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.dexgen.dex.code.form;
18
19import com.android.dexgen.dex.code.DalvInsn;
20import com.android.dexgen.dex.code.InsnFormat;
21import com.android.dexgen.dex.code.TargetInsn;
22import com.android.dexgen.rop.code.RegisterSpecList;
23import com.android.dexgen.util.AnnotatedOutput;
24
25/**
26 * Instruction format {@code 21t}. See the instruction format spec
27 * for details.
28 */
29public final class Form21t extends InsnFormat {
30    /** {@code non-null;} unique instance of this class */
31    public static final InsnFormat THE_ONE = new Form21t();
32
33    /**
34     * Constructs an instance. This class is not publicly
35     * instantiable. Use {@link #THE_ONE}.
36     */
37    private Form21t() {
38        // This space intentionally left blank.
39    }
40
41    /** {@inheritDoc} */
42    @Override
43    public String insnArgString(DalvInsn insn) {
44        RegisterSpecList regs = insn.getRegisters();
45        return regs.get(0).regString() + ", " + branchString(insn);
46    }
47
48    /** {@inheritDoc} */
49    @Override
50    public String insnCommentString(DalvInsn insn, boolean noteIndices) {
51        return branchComment(insn);
52    }
53
54    /** {@inheritDoc} */
55    @Override
56    public int codeSize() {
57        return 2;
58    }
59
60    /** {@inheritDoc} */
61    @Override
62    public boolean isCompatible(DalvInsn insn) {
63        RegisterSpecList regs = insn.getRegisters();
64
65        if (!((insn instanceof TargetInsn) &&
66              (regs.size() == 1) &&
67              unsignedFitsInByte(regs.get(0).getReg()))) {
68            return false;
69        }
70
71        TargetInsn ti = (TargetInsn) insn;
72        return ti.hasTargetOffset() ? branchFits(ti) : true;
73    }
74
75    /** {@inheritDoc} */
76    @Override
77    public boolean branchFits(TargetInsn insn) {
78        int offset = insn.getTargetOffset();
79
80        // Note: A zero offset would fit, but it is prohibited by the spec.
81        return (offset != 0) && signedFitsInShort(offset);
82    }
83
84    /** {@inheritDoc} */
85    @Override
86    public InsnFormat nextUp() {
87        return Form31t.THE_ONE;
88    }
89
90    /** {@inheritDoc} */
91    @Override
92    public void writeTo(AnnotatedOutput out, DalvInsn insn) {
93        RegisterSpecList regs = insn.getRegisters();
94        int offset = ((TargetInsn) insn).getTargetOffset();
95
96        write(out,
97              opcodeUnit(insn, regs.get(0).getReg()),
98              (short) offset);
99    }
100}
101