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 * Copyright (c) 2010, 2015, 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 jdk.nashorn.internal.parser;

import static jdk.nashorn.internal.parser.TokenKind.LITERAL;

import jdk.nashorn.internal.runtime.Source;

/**

 * A token is a 64 bit long value that represents a basic parse/lex unit.

 * This class provides static methods to manipulate lexer tokens.

 */

public class Token {

    /**

     * We use 28 bits for the position and 28 bits for the length of the token.

     * This limits the maximal length of code we can handle to 2 ^ 28 - 1 bytes.

     */

    public final static int LENGTH_MASK = 0xfffffff;

    // The first 8 bits are used for the token type, followed by length and position

    private final static int LENGTH_SHIFT = 8;

    private final static int POSITION_SHIFT  = 36;

    private Token() {

    }

    /**

     * Create a compact form of token information.

     * @param type     Type of token.

     * @param position Start position of the token in the source.

     * @param length   Length of the token.

     * @return Token descriptor.

     */

    public static long toDesc(final TokenType type, final int position, final int length) {

        assert position <= LENGTH_MASK && length <= LENGTH_MASK;

        return (long)position << POSITION_SHIFT |

               (long)length   << LENGTH_SHIFT  |

               type.ordinal();

    }

    /**

     * Extract token position from a token descriptor.

     * @param token Token descriptor.

     * @return Start position of the token in the source.

     */

    public static int descPosition(final long token) {

        return (int)(token >>> POSITION_SHIFT);

    }

    /**

     * Normally returns the token itself, except in case of string tokens

     * which report their position past their opening delimiter and thus

     * need to have position and length adjusted.

     *

     * @param token Token descriptor.

     * @return same or adjusted token.

     */

    public static long withDelimiter(final long token) {

        final TokenType tokenType = Token.descType(token);

        switch(tokenType) {

            case STRING:

            case ESCSTRING:

            case EXECSTRING:

            case TEMPLATE:

            case TEMPLATE_TAIL: {

                final int start = Token.descPosition(token) - 1;

                final int len = Token.descLength(token) + 2;

                return toDesc(tokenType, start, len);

            }

            case TEMPLATE_HEAD:

            case TEMPLATE_MIDDLE: {

                final int start = Token.descPosition(token) - 1;

                final int len = Token.descLength(token) + 3;

                return toDesc(tokenType, start, len);

            }

            default: {

                return token;

            }

        }

    }

    /**

     * Extract token length from a token descriptor.

     * @param token Token descriptor.

     * @return Length of the token.

     */

    public static int descLength(final long token) {

        return (int)((token >>> LENGTH_SHIFT) & LENGTH_MASK);

    }

    /**

     * Extract token type from a token descriptor.

     * @param token Token descriptor.

     * @return Type of token.

     */

    public static TokenType descType(final long token) {

        return TokenType.getValues()[(int)token & 0xff];

    }

    /**

     * Change the token to use a new type.

     *

     * @param token   The original token.

     * @param newType The new token type.

     * @return The recast token.

     */

    public static long recast(final long token, final TokenType newType) {

        return token & ~0xFFL | newType.ordinal();

    }

    /**

     * Return a string representation of a token.

     * @param source  Token source.

     * @param token   Token descriptor.

     * @param verbose True to include details.

     * @return String representation.

     */

    public static String toString(final Source source, final long token, final boolean verbose) {

        final TokenType type = Token.descType(token);

        String result;

        if (source != null && type.getKind() == LITERAL) {

            result = source.getString(token);

        } else {

            result = type.getNameOrType();

        }

        if (verbose) {

            final int position = Token.descPosition(token);

            final int length = Token.descLength(token);

            result += " (" + position + ", " + length + ")";

        }

        return result;

    }

    /**

     * String conversion of token

     *

     * @param source the source

     * @param token  the token

     *

     * @return token as string

     */

    public static String toString(final Source source, final long token) {

        return Token.toString(source, token, false);

    }

    /**

     * String conversion of token - version without source given

     *

     * @param token  the token

     *

     * @return token as string

     */

    public static String toString(final long token) {

        return Token.toString(null, token, false);

    }

    /**

     * Static hash code computation function token

     *

     * @param token a token

     *

     * @return hash code for token

     */

    public static int hashCode(final long token) {

        return (int)(token ^ token >>> 32);

    }

}