Encoding.cs :  » 2.6.4-mono-.net-core » System.Text » System » Text » C# / CSharp Open Source

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C# / CSharp Open Source » 2.6.4 mono .net core » System.Text 
System.Text » System » Text » Encoding.cs
/*
   * Encoding.cs - Implementation of the "System.Text.Encoding" class.
 *
 * Copyright (c) 2001, 2002  Southern Storm Software, Pty Ltd
 * Copyright (c) 2002, Ximian, Inc.
 * Copyright (c) 2003, 2004 Novell, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

namespace System.Text{

using System;
using System.Reflection;
using System.Globalization;
using System.Security;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

[Serializable]
[ComVisible (true)]
public abstract class Encoding : ICloneable
{
  // Code page used by this encoding.
  internal int codePage;
  internal int windows_code_page;
  bool is_readonly = true;

  // Constructor.
  protected Encoding ()
  {
  }

#if ECMA_COMPAT
  protected internal
#else
  protected
#endif
  Encoding (int codePage)
  {
    this.codePage = windows_code_page = codePage;

    switch (codePage) {
    default:
      // MS has "InternalBestFit{Decoder|Encoder}Fallback
      // here, but we dunno what they are for.
      decoder_fallback = DecoderFallback.ReplacementFallback;
      encoder_fallback = EncoderFallback.ReplacementFallback;
      break;
    case 20127: // ASCII
    case 54936: // GB18030
      decoder_fallback = DecoderFallback.ReplacementFallback;
      encoder_fallback = EncoderFallback.ReplacementFallback;
      break;
    case 1200: // UTF16
    case 1201: // UTF16
    case 12000: // UTF32
    case 12001: // UTF32
    case 65000: // UTF7
    case 65001: // UTF8
      decoder_fallback = DecoderFallback.StandardSafeFallback;
      encoder_fallback = EncoderFallback.StandardSafeFallback;
      break;
    }
  }

  // until we change the callers:
  internal static string _ (string arg) {
    return arg;
  }

  DecoderFallback decoder_fallback;
  EncoderFallback encoder_fallback;

  [ComVisible (false)]
  public bool IsReadOnly {
    get { return is_readonly; }
  }

  [ComVisible (false)]
  public virtual bool IsSingleByte {
    get { return false; }
  }

  [ComVisible (false)]
  public DecoderFallback DecoderFallback {
    get { return decoder_fallback; }
    set {
      if (IsReadOnly)
        throw new InvalidOperationException ("This Encoding is readonly.");
      if (value == null)
        throw new ArgumentNullException ();
      decoder_fallback = value;
    }
  }

  [ComVisible (false)]
  public EncoderFallback EncoderFallback {
    get { return encoder_fallback; }
    set {
      if (IsReadOnly)
        throw new InvalidOperationException ("This Encoding is readonly.");
      if (value == null)
        throw new ArgumentNullException ();
      encoder_fallback = value;
    }
  }

  internal void SetFallbackInternal (EncoderFallback e, DecoderFallback d)
  {
    if (e != null)
      encoder_fallback = e;
    if (d != null)
      decoder_fallback = d;
  }

  // Convert between two encodings.
  public static byte[] Convert (Encoding srcEncoding, Encoding dstEncoding,
                 byte[] bytes)
  {
    if (srcEncoding == null) {
      throw new ArgumentNullException ("srcEncoding");
    }
    if (dstEncoding == null) {
      throw new ArgumentNullException ("dstEncoding");
    }
    if (bytes == null) {
      throw new ArgumentNullException ("bytes");
    }
    return dstEncoding.GetBytes (srcEncoding.GetChars (bytes, 0, bytes.Length));
  }
  public static byte[] Convert (Encoding srcEncoding, Encoding dstEncoding,
                 byte[] bytes, int index, int count)
  {
    if (srcEncoding == null) {
      throw new ArgumentNullException ("srcEncoding");
    }
    if (dstEncoding == null) {
      throw new ArgumentNullException ("dstEncoding");
    }
    if (bytes == null) {
      throw new ArgumentNullException ("bytes");
    }
    if (index < 0 || index > bytes.Length) {
      throw new ArgumentOutOfRangeException
        ("index", _("ArgRange_Array"));
    }
    if (count < 0 || (bytes.Length - index) < count) {
      throw new ArgumentOutOfRangeException
        ("count", _("ArgRange_Array"));
    }
    return dstEncoding.GetBytes (srcEncoding.GetChars (bytes, index, count));
  }

