aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/go/_std_1.22/src/mime/multipart/writer.go
blob: d1ff151a7d1d6441bf8a9209bdd0529a6d29066d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
// 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"
	"sort"
	"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 non-empty and
// at most 70 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) > 70 {
		return errors.New("mime: invalid boundary length")
	}
	end := len(boundary) - 1
	for i, b := range boundary {
		if 'A' <= b && b <= 'Z' || 'a' <= b && b <= 'z' || '0' <= b && b <= '9' {
			continue
		}
		switch b {
		case '\'', '(', ')', '+', '_', ',', '-', '.', '/', ':', '=', '?':
			continue
		case ' ':
			if i != end {
				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 {
	b := w.boundary
	// We must quote the boundary if it contains any of the
	// tspecials characters defined by RFC 2045, or space.
	if strings.ContainsAny(b, `()<>@,;:\"/[]?= `) {
		b = `"` + b + `"`
	}
	return "multipart/form-data; boundary=" + b
}

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)
	}

	keys := make([]string, 0, len(header))
	for k := range header {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	for _, k := range keys {
		for _, v := range header[k] {
			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
}