diff -r 000000000000 -r 6474c204b198 dom/encoding/EncodingUtils.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/encoding/EncodingUtils.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,119 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_encodingutils_h_
+#define mozilla_dom_encodingutils_h_
+
+#include "nsDataHashtable.h"
+#include "nsString.h"
+
+class nsIUnicodeDecoder;
+class nsIUnicodeEncoder;
+
+namespace mozilla {
+namespace dom {
+
+class EncodingUtils
+{
+public:
+
+  /**
+   * Implements get an encoding algorithm from Encoding spec.
+   * http://encoding.spec.whatwg.org/#concept-encoding-get
+   * Given a label, this function returns the corresponding encoding or a
+   * false.
+   * The returned name may not be lowercased due to compatibility with
+   * our internal implementations.
+   *
+   * @param      aLabel, incoming label describing charset to be decoded.
+   * @param      aRetEncoding, returning corresponding encoding for label.
+   * @return     false if no encoding was found for label.
+   *             true if valid encoding found.
+   */
+  static bool FindEncodingForLabel(const nsACString& aLabel,
+                                   nsACString& aOutEncoding);
+
+  static bool FindEncodingForLabel(const nsAString& aLabel,
+                                   nsACString& aOutEncoding)
+  {
+    return FindEncodingForLabel(NS_ConvertUTF16toUTF8(aLabel), aOutEncoding);
+  }
+
+  /**
+   * Remove any leading and trailing space characters, following the
+   * definition of space characters from Encoding spec.
+   * http://encoding.spec.whatwg.org/#terminology
+   * Note that nsAString::StripWhitespace() doesn't exactly match the
+   * definition. It also removes all matching chars in the string,
+   * not just leading and trailing.
+   *
+   * @param      aString, string to be trimmed.
+   */
+  template<class T>
+  static void TrimSpaceCharacters(T& aString)
+  {
+    aString.Trim(" \t\n\f\r");
+  }
+
+  /**
+   * Check is the encoding is ASCII-compatible in the sense that Basic Latin
+   * encodes to ASCII bytes. (The reverse may not be true!)
+   *
+   * @param aPreferredName a preferred encoding label
+   * @return whether the encoding is ASCII-compatible
+   */
+  static bool IsAsciiCompatible(const nsACString& aPreferredName);
+
+  /**
+   * Instantiates a decoder for an encoding. The input must be a
+   * Gecko-canonical encoding name.
+   * @param aEncoding a Gecko-canonical encoding name
+   * @return a decoder
+   */
+  static already_AddRefed<nsIUnicodeDecoder>
+  DecoderForEncoding(const char* aEncoding)
+  {
+    nsDependentCString encoding(aEncoding);
+    return DecoderForEncoding(encoding);
+  }
+
+  /**
+   * Instantiates a decoder for an encoding. The input must be a
+   * Gecko-canonical encoding name
+   * @param aEncoding a Gecko-canonical encoding name
+   * @return a decoder
+   */
+  static already_AddRefed<nsIUnicodeDecoder>
+  DecoderForEncoding(const nsACString& aEncoding);
+
+  /**
+   * Instantiates an encoder for an encoding. The input must be a
+   * Gecko-canonical encoding name.
+   * @param aEncoding a Gecko-canonical encoding name
+   * @return an encoder
+   */
+  static already_AddRefed<nsIUnicodeEncoder>
+  EncoderForEncoding(const char* aEncoding)
+  {
+    nsDependentCString encoding(aEncoding);
+    return EncoderForEncoding(encoding);
+  }
+
+  /**
+   * Instantiates an encoder for an encoding. The input must be a
+   * Gecko-canonical encoding name.
+   * @param aEncoding a Gecko-canonical encoding name
+   * @return an encoder
+   */
+  static already_AddRefed<nsIUnicodeEncoder>
+  EncoderForEncoding(const nsACString& aEncoding);
+
+private:
+  EncodingUtils() MOZ_DELETE;
+};
+
+} // dom
+} // mozilla
+
+#endif // mozilla_dom_encodingutils_h_