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
|
// Copyright 2021 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package typesniffer
import (
"bytes"
"fmt"
"io"
"net/http"
"regexp"
"strings"
"code.gitea.io/gitea/modules/util"
)
// Use at most this many bytes to determine Content Type.
const sniffLen = 1024
const (
// SvgMimeType MIME type of SVG images.
SvgMimeType = "image/svg+xml"
// AvifMimeType MIME type of AVIF images
AvifMimeType = "image/avif"
// ApplicationOctetStream MIME type of binary files.
ApplicationOctetStream = "application/octet-stream"
)
var (
svgComment = regexp.MustCompile(`(?s)<!--.*?-->`)
svgTagRegex = regexp.MustCompile(`(?si)\A\s*(?:(<!DOCTYPE\s+svg([\s:]+.*?>|>))\s*)*<svg\b`)
svgTagInXMLRegex = regexp.MustCompile(`(?si)\A<\?xml\b.*?\?>\s*(?:(<!DOCTYPE\s+svg([\s:]+.*?>|>))\s*)*<svg\b`)
)
// SniffedType contains information about a blobs type.
type SniffedType struct {
contentType string
}
// IsText etects if content format is plain text.
func (ct SniffedType) IsText() bool {
return strings.Contains(ct.contentType, "text/")
}
// IsImage detects if data is an image format
func (ct SniffedType) IsImage() bool {
return strings.Contains(ct.contentType, "image/")
}
// IsSvgImage detects if data is an SVG image format
func (ct SniffedType) IsSvgImage() bool {
return strings.Contains(ct.contentType, SvgMimeType)
}
// IsPDF detects if data is a PDF format
func (ct SniffedType) IsPDF() bool {
return strings.Contains(ct.contentType, "application/pdf")
}
// IsVideo detects if data is an video format
func (ct SniffedType) IsVideo() bool {
return strings.Contains(ct.contentType, "video/")
}
// IsAudio detects if data is an video format
func (ct SniffedType) IsAudio() bool {
return strings.Contains(ct.contentType, "audio/")
}
// IsRepresentableAsText returns true if file content can be represented as
// plain text or is empty.
func (ct SniffedType) IsRepresentableAsText() bool {
return ct.IsText() || ct.IsSvgImage()
}
// IsBrowsableBinaryType returns whether a non-text type can be displayed in a browser
func (ct SniffedType) IsBrowsableBinaryType() bool {
return ct.IsImage() || ct.IsSvgImage() || ct.IsPDF() || ct.IsVideo() || ct.IsAudio()
}
// GetMimeType returns the mime type
func (ct SniffedType) GetMimeType() string {
return strings.SplitN(ct.contentType, ";", 2)[0]
}
// DetectContentType extends http.DetectContentType with more content types. Defaults to text/unknown if input is empty.
func DetectContentType(data []byte) SniffedType {
if len(data) == 0 {
return SniffedType{"text/unknown"}
}
ct := http.DetectContentType(data)
if len(data) > sniffLen {
data = data[:sniffLen]
}
// SVG is unsupported by http.DetectContentType, https://github.com/golang/go/issues/15888
detectByHTML := strings.Contains(ct, "text/plain") || strings.Contains(ct, "text/html")
detectByXML := strings.Contains(ct, "text/xml")
if detectByHTML || detectByXML {
dataProcessed := svgComment.ReplaceAll(data, nil)
dataProcessed = bytes.TrimSpace(dataProcessed)
if detectByHTML && svgTagRegex.Match(dataProcessed) ||
detectByXML && svgTagInXMLRegex.Match(dataProcessed) {
ct = SvgMimeType
}
}
// AVIF is unsupported by http.DetectContentType
// Signature taken from https://stackoverflow.com/a/68322450
if bytes.Index(data, []byte("ftypavif")) == 4 {
ct = AvifMimeType
}
if strings.HasPrefix(ct, "audio/") && bytes.HasPrefix(data, []byte("ID3")) {
// The MP3 detection is quite inaccurate, any content with "ID3" prefix will result in "audio/mpeg".
// So remove the "ID3" prefix and detect again, if result is text, then it must be text content.
// This works especially because audio files contain many unprintable/invalid characters like `0x00`
ct2 := http.DetectContentType(data[3:])
if strings.HasPrefix(ct2, "text/") {
ct = ct2
}
}
if ct == "application/ogg" {
dataHead := data
if len(dataHead) > 256 {
dataHead = dataHead[:256] // only need to do a quick check for the file header
}
if bytes.Contains(dataHead, []byte("theora")) || bytes.Contains(dataHead, []byte("dirac")) {
ct = "video/ogg" // ogg is only used for some video formats, and it's not popular
} else {
ct = "audio/ogg" // for most cases, it is used as an audio container
}
}
return SniffedType{ct}
}
// DetectContentTypeFromReader guesses the content type contained in the reader.
func DetectContentTypeFromReader(r io.Reader) (SniffedType, error) {
buf := make([]byte, sniffLen)
n, err := util.ReadAtMost(r, buf)
if err != nil {
return SniffedType{}, fmt.Errorf("DetectContentTypeFromReader io error: %w", err)
}
buf = buf[:n]
return DetectContentType(buf), nil
}
|