  // Determine if two Encoding objects are equal.
  public override bool Equals (Object value)
  {
    Encoding enc = (value as Encoding);
    if (enc != null) {
      return codePage == enc.codePage &&
        DecoderFallback.Equals (enc.DecoderFallback) &&
        EncoderFallback.Equals (enc.EncoderFallback);
    } else {
      return false;
    }
  }

  // Get the number of characters needed to encode a character buffer.
  public abstract int GetByteCount (char[] chars, int index, int count);

  // Convenience wrappers for "GetByteCount".
  public virtual int GetByteCount (String s)
  {
    if (s == null)
      throw new ArgumentNullException ("s");

    if (s.Length == 0)
      return 0;
    unsafe {
      fixed (char* cptr = s) {
        return GetByteCount (cptr, s.Length);
      }
    }
  }
  public virtual int GetByteCount (char[] chars)
  {
    if (chars != null) {
      return GetByteCount (chars, 0, chars.Length);
    } else {
      throw new ArgumentNullException ("chars");
    }
  }

  // Get the bytes that result from encoding a character buffer.
  public abstract int GetBytes (char[] chars, int charIndex, int charCount,
                 byte[] bytes, int byteIndex);

  // Convenience wrappers for "GetBytes".
  public virtual int GetBytes (String s, int charIndex, int charCount,
                byte[] bytes, int byteIndex)
  {
    if (s == null)
      throw new ArgumentNullException ("s");
    if (charIndex < 0 || charIndex > s.Length)
      throw new ArgumentOutOfRangeException ("charIndex", _("ArgRange_Array"));
    if (charCount < 0 || charIndex > (s.Length - charCount))
      throw new ArgumentOutOfRangeException ("charCount", _("ArgRange_Array"));
    if (byteIndex < 0 || byteIndex > bytes.Length)
      throw new ArgumentOutOfRangeException ("byteIndex", _("ArgRange_Array"));

    if (charCount == 0 || bytes.Length == byteIndex)
      return 0;
    unsafe {
      fixed (char* cptr = s) {
        fixed (byte* bptr = bytes) {
          return GetBytes (cptr + charIndex,
            charCount,
            bptr + byteIndex,
            bytes.Length - byteIndex);
        }
      }
    }
  }
  public virtual byte[] GetBytes (String s)
  {
    if (s == null)
      throw new ArgumentNullException ("s");

    if (s.Length == 0)
      return new byte [0];
    int byteCount = GetByteCount (s);
    if (byteCount == 0)
      return new byte [0];
    unsafe {
      fixed (char* cptr = s) {
        byte [] bytes = new byte [byteCount];
        fixed (byte* bptr = bytes) {
          GetBytes (cptr, s.Length,
            bptr, byteCount);
          return bytes;
        }
      }
    }
  }

  public virtual byte[] GetBytes (char[] chars, int index, int count)
  {
    int numBytes = GetByteCount (chars, index, count);
    byte[] bytes = new byte [numBytes];
    GetBytes (chars, index, count, bytes, 0);
    return bytes;
  }
  public virtual byte[] GetBytes (char[] chars)
  {
    int numBytes = GetByteCount (chars, 0, chars.Length);
    byte[] bytes = new byte [numBytes];
    GetBytes (chars, 0, chars.Length, bytes, 0);
    return bytes;
  }

  // Get the number of characters needed to decode a byte buffer.
  public abstract int GetCharCount (byte[] bytes, int index, int count);

  // Convenience wrappers for "GetCharCount".
  public virtual int GetCharCount (byte[] bytes)
  {
    if (bytes == null) {
      throw new ArgumentNullException ("bytes");
    }
    return GetCharCount (bytes, 0, bytes.Length);
  }

  // Get the characters that result from decoding a byte buffer.
  public abstract int GetChars (byte[] bytes, int byteIndex, int byteCount,
                 char[] chars, int charIndex);

