/*
 * Copyright (C) 2004, 2006, 2008, 2010 Apple 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 "wtf/text/TextCodecUTF16.h"

#include "wtf/PassOwnPtr.h"
#include "wtf/text/CString.h"
#include "wtf/text/StringBuffer.h"
#include "wtf/text/WTFString.h"
#include "wtf/unicode/CharacterNames.h"

using namespace std;

namespace WTF {

void TextCodecUTF16::registerEncodingNames(EncodingNameRegistrar registrar)
{
    registrar("UTF-16LE", "UTF-16LE");
    registrar("UTF-16BE", "UTF-16BE");

    registrar("ISO-10646-UCS-2", "UTF-16LE");
    registrar("UCS-2", "UTF-16LE");
    registrar("UTF-16", "UTF-16LE");
    registrar("Unicode", "UTF-16LE");
    registrar("csUnicode", "UTF-16LE");
    registrar("unicodeFEFF", "UTF-16LE");

    registrar("unicodeFFFE", "UTF-16BE");
}

static PassOwnPtr<TextCodec> newStreamingTextDecoderUTF16LE(const TextEncoding&, const void*)
{
    return adoptPtr(new TextCodecUTF16(true));
}

static PassOwnPtr<TextCodec> newStreamingTextDecoderUTF16BE(const TextEncoding&, const void*)
{
    return adoptPtr(new TextCodecUTF16(false));
}

void TextCodecUTF16::registerCodecs(TextCodecRegistrar registrar)
{
    registrar("UTF-16LE", newStreamingTextDecoderUTF16LE, 0);
    registrar("UTF-16BE", newStreamingTextDecoderUTF16BE, 0);
}

String TextCodecUTF16::decode(const char* bytes, size_t length, FlushBehavior flush, bool, bool& sawError)
{
    // For compatibility reasons, ignore flush from fetch EOF.
    const bool reallyFlush = flush != DoNotFlush && flush != FetchEOF;

    if (!length) {
        if (!reallyFlush || !m_haveBufferedByte)
            return String();
        sawError = true;
        return String(&Unicode::replacementCharacter, 1);
    }

    // FIXME: This should generate an error if there is an unpaired surrogate.

    const unsigned char* p = reinterpret_cast<const unsigned char*>(bytes);
    size_t numBytes = length + m_haveBufferedByte;
    size_t numCharsIn = numBytes / 2;
    size_t numCharsOut = ((numBytes & 1) && reallyFlush) ? numCharsIn + 1 : numCharsIn;

    StringBuffer<UChar> buffer(numCharsOut);
    UChar* q = buffer.characters();

    if (m_haveBufferedByte) {
        UChar c;
        if (m_littleEndian)
            c = m_bufferedByte | (p[0] << 8);
        else
            c = (m_bufferedByte << 8) | p[0];
        *q++ = c;
        m_haveBufferedByte = false;
        p += 1;
        numCharsIn -= 1;
    }

    if (m_littleEndian) {
        for (size_t i = 0; i < numCharsIn; ++i) {
            UChar c = p[0] | (p[1] << 8);
            p += 2;
            *q++ = c;
        }
    } else {
        for (size_t i = 0; i < numCharsIn; ++i) {
            UChar c = (p[0] << 8) | p[1];
            p += 2;
            *q++ = c;
        }
    }

    if (numBytes & 1) {
        ASSERT(!m_haveBufferedByte);

        if (reallyFlush) {
            sawError = true;
            *q++ = Unicode::replacementCharacter;
        } else {
            m_haveBufferedByte = true;
            m_bufferedByte = p[0];
        }
    }

    buffer.shrink(q - buffer.characters());

    return String::adopt(buffer);
}

CString TextCodecUTF16::encode(const UChar* characters, size_t length, UnencodableHandling)
{
    // We need to be sure we can double the length without overflowing.
    // Since the passed-in length is the length of an actual existing
    // character buffer, each character is two bytes, and we know
    // the buffer doesn't occupy the entire address space, we can
    // assert here that doubling the length does not overflow size_t
    // and there's no need for a runtime check.
    ASSERT(length <= numeric_limits<size_t>::max() / 2);

    char* bytes;
    CString result = CString::newUninitialized(length * 2, bytes);

    // FIXME: CString is not a reasonable data structure for encoded UTF-16, which will have
    // null characters inside it. Perhaps the result of encode should not be a CString.
    if (m_littleEndian) {
        for (size_t i = 0; i < length; ++i) {
            UChar c = characters[i];
            bytes[i * 2] = c;
            bytes[i * 2 + 1] = c >> 8;
        }
    } else {
        for (size_t i = 0; i < length; ++i) {
            UChar c = characters[i];
            bytes[i * 2] = c >> 8;
            bytes[i * 2 + 1] = c;
        }
    }

    return result;
}

CString TextCodecUTF16::encode(const LChar* characters, size_t length, UnencodableHandling)
{
    // In the LChar case, we do actually need to perform this check in release.  :)
    RELEASE_ASSERT(length <= numeric_limits<size_t>::max() / 2);

    char* bytes;
    CString result = CString::newUninitialized(length * 2, bytes);

    if (m_littleEndian) {
        for (size_t i = 0; i < length; ++i) {
            bytes[i * 2] = characters[i];
            bytes[i * 2 + 1] = 0;
        }
    } else {
        for (size_t i = 0; i < length; ++i) {
            bytes[i * 2] = 0;
            bytes[i * 2 + 1] = characters[i];
        }
    }

    return result;
}

} // namespace WTF