/*

 * 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 java.lang;

import java.io.UnsupportedEncodingException;

import java.lang.ref.SoftReference;

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.CharacterCodingException;

import java.nio.charset.CoderResult;

import java.nio.charset.CodingErrorAction;

import java.nio.charset.IllegalCharsetNameException;

import java.nio.charset.MalformedInputException;

import java.nio.charset.UnmappableCharacterException;

import java.nio.charset.UnsupportedCharsetException;

import java.util.Arrays;

import jdk.internal.HotSpotIntrinsicCandidate;

import sun.nio.cs.HistoricallyNamedCharset;

import sun.nio.cs.ArrayDecoder;

import sun.nio.cs.ArrayEncoder;

import static java.lang.String.LATIN1;

import static java.lang.String.UTF16;

import static java.lang.String.COMPACT_STRINGS;

import static java.lang.Character.isSurrogate;

import static java.lang.Character.highSurrogate;

import static java.lang.Character.lowSurrogate;

import static java.lang.Character.isSupplementaryCodePoint;

import static java.lang.StringUTF16.putChar;

/**

 * Utility class for string encoding and decoding.

 */

class StringCoding {

    private StringCoding() { }

    /** The cached coders for each thread */

    private static final ThreadLocal<SoftReference<StringDecoder>> decoder =

        new ThreadLocal<>();

    private static final ThreadLocal<SoftReference<StringEncoder>> encoder =

        new ThreadLocal<>();

    private static final Charset ISO_8859_1 = sun.nio.cs.ISO_8859_1.INSTANCE;

    private static final Charset US_ASCII = sun.nio.cs.US_ASCII.INSTANCE;

    private static final Charset UTF_8 = sun.nio.cs.UTF_8.INSTANCE;

    private static <T> T deref(ThreadLocal<SoftReference<T>> tl) {

        SoftReference<T> sr = tl.get();

        if (sr == null)

            return null;

        return sr.get();

    }

    private static <T> void set(ThreadLocal<SoftReference<T>> tl, T ob) {

        tl.set(new SoftReference<>(ob));

    }

    // Trim the given byte array to the given length

    private static byte[] safeTrim(byte[] ba, int len, boolean isTrusted) {

        if (len == ba.length && (isTrusted || System.getSecurityManager() == null))

            return ba;

        else

            return Arrays.copyOf(ba, len);

    }

    private static int scale(int len, float expansionFactor) {

        // We need to perform double, not float, arithmetic; otherwise

        // we lose low order bits when len is larger than 2**24.

        return (int)(len * (double)expansionFactor);

    }

    private static Charset lookupCharset(String csn) {

        if (Charset.isSupported(csn)) {

            try {

                return Charset.forName(csn);

            } catch (UnsupportedCharsetException x) {

                throw new Error(x);

            }

        }

        return null;

    }

    static class Result {

        byte[] value;

        byte coder;

        Result with() {

            coder = COMPACT_STRINGS ? LATIN1 : UTF16;

            value = new byte[0];

            return this;

        }

        Result with(char[] val, int off, int len) {

            if (String.COMPACT_STRINGS) {

                byte[] bs = StringUTF16.compress(val, off, len);

                if (bs != null) {

                    value = bs;

                    coder = LATIN1;

                    return this;

                }

            }

            coder = UTF16;

            value = StringUTF16.toBytes(val, off, len);

            return this;

        }

        Result with(byte[] val, byte coder) {

            this.coder = coder;

            value = val;

            return this;

        }

    }

    @HotSpotIntrinsicCandidate

    public static boolean hasNegatives(byte[] ba, int off, int len) {

        for (int i = off; i < off + len; i++) {

            if (ba[i] < 0) {

                return true;

            }

        }

        return false;

    }

    // -- Decoding --

    static class StringDecoder {

        private final String requestedCharsetName;

        private final Charset cs;

        private final boolean isASCIICompatible;

        private final CharsetDecoder cd;

        protected final Result result;

        StringDecoder(Charset cs, String rcn) {

            this.requestedCharsetName = rcn;

            this.cs = cs;

            this.cd = cs.newDecoder()

