UTF8StreamEncoder.cc

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/*
 * UTF8StreamEncoder.cc
 *
 * Smalltalk like class library for C++
 * UTF-8 encoding translator.
 *
 * Copyright (c) 2005 Milan Cermak
 */
/*
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <stlib/UTF8StreamEncoder.h>
#include <stlib/Character.h>
#include <stlib/Integer.h>
#include <stlib/Stream.h>
#include <stlib/String.h>

namespace Core {

/* Class-accessing protocol */
String *UTF8StreamEncoder::className(void) const
{
    return new String("UTF8StreamEncoder");
}

/* Accessing protocol */
Character *UTF8StreamEncoder::decodeFrom(Stream *stream)
{
    unsigned long charValue = 0;
    unsigned char byteCount;
    int byteValue;

    Object *item = stream->next();
    if (item == nil) {
        /* End of stream reached */
        return nil;
    }

    byteValue = dynamic_cast<Integer *>(item)->asLong();
    if (byteValue < 128) {
        byteCount = 0;
    } else if (byteValue < 224) {
        byteCount = 1;
        byteValue = byteValue & 31;
    } else if (byteValue < 240) {
        byteCount = 2;
        byteValue = byteValue & 15;
    } else if (byteValue < 248) {
        byteCount = 3;
        byteValue = byteValue & 7;
    } else if (byteValue < 252) {
        byteCount = 4;
        byteValue = byteValue & 3;
    } else if (byteValue < 254) {
        byteCount = 5;
        byteValue = byteValue & 1;
    } else {
        error(new String("Illegal UTF-8 code."), new String(__PRETTY_FUNCTION__));
    }
    charValue = byteValue;
    for (int i = 0; i < byteCount; i++) {
        byteValue = dynamic_cast<Integer *>(stream->next())->asLong();
        charValue = (charValue << 6) + (byteValue & 63);
    }
    return Character::value(charValue);
}

void UTF8StreamEncoder::encodeTo(Stream *stream, Character *character)
{
    unsigned long value = character->asInteger();
    unsigned char bitfill = 0, byteCounter = 0;
    unsigned char buffer[6];

    if (value < 128) {
        stream->nextPut(Integer::value(value));
        return;
    }
    /* value is greater than 127 => need more bytes to encode */
    do {
        int byteValue;
        bitfill = (bitfill << 1) + 1;
        byteCounter++;
        byteValue = value & 63;
        value = value >> 6;
        if (value > 0)
            buffer[byteCounter-1] = 0x80 | byteValue;
        else
            buffer[byteCounter-1] = (bitfill << (8 - byteCounter)) | byteValue;
    } while (value > 0);

    for (int i = byteCounter - 1; i >= 0; i--) {
        stream->nextPut(Integer::value(buffer[i]));
    }
}

}; /* namespace Core */

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