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// 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 mimeTypes = 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",
}
var mimeLock sync.RWMutex
var once sync.Once
// 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 "".
//
// 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
//
// Windows system mime types are extracted from registry.
//
// Text types have the charset parameter set to "utf-8" by default.
func TypeByExtension(ext string) string {
once.Do(initMime)
mimeLock.RLock()
typename := mimeTypes[ext]
mimeLock.RUnlock()
return typename
}
// 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 ext == "" || ext[0] != '.' {
return fmt.Errorf(`mime: extension "%s" 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)
}
mimeLock.Lock()
mimeTypes[extension] = mimeType
mimeLock.Unlock()
return nil
}