/*
* Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
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*/
package com.sun.tools.classfile;
import java.util.Locale;
/**
* See JVMS, chapter 6.
*
* <p><b>This is NOT part of any supported API.
* If you write code that depends on this, you do so at your own risk.
* This code and its internal interfaces are subject to change or
* deletion without notice.</b>
*
* @see Code_attribute#getInstructions
*/
public class Instruction {
/** The kind of an instruction, as determined by the position, size and
* types of its operands. */
public static enum Kind {
/** Opcode is not followed by any operands. */
NO_OPERANDS(1),
/** Opcode is followed by a byte indicating a type. */
ATYPE(2),
/** Opcode is followed by a 2-byte branch offset. */
BRANCH(3),
/** Opcode is followed by a 4-byte branch offset. */
BRANCH_W(5),
/** Opcode is followed by a signed byte value. */
BYTE(2),
/** Opcode is followed by a 1-byte index into the constant pool. */
CPREF(2),
/** Opcode is followed by a 2-byte index into the constant pool. */
CPREF_W(3),
/** Opcode is followed by a 2-byte index into the constant pool,
* an unsigned byte value. */
CPREF_W_UBYTE(4),
/** Opcode is followed by a 2-byte index into the constant pool.,
* an unsigned byte value, and a zero byte. */
CPREF_W_UBYTE_ZERO(5),
/** Opcode is followed by variable number of operands, depending
* on the instruction.*/
DYNAMIC(-1),
/** Opcode is followed by a 1-byte reference to a local variable. */
LOCAL(2),
/** Opcode is followed by a 1-byte reference to a local variable,
* and a signed byte value. */
LOCAL_BYTE(3),
/** Opcode is followed by a signed short value. */
SHORT(3),
/** Wide opcode is not followed by any operands. */
WIDE_NO_OPERANDS(2),
/** Wide opcode is followed by a 2-byte index into the local variables array. */
WIDE_LOCAL(4),
/** Wide opcode is followed by a 2-byte index into the constant pool. */
WIDE_CPREF_W(4),
/** Wide opcode is followed by a 2-byte index into the constant pool,
* and a signed short value. */
WIDE_CPREF_W_SHORT(6),
/** Wide opcode is followed by a 2-byte reference to a local variable,
* and a signed short value. */
WIDE_LOCAL_SHORT(6),
/** Opcode was not recognized. */
UNKNOWN(1);
Kind(int length) {
this.length = length;
}
/** The length, in bytes, of this kind of instruction, or -1 is the
* length depends on the specific instruction. */
public final int length;
}
/** A utility visitor to help decode the operands of an instruction.
* @see Instruction#accept */
public interface KindVisitor<R,P> {
/** See {@link Kind#NO_OPERANDS}, {@link Kind#WIDE_NO_OPERANDS}. */
R visitNoOperands(Instruction instr, P p);
/** See {@link Kind#ATYPE}. */
R visitArrayType(Instruction instr, TypeKind kind, P p);
/** See {@link Kind#BRANCH}, {@link Kind#BRANCH_W}. */
R visitBranch(Instruction instr, int offset, P p);
/** See {@link Kind#CPREF}, {@link Kind#CPREF_W}, {@link Kind#WIDE_CPREF_W}. */
R visitConstantPoolRef(Instruction instr, int index, P p);
/** See {@link Kind#CPREF_W_UBYTE}, {@link Kind#CPREF_W_UBYTE_ZERO}, {@link Kind#WIDE_CPREF_W_SHORT}. */
R visitConstantPoolRefAndValue(Instruction instr, int index, int value, P p);
/** See {@link Kind#LOCAL}, {@link Kind#WIDE_LOCAL}. */
R visitLocal(Instruction instr, int index, P p);
/** See {@link Kind#LOCAL_BYTE}. */
R visitLocalAndValue(Instruction instr, int index, int value, P p);
/** See {@link Kind#DYNAMIC}. */
R visitLookupSwitch(Instruction instr, int default_, int npairs, int[] matches, int[] offsets, P p);
/** See {@link Kind#DYNAMIC}. */
R visitTableSwitch(Instruction instr, int default_, int low, int high, int[] offsets, P p);
/** See {@link Kind#BYTE}, {@link Kind#SHORT}. */
R visitValue(Instruction instr, int value, P p);
/** Instruction is unrecognized. */
R visitUnknown(Instruction instr, P p);
}
/** The kind of primitive array type to create.
