		".t2":  "text/test; charset=utf-8",
+		".pNg": "image/png",
+	}
+}
diff --git a/src/mime/type_test.go b/src/mime/type_test.go
new file mode 100644
index 000000000..d2d254ae9
--- /dev/null
+++ b/src/mime/type_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 mime
+
+import (
+	"testing"
+)
+
+var typeTests = initMimeForTests()
+
+func TestTypeByExtension(t *testing.T) {
+	for ext, want := range typeTests {
+		val := TypeByExtension(ext)
+		if val != want {
+			t.Errorf("TypeByExtension(%q) = %q, want %q", ext, val, want)
+		}
+	}
+}
+
+func TestTypeByExtensionCase(t *testing.T) {
+	const custom = "test/test; charset=iso-8859-1"
+	const caps = "test/test; WAS=ALLCAPS"
+	if err := AddExtensionType(".TEST", caps); err != nil {
+		t.Fatalf("error %s for AddExtension(%s)", err, custom)
+	}
+	if err := AddExtensionType(".tesT", custom); err != nil {
+		t.Fatalf("error %s for AddExtension(%s)", err, custom)
+	}
+
+	// case-sensitive lookup
+	if got := TypeByExtension(".tesT"); got != custom {
+		t.Fatalf("for .tesT, got %q; want %q", got, custom)
+	}
+	if got := TypeByExtension(".TEST"); got != caps {
+		t.Fatalf("for .TEST, got %q; want %s", got, caps)
+	}
+
+	// case-insensitive
+	if got := TypeByExtension(".TesT"); got != custom {
+		t.Fatalf("for .TesT, got %q; want %q", got, custom)
+	}
+}
+
+func TestLookupMallocs(t *testing.T) {
+	n := testing.AllocsPerRun(10000, func() {
+		TypeByExtension(".html")
+		TypeByExtension(".HtML")
+	})
+	if n > 0 {
+		t.Errorf("allocs = %v; want 0", n)
+	}
+}
diff --git a/src/mime/type_unix.go b/src/mime/type_unix.go
new file mode 100644
index 000000000..3e404cf74
--- /dev/null
+++ b/src/mime/type_unix.go
@@ -0,0 +1,60 @@
+// 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.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+package mime
+
+import (
+	"bufio"
+	"os"
+	"strings"
+)
+
+var typeFiles = []string{
+	"/etc/mime.types",
+	"/etc/apache2/mime.types",
+	"/etc/apache/mime.types",
+}
+
+func loadMimeFile(filename string) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) <= 1 || fields[0][0] == '#' {
+			continue
+		}
+		mimeType := fields[0]
+		for _, ext := range fields[1:] {
+			if ext[0] == '#' {
+				break
+			}
+			setExtensionType("."+ext, mimeType)
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		panic(err)
+	}
+}
+
+func initMime() {
+	for _, filename := range typeFiles {
+		loadMimeFile(filename)
+	}
+}
+
+func initMimeForTests() map[string]string {
+	typeFiles = []string{"testdata/test.types"}
+	return map[string]string{
+		".T1":  "application/test",
+		".t2":  "text/test; charset=utf-8",
+		".png": "image/png",
+	}
+}
diff --git a/src/mime/type_windows.go b/src/mime/type_windows.go
new file mode 100644
index 000000000..ae758d78b
--- /dev/null
+++ b/src/mime/type_windows.go
@@ -0,0 +1,63 @@
+// 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 mime
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func initMime() {
+	var root syscall.Handle
+	rootpathp, _ := syscall.UTF16PtrFromString(`\`)
+	if syscall.RegOpenKeyEx(syscall.HKEY_CLASSES_ROOT, rootpathp,
+		0, syscall.KEY_READ, &root) != nil {
+		return
+	}
+	defer syscall.RegCloseKey(root)
+	var count uint32
+	if syscall.RegQueryInfoKey(root, nil, nil, nil, &count, nil, nil, nil, nil, nil, nil, nil) != nil {
+		return
+	}
+	var buf [1 << 10]uint16
+	for i := uint32(0); i < count; i++ {
+		n := uint32(len(buf))
+		if syscall.RegEnumKeyEx(root, i, &buf[0], &n, nil, nil, nil, nil) != nil {
+			continue
+		}
+		ext := syscall.UTF16ToString(buf[:])
+		if len(ext) < 2 || ext[0] != '.' { // looking for extensions only
+			continue
+		}
+		var h syscall.Handle
+		extpathp, _ := syscall.UTF16PtrFromString(`\` + ext)
+		if syscall.RegOpenKeyEx(
+			syscall.HKEY_CLASSES_ROOT, extpathp,
+			0, syscall.KEY_READ, &h) != nil {
+			continue
+		}
+		var typ uint32
+		n = uint32(len(buf) * 2) // api expects array of bytes, not uint16
+		contenttypep, _ := syscall.UTF16PtrFromString("Content Type")
+		if syscall.RegQueryValueEx(
+			h, contenttypep,
+			nil, &typ, (*byte)(unsafe.Pointer(&buf[0])), &n) != nil {
+			syscall.RegCloseKey(h)
+			continue
+		}
+		syscall.RegCloseKey(h)
+		if typ != syscall.REG_SZ { // null terminated strings only
+			continue
+		}
+		mimeType := syscall.UTF16ToString(buf[:])
+		setExtensionType(ext, mimeType)
+	}
+}
+
+func initMimeForTests() map[string]string {
+	return map[string]string{
+		".PnG": "image/png",
+	}
+}