Imported Upstream version 1.4upstream/1.4

1 files changed, 121 insertions, 0 deletions

diff --git a/src/mime/type.go b/src/mime/type.go
new file mode 100644
index 000000000..ffda1f0ce
--- /dev/null
+++ b/src/mime/type.go
@@ -0,0 +1,121 @@
+// 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 (
+	mimeLock       sync.RWMutex
+	mimeTypesLower = 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",
+	}
+	mimeTypes = clone(mimeTypesLower)
+)
+
+func clone(m map[string]string) map[string]string {
+	m2 := make(map[string]string, len(m))
+	for k, v := range m {
+		m2[k] = v
+		if strings.ToLower(k) != k {
+			panic("keys in mimeTypesLower must be lowercase")
+		}
+	}
+	return m2
+}
+
+var once sync.Once // guards initMime
+
+// 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 "".
+//
+// Extensions are looked up first case-sensitively, then case-insensitively.
+//
+// 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
+//
+// On Windows, MIME types are extracted from the registry.
+//
+// Text types have the charset parameter set to "utf-8" by default.
+func TypeByExtension(ext string) string {
+	once.Do(initMime)
+	mimeLock.RLock()
+	defer mimeLock.RUnlock()
+
+	// Case-sensitive lookup.
+	v := mimeTypes[ext]
+	if v != "" {
+		return v
+	}
+
+	// Case-insensitive lookup.
+	// Optimistically assume a short ASCII extension and be
+	// allocation-free in that case.
+	var buf [10]byte
+	lower := buf[:0]
+	const utf8RuneSelf = 0x80 // from utf8 package, but not importing it.
+	for i := 0; i < len(ext); i++ {
+		c := ext[i]
+		if c >= utf8RuneSelf {
+			// Slow path.
+			return mimeTypesLower[strings.ToLower(ext)]
+		}
+		if 'A' <= c && c <= 'Z' {
+			lower = append(lower, c+('a'-'A'))
+		} else {
+			lower = append(lower, c)
+		}
+	}
+	// The conversion from []byte to string doesn't allocate in
+	// a map lookup.
+	return mimeTypesLower[string(lower)]
+}
+
+// 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 !strings.HasPrefix(ext, ".") {
+		return fmt.Errorf(`mime: extension %q 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)
+	}
+	extLower := strings.ToLower(extension)
+
+	mimeLock.Lock()
+	mimeTypes[extension] = mimeType
+	mimeTypesLower[extLower] = mimeType
+	mimeLock.Unlock()
+	return nil
+}