/*
 * Copyright 2000-2008 Sun Microsystems, Inc.  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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package sun.nio.cs;

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

/* Legal UTF-8 Byte Sequences
 *
 * #    Code Points      Bits   Bit/Byte pattern
 * 1                     7      0xxxxxxx
 *      U+0000..U+007F          00..7F
 *
 * 2                     11     110xxxxx    10xxxxxx
 *      U+0080..U+07FF          C2..DF      80..BF
 *
 * 3                     16     1110xxxx    10xxxxxx    10xxxxxx
 *      U+0800..U+0FFF          E0          A0..BF      80..BF
 *      U+1000..U+FFFF          E1..EF      80..BF      80..BF
 *
 * 4                     21     11110xxx    10xxxxxx    10xxxxxx    10xxxxxx
 *     U+10000..U+3FFFF         F0          90..BF      80..BF      80..BF
 *     U+40000..U+FFFFF         F1..F3      80..BF      80..BF      80..BF
 *    U+100000..U10FFFF         F4          80..8F      80..BF      80..BF
 *
 */

class UTF_8 extends Unicode
{
    public UTF_8() {
        super("UTF-8", StandardCharsets.aliases_UTF_8);
    }

    public String historicalName() {
        return "UTF8";
    }

    public CharsetDecoder newDecoder() {
        return new Decoder(this);
    }

    public CharsetEncoder newEncoder() {
        return new Encoder(this);
    }

    static final void updatePositions(Buffer src, int sp,
                                      Buffer dst, int dp) {
        src.position(sp - src.arrayOffset());
        dst.position(dp - dst.arrayOffset());
    }

    private static class Decoder extends CharsetDecoder {
        private Decoder(Charset cs) {
            super(cs, 1.0f, 1.0f);
        }

        private static boolean isNotContinuation(int b) {
            return (b & 0xc0) != 0x80;
        }

        //  [C2..DF] [80..BF]
        private static boolean isMalformed2(int b1, int b2) {
            return (b1 & 0x1e) == 0x0 || (b2 & 0xc0) != 0x80;
        }

        //  [E0]     [A0..BF] [80..BF]
        //  [E1..EF] [80..BF] [80..BF]
        private static boolean isMalformed3(int b1, int b2, int b3) {
            return (b1 == (byte)0xe0 && (b2 & 0xe0) == 0x80) ||
                   (b2 & 0xc0) != 0x80 || (b3 & 0xc0) != 0x80;
        }

        //  [F0]     [90..BF] [80..BF] [80..BF]
        //  [F1..F3] [80..BF] [80..BF] [80..BF]
        //  [F4]     [80..8F] [80..BF] [80..BF]
        //  only check 80-be range here, the [0xf0,0x80...] and [0xf4,0x90-...]
        //  will be checked by Surrogate.neededFor(uc)
        private static boolean isMalformed4(int b2, int b3, int b4) {
            return (b2 & 0xc0) != 0x80 || (b3 & 0xc0) != 0x80 ||
                   (b4 & 0xc0) != 0x80;
        }

        private static CoderResult lookupN(ByteBuffer src, int n)
        {
            for (int i = 1; i < n; i++) {
               if (isNotContinuation(src.get()))
                   return CoderResult.malformedForLength(i);
            }
            return CoderResult.malformedForLength(n);
        }

        private static CoderResult malformedN(ByteBuffer src, int nb) {
            switch (nb) {
            case 1:
                int b1 = src.get();
                if ((b1 >> 2) == -2) {
                    // 5 bytes 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
                    if (src.remaining() < 4)
                        return CoderResult.UNDERFLOW;
                    return lookupN(src, 5);
                }
                if ((b1 >> 1) == -2) {
                    // 6 bytes 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
                    if (src.remaining() < 5)
                        return CoderResult.UNDERFLOW;
                    return lookupN(src, 6);
                }
                return CoderResult.malformedForLength(1);
            case 2:                    // always 1
                return CoderResult.malformedForLength(1);
            case 3:
                b1 = src.get();
                int b2 = src.get();    // no need to lookup b3
                return CoderResult.malformedForLength(
                    ((b1 == (byte)0xe0 && (b2 & 0xe0) == 0x80) ||
                     isNotContinuation(b2))?1:2);
            case 4:  // we don't care the speed here
                b1 = src.get() & 0xff;
                b2 = src.get() & 0xff;
                if (b1 > 0xf4 ||
                    (b1 == 0xf0 && (b2 < 0x90 || b2 > 0xbf)) ||
                    (b1 == 0xf4 && (b2 & 0xf0) != 0x80) ||
                    isNotContinuation(b2))
                    return CoderResult.malformedForLength(1);
                if (isNotContinuation(src.get()))
                    return CoderResult.malformedForLength(2);
                return CoderResult.malformedForLength(3);
            default:
                assert false;
                return null;
            }
        }

