org.antlr.v4.runtime.misc.Interval.java Source code

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Here is the source code for org.antlr.v4.runtime.misc.Interval.java

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/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */
package org.antlr.v4.runtime.misc;

/** An immutable inclusive interval a..b */
public class Interval {
    public static final int INTERVAL_POOL_MAX_VALUE = 1000;

    public static final Interval INVALID = new Interval(-1, -2);

    static Interval[] cache = new Interval[INTERVAL_POOL_MAX_VALUE + 1];

    public int a;
    public int b;

    public static int creates = 0;
    public static int misses = 0;
    public static int hits = 0;
    public static int outOfRange = 0;

    public Interval(int a, int b) {
        this.a = a;
        this.b = b;
    }

    /** Interval objects are used readonly so share all with the
     *  same single value a==b up to some max size.  Use an array as a perfect hash.
     *  Return shared object for 0..INTERVAL_POOL_MAX_VALUE or a new
     *  Interval object with a..a in it.  On Java.g4, 218623 IntervalSets
     *  have a..a (set with 1 element).
     */
    public static Interval of(int a, int b) {
        // cache just a..a
        if (a != b || a < 0 || a > INTERVAL_POOL_MAX_VALUE) {
            return new Interval(a, b);
        }
        if (cache[a] == null) {
            cache[a] = new Interval(a, a);
        }
        return cache[a];
    }

    /** return number of elements between a and b inclusively. x..x is length 1.
     *  if b &lt; a, then length is 0.  9..10 has length 2.
     */
    public int length() {
        if (b < a)
            return 0;
        return b - a + 1;
    }

    @Override
    public boolean equals(Object o) {
        if (o == null || !(o instanceof Interval)) {
            return false;
        }
        Interval other = (Interval) o;
        return this.a == other.a && this.b == other.b;
    }

    @Override
    public int hashCode() {
        int hash = 23;
        hash = hash * 31 + a;
        hash = hash * 31 + b;
        return hash;
    }

    /** Does this start completely before other? Disjoint */
    public boolean startsBeforeDisjoint(Interval other) {
        return this.a < other.a && this.b < other.a;
    }

    /** Does this start at or before other? Nondisjoint */
    public boolean startsBeforeNonDisjoint(Interval other) {
        return this.a <= other.a && this.b >= other.a;
    }

    /** Does this.a start after other.b? May or may not be disjoint */
    public boolean startsAfter(Interval other) {
        return this.a > other.a;
    }

    /** Does this start completely after other? Disjoint */
    public boolean startsAfterDisjoint(Interval other) {
        return this.a > other.b;
    }

    /** Does this start after other? NonDisjoint */
    public boolean startsAfterNonDisjoint(Interval other) {
        return this.a > other.a && this.a <= other.b; // this.b>=other.b implied
    }

    /** Are both ranges disjoint? I.e., no overlap? */
    public boolean disjoint(Interval other) {
        return startsBeforeDisjoint(other) || startsAfterDisjoint(other);
    }

    /** Are two intervals adjacent such as 0..41 and 42..42? */
    public boolean adjacent(Interval other) {
        return this.a == other.b + 1 || this.b == other.a - 1;
    }

    public boolean properlyContains(Interval other) {
        return other.a >= this.a && other.b <= this.b;
    }

    /** Return the interval computed from combining this and other */
    public Interval union(Interval other) {
        return Interval.of(Math.min(a, other.a), Math.max(b, other.b));
    }

    /** Return the interval in common between this and o */
    public Interval intersection(Interval other) {
        return Interval.of(Math.max(a, other.a), Math.min(b, other.b));
    }

    /** Return the interval with elements from this not in other;
     *  other must not be totally enclosed (properly contained)
     *  within this, which would result in two disjoint intervals
     *  instead of the single one returned by this method.
     */
    public Interval differenceNotProperlyContained(Interval other) {
        Interval diff = null;
        // other.a to left of this.a (or same)
        if (other.startsBeforeNonDisjoint(this)) {
            diff = Interval.of(Math.max(this.a, other.b + 1), this.b);
        }

        // other.a to right of this.a
        else if (other.startsAfterNonDisjoint(this)) {
            diff = Interval.of(this.a, other.a - 1);
        }
        return diff;
    }

    @Override
    public String toString() {
        return a + ".." + b;
    }
}