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