utf7encoding.cs

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						("index", _("ArgRange_Array"));
				}
				if(count < 0 || count > (bytes.Length - index))
				{
					throw new ArgumentOutOfRangeException
						("count", _("ArgRange_Array"));
				}

				// Determine the length of the result.
				int length = 0;
				int byteval, b64value;
				bool normal = ((leftOver & 0x01000000) == 0);
				bool prevIsPlus = ((leftOver & 0x02000000) != 0);
				int leftOverSize = ((leftOver >> 16) & 0xFF);
				sbyte[] base64 = base64Values;
				while(count > 0)
				{
					byteval = (int)(bytes[index++]);
					--count;
					if(normal)
					{
						if(byteval != '+')
						{
							// Directly-encoded character.
							++length;
						}
						else
						{
							// Start of a base64-encoded character.
							normal = false;
							prevIsPlus = true;
						}
					}
					else
					{
						// Process the next byte in a base64 sequence.
						if(byteval == (int)'-')
						{
							// End of a base64 sequence.
							if(prevIsPlus || leftOverSize > 0)
							{
								++length;
								leftOverSize = 0;
							}
							normal = true;
						}
						else if((b64value = base64[byteval]) != -1)
						{
							// Extra character in a base64 sequence.
							leftOverSize += 6;
							if(leftOverSize >= 16)
							{
								++length;
								leftOverSize -= 16;
							}
						}
						else
						{
							// Normal character terminating a base64 sequence.
							if(leftOverSize > 0)
							{
								++length;
								leftOverSize = 0;
							}
							++length;
							normal = true;
						}
						prevIsPlus = false;
					}
				}

				// Return the final length to the caller.
				return length;
			}

	// Get the number of characters needed to decode a byte buffer.
	public override int GetCharCount(byte[] bytes, int index, int count)
			{
				return InternalGetCharCount(bytes, index, count, 0);
			}

	// Internal version of "GetChars" that can handle a
	// rolling state between calls.
	private static int InternalGetChars
				(byte[] bytes, int byteIndex, int byteCount,
				 char[] chars, int charIndex, ref int leftOver)
			{
				// Validate the parameters.
				if(bytes == null)
				{
					throw new ArgumentNullException("bytes");
				}
				if(chars == null)
				{
					throw new ArgumentNullException("chars");
				}
				if(byteIndex < 0 || byteIndex > bytes.Length)
				{
					throw new ArgumentOutOfRangeException
						("byteIndex", _("ArgRange_Array"));
				}
				if(byteCount < 0 || byteCount > (bytes.Length - byteIndex))
				{
					throw new ArgumentOutOfRangeException
						("byteCount", _("ArgRange_Array"));
				}
				if(charIndex < 0 || charIndex > chars.Length)
				{
					throw new ArgumentOutOfRangeException
						("charIndex", _("ArgRange_Array"));
				}

				// Convert the bytes into characters.
				int posn = charIndex;
				int charLength = chars.Length;
				int byteval, b64value;
				bool normal = ((leftOver & 0x01000000) == 0);
				bool prevIsPlus = ((leftOver & 0x02000000) != 0);
				int leftOverSize = ((leftOver >> 16) & 0xFF);
				int leftOverBits = (leftOver & 0xFFFF);
				sbyte[] base64 = base64Values;
				while(byteCount > 0)
				{
					byteval = (int)(bytes[byteIndex++]);
					--byteCount;
					if(normal)
					{
						if(byteval != '+')
						{
							// Directly-encoded character.
							if(posn >= charLength)
							{
								throw new ArgumentException
									(_("Arg_InsufficientSpace"), "chars");
							}
							chars[posn++] = (char)byteval;
						}
						else
						{
							// Start of a base64-encoded character.
							normal = false;
							prevIsPlus = true;
						}
					}
					else
					{
						// Process the next byte in a base64 sequence.
						if(byteval == (int)'-')
						{
							// End of a base64 sequence.
							if(prevIsPlus)
							{
								if(posn >= charLength)
								{
									throw new ArgumentException
										(_("Arg_InsufficientSpace"), "chars");
								}
								chars[posn++] = '+';
							}
							else if(leftOverSize > 0)
							{
								if(posn >= charLength)
								{
									throw new ArgumentException
										(_("Arg_InsufficientSpace"), "chars");
								}
								chars[posn++] =
									(char)(leftOverBits << (16 - leftOverSize));
								leftOverSize = 0;
								leftOverBits = 0;
							}
							normal = true;
						}
						else if((b64value = base64[byteval]) != -1)
						{
							// Extra character in a base64 sequence.
							leftOverBits = (leftOverBits << 6) | b64value;
							leftOverSize += 6;
							if(leftOverSize >= 16)
							{
								if(posn >= charLength)
								{
									throw new ArgumentException
										(_("Arg_InsufficientSpace"), "chars");
								}
								leftOverSize -= 16;
								chars[posn++] =
									(char)(leftOverBits >> leftOverSize);
								leftOverBits &= ((1 << leftOverSize) - 1);
							}
						}
						else
						{
							// Normal character terminating a base64 sequence.
							if(leftOverSize > 0)
							{
								if(posn >= charLength)
								{
									throw new ArgumentException
										(_("Arg_InsufficientSpace"), "chars");
								}
								chars[posn++] =
									(char)(leftOverBits << (16 - leftOverSize));
								leftOverSize = 0;
								leftOverBits = 0;
							}
							if(posn >= charLength)
							{
								throw new ArgumentException
									(_("Arg_InsufficientSpace"), "chars");
							}
							chars[posn++] = (char)byteval;
							normal = true;
						}
						prevIsPlus = false;
					}
				}
				leftOver = (leftOverBits | (leftOverSize << 16) |
						    (normal ? 0 : 0x01000000) |
						    (prevIsPlus ? 0x02000000 : 0));

