1/*
2 * Copyright (c) 2010, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package jdk.nashorn.internal.parser;
27
28import static jdk.nashorn.internal.parser.TokenKind.LITERAL;
29
30import jdk.nashorn.internal.runtime.Source;
31
32/**
33 * A token is a 64 bit long value that represents a basic parse/lex unit.
34 * This class provides static methods to manipulate lexer tokens.
35 */
36public class Token {
37
38    /**
39     * We use 28 bits for the position and 28 bits for the length of the token.
40     * This limits the maximal length of code we can handle to 2 ^ 28 - 1 bytes.
41     */
42    public final static int LENGTH_MASK = 0xfffffff;
43
44    // The first 8 bits are used for the token type, followed by length and position
45    private final static int LENGTH_SHIFT = 8;
46    private final static int POSITION_SHIFT  = 36;
47
48    private Token() {
49    }
50
51    /**
52     * Create a compact form of token information.
53     * @param type     Type of token.
54     * @param position Start position of the token in the source.
55     * @param length   Length of the token.
56     * @return Token descriptor.
57     */
58    public static long toDesc(final TokenType type, final int position, final int length) {
59        assert position <= LENGTH_MASK && length <= LENGTH_MASK;
60        return (long)position << POSITION_SHIFT |
61               (long)length   << LENGTH_SHIFT  |
62               type.ordinal();
63    }
64
65    /**
66     * Extract token position from a token descriptor.
67     * @param token Token descriptor.
68     * @return Start position of the token in the source.
69     */
70    public static int descPosition(final long token) {
71        return (int)(token >>> POSITION_SHIFT);
72    }
73
74    /**
75     * Normally returns the token itself, except in case of string tokens
76     * which report their position past their opening delimiter and thus
77     * need to have position and length adjusted.
78     *
79     * @param token Token descriptor.
80     * @return same or adjusted token.
81     */
82    public static long withDelimiter(final long token) {
83        final TokenType tokenType = Token.descType(token);
84        switch(tokenType) {
85            case STRING:
86            case ESCSTRING:
87            case EXECSTRING:
88            case TEMPLATE:
89            case TEMPLATE_TAIL: {
90                final int start = Token.descPosition(token) - 1;
91                final int len = Token.descLength(token) + 2;
92                return toDesc(tokenType, start, len);
93            }
94            case TEMPLATE_HEAD:
95            case TEMPLATE_MIDDLE: {
96                final int start = Token.descPosition(token) - 1;
97                final int len = Token.descLength(token) + 3;
98                return toDesc(tokenType, start, len);
99            }
100            default: {
101                return token;
102            }
103        }
104    }
105
106    /**
107     * Extract token length from a token descriptor.
108     * @param token Token descriptor.
109     * @return Length of the token.
110     */
111    public static int descLength(final long token) {
112        return (int)((token >>> LENGTH_SHIFT) & LENGTH_MASK);
113    }
114
115    /**
116     * Extract token type from a token descriptor.
117     * @param token Token descriptor.
118     * @return Type of token.
119     */
120    public static TokenType descType(final long token) {
121        return TokenType.getValues()[(int)token & 0xff];
122    }
123
124    /**
125     * Change the token to use a new type.
126     *
127     * @param token   The original token.
128     * @param newType The new token type.
129     * @return The recast token.
130     */
131    public static long recast(final long token, final TokenType newType) {
132        return token & ~0xFFL | newType.ordinal();
133    }
134
135    /**
136     * Return a string representation of a token.
137     * @param source  Token source.
138     * @param token   Token descriptor.
139     * @param verbose True to include details.
140     * @return String representation.
141     */
142    public static String toString(final Source source, final long token, final boolean verbose) {
143        final TokenType type = Token.descType(token);
144        String result;
145
146        if (source != null && type.getKind() == LITERAL) {
147            result = source.getString(token);
148        } else {
149            result = type.getNameOrType();
150        }
151
152        if (verbose) {
153            final int position = Token.descPosition(token);
154            final int length = Token.descLength(token);
155            result += " (" + position + ", " + length + ")";
156        }
157
158        return result;
159    }
160
161    /**
162     * String conversion of token
163     *
164     * @param source the source
165     * @param token  the token
166     *
167     * @return token as string
168     */
169    public static String toString(final Source source, final long token) {
170        return Token.toString(source, token, false);
171    }
172
173    /**
174     * String conversion of token - version without source given
175     *
176     * @param token  the token
177     *
178     * @return token as string
179     */
180    public static String toString(final long token) {
181        return Token.toString(null, token, false);
182    }
183
184    /**
185     * Static hash code computation function token
186     *
187     * @param token a token
188     *
189     * @return hash code for token
190     */
191    public static int hashCode(final long token) {
192        return (int)(token ^ token >>> 32);
193    }
194
195}
196