/*

 * Copyright (C) 2004, 2006 Apple Computer, Inc.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY

 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 

 */

#include "config.h"

#include "TextDecoder.h"

#include "TextEncodingRegistry.h"

// FIXME: Would be nice to also handle BOM for UTF-7 and UTF-32.

namespace WebCore {

TextDecoder::TextDecoder(const TextEncoding& encoding)

    : m_encoding(encoding)

    , m_checkedForBOM(false)

    , m_numBufferedBytes(0)

{

}

void TextDecoder::reset(const TextEncoding& encoding)

{

    m_encoding = encoding;

    m_codec.clear();

    m_checkedForBOM = false;

    m_numBufferedBytes = 0;

}

String TextDecoder::checkForBOM(const char* data, size_t length, bool flush)

{

    // Check to see if we found a BOM.

    size_t numBufferedBytes = m_numBufferedBytes;

    size_t buf1Len = numBufferedBytes;

    size_t buf2Len = length;

    const unsigned char* buf1 = m_bufferedBytes;

    const unsigned char* buf2 = reinterpret_cast<const unsigned char*>(data);

    unsigned char c1 = buf1Len ? (--buf1Len, *buf1++) : buf2Len ? (--buf2Len, *buf2++) : 0;

    unsigned char c2 = buf1Len ? (--buf1Len, *buf1++) : buf2Len ? (--buf2Len, *buf2++) : 0;

    unsigned char c3 = buf1Len ? (--buf1Len, *buf1++) : buf2Len ? (--buf2Len, *buf2++) : 0;

    unsigned char c4 = buf2Len ? (--buf2Len, *buf2++) : 0;

    const TextEncoding* encodingConsideringBOM = &m_encoding;

    bool foundBOM = true;

    if (c1 == 0xFF && c2 == 0xFE) {

        if (c3 != 0 || c4 != 0) 

            encodingConsideringBOM = &UTF16LittleEndianEncoding();

        else if (numBufferedBytes + length > sizeof(m_bufferedBytes))

            encodingConsideringBOM = &UTF32LittleEndianEncoding();

        else

            foundBOM = false;

    }

    else if (c1 == 0xEF && c2 == 0xBB && c3 == 0xBF)

        encodingConsideringBOM = &UTF8Encoding();

    else if (c1 == 0xFE && c2 == 0xFF)

        encodingConsideringBOM = &UTF16BigEndianEncoding();

    else if (c1 == 0 && c2 == 0 && c3 == 0xFE && c4 == 0xFF)

        encodingConsideringBOM = &UTF32BigEndianEncoding();

    else

        foundBOM = false;

    if (!foundBOM && numBufferedBytes + length <= sizeof(m_bufferedBytes) && !flush) {

        // Continue to look for the BOM.

        memcpy(&m_bufferedBytes[numBufferedBytes], data, length);

        m_numBufferedBytes += length;

        return "";

    }

    // Done checking for BOM.

    m_codec.set(newTextCodec(*encodingConsideringBOM).release());

    if (!m_codec)

        return String();

    m_checkedForBOM = true;

    // Handle case where we have some buffered bytes to deal with.

    if (numBufferedBytes) {

        char bufferedBytes[sizeof(m_bufferedBytes)];

        memcpy(bufferedBytes, m_bufferedBytes, numBufferedBytes);

        m_numBufferedBytes = 0;

        return m_codec->decode(bufferedBytes, numBufferedBytes, false)

            + m_codec->decode(data, length, flush);

    }

    return m_codec->decode(data, length, flush);

}

} // namespace WebCore