UTF8Encoding.cpp

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//
// UTF8Encoding.cpp
//
// $Id: //poco/1.3/Foundation/src/UTF8Encoding.cpp#4 $
//
// Library: Foundation
// Package: Text
// Module:  UTF8Encoding
//
// 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.
//


#include "Poco/UTF8Encoding.h"
#include "Poco/String.h"


namespace Poco {


const char* UTF8Encoding::_names[] =
{
        "UTF-8",
        "UTF8",
        NULL
};


const TextEncoding::CharacterMap UTF8Encoding::_charMap = 
{
        /* 00 */        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 
        /* 10 */        0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 
        /* 20 */        0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 
        /* 30 */        0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 
        /* 40 */        0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 
        /* 50 */        0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, 
        /* 60 */        0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 
        /* 70 */        0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 
        /* 80 */          -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1, 
        /* 90 */          -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1, 
        /* a0 */          -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1, 
        /* b0 */          -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1,   -1, 
        /* c0 */          -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2, 
        /* d0 */          -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2,   -2, 
        /* e0 */          -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3,   -3, 
        /* f0 */          -4,   -4,   -4,   -4,   -4,   -4,   -4,   -4,   -5,   -5,   -5,   -5,   -6,   -6,   -1,   -1, 
};


UTF8Encoding::UTF8Encoding()
{
}


UTF8Encoding::~UTF8Encoding()
{
}


const char* UTF8Encoding::canonicalName() const
{
        return _names[0];
}


bool UTF8Encoding::isA(const std::string& encodingName) const
{
        for (const char** name = _names; *name; ++name)
        {
                if (Poco::icompare(encodingName, *name) == 0)
                        return true;
        }
        return false;
}


const TextEncoding::CharacterMap& UTF8Encoding::characterMap() const
{
        return _charMap;
}


bool UTF8Encoding::isLegal(const unsigned char *bytes, int length)
{
        // Note: The following is loosely based on the isLegalUTF8 function
        // from ftp://ftp.unicode.org/Public/PROGRAMS/CVTUTF/ConvertUTF.c
        // Excuse the ugliness...
        
        if (0 == bytes || 0 == length) return false;

    unsigned char a;
    const unsigned char* srcptr = bytes + length;
    switch (length)
        {
        default:
                return false;
                // Everything else falls through when true.
        case 4:
                if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
        case 3: 
                if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
        case 2:
                if ((a = (*--srcptr)) > 0xBF) return false;
                switch (*bytes) 
                {
                case 0xE0:
                        if (a < 0xA0) return false; 
                        break;
                case 0xED:
                        if (a > 0x9F) return false; 
                        break;
                case 0xF0:
                        if (a < 0x90) return false; 
                        break;
                case 0xF4:
                        if (a > 0x8F) return false; 
                        break;
                default:
                        if (a < 0x80) return false;
                }
        case 1:
                if (*bytes >= 0x80 && *bytes < 0xC2) return false;
    }
        return *bytes <= 0xF4;
}


int UTF8Encoding::convert(const unsigned char* bytes) const
{
        int n = _charMap[*bytes];
        int uc;
        
        switch (n)
        {
        case -6:
        case -5:
        case -1:
                return -1;
        case -4: 
        case -3: 
        case -2:
                if (!isLegal(bytes, -n)) return -1;
                uc = *bytes & ((0x07 << (n + 4)) | 0x03);
                break;
        default:
                return n;
        }

        while (n++ < -1) 
        {       
                uc <<= 6;
                uc |= (*++bytes & 0x3F);
        }
        return uc;
}


int UTF8Encoding::convert(int ch, unsigned char* bytes, int length) const
{
#ifdef _DEBUG
        unsigned char* lb = bytes;
#endif

        if (ch <= 0x7F)
        {
                if (bytes && length >= 1)
                        *bytes = (unsigned char) ch;
                return 1;
        }
        else if (ch <= 0x7FF)
        {
                if (bytes && length >= 2)
                {
                        *bytes++ = (unsigned char) (((ch >> 6) & 0x1F) | 0xC0);
                        *bytes   = (unsigned char) ((ch & 0x3F) | 0x80);
                }
                poco_assert_dbg (isLegal(lb, 2));
                return 2;
        }
        else if (ch <= 0xFFFF)
        {
                if (bytes && length >= 3)
                {
                        *bytes++ = (unsigned char) (((ch >> 12) & 0x0F) | 0xE0);
                        *bytes++ = (unsigned char) (((ch >> 6) & 0x3F) | 0x80);
                        *bytes   = (unsigned char) ((ch & 0x3F) | 0x80);
                }
                poco_assert_dbg (isLegal(lb, 3));
                return 3;
        }
        else if (ch <= 0x10FFFF)
        {
                if (bytes && length >= 4)
                {
                        *bytes++ = (unsigned char) (((ch >> 18) & 0x07) | 0xF0);
                        *bytes++ = (unsigned char) (((ch >> 12) & 0x3F) | 0x80);
                        *bytes++ = (unsigned char) (((ch >> 6) & 0x3F) | 0x80);
                        *bytes   = (unsigned char) ((ch & 0x3F) | 0x80);
                }
                poco_assert_dbg (isLegal(lb, 4));
                return 4;
        }
        else return 0;
}


} // namespace Poco