        private static CoderResult malformed(ByteBuffer src, int sp,
                                             CharBuffer dst, int dp,
                                             int nb)
        {
            src.position(sp - src.arrayOffset());
            CoderResult cr = malformedN(src, nb);
            updatePositions(src, sp, dst, dp);
            return cr;
        }

        private static CoderResult malformed(ByteBuffer src,
                                             int mark, int nb)
        {
            src.position(mark);
            CoderResult cr = malformedN(src, nb);
            src.position(mark);
            return cr;
        }

        private static CoderResult xflow(Buffer src, int sp, int sl,
                                         Buffer dst, int dp, int nb) {
            updatePositions(src, sp, dst, dp);
            return (nb == 0 || sl - sp < nb)
                   ?CoderResult.UNDERFLOW:CoderResult.OVERFLOW;
        }

        private static CoderResult xflow(Buffer src, int mark, int nb) {
            CoderResult cr = (nb == 0 || src.remaining() < (nb - 1))
                             ?CoderResult.UNDERFLOW:CoderResult.OVERFLOW;
            src.position(mark);
            return cr;
        }

        private CoderResult decodeArrayLoop(ByteBuffer src,
                                            CharBuffer dst)
        {
            // This method is optimized for ASCII input.
            byte[] sa = src.array();
            int sp = src.arrayOffset() + src.position();
            int sl = src.arrayOffset() + src.limit();

            char[] da = dst.array();
            int dp = dst.arrayOffset() + dst.position();
            int dl = dst.arrayOffset() + dst.limit();
            int dlASCII = dp + Math.min(sl - sp, dl - dp);

            // ASCII only loop
            while (dp < dlASCII && sa[sp] >= 0)
                da[dp++] = (char)sa[sp++];

            while (sp < sl) {
                int b1 = sa[sp];
                if (b1  >= 0) {
                    // 1 byte, 7 bits: 0xxxxxxx
                    if (dp >= dl)
                        return xflow(src, sp, sl, dst, dp, 1);
                    da[dp++] = (char)b1;
                    sp++;
                } else if ((b1 >> 5) == -2) {
                    // 2 bytes, 11 bits: 110xxxxx 10xxxxxx
                    if (sl - sp < 2 || dp >= dl)
                        return xflow(src, sp, sl, dst, dp, 2);
                    int b2 = sa[sp + 1];
                    if (isMalformed2(b1, b2))
                        return malformed(src, sp, dst, dp, 2);
                    da[dp++] = (char) (((b1 << 6) ^ b2) ^ 0x0f80);
                    sp += 2;
                } else if ((b1 >> 4) == -2) {
                    // 3 bytes, 16 bits: 1110xxxx 10xxxxxx 10xxxxxx
                    if (sl - sp < 3 || dp >= dl)
                        return xflow(src, sp, sl, dst, dp, 3);
                    int b2 = sa[sp + 1];
                    int b3 = sa[sp + 2];
                    if (isMalformed3(b1, b2, b3))
                        return malformed(src, sp, dst, dp, 3);
                    da[dp++] = (char) (((b1 << 12) ^ (b2 << 6) ^ b3) ^ 0x1f80);
                    sp += 3;
                } else if ((b1 >> 3) == -2) {
                    // 4 bytes, 21 bits: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
                    if (sl - sp < 4 || dl - dp < 2)
                        return xflow(src, sp, sl, dst, dp, 4);
                    int b2 = sa[sp + 1];
                    int b3 = sa[sp + 2];
                    int b4 = sa[sp + 3];
                    int uc = ((b1 & 0x07) << 18) |
                             ((b2 & 0x3f) << 12) |
                             ((b3 & 0x3f) << 06) |
                             (b4 & 0x3f);
                    if (isMalformed4(b2, b3, b4) ||
                        !Surrogate.neededFor(uc)) {
                        return malformed(src, sp, dst, dp, 4);
                    }
                    da[dp++] = Surrogate.high(uc);
                    da[dp++] = Surrogate.low(uc);
                    sp += 4;
                } else
                    return malformed(src, sp, dst, dp, 1);
            }
            return xflow(src, sp, sl, dst, dp, 0);
        }