                .onMalformedInput(CodingErrorAction.REPLACE)

                .onUnmappableCharacter(CodingErrorAction.REPLACE);

            this.result = new Result();

            this.isASCIICompatible = (cd instanceof ArrayDecoder) &&

                    ((ArrayDecoder)cd).isASCIICompatible();

        }

        String charsetName() {

            if (cs instanceof HistoricallyNamedCharset)

                return ((HistoricallyNamedCharset)cs).historicalName();

            return cs.name();

        }

        final String requestedCharsetName() {

            return requestedCharsetName;

        }

        Result decode(byte[] ba, int off, int len) {

            if (len == 0) {

                return result.with();

            }

            // fastpath for ascii compatible

            if (isASCIICompatible && !hasNegatives(ba, off, len)) {

                if (COMPACT_STRINGS) {

                    return result.with(Arrays.copyOfRange(ba, off, off + len),

                                      LATIN1);

                } else {

                    return result.with(StringLatin1.inflate(ba, off, len), UTF16);

                }

            }

            int en = scale(len, cd.maxCharsPerByte());

            char[] ca = new char[en];

            if (cd instanceof ArrayDecoder) {

                int clen = ((ArrayDecoder)cd).decode(ba, off, len, ca);

                return result.with(ca, 0, clen);

            }

            cd.reset();

            ByteBuffer bb = ByteBuffer.wrap(ba, off, len);

            CharBuffer cb = CharBuffer.wrap(ca);

            try {

                CoderResult cr = cd.decode(bb, cb, true);

                if (!cr.isUnderflow())

                    cr.throwException();

                cr = cd.flush(cb);

                if (!cr.isUnderflow())

                    cr.throwException();

            } catch (CharacterCodingException x) {

                // Substitution is always enabled,

                // so this shouldn't happen

                throw new Error(x);

            }

            return result.with(ca, 0, cb.position());

        }

    }

    static Result decode(String charsetName, byte[] ba, int off, int len)

        throws UnsupportedEncodingException

    {

        StringDecoder sd = deref(decoder);

        String csn = (charsetName == null) ? "ISO-8859-1" : charsetName;

        if ((sd == null) || !(csn.equals(sd.requestedCharsetName())

                              || csn.equals(sd.charsetName()))) {

            sd = null;

            try {

                Charset cs = lookupCharset(csn);

                if (cs != null) {

                    if (cs == UTF_8) {

                        return decodeUTF8(ba, off, len, true);

                    }

                    if (cs == ISO_8859_1) {

                        return decodeLatin1(ba, off, len);

                    }

                    if (cs == US_ASCII) {

                        return decodeASCII(ba, off, len);

                    }

                    sd = new StringDecoder(cs, csn);

                }

            } catch (IllegalCharsetNameException x) {}

            if (sd == null)

                throw new UnsupportedEncodingException(csn);

            set(decoder, sd);

        }

        return sd.decode(ba, off, len);

    }

    static Result decode(Charset cs, byte[] ba, int off, int len) {

        if (cs == UTF_8) {

            return decodeUTF8(ba, off, len, true);

        }

        if (cs == ISO_8859_1) {

            return decodeLatin1(ba, off, len);

        }

        if (cs == US_ASCII) {

            return decodeASCII(ba, off, len);

        }

        // (1)We never cache the "external" cs, the only benefit of creating

        // an additional StringDe/Encoder object to wrap it is to share the

        // de/encode() method. These SD/E objects are short-lived, the young-gen

        // gc should be able to take care of them well. But the best approach

        // is still not to generate them if not really necessary.

        // (2)The defensive copy of the input byte/char[] has a big performance

        // impact, as well as the outgoing result byte/char[]. Need to do the

        // optimization check of (sm==null && classLoader0==null) for both.

        // (3)There might be a timing gap in isTrusted setting. getClassLoader0()

        // is only checked (and then isTrusted gets set) when (SM==null). It is

        // possible that the SM==null for now but then SM is NOT null later

        // when safeTrim() is invoked...the "safe" way to do is to redundant

        // check (... && (isTrusted || SM == null || getClassLoader0())) in trim

        // but it then can be argued that the SM is null when the operation

        // is started...

