/*

 * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package sun.nio.cs;

import java.nio.ByteBuffer;

import java.nio.CharBuffer;

import java.nio.charset.Charset;

import java.nio.charset.CharsetDecoder;

import java.nio.charset.CoderResult;

import java.nio.charset.CharacterCodingException;

import java.nio.charset.MalformedInputException;

abstract class UnicodeDecoder extends CharsetDecoder {

    protected static final char BYTE_ORDER_MARK = (char) 0xfeff;

    protected static final char REVERSED_MARK = (char) 0xfffe;

    protected static final int NONE = 0;

    protected static final int BIG = 1;

    protected static final int LITTLE = 2;

    private final int expectedByteOrder;

    private int currentByteOrder;

    private int defaultByteOrder = BIG;

    public UnicodeDecoder(Charset cs, int bo) {

        super(cs, 0.5f, 1.0f);

        expectedByteOrder = currentByteOrder = bo;

    }

    public UnicodeDecoder(Charset cs, int bo, int defaultBO) {

        this(cs, bo);

        defaultByteOrder = defaultBO;

    }

    private char decode(int b1, int b2) {

        if (currentByteOrder == BIG)

            return (char)((b1 << 8) | b2);

        else

            return (char)((b2 << 8) | b1);

    }

    protected CoderResult decodeLoop(ByteBuffer src, CharBuffer dst) {

        int mark = src.position();

        try {

            while (src.remaining() > 1) {

                int b1 = src.get() & 0xff;

                int b2 = src.get() & 0xff;

                // Byte Order Mark interpretation

                if (currentByteOrder == NONE) {

                    char c = (char)((b1 << 8) | b2);

                    if (c == BYTE_ORDER_MARK) {

                        currentByteOrder = BIG;

                        mark += 2;

                        continue;

                    } else if (c == REVERSED_MARK) {

                        currentByteOrder = LITTLE;

                        mark += 2;

                        continue;

                    } else {

                        currentByteOrder = defaultByteOrder;

                        // FALL THROUGH to process b1, b2 normally

                    }

                }

                char c = decode(b1, b2);

                // Surrogates

                if (Character.isSurrogate(c)) {

                    if (Character.isHighSurrogate(c)) {

                        if (src.remaining() < 2)

                            return CoderResult.UNDERFLOW;

                        char c2 = decode(src.get() & 0xff, src.get() & 0xff);

                        if (!Character.isLowSurrogate(c2))

                            return CoderResult.malformedForLength(4);

                        if (dst.remaining() < 2)

                            return CoderResult.OVERFLOW;

                        mark += 4;

                        dst.put(c);

                        dst.put(c2);

                        continue;

                    }

                    // Unpaired low surrogate

                    return CoderResult.malformedForLength(2);

                }

                if (!dst.hasRemaining())

                    return CoderResult.OVERFLOW;

                mark += 2;

                dst.put(c);

            }

            return CoderResult.UNDERFLOW;

        } finally {

            src.position(mark);

        }

    }

    protected void implReset() {

        currentByteOrder = expectedByteOrder;

    }

}