  // Convenience wrappers for "GetChars".
  public virtual char[] GetChars (byte[] bytes, int index, int count)
  {
    int numChars = GetCharCount (bytes, index, count);
    char[] chars = new char [numChars];
    GetChars (bytes, index, count, chars, 0);
    return chars;
  }
  public virtual char[] GetChars (byte[] bytes)
  {
    if (bytes == null) {
      throw new ArgumentNullException ("bytes");
    }
    int numChars = GetCharCount (bytes, 0, bytes.Length);
    char[] chars = new char [numChars];
    GetChars (bytes, 0, bytes.Length, chars, 0);
    return chars;
  }

  // Get a decoder that forwards requests to this object.
  public virtual Decoder GetDecoder ()
  {
    return new ForwardingDecoder (this);
  }

  // Get an encoder that forwards requests to this object.
  public virtual Encoder GetEncoder ()
  {
    return new ForwardingEncoder (this);
  }

  // Loaded copy of the "I18N" assembly.  We need to move
  // this into a class in "System.Private" eventually.
  private static Assembly i18nAssembly;
  private static bool i18nDisabled;

  // Invoke a specific method on the "I18N" manager object.
  // Returns NULL if the method failed.
  private static Object InvokeI18N (String name, params Object[] args)
  {
    lock (lockobj) {
      // Bail out if we previously detected that there
      // is insufficent engine support for I18N handling.
      if (i18nDisabled) {
        return null;
      }

      // Find or load the "I18N" assembly.
      if (i18nAssembly == null) {
        try {
          try {
            i18nAssembly = Assembly.Load (Consts.AssemblyI18N);
          } catch (NotImplementedException) {
            // Assembly loading unsupported by the engine.
            i18nDisabled = true;
            return null;
          }
          if (i18nAssembly == null) {
            return null;
          }
        } catch (SystemException) {
          return null;
        }
      }

      // Find the "I18N.Common.Manager" class.
      Type managerClass;
      try {
        managerClass = i18nAssembly.GetType ("I18N.Common.Manager");
      } catch (NotImplementedException) {
        // "GetType" is not supported by the engine.
        i18nDisabled = true;
        return null;
      }
      if (managerClass == null) {
        return null;
      }

      // Get the value of the "PrimaryManager" property.
      Object manager;
      try {
        manager = managerClass.InvokeMember
            ("PrimaryManager",
             BindingFlags.GetProperty |
               BindingFlags.Static |
              BindingFlags.Public,
             null, null, null, null, null, null);
        if (manager == null) {
          return null;
        }
      } catch (MissingMethodException) {
        return null;
      } catch (SecurityException) {
        return null;
      } catch (NotImplementedException) {
        // "InvokeMember" is not supported by the engine.
        i18nDisabled = true;
        return null;
      }

      // Invoke the requested method on the manager.
      try {
        return managerClass.InvokeMember
            (name,
             BindingFlags.InvokeMethod |
               BindingFlags.Instance |
              BindingFlags.Public,
             null, manager, args, null, null, null);
      } catch (MissingMethodException) {
        return null;
      } catch (SecurityException) {
        return null;
      }
    }
  }

  // Get an encoder for a specific code page.
#if ECMA_COMPAT
  private
#else
  public
#endif
  static Encoding GetEncoding (int codepage)
  {
    if (codepage < 0 || codepage > 0xffff)
      throw new ArgumentOutOfRangeException ("codepage", 
        "Valid values are between 0 and 65535, inclusive.");

    // Check for the builtin code pages first.
    switch (codepage) {
      case 0: return Default;

      case ASCIIEncoding.ASCII_CODE_PAGE:
        return ASCII;

      case UTF7Encoding.UTF7_CODE_PAGE:
        return UTF7;

      case UTF8Encoding.UTF8_CODE_PAGE:
        return UTF8;

      case UTF32Encoding.UTF32_CODE_PAGE:
        return UTF32;

      case UTF32Encoding.BIG_UTF32_CODE_PAGE:
        return BigEndianUTF32;

      case UnicodeEncoding.UNICODE_CODE_PAGE:
        return Unicode;

      case UnicodeEncoding.BIG_UNICODE_CODE_PAGE:
        return BigEndianUnicode;

#if !MOONLIGHT
      case Latin1Encoding.ISOLATIN_CODE_PAGE:
        return ISOLatin1;
#endif
      default: break;
    }
#if !MOONLIGHT
    // Try to obtain a code page handler from the I18N handler.
    Encoding enc = (Encoding)(InvokeI18N ("GetEncoding", codepage));
    if (enc != null) {
      enc.is_readonly = true;
      return enc;
    }