        private CoderResult decodeBufferLoop(ByteBuffer src,
                                             CharBuffer dst)
        {
            int mark = src.position();
            int limit = src.limit();
            while (mark < limit) {
                int b1 = src.get();
                if (b1 >= 0) {
                    // 1 byte, 7 bits: 0xxxxxxx
                    if (dst.remaining() < 1)
                        return xflow(src, mark, 1);  //overflow
                    dst.put((char)b1);
                    mark++;
                } else if ((b1 >> 5) == -2) {
                    // 2 bytes, 11 bits: 110xxxxx 10xxxxxx
                    if (limit - mark < 2|| dst.remaining() < 1)
                        return xflow(src, mark, 2);
                    int b2 = src.get();
                    if (isMalformed2(b1, b2))
                        return malformed(src, mark, 2);
                    dst.put((char) (((b1 << 6) ^ b2) ^ 0x0f80));
                    mark += 2;
                } else if ((b1 >> 4) == -2) {
                    // 3 bytes, 16 bits: 1110xxxx 10xxxxxx 10xxxxxx
                    if (limit - mark < 3 || dst.remaining() < 1)
                        return xflow(src, mark, 3);
                    int b2 = src.get();
                    int b3 = src.get();
                    if (isMalformed3(b1, b2, b3))
                        return malformed(src, mark, 3);
                    dst.put((char) (((b1 << 12) ^ (b2 << 6) ^ b3) ^ 0x1f80));
                    mark += 3;
                } else if ((b1 >> 3) == -2) {
                    // 4 bytes, 21 bits: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
                    if (limit - mark < 4 || dst.remaining() < 2)
                        return xflow(src, mark, 4);
                    int b2 = src.get();
                    int b3 = src.get();
                    int b4 = src.get();
                    int uc = ((b1 & 0x07) << 18) |
                             ((b2 & 0x3f) << 12) |
                             ((b3 & 0x3f) << 06) |
                             (b4 & 0x3f);
                    if (isMalformed4(b2, b3, b4) ||
                        !Surrogate.neededFor(uc)) { // shortest form check
                        return malformed(src, mark, 4);
                    }
                    dst.put(Surrogate.high(uc));
                    dst.put(Surrogate.low(uc));
                    mark += 4;
                } else {
                    return malformed(src, mark, 1);
                }
            }
            return xflow(src, mark, 0);
        }

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

    private static class Encoder extends CharsetEncoder {

        private Encoder(Charset cs) {
            super(cs, 1.1f, 4.0f);
        }

        public boolean canEncode(char c) {
            return !Character.isSurrogate(c);
        }

        public boolean isLegalReplacement(byte[] repl) {
            return ((repl.length == 1 && repl[0] >= 0) ||
                    super.isLegalReplacement(repl));
        }

        private static CoderResult overflow(CharBuffer src, int sp,
                                            ByteBuffer dst, int dp) {
            updatePositions(src, sp, dst, dp);
            return CoderResult.OVERFLOW;
        }

        private static CoderResult overflow(CharBuffer src, int mark) {
            src.position(mark);
            return CoderResult.OVERFLOW;
        }

        private Surrogate.Parser sgp;
        private CoderResult encodeArrayLoop(CharBuffer src,
                                            ByteBuffer dst)
        {
            char[] sa = src.array();
            int sp = src.arrayOffset() + src.position();
            int sl = src.arrayOffset() + src.limit();

            byte[] da = dst.array();
            int dp = dst.arrayOffset() + dst.position();
            int dl = dst.arrayOffset() + dst.limit();
            int dlASCII = dp + Math.min(sl - sp, dl - dp);

