source: XMLIO_V2/external/src/POCO/Foundation.save/Poco/TextEncoding.h @ 80

//
// TextEncoding.h
//
// $Id: //poco/1.3/Foundation/include/Poco/TextEncoding.h#4 $
//
// Library: Foundation
// Package: Text
// Module:  TextEncoding
//
// Definition of the abstract TextEncoding class.
//
// Copyright (c) 2004-2007, 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"
#include "Poco/SharedPtr.h"


namespace Poco {


class TextEncodingManager;


class Foundation_API TextEncoding
        /// An abstract base class for implementing text encodings
        /// like UTF-8 or ISO 8859-1. 
        ///
        /// Subclasses must override the canonicalName(), isA(),
        /// characterMap() and convert() methods and need to be
        /// thread safe and stateless.
        ///
        /// TextEncoding also provides static member functions
        /// for managing mappings from encoding names to
        /// TextEncoding objects.
{
public:
        typedef SharedPtr<TextEncoding> Ptr;
        
        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 char* canonicalName() const = 0;
                /// Returns the canonical name of this encoding,
                /// e.g. "ISO-8859-1". Encoding name comparisons are case
                /// insensitive.

        virtual bool isA(const std::string& encodingName) const = 0;
                /// Returns true if the given name is one of the names of this encoding.
                /// For example, the "ISO-8859-1" encoding is also known as "Latin-1".
                ///
                /// Encoding name comparision are be case insensitive.
                        
        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 
                /// sequenceLength(bytes, length) == -n, with length >= 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 queryConvert(const unsigned char* bytes, int length) const;
                /// The queryConvert function is used to convert single byte characters 
                /// or multibyte sequences;
                /// bytes will point to a byte sequence of length bytes.
                ///
                /// The queryConvert function must return the Unicode scalar value
                /// represented by this byte sequence or -1 if the byte sequence is malformed
                /// or -n where n is number of bytes requested for the sequence, if lenght is 
                /// shorter than the sequence.
                /// The length of the sequence might not be determined by the first byte, 
                /// in which case the conversion becomes an iterative process:
                /// First call with length == 1 might return -2,
                /// Then a second call with lenght == 2 might return -4
                /// Eventually, the third call with length == 4 should return either a 
                /// Unicode scalar value, or -1 if the byte sequence is malformed.
                /// The default implementation returns (int) bytes[0].

        virtual int sequenceLength(const unsigned char* bytes, int length) const;
                /// The sequenceLength function is used to get the lenth of the sequence pointed
                /// by bytes. The length paramater should be greater or equal to the length of 
                /// the sequence.
                ///
                /// The sequenceLength function must return the lenght of the sequence
                /// represented by this byte sequence or a negative value -n if length is 
                /// shorter than the sequence, where n is the number of byte requested 
                /// to determine the length of the sequence.
                /// The length of the sequence might not be determined by the first byte, 
                /// in which case the conversion becomes an iterative process as long as the 
                /// result is negative:
                /// First call with length == 1 might return -2,
                /// Then a second call with lenght == 2 might return -4
                /// Eventually, the third call with length == 4 should return 4.
                /// The default implementation returns 1.

        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.

        static TextEncoding& byName(const std::string& encodingName);
                /// Returns the TextEncoding object for the given encoding name.
                ///
                /// Throws a NotFoundException if the encoding with given name is not available.
                
        static TextEncoding::Ptr find(const std::string& encodingName);
                /// Returns a pointer to the TextEncoding object for the given encodingName,
                /// or NULL if no such TextEncoding object exists.

        static void add(TextEncoding::Ptr encoding);
                /// Adds the given TextEncoding to the table of text encodings,
                /// under the encoding's canonical name.
                ///
                /// If an encoding with the given name is already registered,
                /// it is replaced.

        static void add(TextEncoding::Ptr encoding, const std::string& name);
                /// Adds the given TextEncoding to the table of text encodings,
                /// under the given name.
                ///
                /// If an encoding with the given name is already registered,
                /// it is replaced.

        static void remove(const std::string& encodingName);
                /// Removes the encoding with the given name from the table
                /// of text encodings.

        static TextEncoding::Ptr global(TextEncoding::Ptr encoding);
                /// Sets global TextEncoding object.
                ///
                /// This function sets the global encoding to the argument and returns a
                /// reference of the previous global encoding.

        static TextEncoding& global();
                /// Return the current global TextEncoding object

        static const std::string GLOBAL;
                /// Name of the global TextEncoding, which is the empty string.
                
protected:
        static TextEncodingManager& manager();
                /// Returns the TextEncodingManager.
};


} // namespace Poco


#endif // Foundation_TextEncoding_INCLUDED