dom/encoding/EncodingUtils.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   3  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef mozilla_dom_encodingutils_h_
   6 #define mozilla_dom_encodingutils_h_
   7
   8 #include "nsDataHashtable.h"
   9 #include "nsString.h"
  10
  11 class nsIUnicodeDecoder;
  12 class nsIUnicodeEncoder;
  13
  14 namespace mozilla {
  15 namespace dom {
  16
  17 class EncodingUtils
  18 {
  19 public:
  20
  21   /**
  22    * Implements get an encoding algorithm from Encoding spec.
  23    * http://encoding.spec.whatwg.org/#concept-encoding-get
  24    * Given a label, this function returns the corresponding encoding or a
  25    * false.
  26    * The returned name may not be lowercased due to compatibility with
  27    * our internal implementations.
  28    *
  29    * @param      aLabel, incoming label describing charset to be decoded.
  30    * @param      aOutEncoding, returning corresponding encoding for label.
  31    * @return     false if no encoding was found for label.
  32    *             true if valid encoding found.
  33    */
  34   static bool FindEncodingForLabel(const nsACString& aLabel,
  35                                    nsACString& aOutEncoding);
  36
  37   static bool FindEncodingForLabel(const nsAString& aLabel,
  38                                    nsACString& aOutEncoding)
  39   {
  40     return FindEncodingForLabel(NS_ConvertUTF16toUTF8(aLabel), aOutEncoding);
  41   }
  42
  43   /**
  44    * Like FindEncodingForLabel() except labels that map to "replacement"
  45    * are treated as unknown.
  46    *
  47    * @param      aLabel, incoming label describing charset to be decoded.
  48    * @param      aOutEncoding, returning corresponding encoding for label.
  49    * @return     false if no encoding was found for label.
  50    *             true if valid encoding found.
  51    */
  52   static bool FindEncodingForLabelNoReplacement(const nsACString& aLabel,
  53                                                 nsACString& aOutEncoding);
  54
  55   static bool FindEncodingForLabelNoReplacement(const nsAString& aLabel,
  56                                                 nsACString& aOutEncoding)
  57   {
  58     return FindEncodingForLabelNoReplacement(NS_ConvertUTF16toUTF8(aLabel),
  59                                              aOutEncoding);
  60   }
  61
  62   /**
  63    * Remove any leading and trailing space characters, following the
  64    * definition of space characters from Encoding spec.
  65    * http://encoding.spec.whatwg.org/#terminology
  66    * Note that nsAString::StripWhitespace() doesn't exactly match the
  67    * definition. It also removes all matching chars in the string,
  68    * not just leading and trailing.
  69    *
  70    * @param      aString, string to be trimmed.
  71    */
  72   template<class T>
  73   static void TrimSpaceCharacters(T& aString)
  74   {
  75     aString.Trim(" \t\n\f\r");
  76   }
  77
  78   /**
  79    * Check is the encoding is ASCII-compatible in the sense that Basic Latin
  80    * encodes to ASCII bytes. (The reverse may not be true!)
  81    *
  82    * @param aPreferredName a preferred encoding label
  83    * @return whether the encoding is ASCII-compatible
  84    */
  85   static bool IsAsciiCompatible(const nsACString& aPreferredName);
  86
  87   /**
  88    * Instantiates a decoder for an encoding. The input must be a
  89    * Gecko-canonical encoding name.
  90    * @param aEncoding a Gecko-canonical encoding name
  91    * @return a decoder
  92    */
  93   static already_AddRefed<nsIUnicodeDecoder>
  94   DecoderForEncoding(const char* aEncoding)
  95   {
  96     nsDependentCString encoding(aEncoding);
  97     return DecoderForEncoding(encoding);
  98   }
  99
 100   /**
 101    * Instantiates a decoder for an encoding. The input must be a
 102    * Gecko-canonical encoding name
 103    * @param aEncoding a Gecko-canonical encoding name
 104    * @return a decoder
 105    */
 106   static already_AddRefed<nsIUnicodeDecoder>
 107   DecoderForEncoding(const nsACString& aEncoding);
 108
 109   /**
 110    * Instantiates an encoder for an encoding. The input must be a
 111    * Gecko-canonical encoding name.
 112    * @param aEncoding a Gecko-canonical encoding name
 113    * @return an encoder
 114    */
 115   static already_AddRefed<nsIUnicodeEncoder>
 116   EncoderForEncoding(const char* aEncoding)
 117   {
 118     nsDependentCString encoding(aEncoding);
 119     return EncoderForEncoding(encoding);
 120   }
 121
 122   /**
 123    * Instantiates an encoder for an encoding. The input must be a
 124    * Gecko-canonical encoding name.
 125    * @param aEncoding a Gecko-canonical encoding name
 126    * @return an encoder
 127    */
 128   static already_AddRefed<nsIUnicodeEncoder>
 129   EncoderForEncoding(const nsACString& aEncoding);
 130
 131   /**
 132    * Finds a Gecko language group string (e.g. x-western) for a Gecko-canonical
 133    * encoding name.
 134    *
 135    * @param      aEncoding, incoming label describing charset to be decoded.
 136    * @param      aOutGroup, returning corresponding language group.
 137    */
 138   static void LangGroupForEncoding(const nsACString& aEncoding,
 139                                    nsACString& aOutGroup);
 140
 141 private:
 142   EncodingUtils() = delete;
 143 };
 144
 145 } // dom
 146 } // mozilla
 147
 148 #endif // mozilla_dom_encodingutils_h_