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comparison src/main/java/nl/cwi/monetdb/mcl/parser/MCLParser.java @ 0:a5a898f6886c

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Copy of MonetDB java directory changeset e6e32756ad31.
author Sjoerd Mullender <sjoerd@acm.org>
date Wed, 21 Sep 2016 09:34:48 +0200 (2016-09-21)
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children f1de7262d8d9 b9b35ca2eec2
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-1:000000000000 0:a5a898f6886c
1 /*
2 * This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
5 *
6 * Copyright 1997 - July 2008 CWI, August 2008 - 2016 MonetDB B.V.
7 */
8
9 package nl.cwi.monetdb.mcl.parser;
10
11
12 /**
13 * Interface for parsers in MCL. The parser family in MCL is set up as
14 * a reusable object. This allows the same parser to be used again for
15 * the same type of work. While this is a very unnatural solution in
16 * the Java language, it prevents many object creations on a low level
17 * of the protocol. This favours performance.
18 *
19 * A typical parser has a method parse() which takes a String, and the
20 * methods hasNext() and next() to retrieve the values that were
21 * extracted by the parser. Parser specific methods may be available to
22 * perform common tasks.
23 *
24 * @author Fabian Groffen
25 */
26 public abstract class MCLParser {
27 /** The String values found while parsing. Public, you may touch it. */
28 public final String values[];
29 /** The int values found while parsing. Public, you may touch it. */
30 public final int intValues[];
31 private int colnr;
32
33 /**
34 * Creates an MCLParser targetted at a given number of field values.
35 * The lines parsed by an instance of this MCLParser should have
36 * exactly capacity field values.
37 *
38 * @param capacity the number of field values to expect
39 */
40 protected MCLParser(int capacity) {
41 values = new String[capacity];
42 intValues = new int[capacity];
43 }
44
45 /**
46 * Parse the given string, and populate the internal field array
47 * to allow for next() and hasNext() calls.
48 *
49 * @param source the String containing the line to parse
50 * @return value
51 * @throws MCLParseException if source cannot be (fully) parsed by
52 * this parser
53 * @see #next()
54 * @see #nextInt()
55 * @see #hasNext()
56 */
57 abstract public int parse(String source) throws MCLParseException;
58
59 /**
60 * Repositions the internal field offset to the start, such that the
61 * next call to next() will return the first field again.
62 */
63 final public void reset() {
64 colnr = 0;
65 }
66
67 /**
68 * Returns whether the next call to next() or nextInt() succeeds.
69 *
70 * @return true if the next call to next() or nextInt() is bound to
71 * succeed
72 * @see #next()
73 * @see #nextInt()
74 */
75 final public boolean hasNext() {
76 return colnr < values.length;
77 }
78
79 /**
80 * Returns the current field value, and advances the field counter
81 * to the next value. This method may fail with a RuntimeError if
82 * the current field counter is out of bounds. Call hasNext() to
83 * determine if the call to next() will succeed.
84 *
85 * @return the current field value
86 * @see #nextInt()
87 * @see #hasNext()
88 */
89 final public String next() {
90 return values[colnr++];
91 }
92
93 /**
94 * Returns the current field value as integer, and advances the
95 * field counter to the next value. This method has the same
96 * characteristics as the next() method, apart from returning the
97 * field value as an integer.
98 *
99 * @return the current field value as integer
100 * @see #next()
101 */
102 final public int nextInt() {
103 return intValues[colnr++];
104 }
105 }