    // Build a code page class name.
    String cpName = "System.Text.CP" + codepage.ToString ();

    // Look for a code page converter in this assembly.
    Assembly assembly = Assembly.GetExecutingAssembly ();
    Type type = assembly.GetType (cpName);
    if (type != null) {
      enc = (Encoding)(Activator.CreateInstance (type));
      enc.is_readonly = true;
      return enc;
    }

    // Look in any assembly, in case the application
    // has provided its own code page handler.
    type = Type.GetType (cpName);
    if (type != null) {
      enc = (Encoding)(Activator.CreateInstance (type));
      enc.is_readonly = true;
      return enc;
    }
#endif // !NET_2_1
    // We have no idea how to handle this code page.
    throw new NotSupportedException
      (String.Format ("CodePage {0} not supported", codepage.ToString ()));
  }

#if !ECMA_COMPAT

  [ComVisible (false)]
  public virtual object Clone ()
  {
    Encoding e = (Encoding) MemberwiseClone ();
    e.is_readonly = false;
    return e;
  }

#if !MOONLIGHT

  public static Encoding GetEncoding (int codepage,
    EncoderFallback encoderFallback, DecoderFallback decoderFallback)
  {
    if (encoderFallback == null)
      throw new ArgumentNullException ("encoderFallback");
    if (decoderFallback == null)
      throw new ArgumentNullException ("decoderFallback");

    Encoding e = GetEncoding (codepage).Clone () as Encoding;
    e.is_readonly = false;
    e.encoder_fallback = encoderFallback;
    e.decoder_fallback = decoderFallback;
    return e;
  }

  public static Encoding GetEncoding (string name,
    EncoderFallback encoderFallback, DecoderFallback decoderFallback)
  {
    if (encoderFallback == null)
      throw new ArgumentNullException ("encoderFallback");
    if (decoderFallback == null)
      throw new ArgumentNullException ("decoderFallback");

    Encoding e = GetEncoding (name).Clone () as Encoding;
    e.is_readonly = false;
    e.encoder_fallback = encoderFallback;
    e.decoder_fallback = decoderFallback;
    return e;
  }

#endif // !NET_2_1

  static EncodingInfo [] encoding_infos;

  // FIXME: As everyone would agree, this implementation is so *hacky*
  // and could be very easily broken. But since there is a test for
  // this method to make sure that this method always returns
  // the same number and content of encoding infos, this won't
  // matter practically.
  public static EncodingInfo[] GetEncodings ()
  {
    if (encoding_infos == null) {
      int [] codepages = new int [] {
        37, 437, 500, 708,
        850, 852, 855, 857, 858, 860, 861, 862, 863, 
        864, 865, 866, 869, 870, 874, 875,
        932, 936, 949, 950,
        1026, 1047, 1140, 1141, 1142, 1143, 1144,
        1145, 1146, 1147, 1148, 1149,
        1200, 1201, 1250, 1251, 1252, 1253, 1254,
        1255, 1256, 1257, 1258,
        10000, 10079, 12000, 12001,
        20127, 20273, 20277, 20278, 20280, 20284,
        20285, 20290, 20297, 20420, 20424, 20866,
        20871, 21025, 21866, 28591, 28592, 28593,
        28594, 28595, 28596, 28597, 28598, 28599,
        28605, 38598,
        50220, 50221, 50222, 51932, 51949, 54936,
        57002, 57003, 57004, 57005, 57006, 57007,
        57008, 57009, 57010, 57011,
        65000, 65001};

      encoding_infos = new EncodingInfo [codepages.Length];
      for (int i = 0; i < codepages.Length; i++)
        encoding_infos [i] = new EncodingInfo (codepages [i]);
    }
    return encoding_infos;
  }

#if !MOONLIGHT
  [ComVisible (false)]
  public bool IsAlwaysNormalized ()
  {
    return IsAlwaysNormalized (NormalizationForm.FormC);
  }

  [ComVisible (false)]
  public virtual bool IsAlwaysNormalized (NormalizationForm form)
  {
    // umm, ASCIIEncoding should have overriden this method, no?
    return form == NormalizationForm.FormC && this is ASCIIEncoding;
  }
#endif // NET_2_1

