libgo/go/mime/type.go

   1 // Copyright 2010 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Package mime implements parts of the MIME spec.
   6 package mime
   7
   8 import (
   9         "fmt"
  10         "strings"
  11         "sync"
  12 )
  13
  14 var mimeTypes = map[string]string{
  15         ".css":  "text/css; charset=utf-8",
  16         ".gif":  "image/gif",
  17         ".htm":  "text/html; charset=utf-8",
  18         ".html": "text/html; charset=utf-8",
  19         ".jpg":  "image/jpeg",
  20         ".js":   "application/x-javascript",
  21         ".pdf":  "application/pdf",
  22         ".png":  "image/png",
  23         ".xml":  "text/xml; charset=utf-8",
  24 }
  25
  26 var mimeLock sync.RWMutex
  27
  28 var once sync.Once
  29
  30 // TypeByExtension returns the MIME type associated with the file extension ext.
  31 // The extension ext should begin with a leading dot, as in ".html".
  32 // When ext has no associated type, TypeByExtension returns "".
  33 //
  34 // The built-in table is small but on unix it is augmented by the local
  35 // system's mime.types file(s) if available under one or more of these
  36 // names:
  37 //
  38 //   /etc/mime.types
  39 //   /etc/apache2/mime.types
  40 //   /etc/apache/mime.types
  41 //
  42 // Windows system mime types are extracted from registry.
  43 //
  44 // Text types have the charset parameter set to "utf-8" by default.
  45 func TypeByExtension(ext string) string {
  46         once.Do(initMime)
  47         mimeLock.RLock()
  48         typename := mimeTypes[ext]
  49         mimeLock.RUnlock()
  50         return typename
  51 }
  52
  53 // AddExtensionType sets the MIME type associated with
  54 // the extension ext to typ.  The extension should begin with
  55 // a leading dot, as in ".html".
  56 func AddExtensionType(ext, typ string) error {
  57         if ext == "" || ext[0] != '.' {
  58                 return fmt.Errorf(`mime: extension "%s" misses dot`, ext)
  59         }
  60         once.Do(initMime)
  61         return setExtensionType(ext, typ)
  62 }
  63
  64 func setExtensionType(extension, mimeType string) error {
  65         _, param, err := ParseMediaType(mimeType)
  66         if err != nil {
  67                 return err
  68         }
  69         if strings.HasPrefix(mimeType, "text/") && param["charset"] == "" {
  70                 param["charset"] = "utf-8"
  71                 mimeType = FormatMediaType(mimeType, param)
  72         }
  73         mimeLock.Lock()
  74         mimeTypes[extension] = mimeType
  75         mimeLock.Unlock()
  76         return nil
  77 }