        CharsetDecoder cd = cs.newDecoder();

        // ascii fastpath

        if ((cd instanceof ArrayDecoder) &&

            ((ArrayDecoder)cd).isASCIICompatible() && !hasNegatives(ba, off, len)) {

            return decodeLatin1(ba, off, len);

        }

        int en = scale(len, cd.maxCharsPerByte());

        if (len == 0) {

            return new Result().with();

        }

        cd.onMalformedInput(CodingErrorAction.REPLACE)

          .onUnmappableCharacter(CodingErrorAction.REPLACE)

          .reset();

        char[] ca = new char[en];

        if (cd instanceof ArrayDecoder) {

            int clen = ((ArrayDecoder)cd).decode(ba, off, len, ca);

            return new Result().with(ca, 0, clen);

        }

        if (cs.getClass().getClassLoader0() != null &&

            System.getSecurityManager() != null) {

            ba = Arrays.copyOfRange(ba, off, off + len);

            off = 0;

        }

        ByteBuffer bb = ByteBuffer.wrap(ba, off, len);

        CharBuffer cb = CharBuffer.wrap(ca);

        try {

            CoderResult cr = cd.decode(bb, cb, true);

            if (!cr.isUnderflow())

                cr.throwException();

            cr = cd.flush(cb);

            if (!cr.isUnderflow())

                cr.throwException();

        } catch (CharacterCodingException x) {

            // Substitution is always enabled,

            // so this shouldn't happen

            throw new Error(x);

        }

        return new Result().with(ca, 0, cb.position());

    }

    static Result decode(byte[] ba, int off, int len) {

        Charset cs = Charset.defaultCharset();

        if (cs == UTF_8) {

            return decodeUTF8(ba, off, len, true);

        }

        if (cs == ISO_8859_1) {

            return decodeLatin1(ba, off, len);

        }

        if (cs == US_ASCII) {

            return decodeASCII(ba, off, len);

        }

        StringDecoder sd = deref(decoder);

        if (sd == null || !cs.name().equals(sd.cs.name())) {

            sd = new StringDecoder(cs, cs.name());

            set(decoder, sd);

        }

        return sd.decode(ba, off, len);

    }

    // -- Encoding --

    private static class StringEncoder {

        private Charset cs;

        private CharsetEncoder ce;

        private final boolean isASCIICompatible;

        private final String requestedCharsetName;

        private final boolean isTrusted;

        private StringEncoder(Charset cs, String rcn) {

            this.requestedCharsetName = rcn;

            this.cs = cs;

            this.ce = cs.newEncoder()

                .onMalformedInput(CodingErrorAction.REPLACE)

                .onUnmappableCharacter(CodingErrorAction.REPLACE);

            this.isTrusted = (cs.getClass().getClassLoader0() == null);

            this.isASCIICompatible = (ce instanceof ArrayEncoder) &&

                    ((ArrayEncoder)ce).isASCIICompatible();

        }

        String charsetName() {

            if (cs instanceof HistoricallyNamedCharset)

                return ((HistoricallyNamedCharset)cs).historicalName();

            return cs.name();

        }

        final String requestedCharsetName() {

            return requestedCharsetName;

        }

        byte[] encode(byte coder, byte[] val) {

            // fastpath for ascii compatible

            if (coder == LATIN1 && isASCIICompatible &&

                !hasNegatives(val, 0, val.length)) {

                return Arrays.copyOf(val, val.length);

            }

            int len = val.length >> coder;  // assume LATIN1=0/UTF16=1;

            int en = scale(len, ce.maxBytesPerChar());

            byte[] ba = new byte[en];

            if (len == 0) {

                return ba;

            }

            if (ce instanceof ArrayEncoder) {

                int blen = (coder == LATIN1 ) ? ((ArrayEncoder)ce).encodeFromLatin1(val, 0, len, ba)

