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TextEncoding.h

//
// TextEncoding.h
//
// $Id: //poco/1.2/Foundation/include/Poco/TextEncoding.h#1 $
//
// Library: Foundation
// Package: Text
// Module:  TextEncoding
//
// Definition of the abstract TextEncoding class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// 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, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_TextEncoding_INCLUDED
#define Foundation_TextEncoding_INCLUDED


#include "Poco/Foundation.h"


namespace Poco {


00049 class Foundation_API TextEncoding
      /// An abstract base class for implementing text encodings
      /// like UTF-8 or ISO 8859-1. 
      ///
      /// Subclasses must override the characterMap() and convert()
      /// methods.
{
public:
      enum
      {
            MAX_SEQUENCE_LENGTH = 6 /// The maximum character byte sequence length supported.
      };
      
      typedef int CharacterMap[256];
            /// The map[b] member gives information about byte sequences
            /// whose first byte is b.
            /// If map[b] is c where c is >= 0, then b by itself encodes the Unicode scalar value c.
            /// If map[b] is -1, then the byte sequence is malformed.
            /// If map[b] is -n, where n >= 2, then b is the first byte of an n-byte
            /// sequence that encodes a single Unicode scalar value. Byte sequences up
            /// to 6 bytes in length are supported.

      virtual ~TextEncoding();
            /// Destroys the encoding.
                  
      virtual const CharacterMap& characterMap() const = 0;
            /// Returns the CharacterMap for the encoding.
            /// The CharacterMap should be kept in a static member. As
            /// characterMap() can be called frequently, it should be
            /// implemented in such a way that it just returns a static
            /// map. If the map is built at runtime, this should be
            /// done in the constructor.
            
      virtual int convert(const unsigned char* bytes) const;
            /// The convert function is used to convert multibyte sequences;
            /// bytes will point to a byte sequence of n bytes where 
            /// getCharacterMap()[*bytes] == -n.
            ///
            /// The convert function must return the Unicode scalar value
            /// represented by this byte sequence or -1 if the byte sequence is malformed.
            /// The default implementation returns (int) bytes[0].

      virtual int convert(int ch, unsigned char* bytes, int length) const;
            /// Transform the Unicode character ch into the encoding's 
            /// byte sequence. The method returns the number of bytes
            /// used. The method must not use more than length characters.
            /// Bytes and length can also be null - in this case only the number
            /// of bytes required to represent ch is returned.
            /// If the character cannot be converted, 0 is returned and
            /// the byte sequence remains unchanged.
            /// The default implementation simply returns 0.
};


} // namespace Poco


#endif // Foundation_TextEncoding_INCLUDED

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