  // Table of builtin web encoding names and the corresponding code pages.
  private static readonly object[] encodings =
    {
      ASCIIEncoding.ASCII_CODE_PAGE,
      "ascii", "us_ascii", "us", "ansi_x3.4_1968",
      "ansi_x3.4_1986", "cp367", "csascii", "ibm367",
      "iso_ir_6", "iso646_us", "iso_646.irv:1991",

      UTF7Encoding.UTF7_CODE_PAGE,
      "utf_7", "csunicode11utf7", "unicode_1_1_utf_7",
      "unicode_2_0_utf_7", "x_unicode_1_1_utf_7",
      "x_unicode_2_0_utf_7",

      UTF8Encoding.UTF8_CODE_PAGE,
      "utf_8", "unicode_1_1_utf_8", "unicode_2_0_utf_8",
      "x_unicode_1_1_utf_8", "x_unicode_2_0_utf_8",

      UnicodeEncoding.UNICODE_CODE_PAGE,
      "utf_16", "UTF_16LE", "ucs_2", "unicode",
      "iso_10646_ucs2",

      UnicodeEncoding.BIG_UNICODE_CODE_PAGE,
      "unicodefffe", "utf_16be",

      UTF32Encoding.UTF32_CODE_PAGE,
      "utf_32", "UTF_32LE", "ucs_4",

      UTF32Encoding.BIG_UTF32_CODE_PAGE,
      "UTF_32BE",

#if !MOONLIGHT
      Latin1Encoding.ISOLATIN_CODE_PAGE,
      "iso_8859_1", "latin1"
#endif // !NET_2_1
    };

  // Get an encoding object for a specific web encoding name.
  public static Encoding GetEncoding (String name)
  {
    // Validate the parameters.
    if (name == null) {
      throw new ArgumentNullException ("name");
    }

    string converted = name.ToLowerInvariant ().Replace ('-', '_');
    
    // Search the table for a name match.
    int code = 0;
    for (int i = 0; i < encodings.Length; ++i) {
      object o = encodings [i];
      
      if (o is int){
        code = (int) o;
        continue;
      }
      
      if (converted == ((string)encodings [i]))
        return GetEncoding (code);
    }
#if !MOONLIGHT
    // Try to obtain a web encoding handler from the I18N handler.
    Encoding enc = (Encoding)(InvokeI18N ("GetEncoding", name));
    if (enc != null) {
      return enc;
    }

    // Build a web encoding class name.
    String encName = "System.Text.ENC" + converted;
             

    // Look for a code page converter in this assembly.
    Assembly assembly = Assembly.GetExecutingAssembly ();
    Type type = assembly.GetType (encName);
    if (type != null) {
      return (Encoding)(Activator.CreateInstance (type));
    }

    // Look in any assembly, in case the application
    // has provided its own code page handler.
    type = Type.GetType (encName);
    if (type != null) {
      return (Encoding)(Activator.CreateInstance (type));
    }
#endif
    // We have no idea how to handle this encoding name.
    throw new ArgumentException (String.Format ("Encoding name '{0}' not "
      + "supported", name), "name");
  }

#endif // !ECMA_COMPAT

  // Get a hash code for this instance.
  public override int GetHashCode ()
  {
    return DecoderFallback.GetHashCode () << 24 + EncoderFallback.GetHashCode () << 16 + codePage;
  }

  // Get the maximum number of bytes needed to encode a
  // specified number of characters.
  public abstract int GetMaxByteCount (int charCount);

  // Get the maximum number of characters needed to decode a
  // specified number of bytes.
  public abstract int GetMaxCharCount (int byteCount);

  // Get the identifying preamble for this encoding.
  public virtual byte[] GetPreamble ()
  {
    return new byte [0];
  }

  // Decode a buffer of bytes into a string.
  public virtual String GetString (byte[] bytes, int index, int count)
  {
    return new String (GetChars(bytes, index, count));
  }
  public virtual String GetString (byte[] bytes)
  {
    if (bytes == null)
      throw new ArgumentNullException ("bytes");

    return GetString (bytes, 0, bytes.Length);
  }

#if !ECMA_COMPAT

  internal string body_name;
  internal string encoding_name;
  internal string header_name;
  internal bool is_mail_news_display;
  internal bool is_mail_news_save;
  internal bool is_browser_save = false;
  internal bool is_browser_display = false;
  internal string web_name;

  // Get the mail body name for this encoding.
  public virtual String BodyName
  {
    get {
      return body_name;
    }
  }

