1/*
2 * [The "BSD license"]
3 *  Copyright (c) 2010 Terence Parr
4 *  All rights reserved.
5 *
6 *  Redistribution and use in source and binary forms, with or without
7 *  modification, are permitted provided that the following conditions
8 *  are met:
9 *  1. Redistributions of source code must retain the above copyright
10 *      notice, this list of conditions and the following disclaimer.
11 *  2. Redistributions in binary form must reproduce the above copyright
12 *      notice, this list of conditions and the following disclaimer in the
13 *      documentation and/or other materials provided with the distribution.
14 *  3. The name of the author may not be used to endorse or promote products
15 *      derived from this software without specific prior written permission.
16 *
17 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28package org.antlr.misc;
29
30/** An immutable inclusive interval a..b */
31public class Interval {
32	public static final int INTERVAL_POOL_MAX_VALUE = 1000;
33
34	static Interval[] cache = new Interval[INTERVAL_POOL_MAX_VALUE+1];
35
36	public int a;
37	public int b;
38
39	public static int creates = 0;
40	public static int misses = 0;
41	public static int hits = 0;
42	public static int outOfRange = 0;
43
44	public Interval(int a, int b) { this.a=a; this.b=b; }
45
46	/** Interval objects are used readonly so share all with the
47	 *  same single value a==b up to some max size.  Use an array as a perfect hash.
48	 *  Return shared object for 0..INTERVAL_POOL_MAX_VALUE or a new
49	 *  Interval object with a..a in it.  On Java.g, 218623 IntervalSets
50	 *  have a..a (set with 1 element).
51	 */
52	public static Interval create(int a, int b) {
53		//return new Interval(a,b);
54		// cache just a..a
55		if ( a!=b || a<0 || a>INTERVAL_POOL_MAX_VALUE ) {
56			return new Interval(a,b);
57		}
58		if ( cache[a]==null ) {
59			cache[a] = new Interval(a,a);
60		}
61		return cache[a];
62	}
63
64	public boolean equals(Object o) {
65		if ( o==null ) {
66			return false;
67		}
68		Interval other = (Interval)o;
69		return this.a==other.a && this.b==other.b;
70	}
71
72	/** Does this start completely before other? Disjoint */
73	public boolean startsBeforeDisjoint(Interval other) {
74		return this.a<other.a && this.b<other.a;
75	}
76
77	/** Does this start at or before other? Nondisjoint */
78	public boolean startsBeforeNonDisjoint(Interval other) {
79		return this.a<=other.a && this.b>=other.a;
80	}
81
82	/** Does this.a start after other.b? May or may not be disjoint */
83	public boolean startsAfter(Interval other) { return this.a>other.a; }
84
85	/** Does this start completely after other? Disjoint */
86	public boolean startsAfterDisjoint(Interval other) {
87		return this.a>other.b;
88	}
89
90	/** Does this start after other? NonDisjoint */
91	public boolean startsAfterNonDisjoint(Interval other) {
92		return this.a>other.a && this.a<=other.b; // this.b>=other.b implied
93	}
94
95	/** Are both ranges disjoint? I.e., no overlap? */
96	public boolean disjoint(Interval other) {
97		return startsBeforeDisjoint(other) || startsAfterDisjoint(other);
98	}
99
100	/** Are two intervals adjacent such as 0..41 and 42..42? */
101	public boolean adjacent(Interval other) {
102		return this.a == other.b+1 || this.b == other.a-1;
103	}
104
105	public boolean properlyContains(Interval other) {
106		return other.a >= this.a && other.b <= this.b;
107	}
108
109	/** Return the interval computed from combining this and other */
110	public Interval union(Interval other) {
111		return Interval.create(Math.min(a,other.a), Math.max(b,other.b));
112	}
113
114	/** Return the interval in common between this and o */
115	public Interval intersection(Interval other) {
116		return Interval.create(Math.max(a,other.a), Math.min(b,other.b));
117	}
118
119	/** Return the interval with elements from this not in other;
120	 *  other must not be totally enclosed (properly contained)
121	 *  within this, which would result in two disjoint intervals
122	 *  instead of the single one returned by this method.
123	 */
124	public Interval differenceNotProperlyContained(Interval other) {
125		Interval diff = null;
126		// other.a to left of this.a (or same)
127		if ( other.startsBeforeNonDisjoint(this) ) {
128			diff = Interval.create(Math.max(this.a,other.b+1),
129								   this.b);
130		}
131
132		// other.a to right of this.a
133		else if ( other.startsAfterNonDisjoint(this) ) {
134			diff = Interval.create(this.a, other.a-1);
135		}
136		return diff;
137	}
138
139	public String toString() {
140		return a+".."+b;
141	}
142}
143