1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.text;
18
19import java.lang.reflect.Array;
20import java.util.Arrays;
21
22/**
23 * A cached set of spans. Caches the result of {@link Spanned#getSpans(int, int, Class)} and then
24 * provides faster access to {@link Spanned#nextSpanTransition(int, int, Class)}.
25 *
26 * Fields are left public for a convenient direct access.
27 *
28 * Note that empty spans are ignored by this class.
29 * @hide
30 */
31public class SpanSet<E> {
32    private final Class<? extends E> classType;
33
34    int numberOfSpans;
35    E[] spans;
36    int[] spanStarts;
37    int[] spanEnds;
38    int[] spanFlags;
39
40    SpanSet(Class<? extends E> type) {
41        classType = type;
42        numberOfSpans = 0;
43    }
44
45    @SuppressWarnings("unchecked")
46    public void init(Spanned spanned, int start, int limit) {
47        final E[] allSpans = spanned.getSpans(start, limit, classType);
48        final int length = allSpans.length;
49
50        if (length > 0 && (spans == null || spans.length < length)) {
51            // These arrays may end up being too large because of the discarded empty spans
52            spans = (E[]) Array.newInstance(classType, length);
53            spanStarts = new int[length];
54            spanEnds = new int[length];
55            spanFlags = new int[length];
56        }
57
58        int prevNumberOfSpans = numberOfSpans;
59        numberOfSpans = 0;
60        for (int i = 0; i < length; i++) {
61            final E span = allSpans[i];
62
63            final int spanStart = spanned.getSpanStart(span);
64            final int spanEnd = spanned.getSpanEnd(span);
65            if (spanStart == spanEnd) continue;
66
67            final int spanFlag = spanned.getSpanFlags(span);
68
69            spans[numberOfSpans] = span;
70            spanStarts[numberOfSpans] = spanStart;
71            spanEnds[numberOfSpans] = spanEnd;
72            spanFlags[numberOfSpans] = spanFlag;
73
74            numberOfSpans++;
75        }
76
77        // cleanup extra spans left over from previous init() call
78        if (numberOfSpans < prevNumberOfSpans) {
79            // prevNumberofSpans was > 0, therefore spans != null
80            Arrays.fill(spans, numberOfSpans, prevNumberOfSpans, null);
81        }
82    }
83
84    /**
85     * Returns true if there are spans intersecting the given interval.
86     * @param end must be strictly greater than start
87     */
88    public boolean hasSpansIntersecting(int start, int end) {
89        for (int i = 0; i < numberOfSpans; i++) {
90            // equal test is valid since both intervals are not empty by construction
91            if (spanStarts[i] >= end || spanEnds[i] <= start) continue;
92            return true;
93        }
94        return false;
95    }
96
97    /**
98     * Similar to {@link Spanned#nextSpanTransition(int, int, Class)}
99     */
100    int getNextTransition(int start, int limit) {
101        for (int i = 0; i < numberOfSpans; i++) {
102            final int spanStart = spanStarts[i];
103            final int spanEnd = spanEnds[i];
104            if (spanStart > start && spanStart < limit) limit = spanStart;
105            if (spanEnd > start && spanEnd < limit) limit = spanEnd;
106        }
107        return limit;
108    }
109
110    /**
111     * Removes all internal references to the spans to avoid memory leaks.
112     */
113    public void recycle() {
114        if (spans != null) {
115            Arrays.fill(spans, 0, numberOfSpans, null);
116        }
117    }
118}
119