  // Get the code page represented by this object.
  public virtual int CodePage
  {
    get {
      return codePage;
    }
  }

  // Get the human-readable name for this encoding.
  public virtual String EncodingName
  {
    get {
      return encoding_name;
    }
  }

  // Get the mail agent header name for this encoding.
  public virtual String HeaderName
  {
    get {
      return header_name;
    }
  }

  // Determine if this encoding can be displayed in a Web browser.
  public virtual bool IsBrowserDisplay
  {
    get {
      return is_browser_display;
    }
  }

  // Determine if this encoding can be saved from a Web browser.
  public virtual bool IsBrowserSave
  {
    get {
      return is_browser_save;
    }
  }

  // Determine if this encoding can be displayed in a mail/news agent.
  public virtual bool IsMailNewsDisplay
  {
    get {
      return is_mail_news_display;
    }
  }

  // Determine if this encoding can be saved from a mail/news agent.
  public virtual bool IsMailNewsSave
  {
    get {
      return is_mail_news_save;
    }
  }

  // Get the IANA-preferred Web name for this encoding.
  public virtual String WebName
  {
    get {
      return web_name;
    }
  }

  // Get the Windows code page represented by this object.
  public virtual int WindowsCodePage
  {
    get {
      // We make no distinction between normal and
      // Windows code pages in this implementation.
      return windows_code_page;
    }
  }

#endif // !ECMA_COMPAT

  // Storage for standard encoding objects.
  static volatile Encoding asciiEncoding;
  static volatile Encoding bigEndianEncoding;
  static volatile Encoding defaultEncoding;
  static volatile Encoding utf7Encoding;
  static volatile Encoding utf8EncodingWithMarkers;
  static volatile Encoding utf8EncodingWithoutMarkers;
  static volatile Encoding unicodeEncoding;
  static volatile Encoding isoLatin1Encoding;
  static volatile Encoding utf8EncodingUnsafe;
  static volatile Encoding utf32Encoding;
  static volatile Encoding bigEndianUTF32Encoding;

  static readonly object lockobj = new object ();

  // Get the standard ASCII encoding object.
  public static Encoding ASCII
  {
    get {
      if (asciiEncoding == null) {
        lock (lockobj) {
          if (asciiEncoding == null) {
            asciiEncoding = new ASCIIEncoding ();
//            asciiEncoding.is_readonly = true;
          }
        }
      }

      return asciiEncoding;
    }
  }

  // Get the standard big-endian Unicode encoding object.
  public static Encoding BigEndianUnicode
  {
    get {
      if (bigEndianEncoding == null) {
        lock (lockobj) {
          if (bigEndianEncoding == null) {
            bigEndianEncoding = new UnicodeEncoding (true, true);
//            bigEndianEncoding.is_readonly = true;
          }
        }
      }

      return bigEndianEncoding;
    }
  }

  [MethodImpl (MethodImplOptions.InternalCall)]
  extern internal static string InternalCodePage (ref int code_page);
  
  // Get the default encoding object.
  public static Encoding Default
  {
    get {
      if (defaultEncoding == null) {
        lock (lockobj) {
          if (defaultEncoding == null) {
            // See if the underlying system knows what
            // code page handler we should be using.
            int code_page = 1;
            
            string code_page_name = InternalCodePage (ref code_page);
            try {
              if (code_page == -1)
                defaultEncoding = GetEncoding (code_page_name);
              else {
                // map the codepage from internal to our numbers
                code_page = code_page & 0x0fffffff;
                switch (code_page){
                case 1: code_page = ASCIIEncoding.ASCII_CODE_PAGE; break;
                case 2: code_page = UTF7Encoding.UTF7_CODE_PAGE; break;
                case 3: code_page = UTF8Encoding.UTF8_CODE_PAGE; break;
                case 4: code_page = UnicodeEncoding.UNICODE_CODE_PAGE; break;
                case 5: code_page = UnicodeEncoding.BIG_UNICODE_CODE_PAGE; break;
#if !MOONLIGHT
                case 6: code_page = Latin1Encoding.ISOLATIN_CODE_PAGE; break;
#endif
                }
                defaultEncoding = GetEncoding (code_page);
              }
            } catch (NotSupportedException) {
#if MOONLIGHT
              defaultEncoding = UTF8;
#else
              // code_page is not supported on underlying platform
              defaultEncoding = UTF8Unmarked;
#endif
            } catch (ArgumentException) {
              // code_page_name is not a valid code page, or is 
              // not supported by underlying OS
#if MOONLIGHT
              defaultEncoding = UTF8;
#else
              defaultEncoding = UTF8Unmarked;
#endif
            }
            defaultEncoding.is_readonly = true;
          }
        }
      }