                                              : ((ArrayEncoder)ce).encodeFromUTF16(val, 0, len, ba);

                if (blen != -1) {

                    return safeTrim(ba, blen, isTrusted);

                }

            }

            char[] ca = (coder == LATIN1 ) ? StringLatin1.toChars(val)

                                           : StringUTF16.toChars(val);

            ce.reset();

            ByteBuffer bb = ByteBuffer.wrap(ba);

            CharBuffer cb = CharBuffer.wrap(ca, 0, len);

            try {

                CoderResult cr = ce.encode(cb, bb, true);

                if (!cr.isUnderflow())

                    cr.throwException();

                cr = ce.flush(bb);

                if (!cr.isUnderflow())

                    cr.throwException();

            } catch (CharacterCodingException x) {

                // Substitution is always enabled,

                // so this shouldn't happen

                throw new Error(x);

            }

            return safeTrim(ba, bb.position(), isTrusted);

        }

    }

    static byte[] encode(String charsetName, byte coder, byte[] val)

        throws UnsupportedEncodingException

    {

        StringEncoder se = deref(encoder);

        String csn = (charsetName == null) ? "ISO-8859-1" : charsetName;

        if ((se == null) || !(csn.equals(se.requestedCharsetName())

                              || csn.equals(se.charsetName()))) {

            se = null;

            try {

                Charset cs = lookupCharset(csn);

                if (cs != null) {

                    if (cs == UTF_8) {

                        return encodeUTF8(coder, val, true);

                    }

                    if (cs == ISO_8859_1) {

                        return encode8859_1(coder, val);

                    }

                    if (cs == US_ASCII) {

                        return encodeASCII(coder, val);

                    }

                    se = new StringEncoder(cs, csn);

                }

            } catch (IllegalCharsetNameException x) {}

            if (se == null) {

                throw new UnsupportedEncodingException (csn);

            }

            set(encoder, se);

        }

        return se.encode(coder, val);

    }

    static byte[] encode(Charset cs, byte coder, byte[] val) {

        if (cs == UTF_8) {

            return encodeUTF8(coder, val, true);

        }

        if (cs == ISO_8859_1) {

            return encode8859_1(coder, val);

        }

        if (cs == US_ASCII) {

            return encodeASCII(coder, val);

        }

        CharsetEncoder ce = cs.newEncoder();

        // fastpath for ascii compatible

        if (coder == LATIN1 && (((ce instanceof ArrayEncoder) &&

                                 ((ArrayEncoder)ce).isASCIICompatible() &&

                                 !hasNegatives(val, 0, val.length)))) {

            return Arrays.copyOf(val, val.length);

        }

        int len = val.length >> coder;  // assume LATIN1=0/UTF16=1;

        int en = scale(len, ce.maxBytesPerChar());

        byte[] ba = new byte[en];

        if (len == 0) {

            return ba;

        }

        ce.onMalformedInput(CodingErrorAction.REPLACE)

          .onUnmappableCharacter(CodingErrorAction.REPLACE)

          .reset();

        if (ce instanceof ArrayEncoder) {

            int blen = (coder == LATIN1 ) ? ((ArrayEncoder)ce).encodeFromLatin1(val, 0, len, ba)

                                          : ((ArrayEncoder)ce).encodeFromUTF16(val, 0, len, ba);

            if (blen != -1) {

                return safeTrim(ba, blen, true);

            }

        }

        boolean isTrusted = cs.getClass().getClassLoader0() == null ||

                            System.getSecurityManager() == null;

        char[] ca = (coder == LATIN1 ) ? StringLatin1.toChars(val)

                                       : StringUTF16.toChars(val);

        ByteBuffer bb = ByteBuffer.wrap(ba);

        CharBuffer cb = CharBuffer.wrap(ca, 0, len);

        try {

            CoderResult cr = ce.encode(cb, bb, true);

            if (!cr.isUnderflow())

                cr.throwException();

            cr = ce.flush(bb);

            if (!cr.isUnderflow())

                cr.throwException();

        } catch (CharacterCodingException x) {

            throw new Error(x);

        }

        return safeTrim(ba, bb.position(), isTrusted);

    }