/*
 * Copyright (c) 2002, 2005, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */



package sun.nio.cs.ext;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CoderResult;

abstract class DoubleByteDecoder
    extends CharsetDecoder
{

    private short index1[];

    /*
     * 2nd level index, provided by subclass
     * every string has 0x10*(end-start+1) characters.
     */
    private String  index2[];

    protected int start;
    protected int end;

    protected static final char REPLACE_CHAR = '\uFFFD';
    protected char highSurrogate;
    protected char lowSurrogate;

    protected DoubleByteDecoder(Charset cs, short[] index1, String[] index2,
                                int start, int end ) {
        super(cs, 0.5f, 1.0f);
        this.index1 = index1;
        this.index2 = index2;
        this.start = start;
        this.end = end;
    }

    private CoderResult decodeArrayLoop(ByteBuffer src, CharBuffer dst) {
        byte[] sa = src.array();
        int sp = src.arrayOffset() + src.position();
        int sl = src.arrayOffset() + src.limit();
        assert (sp <= sl);
        sp = (sp <= sl ? sp : sl);
        char[] da = dst.array();
        int dp = dst.arrayOffset() + dst.position();
        int dl = dst.arrayOffset() + dst.limit();
        assert (dp <= dl);
        dp = (dp <= dl ? dp : dl);

        try {
            while (sp < sl) {
                int b1, b2;
                b1 = sa[sp];
                int inputSize = 1;
                int outputSize = 1;
                highSurrogate = lowSurrogate = 0;
                char c = decodeSingle(b1);
                if (c == REPLACE_CHAR) {
                    b1 &= 0xff;
                    if (sl - sp < 2)
                        return CoderResult.UNDERFLOW;
                    b2 = sa[sp + 1] & 0xff;
                    c = decodeDouble(b1, b2);
                    inputSize = 2;
                    if (c == REPLACE_CHAR)
                        return CoderResult.unmappableForLength(inputSize);
                    outputSize = (highSurrogate > 0) ? 2: 1;
                }

                if (dl - dp < outputSize)
                    return CoderResult.OVERFLOW;
                if (outputSize == 2) {
                    da[dp++] = highSurrogate;
                    da[dp++] = lowSurrogate;
                } else {
                    da[dp++] = c;
                }
                sp += inputSize;
            }
            return CoderResult.UNDERFLOW;
        } finally {
            src.position(sp - src.arrayOffset());
            dst.position(dp - dst.arrayOffset());
        }
    }

    private CoderResult decodeBufferLoop(ByteBuffer src, CharBuffer dst) {
        int mark = src.position();
        int inputSize = 0;
        int outputSize = 0;
        try {
            while (src.hasRemaining()) {
                int b1 = src.get();
                inputSize = 1;
                outputSize = 1;
                highSurrogate = lowSurrogate = 0;

                char c = decodeSingle(b1);

                if (c == REPLACE_CHAR) {
                    if (src.remaining() < 1)
                        return CoderResult.UNDERFLOW;
                    b1 &= 0xff;
                    int b2 = src.get() & 0xff;
                    inputSize = 2;

                    c = decodeDouble(b1, b2);

                    if (c == REPLACE_CHAR)
                        return CoderResult.unmappableForLength(2);

                    outputSize =  (highSurrogate > 0) ? 2: 1;
                }
                if (dst.remaining() < outputSize)
                    return CoderResult.OVERFLOW;
                mark += inputSize;

                if (outputSize == 2) {
                    dst.put(highSurrogate);
                    dst.put(lowSurrogate);
                } else {
                    dst.put(c);
                }
            }
            return CoderResult.UNDERFLOW;
        } finally {
            src.position(mark);
        }
    }

    protected CoderResult decodeLoop(ByteBuffer src, CharBuffer dst) {
        if (src.hasArray() && dst.hasArray())
            return decodeArrayLoop(src, dst);
        else
            return decodeBufferLoop(src, dst);
    }

    /*
     * Can be changed by subclass
     */
    protected char decodeSingle(int b) {
        if (b >= 0)
            return (char) b;
        return REPLACE_CHAR;
    }

    protected char decodeDouble(int byte1, int byte2) {
        if (((byte1 < 0) || (byte1 > index1.length))
            || ((byte2 < start) || (byte2 > end)))
            return REPLACE_CHAR;

        int n = (index1[byte1] & 0xf) * (end - start + 1) + (byte2 - start);
        return index2[index1[byte1] >> 4].charAt(n);
    }
}