      return defaultEncoding;
    }
  }

#if !MOONLIGHT

  // Get the ISO Latin1 encoding object.
  private static Encoding ISOLatin1
  {
    get {
      if (isoLatin1Encoding == null) {
        lock (lockobj) {
          if (isoLatin1Encoding == null) {
            isoLatin1Encoding = new Latin1Encoding ();
//            isoLatin1Encoding.is_readonly = true;
          }
        }
      }

      return isoLatin1Encoding;
    }
  }

#endif

  // Get the standard UTF-7 encoding object.
#if ECMA_COMPAT
  private
#else
  public
#endif
  static Encoding UTF7
  {
    get {
      if (utf7Encoding == null) {
        lock (lockobj) {
          if (utf7Encoding == null) {
            utf7Encoding = new UTF7Encoding ();
//            utf7Encoding.is_readonly = true;
          }
        }
      }

      return utf7Encoding;
    }
  }

  // Get the standard UTF-8 encoding object.
  public static Encoding UTF8
  {
    get {
      if (utf8EncodingWithMarkers == null) {
        lock (lockobj) {
          if (utf8EncodingWithMarkers == null) {
            utf8EncodingWithMarkers = new UTF8Encoding (true);
//            utf8EncodingWithMarkers.is_readonly = true;
          }
        }
      }

      return utf8EncodingWithMarkers;
    }
  }

  //
  // Only internal, to be used by the class libraries: Unmarked and non-input-validating
  //
  internal static Encoding UTF8Unmarked {
    get {
      if (utf8EncodingWithoutMarkers == null) {
        lock (lockobj){
          if (utf8EncodingWithoutMarkers == null){
            utf8EncodingWithoutMarkers = new UTF8Encoding (false, false);
//            utf8EncodingWithoutMarkers.is_readonly = true;
          }
        }
      }

      return utf8EncodingWithoutMarkers;
    }
  }
  
  //
  // Only internal, to be used by the class libraries: Unmarked and non-input-validating
  //
  internal static Encoding UTF8UnmarkedUnsafe {
    get {
      if (utf8EncodingUnsafe == null) {
        lock (lockobj){
          if (utf8EncodingUnsafe == null){
            utf8EncodingUnsafe = new UTF8Encoding (false, false);
            utf8EncodingUnsafe.is_readonly = false;
            utf8EncodingUnsafe.DecoderFallback = new DecoderReplacementFallback (String.Empty);
            utf8EncodingUnsafe.is_readonly = true;
          }
        }
      }

      return utf8EncodingUnsafe;
    }
  }
  
  // Get the standard little-endian Unicode encoding object.
  public static Encoding Unicode
  {
    get {
      if (unicodeEncoding == null) {
        lock (lockobj) {
          if (unicodeEncoding == null) {
            unicodeEncoding = new UnicodeEncoding (false, true);
//            unicodeEncoding.is_readonly = true;
          }
        }
      }

      return unicodeEncoding;
    }
  }

  // Get the standard little-endian UTF-32 encoding object.
  public static Encoding UTF32
  {
    get {
      if (utf32Encoding == null) {
        lock (lockobj) {
          if (utf32Encoding == null) {
            utf32Encoding = new UTF32Encoding (false, true);
//            utf32Encoding.is_readonly = true;
          }
        }
      }

      return utf32Encoding;
    }
  }

  // Get the standard big-endian UTF-32 encoding object.
  internal static Encoding BigEndianUTF32
  {
    get {
      if (bigEndianUTF32Encoding == null) {
        lock (lockobj) {
          if (bigEndianUTF32Encoding == null) {
            bigEndianUTF32Encoding = new UTF32Encoding (true, true);
//            bigEndianUTF32Encoding.is_readonly = true;
          }
        }
      }

      return bigEndianUTF32Encoding;
    }
  }

  // Forwarding decoder implementation.
  private sealed class ForwardingDecoder : Decoder
  {
    private Encoding encoding;

