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123 lines
3.9 KiB
C++
123 lines
3.9 KiB
C++
//
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// DoubleByteEncoding.h
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//
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// Library: Encodings
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// Package: Encodings
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// Module: DoubleByteEncoding
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//
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// Definition of the DoubleByteEncoding class.
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//
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// Copyright (c) 2018, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Encodings_DoubleByteEncoding_INCLUDED
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#define Encodings_DoubleByteEncoding_INCLUDED
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#include "Poco/Encodings.h"
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#include "Poco/TextEncoding.h"
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namespace Poco {
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class Encodings_API DoubleByteEncoding: public TextEncoding
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/// This abstract class is a base class for various double-byte character
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/// set (DBCS) encodings.
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///
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/// Double-byte encodings are variants of multi-byte encodings
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/// where (Unicode) each code point is represented by one or
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/// two bytes. Unicode code points are restricted to the
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/// Basic Multilingual Plane.
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///
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/// Subclasses must provide encoding names, a static CharacterMap, as well
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/// as static Mapping and reverse Mapping tables, and provide these to the
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/// DoubleByteEncoding constructor.
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{
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public:
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struct Mapping
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{
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Poco::UInt16 from;
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Poco::UInt16 to;
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};
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// TextEncoding
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const char* canonicalName() const;
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bool isA(const std::string& encodingName) const;
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const CharacterMap& characterMap() const;
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int convert(const unsigned char* bytes) const;
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int convert(int ch, unsigned char* bytes, int length) const;
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int queryConvert(const unsigned char* bytes, int length) const;
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int sequenceLength(const unsigned char* bytes, int length) const;
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protected:
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DoubleByteEncoding(const char** names, const TextEncoding::CharacterMap& charMap, const Mapping mappingTable[], std::size_t mappingTableSize, const Mapping reverseMappingTable[], std::size_t reverseMappingTableSize);
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/// Creates a DoubleByteEncoding using the given mapping and reverse-mapping tables.
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///
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/// names must be a static array declared in the derived class,
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/// containing the names of this encoding, declared as:
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///
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/// const char* MyEncoding::_names[] =
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/// {
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/// "myencoding",
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/// "MyEncoding",
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/// NULL
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/// };
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///
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/// The first entry in names must be the canonical name.
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///
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/// charMap must be a static CharacterMap giving information about double-byte
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/// character sequences.
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///
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/// For each mappingTable item, from must be a value in range 0x0100 to
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// 0xFFFF for double-byte mappings, which the most significant (upper) byte
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/// representing the first character in the sequence and the lower byte
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/// representing the second character in the sequence.
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///
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/// For each reverseMappingTable item, from must be Unicode code point from the
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/// Basic Multilingual Plane, and to is a one-byte or two-byte sequence.
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/// As with mappingTable, a one-byte sequence is in range 0x00 to 0xFF, and a
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/// two-byte sequence is in range 0x0100 to 0xFFFF.
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///
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/// Unicode code points are restricted to the Basic Multilingual Plane
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/// (code points 0x0000 to 0xFFFF).
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///
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/// Items in both tables must be sorted by from, in ascending order.
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~DoubleByteEncoding();
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/// Destroys the DoubleByteEncoding.
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int map(Poco::UInt16 encoded) const;
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/// Maps a double-byte encoded character to its Unicode code point.
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///
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/// Returns the Unicode code point, or -1 if the encoded character is bad
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/// and cannot be mapped.
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int reverseMap(int cp) const;
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/// Maps a Unicode code point to its double-byte representation.
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///
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/// Returns -1 if the code point cannot be mapped, otherwise
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/// a value in range 0 to 0xFF for single-byte mappings, or
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/// 0x0100 to 0xFFFF for double-byte mappings.
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private:
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DoubleByteEncoding();
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const char** _names;
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const TextEncoding::CharacterMap& _charMap;
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const Mapping* _mappingTable;
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const std::size_t _mappingTableSize;
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const Mapping* _reverseMappingTable;
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const std::size_t _reverseMappingTableSize;
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};
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} // namespace Poco
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#endif // Encodings_DoubleByteEncoding_INCLUDED
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