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6819246: improve support for decoding instructions in classfile library
Reviewed-by: ksrini
This commit is contained in:
Jonathan Gibbons
parent
584c02dfa8
commit
dcd2283896
5 changed files with 931 additions and 1076 deletions
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@ -0,0 +1,339 @@
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/*
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* Copyright 2009 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Sun designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Sun in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*/
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package com.sun.tools.classfile;
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/**
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* See JVMS3, chapter 6.
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*
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* <p><b>This is NOT part of any API supported by Sun Microsystems. If
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* you write code that depends on this, you do so at your own risk.
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* This code and its internal interfaces are subject to change or
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* deletion without notice.</b>
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*
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* @see Code_attribute#getInstructions
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*/
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public class Instruction {
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/** The kind of an instruction, as determined by the position, size and
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* types of its operands. */
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public static enum Kind {
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/** Opcode is not followed by any operands. */
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NO_OPERANDS(1),
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/** Opcode is followed by a byte indicating a type. */
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ATYPE(2),
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/** Opcode is followed by a 2-byte branch offset. */
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BRANCH(3),
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/** Opcode is followed by a 4-byte branch offset. */
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BRANCH_W(5),
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/** Opcode is followed by a signed byte value. */
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BYTE(2),
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/** Opcode is followed by a 1-byte index into the constant pool. */
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CPREF(2),
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/** Opcode is followed by a 2-byte index into the constant pool. */
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CPREF_W(3),
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/** Opcode is followed by a 2-byte index into the constant pool,
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* an unsigned byte value. */
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CPREF_W_UBYTE(4),
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/** Opcode is followed by a 2-byte index into the constant pool.,
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* an unsigned byte value, and a zero byte. */
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CPREF_W_UBYTE_ZERO(5),
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/** Opcode is followed by variable number of operands, depending
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* on the instruction.*/
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DYNAMIC(-1),
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/** Opcode is followed by a 1-byte reference to a local variable. */
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LOCAL(2),
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/** Opcode is followed by a 1-byte reference to a local variable,
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* and a signed byte value. */
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LOCAL_BYTE(3),
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/** Opcode is followed by a signed short value. */
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SHORT(3),
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/** Wide opcode is not followed by any operands. */
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WIDE_NO_OPERANDS(2),
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/** Wide opcode is followed by a 2-byte index into the constant pool. */
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WIDE_CPREF_W(4),
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/** Wide opcode is followed by a 2-byte index into the constant pool,
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* and a signed short value. */
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WIDE_CPREF_W_SHORT(6),
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/** Opcode was not recognized. */
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UNKNOWN(1);
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Kind(int length) {
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this.length = length;
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}
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/** The length, in bytes, of this kind of instruction, or -1 is the
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* length depends on the specific instruction. */
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public final int length;
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};
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/** A utility visitor to help decode the operands of an instruction.
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* @see Instruction#accept */
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public interface KindVisitor<R,P> {
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/** See {@link Kind#NO_OPERANDS}, {@link Kind#WIDE_NO_OPERANDS}. */
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R visitNoOperands(Instruction instr, P p);
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/** See {@link Kind#ATYPE}. */
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R visitArrayType(Instruction instr, TypeKind kind, P p);
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/** See {@link Kind#BRANCH}, {@link Kind#BRANCH_W}. */
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R visitBranch(Instruction instr, int offset, P p);
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/** See {@link Kind#CPREF}, {@link Kind#CPREF_W}, {@link Kind#WIDE_CPREF_W}. */
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R visitConstantPoolRef(Instruction instr, int index, P p);
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/** See {@link Kind#CPREF_W_UBYTE}, {@link Kind#CPREF_W_UBYTE_ZERO}, {@link Kind#WIDE_CPREF_W_SHORT}. */
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R visitConstantPoolRefAndValue(Instruction instr, int index, int value, P p);
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/** See {@link Kind#LOCAL}. */
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R visitLocal(Instruction instr, int index, P p);
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/** See {@link Kind#LOCAL_UBYTE}. */
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R visitLocalAndValue(Instruction instr, int index, int value, P p);
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/** See {@link Kind#DYNAMIC}. */
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R visitLookupSwitch(Instruction instr, int default_, int npairs, int[] matches, int[] offsets);
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/** See {@link Kind#DYNAMIC}. */
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R visitTableSwitch(Instruction instr, int default_, int low, int high, int[] offsets);
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/** See {@link Kind#BYTE}, {@link Kind#SHORT}. */
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R visitValue(Instruction instr, int value, P p);
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/** Instruction is unrecognized. */
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R visitUnknown(Instruction instr, P p);
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}
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/** The kind of primitive array type to create.