				// Return the final length to the caller.
				return posn - charIndex;
			}

	// Get the characters that result from decoding a byte buffer.
	public override int GetChars(byte[] bytes, int byteIndex, int byteCount,
								 char[] chars, int charIndex)
			{
				int leftOver = 0;
				return InternalGetChars(bytes, byteIndex, byteCount,
										chars, charIndex, ref leftOver);
			}

	// Get the maximum number of bytes needed to encode a
	// specified number of characters.
	public override int GetMaxByteCount(int charCount)
			{
				if(charCount < 0)
				{
					throw new ArgumentOutOfRangeException
						("charCount", _("ArgRange_NonNegative"));
				}
				return charCount * 5;
			}

	// Get the maximum number of characters needed to decode a
	// specified number of bytes.
	public override int GetMaxCharCount(int byteCount)
			{
				if(byteCount < 0)
				{
					throw new ArgumentOutOfRangeException
						("byteCount", _("ArgRange_NonNegative"));
				}
				return byteCount;
			}

	// Get a UTF7-specific decoder that is attached to this instance.
	public override Decoder GetDecoder()
			{
				return new UTF7Decoder();
			}

	// Get a UTF7-specific encoder that is attached to this instance.
	public override Encoder GetEncoder()
			{
				return new UTF7Encoder(allowOptionals);
			}

#if !ECMA_COMPAT

	// Get the mail body name for this encoding.
	internal override String InternalBodyName
			{
				get
				{
					return "utf-7";
				}
			}

	// Get the human-readable name for this encoding.
	internal override String InternalEncodingName
			{
				get
				{
					return "Unicode (UTF-7)";
				}
			}

	// Get the mail agent header name for this encoding.
	internal override String InternalHeaderName
			{
				get
				{
					return "utf-7";
				}
			}

	// Determine if this encoding can be displayed in a mail/news agent.
	internal override bool InternalIsMailNewsDisplay
			{
				get
				{
					return true;
				}
			}

	// Determine if this encoding can be saved from a mail/news agent.
	internal override bool InternalIsMailNewsSave
			{
				get
				{
					return true;
				}
			}

	// Get the IANA-preferred Web name for this encoding.
	internal override String InternalWebName
			{
				get
				{
					return "utf-7";
				}
			}

	// Get the Windows code page represented by this object.
	internal override int InternalWindowsCodePage
			{
				get
				{
					return UnicodeEncoding.UNICODE_CODE_PAGE;
				}
			}

#endif // !ECMA_COMPAT

	// UTF-7 decoder implementation.
	private sealed class UTF7Decoder : Decoder
	{
		// Internal state.
		private int leftOver;

		// Constructor.
		public UTF7Decoder()
				{
					leftOver = 0;
				}

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

	} // class UTF7Decoder

	// UTF-7 encoder implementation.
	private sealed class UTF7Encoder : Encoder
	{
		private bool allowOptionals;
		private int leftOver;

		// Constructor.
		public UTF7Encoder(bool allowOptionals)
				{
					this.allowOptionals = allowOptionals;
					this.leftOver = 0;
				}

		// Override inherited methods.
		public override int GetByteCount(char[] chars, int index,
										 int count, bool flush)
				{
					return InternalGetByteCount
						(chars, index, count, flush, leftOver, allowOptionals);
				}
		public override int GetBytes(char[] chars, int charIndex,
									 int charCount, byte[] bytes,
									 int byteIndex, bool flush)
				{
					return InternalGetBytes(chars, charIndex, charCount,
											bytes, byteIndex, flush,
											ref leftOver, allowOptionals);
				}

	} // class UTF7Encoder

}; // class UTF7Encoding

}; // namespace System.Text