203 lines
5.2 KiB
Go
203 lines
5.2 KiB
Go
// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package mime implements parts of the MIME spec.
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package mime
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import (
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"fmt"
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"sort"
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"strings"
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"sync"
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)
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var (
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mimeTypes sync.Map // map[string]string; ".Z" => "application/x-compress"
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mimeTypesLower sync.Map // map[string]string; ".z" => "application/x-compress"
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// extensions maps from MIME type to list of lowercase file
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// extensions: "image/jpeg" => [".jpg", ".jpeg"]
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extensionsMu sync.Mutex // Guards stores (but not loads) on extensions.
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extensions sync.Map // map[string][]string; slice values are append-only.
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)
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func clearSyncMap(m *sync.Map) {
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m.Range(func(k, _ any) bool {
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m.Delete(k)
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return true
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})
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}
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// setMimeTypes is used by initMime's non-test path, and by tests.
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func setMimeTypes(lowerExt, mixExt map[string]string) {
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clearSyncMap(&mimeTypes)
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clearSyncMap(&mimeTypesLower)
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clearSyncMap(&extensions)
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for k, v := range lowerExt {
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mimeTypesLower.Store(k, v)
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}
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for k, v := range mixExt {
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mimeTypes.Store(k, v)
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}
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extensionsMu.Lock()
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defer extensionsMu.Unlock()
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for k, v := range lowerExt {
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justType, _, err := ParseMediaType(v)
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if err != nil {
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panic(err)
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}
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var exts []string
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if ei, ok := extensions.Load(justType); ok {
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exts = ei.([]string)
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}
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extensions.Store(justType, append(exts, k))
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}
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}
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var builtinTypesLower = map[string]string{
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".avif": "image/avif",
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".css": "text/css; charset=utf-8",
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".gif": "image/gif",
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".htm": "text/html; charset=utf-8",
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".html": "text/html; charset=utf-8",
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".jpeg": "image/jpeg",
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".jpg": "image/jpeg",
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".js": "text/javascript; charset=utf-8",
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".json": "application/json",
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".mjs": "text/javascript; charset=utf-8",
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".pdf": "application/pdf",
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".png": "image/png",
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".svg": "image/svg+xml",
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".wasm": "application/wasm",
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".webp": "image/webp",
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".xml": "text/xml; charset=utf-8",
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}
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var once sync.Once // guards initMime
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var testInitMime, osInitMime func()
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func initMime() {
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if fn := testInitMime; fn != nil {
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fn()
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} else {
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setMimeTypes(builtinTypesLower, builtinTypesLower)
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osInitMime()
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}
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}
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// TypeByExtension returns the MIME type associated with the file extension ext.
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// The extension ext should begin with a leading dot, as in ".html".
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// When ext has no associated type, TypeByExtension returns "".
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//
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// Extensions are looked up first case-sensitively, then case-insensitively.
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//
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// The built-in table is small but on unix it is augmented by the local
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// system's MIME-info database or mime.types file(s) if available under one or
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// more of these names:
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//
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// /usr/local/share/mime/globs2
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// /usr/share/mime/globs2
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// /etc/mime.types
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// /etc/apache2/mime.types
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// /etc/apache/mime.types
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//
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// On Windows, MIME types are extracted from the registry.
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//
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// Text types have the charset parameter set to "utf-8" by default.
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func TypeByExtension(ext string) string {
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once.Do(initMime)
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// Case-sensitive lookup.
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if v, ok := mimeTypes.Load(ext); ok {
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return v.(string)
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}
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// Case-insensitive lookup.
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// Optimistically assume a short ASCII extension and be
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// allocation-free in that case.
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var buf [10]byte
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lower := buf[:0]
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const utf8RuneSelf = 0x80 // from utf8 package, but not importing it.
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for i := 0; i < len(ext); i++ {
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c := ext[i]
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if c >= utf8RuneSelf {
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// Slow path.
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si, _ := mimeTypesLower.Load(strings.ToLower(ext))
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s, _ := si.(string)
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return s
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}
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if 'A' <= c && c <= 'Z' {
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lower = append(lower, c+('a'-'A'))
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} else {
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lower = append(lower, c)
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}
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}
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si, _ := mimeTypesLower.Load(string(lower))
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s, _ := si.(string)
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return s
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}
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// ExtensionsByType returns the extensions known to be associated with the MIME
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// type typ. The returned extensions will each begin with a leading dot, as in
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// ".html". When typ has no associated extensions, ExtensionsByType returns an
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// nil slice.
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func ExtensionsByType(typ string) ([]string, error) {
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justType, _, err := ParseMediaType(typ)
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if err != nil {
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return nil, err
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}
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once.Do(initMime)
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s, ok := extensions.Load(justType)
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if !ok {
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return nil, nil
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}
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ret := append([]string(nil), s.([]string)...)
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sort.Strings(ret)
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return ret, nil
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}
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// AddExtensionType sets the MIME type associated with
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// the extension ext to typ. The extension should begin with
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// a leading dot, as in ".html".
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func AddExtensionType(ext, typ string) error {
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if !strings.HasPrefix(ext, ".") {
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return fmt.Errorf("mime: extension %q missing leading dot", ext)
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}
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once.Do(initMime)
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return setExtensionType(ext, typ)
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}
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func setExtensionType(extension, mimeType string) error {
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justType, param, err := ParseMediaType(mimeType)
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if err != nil {
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return err
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}
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if strings.HasPrefix(mimeType, "text/") && param["charset"] == "" {
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param["charset"] = "utf-8"
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mimeType = FormatMediaType(mimeType, param)
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}
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extLower := strings.ToLower(extension)
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mimeTypes.Store(extension, mimeType)
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mimeTypesLower.Store(extLower, mimeType)
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extensionsMu.Lock()
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defer extensionsMu.Unlock()
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var exts []string
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if ei, ok := extensions.Load(justType); ok {
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exts = ei.([]string)
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}
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for _, v := range exts {
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if v == extLower {
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return nil
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}
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}
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extensions.Store(justType, append(exts, extLower))
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return nil
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}
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