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 
17 package com.android.dexgen.dex.code;
18 
19 import java.util.ArrayList;
20 
21 /**
22  * Destination for {@link DalvInsn} instances being output. This class
23  * receives and collects instructions in two pieces — a primary
24  * list and a suffix (generally consisting of adjunct data referred to
25  * by the primary list, such as switch case tables) — which it
26  * merges and emits back out in the form of a {@link DalvInsnList}
27  * instance.
28  */
29 public final class OutputCollector {
30     /**
31      * {@code non-null;} the associated finisher (which holds the instruction
32      * list in-progress)
33      */
34     private final OutputFinisher finisher;
35 
36     /**
37      * {@code null-ok;} suffix for the output, or {@code null} if the suffix
38      * has been appended to the main output (by {@link #appendSuffixToOutput})
39      */
40     private ArrayList<DalvInsn> suffix;
41 
42     /**
43      * Constructs an instance.
44      *
45      * @param initialCapacity {@code >= 0;} initial capacity of the output list
46      * @param suffixInitialCapacity {@code >= 0;} initial capacity of the output
47      * suffix
48      * @param regCount {@code >= 0;} register count for the method
49      */
OutputCollector(int initialCapacity, int suffixInitialCapacity, int regCount)50     public OutputCollector(int initialCapacity, int suffixInitialCapacity,
51             int regCount) {
52         this.finisher = new OutputFinisher(initialCapacity, regCount);
53         this.suffix = new ArrayList<DalvInsn>(suffixInitialCapacity);
54     }
55 
56     /**
57      * Adds an instruction to the output.
58      *
59      * @param insn {@code non-null;} the instruction to add
60      */
add(DalvInsn insn)61     public void add(DalvInsn insn) {
62         finisher.add(insn);
63     }
64 
65     /**
66      * Reverses a branch which is buried a given number of instructions
67      * backward in the output. It is illegal to call this unless the
68      * indicated instruction really is a reversible branch.
69      *
70      * @param which how many instructions back to find the branch;
71      * {@code 0} is the most recently added instruction,
72      * {@code 1} is the instruction before that, etc.
73      * @param newTarget {@code non-null;} the new target for the reversed branch
74      */
reverseBranch(int which, CodeAddress newTarget)75     public void reverseBranch(int which, CodeAddress newTarget) {
76         finisher.reverseBranch(which, newTarget);
77     }
78 
79     /**
80      * Adds an instruction to the output suffix.
81      *
82      * @param insn {@code non-null;} the instruction to add
83      */
addSuffix(DalvInsn insn)84     public void addSuffix(DalvInsn insn) {
85         suffix.add(insn);
86     }
87 
88     /**
89      * Gets the results of all the calls on this instance, in the form of
90      * an {@link OutputFinisher}.
91      *
92      * @return {@code non-null;} the output finisher
93      * @throws UnsupportedOperationException if this method has
94      * already been called
95      */
getFinisher()96     public OutputFinisher getFinisher() {
97         if (suffix == null) {
98             throw new UnsupportedOperationException("already processed");
99         }
100 
101         appendSuffixToOutput();
102         return finisher;
103     }
104 
105     /**
106      * Helper for {@link #getFinisher}, which appends the suffix to
107      * the primary output.
108      */
appendSuffixToOutput()109     private void appendSuffixToOutput() {
110         int size = suffix.size();
111 
112         for (int i = 0; i < size; i++) {
113             finisher.add(suffix.get(i));
114         }
115 
116         suffix = null;
117     }
118 }
119