    // Constructor.
    public ForwardingDecoder (Encoding enc)
    {
      encoding = enc;
      DecoderFallback fallback = encoding.DecoderFallback;
      if (fallback != null)
        Fallback = fallback;
    }

    // Override inherited methods.
    public override int GetCharCount (byte[] bytes, int index, int count)
    {
      return encoding.GetCharCount (bytes, index, count);
    }
    public override int GetChars (byte[] bytes, int byteIndex,
                   int byteCount, char[] chars,
                   int charIndex)
    {
      return encoding.GetChars (bytes, byteIndex, byteCount, chars, charIndex);
    }

  } // class ForwardingDecoder

  // Forwarding encoder implementation.
  private sealed class ForwardingEncoder : Encoder
  {
    private Encoding encoding;

    // Constructor.
    public ForwardingEncoder (Encoding enc)
    {
      encoding = enc;
      EncoderFallback fallback = encoding.EncoderFallback;
      if (fallback != null)
        Fallback = fallback;
    }

    // Override inherited methods.
    public override int GetByteCount (char[] chars, int index, int count, bool flush)
    {
      return encoding.GetByteCount (chars, index, count);
    }
    public override int GetBytes (char[] chars, int charIndex,
                   int charCount, byte[] bytes,
                   int byteCount, bool flush)
    {
      return encoding.GetBytes (chars, charIndex, charCount, bytes, byteCount);
    }

  } // class ForwardingEncoder

  [CLSCompliantAttribute(false)]
  [ComVisible (false)]
  public unsafe virtual int GetByteCount (char *chars, int count)
  {
    if (chars == null)
      throw new ArgumentNullException ("chars");
    if (count < 0)
      throw new ArgumentOutOfRangeException ("count");
    char [] c = new char [count];

    for (int p = 0; p < count; p++)
      c [p] = chars [p];

    return GetByteCount (c);
  }

  [CLSCompliantAttribute(false)]
  [ComVisible (false)]
  public unsafe virtual int GetCharCount (byte *bytes, int count)
  {
    if (bytes == null)
      throw new ArgumentNullException ("bytes");
    if (count < 0)
      throw new ArgumentOutOfRangeException ("count");
    
    byte [] ba = new byte [count];
    for (int i = 0; i < count; i++)
      ba [i] = bytes [i];
    return GetCharCount (ba, 0, count);
  }

  [CLSCompliantAttribute(false)]
  [ComVisible (false)]
  public unsafe virtual int GetChars (byte *bytes, int byteCount, char *chars, int charCount)
  {
    if (bytes == null)
      throw new ArgumentNullException ("bytes");
    if (chars == null)
      throw new ArgumentNullException ("chars");
    if (charCount < 0)
      throw new ArgumentOutOfRangeException ("charCount");
    if (byteCount < 0)
      throw new ArgumentOutOfRangeException ("byteCount");
    
    byte [] ba = new byte [byteCount];
    for (int i = 0; i < byteCount; i++)
      ba [i] = bytes [i];
    char [] ret = GetChars (ba, 0, byteCount);
    int top = ret.Length;

    if (top > charCount)
      throw new ArgumentException ("charCount is less than the number of characters produced", "charCount");
    
    for (int i = 0; i < top; i++)
      chars [i] = ret [i];
    return top;
  }

  [CLSCompliantAttribute(false)]
  [ComVisible (false)]
  public unsafe virtual int GetBytes (char *chars, int charCount, byte *bytes, int byteCount)
  {
    if (bytes == null)
      throw new ArgumentNullException ("bytes");
    if (chars == null)
      throw new ArgumentNullException ("chars");
    if (charCount < 0)
      throw new ArgumentOutOfRangeException ("charCount");
    if (byteCount < 0)
      throw new ArgumentOutOfRangeException ("byteCount");
    
    char [] c = new char [charCount];
    
    for (int i = 0; i < charCount; i++)
      c [i] = chars [i];

    byte [] b = GetBytes (c, 0, charCount);
    int top = b.Length;
    if (top > byteCount)
      throw new ArgumentException ("byteCount is less that the number of bytes produced", "byteCount");

    for (int i = 0; i < top; i++)
      bytes [i] = b [i];
    
    return b.Length;
  }
}; // class Encoding

}; // namespace System.Text
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