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
|
// 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
}
|