* See JVMS chapter 6, newarray. */
public static enum TypeKind {
T_BOOLEAN(4, "boolean"),
T_CHAR(5, "char"),
T_FLOAT(6, "float"),
T_DOUBLE(7, "double"),
T_BYTE(8, "byte"),
T_SHORT(9, "short"),
T_INT (10, "int"),
T_LONG (11, "long");
TypeKind(int value, String name) {
this.value = value;
this.name = name;
}
public static TypeKind get(int value) {
switch (value) {
case 4: return T_BOOLEAN;
case 5: return T_CHAR;
case 6: return T_FLOAT;
case 7: return T_DOUBLE;
case 8: return T_BYTE;
case 9: return T_SHORT;
case 10: return T_INT;
case 11: return T_LONG;
default: return null;
}
}
public final int value;
public final String name;
}
/** An instruction is defined by its position in a bytecode array. */
public Instruction(byte[] bytes, int pc) {
this.bytes = bytes;
this.pc = pc;
}
/** Get the position of the instruction within the bytecode array. */
public int getPC() {
return pc;
}
/** Get a byte value, relative to the start of this instruction. */
public int getByte(int offset) {
return bytes[pc + offset];
}
/** Get an unsigned byte value, relative to the start of this instruction. */
public int getUnsignedByte(int offset) {
return getByte(offset) & 0xff;
}
/** Get a 2-byte value, relative to the start of this instruction. */
public int getShort(int offset) {
return (getByte(offset) << 8) | getUnsignedByte(offset + 1);
}
/** Get a unsigned 2-byte value, relative to the start of this instruction. */
public int getUnsignedShort(int offset) {
return getShort(offset) & 0xFFFF;
}
/** Get a 4-byte value, relative to the start of this instruction. */
public int getInt(int offset) {
return (getShort(offset) << 16) | (getUnsignedShort(offset + 2));
}
/** Get the Opcode for this instruction, or null if the instruction is
* unrecognized. */
public Opcode getOpcode() {
int b = getUnsignedByte(0);
switch (b) {
case Opcode.NONPRIV:
case Opcode.PRIV:
case Opcode.WIDE:
return Opcode.get(b, getUnsignedByte(1));
}
return Opcode.get(b);
}
/** Get the mnemonic for this instruction, or a default string if the
* instruction is unrecognized. */
public String getMnemonic() {
Opcode opcode = getOpcode();
if (opcode == null)
return "bytecode " + getUnsignedByte(0);
else
return opcode.toString().toLowerCase(Locale.US);
}
/** Get the length, in bytes, of this instruction, including the opcode
* and all its operands. */
public int length() {
Opcode opcode = getOpcode();
if (opcode == null)
return 1;
switch (opcode) {
case TABLESWITCH: {
int pad = align(pc + 1) - pc;
int low = getInt(pad + 4);
int high = getInt(pad + 8);
return pad + 12 + 4 * (high - low + 1);
}
case LOOKUPSWITCH: {
int pad = align(pc + 1) - pc;
int npairs = getInt(pad + 4);
return pad + 8 + 8 * npairs;
}
default:
return opcode.kind.length;
}
}
/** Get the {@link Kind} of this instruction. */
public Kind getKind() {
Opcode opcode = getOpcode();
return (opcode != null ? opcode.kind : Kind.UNKNOWN);
}
/** Invoke a method on the visitor according to the kind of this
* instruction, passing in the decoded operands for the instruction. */
public <R,P> R accept(KindVisitor<R,P> visitor, P p) {
switch (getKind()) {
case NO_OPERANDS:
return visitor.visitNoOperands(this, p);
case ATYPE:
return visitor.visitArrayType(
this, TypeKind.get(getUnsignedByte(1)), p);
case BRANCH:
return visitor.visitBranch(this, getShort(1), p);
case BRANCH_W:
return visitor.visitBranch(this, getInt(1), p);
case BYTE:
return visitor.visitValue(this, getByte(1), p);
case CPREF:
return visitor.visitConstantPoolRef(this, getUnsignedByte(1), p);
case CPREF_W:
return visitor.visitConstantPoolRef(this, getUnsignedShort(1), p);
case CPREF_W_UBYTE:
case CPREF_W_UBYTE_ZERO:
return visitor.visitConstantPoolRefAndValue(
this, getUnsignedShort(1), getUnsignedByte(3), p);
case DYNAMIC: {
switch (getOpcode()) {
case TABLESWITCH: {
int pad = align(pc + 1) - pc;
int default_ = getInt(pad);
int low = getInt(pad + 4);
int high = getInt(pad + 8);
int[] values = new int[high - low + 1];
for (int i = 0; i < values.length; i++)
values[i] = getInt(pad + 12 + 4 * i);
return visitor.visitTableSwitch(
this, default_, low, high, values, p);
}
case LOOKUPSWITCH: {
int pad = align(pc + 1) - pc;
int default_ = getInt(pad);
int npairs = getInt(pad + 4);
int[] matches = new int[npairs];
int[] offsets = new int[npairs];
for (int i = 0; i < npairs; i++) {
matches[i] = getInt(pad + 8 + i * 8);
offsets[i] = getInt(pad + 12 + i * 8);
}
return visitor.visitLookupSwitch(
this, default_, npairs, matches, offsets, p);
}
default:
throw new IllegalStateException();
}
}
case LOCAL:
return visitor.visitLocal(this, getUnsignedByte(1), p);
case LOCAL_BYTE:
return visitor.visitLocalAndValue(
this, getUnsignedByte(1), getByte(2), p);
case SHORT:
return visitor.visitValue(this, getShort(1), p);
case WIDE_NO_OPERANDS:
return visitor.visitNoOperands(this, p);
case WIDE_LOCAL:
return visitor.visitLocal(this, getUnsignedShort(2), p);
case WIDE_CPREF_W:
return visitor.visitConstantPoolRef(this, getUnsignedShort(2), p);
case WIDE_CPREF_W_SHORT:
return visitor.visitConstantPoolRefAndValue(
this, getUnsignedShort(2), getUnsignedByte(4), p);
case WIDE_LOCAL_SHORT:
return visitor.visitLocalAndValue(
this, getUnsignedShort(2), getShort(4), p);
case UNKNOWN:
return visitor.visitUnknown(this, p);
default:
throw new IllegalStateException();
}
}
private static int align(int n) {
return (n + 3) & ~3;
}
private byte[] bytes;
private int pc;
}