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* See JVMS chapter 6, newarray. */
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public static enum TypeKind {
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T_BOOLEAN(4, "boolean"),
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T_CHAR(5, "char"),
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T_FLOAT(6, "float"),
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T_DOUBLE(7, "double"),
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T_BYTE(8, "byte"),
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T_SHORT(9, "short"),
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T_INT (10, "int"),
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T_LONG (11, "long");
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TypeKind(int value, String name) {
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this.value = value;
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this.name = name;
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}
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public static TypeKind get(int value) {
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switch (value) {
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case 4: return T_BOOLEAN;
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case 5: return T_CHAR;
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case 6: return T_FLOAT;
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case 7: return T_DOUBLE;
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case 8: return T_BYTE;
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case 9: return T_SHORT;
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case 10: return T_INT;
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case 11: return T_LONG;
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default: return null;
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}
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}
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public final int value;
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public final String name;
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}
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/** An instruction is defined by its position in a bytecode array. */
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public Instruction(byte[] bytes, int pc) {
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this.bytes = bytes;
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this.pc = pc;
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}
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/** Get the position of the instruction within the bytecode array. */
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public int getPC() {
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return pc;
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}
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/** Get a byte value, relative to the start of this instruction. */
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public int getByte(int offset) {
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return bytes[pc + offset];
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}
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/** Get an unsigned byte value, relative to the start of this instruction. */
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public int getUnsignedByte(int offset) {
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return getByte(offset) & 0xff;
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}
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/** Get a 2-byte value, relative to the start of this instruction. */
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public int getShort(int offset) {
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return (getByte(offset) << 8) | getUnsignedByte(offset + 1);
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}
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/** Get a unsigned 2-byte value, relative to the start of this instruction. */
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public int getUnsignedShort(int offset) {
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return getShort(offset) & 0xFFFF;
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}
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/** Get a 4-byte value, relative to the start of this instruction. */
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public int getInt(int offset) {
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return (getShort(offset) << 16) | (getUnsignedShort(offset + 2));
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}
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/** Get the Opcode for this instruction, or null if the instruction is
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* unrecognized. */
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public Opcode getOpcode() {
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int b = getUnsignedByte(0);
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switch (b) {
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case Opcode.NONPRIV:
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case Opcode.PRIV:
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case Opcode.WIDE:
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return Opcode.get(b, getUnsignedByte(1));
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}
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return Opcode.get(b);
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}
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/** Get the mnemonic for this instruction, or a default string if the
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* instruction is unrecognized. */
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public String getMnemonic() {
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Opcode opcode = getOpcode();
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if (opcode == null)
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return "bytecode " + getUnsignedByte(0);
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else
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return opcode.toString().toLowerCase();
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}
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/** Get the length, in bytes, of this instruction, including the opcode
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* and all its operands. */
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public int length() {
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Opcode opcode = getOpcode();
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if (opcode == null)
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return 1;
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switch (opcode) {
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case TABLESWITCH: {
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int pad = align(pc + 1) - pc;
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int low = getInt(pad + 4);
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int high = getInt(pad + 8);
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return pad + 12 + 4 * (high - low + 1);
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}
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case LOOKUPSWITCH: {
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int pad = align(pc + 1) - pc;
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int npairs = getInt(pad + 4);
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return pad + 8 + 8 * npairs;
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}
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default:
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return opcode.kind.length;
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}
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}
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/** Get the {@link Kind} of this instruction. */
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public Kind getKind() {
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Opcode opcode = getOpcode();
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return (opcode != null ? opcode.kind : Kind.UNKNOWN);
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}
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/** Invoke a method on the visitor according to the kind of this
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* instruction, passing in the decoded operands for the instruction. */
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public <R,P> R accept(KindVisitor<R,P> visitor, P p) {
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switch (getKind()) {
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case NO_OPERANDS:
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return visitor.visitNoOperands(this, p);
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case ATYPE:
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return visitor.visitArrayType(
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this, TypeKind.get(getUnsignedByte(1)), p);
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case BRANCH:
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return visitor.visitBranch(this, getShort(1), p);
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case BRANCH_W:
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return visitor.visitBranch(this, getInt(1), p);
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case BYTE:
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return visitor.visitValue(this, getByte(1), p);
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case CPREF:
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return visitor.visitConstantPoolRef(this, getUnsignedByte(1), p);
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case CPREF_W:
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return visitor.visitConstantPoolRef(this, getUnsignedShort(1), p);
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case CPREF_W_UBYTE:
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case CPREF_W_UBYTE_ZERO:
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return visitor.visitConstantPoolRefAndValue(
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this, getUnsignedShort(1), getUnsignedByte(3), p);
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case DYNAMIC: {
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switch (getOpcode()) {
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case TABLESWITCH: {
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int pad = align(pc + 1) - pc;
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int default_ = getInt(pad);
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int low = getInt(pad + 4);
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int high = getInt(pad + 8);
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int[] values = new int[high - low + 1];
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for (int i = 0; i < values.length; i++)
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values[i] = getInt(pad + 12 + 4 * i);
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return visitor.visitTableSwitch(
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this, default_, low, high, values);
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}
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case LOOKUPSWITCH: {
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int pad = align(pc + 1) - pc;
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int default_ = getInt(pad);
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int npairs = getInt(pad + 4);
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int[] matches = new int[npairs];
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int[] offsets = new int[npairs];
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for (int i = 0; i < npairs; i++) {
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matches[i] = getInt(pad + 8 + i * 8);
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offsets[i] = getInt(pad + 12 + i * 8);
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}
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return visitor.visitLookupSwitch(
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this, default_, npairs, matches, offsets);
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}
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default:
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throw new IllegalStateException();
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}
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}
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case LOCAL:
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return visitor.visitLocal(this, getUnsignedByte(1), p);
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case LOCAL_BYTE:
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return visitor.visitLocalAndValue(
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this, getUnsignedByte(1), getByte(2), p);
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case SHORT:
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return visitor.visitValue(this, getShort(1), p);
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case WIDE_NO_OPERANDS:
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return visitor.visitNoOperands(this, p);
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case WIDE_CPREF_W:
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return visitor.visitConstantPoolRef(this, getUnsignedShort(2), p);
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case WIDE_CPREF_W_SHORT:
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return visitor.visitConstantPoolRefAndValue(
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this, getUnsignedShort(2), getUnsignedByte(4), p);
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case UNKNOWN:
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return visitor.visitUnknown(this, p);
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default:
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throw new IllegalStateException();
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}
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}
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private static int align(int n) {
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return (n + 3) & ~3;
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}
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private byte[] bytes;
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private int pc;
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}
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