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 // The mime package implements parts of the MIME spec.
   6 package mime
   7
   8 import (
   9         "bufio"
  10         "os"
  11         "strings"
  12         "sync"
  13 )
  14
  15 var typeFiles = []string{
  16         "/etc/mime.types",
  17         "/etc/apache2/mime.types",
  18         "/etc/apache/mime.types",
  19 }
  20
  21 var mimeTypes = map[string]string{
  22         ".css":  "text/css",
  23         ".gif":  "image/gif",
  24         ".htm":  "text/html; charset=utf-8",
  25         ".html": "text/html; charset=utf-8",
  26         ".jpg":  "image/jpeg",
  27         ".js":   "application/x-javascript",
  28         ".pdf":  "application/pdf",
  29         ".png":  "image/png",
  30         ".xml":  "text/xml; charset=utf-8",
  31 }
  32
  33 var mimeLock sync.RWMutex
  34
  35 func loadMimeFile(filename string) {
  36         f, err := os.Open(filename, os.O_RDONLY, 0666)
  37         if err != nil {
  38                 return
  39         }
  40
  41         reader := bufio.NewReader(f)
  42         for {
  43                 line, err := reader.ReadString('\n')
  44                 if err != nil {
  45                         f.Close()
  46                         return
  47                 }
  48                 fields := strings.Fields(line)
  49                 if len(fields) <= 1 || fields[0][0] == '#' {
  50                         continue
  51                 }
  52                 typename := fields[0]
  53                 if strings.HasPrefix(typename, "text/") {
  54                         typename += "; charset=utf-8"
  55                 }
  56                 for _, ext := range fields[1:] {
  57                         if ext[0] == '#' {
  58                                 break
  59                         }
  60                         mimeTypes["."+ext] = typename
  61                 }
  62         }
  63 }
  64
  65 func initMime() {
  66         for _, filename := range typeFiles {
  67                 loadMimeFile(filename)
  68         }
  69 }
  70
  71 var once sync.Once
  72
  73 // TypeByExtension returns the MIME type associated with the file extension ext.
  74 // The extension ext should begin with a leading dot, as in ".html".
  75 // When ext has no associated type, TypeByExtension returns "".
  76 //
  77 // The built-in table is small but is is augmented by the local
  78 // system's mime.types file(s) if available under one or more of these
  79 // names:
  80 //
  81 //   /etc/mime.types
  82 //   /etc/apache2/mime.types
  83 //   /etc/apache/mime.types
  84 func TypeByExtension(ext string) string {
  85         once.Do(initMime)
  86         mimeLock.RLock()
  87         typename := mimeTypes[ext]
  88         mimeLock.RUnlock()
  89         return typename
  90 }
  91
  92 // AddExtensionType sets the MIME type associated with
  93 // the extension ext to typ.  The extension should begin with
  94 // a leading dot, as in ".html".
  95 func AddExtensionType(ext, typ string) os.Error {
  96         once.Do(initMime)
  97         if len(ext) < 1 || ext[0] != '.' {
  98                 return os.EINVAL
  99         }
 100         mimeLock.Lock()
 101         mimeTypes[ext] = typ
 102         mimeLock.Unlock()
 103         return nil
 104 }