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/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * 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).
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package com.sun.tools.classfile;

import java.util.Locale;

/**
 * See JVMS, chapter 6.
 *
 *  

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. * * @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 { /** 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 accept(KindVisitor 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); if (low > high) throw new IllegalStateException(); 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); if (npairs < 0) throw new IllegalStateException(); 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; }





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