ConstantPool.java revision 579d7739c53a2707ad711a2d2cae46d7d782f061 
1/*
2 * Copyright (C) 2007 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 com.android.dx.rop.cst;
18
19/**
20 * Interface for constant pools, which are, more or less, just lists of
21 * {@link Constant} objects.
22 */
23public interface ConstantPool {
24    /**
25     * Get the "size" of the constant pool. This corresponds to the
26     * class file field {@code constant_pool_count}, and is in fact
27     * always at least one more than the actual size of the constant pool,
28     * as element {@code 0} is always invalid.
29     *
30     * @return {@code >= 1;} the size
31     */
32    public int size();
33
34    /**
35     * Get the {@code n}th entry in the constant pool, which must
36     * be valid.
37     *
38     * @param n {@code n >= 0, n < size();} the constant pool index
39     * @return {@code non-null;} the corresponding entry
40     * @throws IllegalArgumentException thrown if {@code n} is
41     * in-range but invalid
42     */
43    public Constant get(int n);
44
45    /**
46     * Get the {@code n}th entry in the constant pool, which must
47     * be valid unless {@code n == 0}, in which case {@code null}
48     * is returned.
49     *
50     * @param n {@code n >= 0, n < size();} the constant pool index
51     * @return {@code null-ok;} the corresponding entry, if {@code n != 0}
52     * @throws IllegalArgumentException thrown if {@code n} is
53     * in-range and non-zero but invalid
54     */
55    public Constant get0Ok(int n);
56
57    /**
58     * Get the {@code n}th entry in the constant pool, or
59     * {@code null} if the index is in-range but invalid. In
60     * particular, {@code null} is returned for index {@code 0}
61     * as well as the index after any entry which is defined to take up
62     * two slots (that is, {@code Long} and {@code Double}
63     * entries).
64     *
65     * @param n {@code n >= 0, n < size();} the constant pool index
66     * @return {@code null-ok;} the corresponding entry, or {@code null} if
67     * the index is in-range but invalid
68     */
69    public Constant getOrNull(int n);
70}
71