            //ASCII only loop
            while (dp < dlASCII && sa[sp] < '\u0080')
                da[dp++] = (byte) sa[sp++];
            while (sp < sl) {
                char c = sa[sp];
                if (c < 0x80) {
                    // Have at most seven bits
                    if (dp >= dl)
                        return overflow(src, sp, dst, dp);
                    da[dp++] = (byte)c;
                } else if (c < 0x800) {
                    // 2 bytes, 11 bits
                    if (dl - dp < 2)
                        return overflow(src, sp, dst, dp);
                    da[dp++] = (byte)(0xc0 | ((c >> 06)));
                    da[dp++] = (byte)(0x80 | (c & 0x3f));
                } else if (Character.isSurrogate(c)) {
                    // Have a surrogate pair
                    if (sgp == null)
                        sgp = new Surrogate.Parser();
                    int uc = sgp.parse(c, sa, sp, sl);
                    if (uc < 0) {
                        updatePositions(src, sp, dst, dp);
                        return sgp.error();
                    }
                    if (dl - dp < 4)
                        return overflow(src, sp, dst, dp);
                    da[dp++] = (byte)(0xf0 | ((uc >> 18)));
                    da[dp++] = (byte)(0x80 | ((uc >> 12) & 0x3f));
                    da[dp++] = (byte)(0x80 | ((uc >> 06) & 0x3f));
                    da[dp++] = (byte)(0x80 | (uc & 0x3f));
                    sp++;  // 2 chars
                } else {
                    // 3 bytes, 16 bits
                    if (dl - dp < 3)
                        return overflow(src, sp, dst, dp);
                    da[dp++] = (byte)(0xe0 | ((c >> 12)));
                    da[dp++] = (byte)(0x80 | ((c >> 06) & 0x3f));
                    da[dp++] = (byte)(0x80 | (c & 0x3f));
                }
                sp++;
            }
            updatePositions(src, sp, dst, dp);
            return CoderResult.UNDERFLOW;
        }

        private CoderResult encodeBufferLoop(CharBuffer src,
                                             ByteBuffer dst)
        {
            int mark = src.position();
            while (src.hasRemaining()) {
                char c = src.get();
                if (c < 0x80) {
                    // Have at most seven bits
                    if (!dst.hasRemaining())
                        return overflow(src, mark);
                    dst.put((byte)c);
                } else if (c < 0x800) {
                    // 2 bytes, 11 bits
                    if (dst.remaining() < 2)
                        return overflow(src, mark);
                    dst.put((byte)(0xc0 | ((c >> 06))));
                    dst.put((byte)(0x80 | (c & 0x3f)));
                } else if (Character.isSurrogate(c)) {
                    // Have a surrogate pair
                    if (sgp == null)
                        sgp = new Surrogate.Parser();
                    int uc = sgp.parse(c, src);
                    if (uc < 0) {
                        src.position(mark);
                        return sgp.error();
                    }
                    if (dst.remaining() < 4)
                        return overflow(src, mark);
                    dst.put((byte)(0xf0 | ((uc >> 18))));
                    dst.put((byte)(0x80 | ((uc >> 12) & 0x3f)));
                    dst.put((byte)(0x80 | ((uc >> 06) & 0x3f)));
                    dst.put((byte)(0x80 | (uc & 0x3f)));
                    mark++;  //2 chars
                } else {
                    // 3 bytes, 16 bits
                    if (dst.remaining() < 3)
                        return overflow(src, mark);
                    dst.put((byte)(0xe0 | ((c >> 12))));
                    dst.put((byte)(0x80 | ((c >> 06) & 0x3f)));
                    dst.put((byte)(0x80 | (c & 0x3f)));
                }
                mark++;
            }
            src.position(mark);
            return CoderResult.UNDERFLOW;
        }

        protected final CoderResult encodeLoop(CharBuffer src,
                                               ByteBuffer dst)
        {
            if (src.hasArray() && dst.hasArray())
                return encodeArrayLoop(src, dst);
            else
                return encodeBufferLoop(src, dst);
        }
    }
}
