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mime: add ExtensionByType method
Added the inverse of TypeByExtension for discovering an appropriate extensions for a given MIME type. Fixes #10144 Change-Id: I6a80e1af3db5d45ad6a4c7ff4ccfdf6a4f424367 Reviewed-on: https://go-review.googlesource.com/7444 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
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@ -26,6 +26,7 @@ var (
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".xml": "text/xml; charset=utf-8",
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}
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mimeTypes = clone(mimeTypesLower)
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extensions = invert(mimeTypesLower)
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)
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func clone(m map[string]string) map[string]string {
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@ -39,6 +40,18 @@ func clone(m map[string]string) map[string]string {
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return m2
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}
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func invert(m map[string]string) map[string][]string {
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m2 := make(map[string][]string, len(m))
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for k, v := range m {
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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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m2[justType] = append(m2[justType], k)
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}
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return m2
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}
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var once sync.Once // guards initMime
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// TypeByExtension returns the MIME type associated with the file extension ext.
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@ -92,6 +105,26 @@ func TypeByExtension(ext string) string {
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return mimeTypesLower[string(lower)]
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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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mimeLock.RLock()
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defer mimeLock.RUnlock()
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s, ok := extensions[justType]
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if !ok {
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return nil, nil
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}
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return append([]string{}, s...), 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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@ -104,7 +137,7 @@ func AddExtensionType(ext, typ string) error {
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}
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func setExtensionType(extension, mimeType string) error {
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_, param, err := ParseMediaType(mimeType)
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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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@ -115,8 +148,14 @@ func setExtensionType(extension, mimeType string) error {
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extLower := strings.ToLower(extension)
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mimeLock.Lock()
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defer mimeLock.Unlock()
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mimeTypes[extension] = mimeType
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mimeTypesLower[extLower] = mimeType
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mimeLock.Unlock()
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for _, v := range extensions[justType] {
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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[justType] = append(extensions[justType], extLower)
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return nil
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}
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@ -5,6 +5,9 @@
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package mime
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import (
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"reflect"
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"sort"
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"strings"
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"testing"
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)
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@ -43,6 +46,59 @@ func TestTypeByExtensionCase(t *testing.T) {
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}
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}
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func TestExtensionsByType(t *testing.T) {
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for want, typ := range typeTests {
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val, err := ExtensionsByType(typ)
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if err != nil {
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t.Errorf("error %s for ExtensionsByType(%q)", err, typ)
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continue
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}
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if len(val) != 1 {
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t.Errorf("ExtensionsByType(%q) = %v; expected exactly 1 entry", typ, val)
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continue
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}
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// We always expect lower case, test data includes upper-case.
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want = strings.ToLower(want)
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if val[0] != want {
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t.Errorf("ExtensionsByType(%q) = %q, want %q", typ, val[0], want)
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}
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}
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}
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func TestExtensionsByTypeMultiple(t *testing.T) {
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const typ = "text/html"
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exts, err := ExtensionsByType(typ)
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if err != nil {
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t.Fatalf("ExtensionsByType(%q) error: %v", typ, err)
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}
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sort.Strings(exts)
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if want := []string{".htm", ".html"}; !reflect.DeepEqual(exts, want) {
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t.Errorf("ExtensionsByType(%q) = %v; want %v", typ, exts, want)
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}
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}
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func TestExtensionsByTypeNoDuplicates(t *testing.T) {
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const (
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typ = "text/html"
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ext = ".html"
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)
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AddExtensionType(ext, typ)
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AddExtensionType(ext, typ)
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exts, err := ExtensionsByType(typ)
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if err != nil {
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t.Fatalf("ExtensionsByType(%q) error: %v", typ, err)
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}
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count := 0
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for _, v := range exts {
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if v == ext {
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count++
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}
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}
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if count != 1 {
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t.Errorf("ExtensionsByType(%q) = %v; want %v once", typ, exts, ext)
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}
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}
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func TestLookupMallocs(t *testing.T) {
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n := testing.AllocsPerRun(10000, func() {
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TypeByExtension(".html")
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