jjg@255: /*
ohair@554:  * Copyright (c) 2009, Oracle and/or its affiliates. All rights reserved.
jjg@255:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jjg@255:  *
jjg@255:  * This code is free software; you can redistribute it and/or modify it
jjg@255:  * under the terms of the GNU General Public License version 2 only, as
ohair@554:  * published by the Free Software Foundation.  Oracle designates this
jjg@255:  * particular file as subject to the "Classpath" exception as provided
ohair@554:  * by Oracle in the LICENSE file that accompanied this code.
jjg@255:  *
jjg@255:  * This code is distributed in the hope that it will be useful, but WITHOUT
jjg@255:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jjg@255:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jjg@255:  * version 2 for more details (a copy is included in the LICENSE file that
jjg@255:  * accompanied this code).
jjg@255:  *
jjg@255:  * You should have received a copy of the GNU General Public License version
jjg@255:  * 2 along with this work; if not, write to the Free Software Foundation,
jjg@255:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jjg@255:  *
ohair@554:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
ohair@554:  * or visit www.oracle.com if you need additional information or have any
ohair@554:  * questions.
jjg@255:  */
jjg@255: 
jjg@255: package com.sun.tools.classfile;
jjg@255: 
jjg@255: /**
jjh@972:  * See JVMS, chapter 6.
jjg@255:  *
jjg@581:  *  <p><b>This is NOT part of any supported API.
jjg@581:  *  If you write code that depends on this, you do so at your own risk.
jjg@255:  *  This code and its internal interfaces are subject to change or
jjg@255:  *  deletion without notice.</b>
jjg@255:  *
jjg@255:  * @see Code_attribute#getInstructions
jjg@255:  */
jjg@255: public class Instruction {
jjg@255:     /** The kind of an instruction, as determined by the position, size and
jjg@255:      *  types of its operands. */
jjg@255:     public static enum Kind {
jjg@255:         /** Opcode is not followed by any operands. */
jjg@255:         NO_OPERANDS(1),
jjg@255:         /** Opcode is followed by a byte indicating a type. */
jjg@255:         ATYPE(2),
jjg@255:         /** Opcode is followed by a 2-byte branch offset. */
jjg@255:         BRANCH(3),
jjg@255:         /** Opcode is followed by a 4-byte branch offset. */
jjg@255:         BRANCH_W(5),
jjg@255:         /** Opcode is followed by a signed byte value. */
jjg@255:         BYTE(2),
jjg@255:         /** Opcode is followed by a 1-byte index into the constant pool. */
jjg@255:         CPREF(2),
jjg@255:         /** Opcode is followed by a 2-byte index into the constant pool. */
jjg@255:         CPREF_W(3),
jjg@255:         /** Opcode is followed by a 2-byte index into the constant pool,
jjg@255:          *  an unsigned byte value. */
jjg@255:         CPREF_W_UBYTE(4),
jjg@255:         /** Opcode is followed by a 2-byte index into the constant pool.,
jjg@255:          *  an unsigned byte value, and a zero byte. */
jjg@255:         CPREF_W_UBYTE_ZERO(5),
jjg@255:         /** Opcode is followed by variable number of operands, depending
jjg@255:          * on the instruction.*/
jjg@255:         DYNAMIC(-1),
jjg@255:         /** Opcode is followed by a 1-byte reference to a local variable. */
jjg@255:         LOCAL(2),
jjg@255:         /** Opcode is followed by a 1-byte reference to a local variable,
jjg@255:          *  and a signed byte value. */
jjg@255:         LOCAL_BYTE(3),
jjg@255:         /** Opcode is followed by a signed short value. */
jjg@255:         SHORT(3),
jjg@255:         /** Wide opcode is not followed by any operands. */
jjg@255:         WIDE_NO_OPERANDS(2),
jjg@255:         /** Wide opcode is followed by a 2-byte index into the constant pool. */
jjg@255:         WIDE_CPREF_W(4),
jjg@255:         /** Wide opcode is followed by a 2-byte index into the constant pool,
jjg@255:          *  and a signed short value. */
jjg@255:         WIDE_CPREF_W_SHORT(6),
jjg@255:         /** Opcode was not recognized. */
jjg@255:         UNKNOWN(1);
jjg@255: 
jjg@255:         Kind(int length) {
jjg@255:             this.length = length;
jjg@255:         }
jjg@255: 
jjg@255:         /** The length, in bytes, of this kind of instruction, or -1 is the
jjg@255:          *  length depends on the specific instruction. */
jjg@255:         public final int length;
jjg@255:     };
jjg@255: 
jjg@255:     /** A utility visitor to help decode the operands of an instruction.
jjg@255:      *  @see Instruction#accept */
jjg@255:     public interface KindVisitor<R,P> {
jjg@255:         /** See {@link Kind#NO_OPERANDS}, {@link Kind#WIDE_NO_OPERANDS}. */
jjg@255:         R visitNoOperands(Instruction instr, P p);
jjg@255:         /** See {@link Kind#ATYPE}. */
jjg@255:         R visitArrayType(Instruction instr, TypeKind kind, P p);
jjg@255:         /** See {@link Kind#BRANCH}, {@link Kind#BRANCH_W}. */
jjg@255:         R visitBranch(Instruction instr, int offset, P p);
jjg@255:         /** See {@link Kind#CPREF}, {@link Kind#CPREF_W}, {@link Kind#WIDE_CPREF_W}. */
jjg@255:         R visitConstantPoolRef(Instruction instr, int index, P p);
jjg@255:         /** See {@link Kind#CPREF_W_UBYTE}, {@link Kind#CPREF_W_UBYTE_ZERO}, {@link Kind#WIDE_CPREF_W_SHORT}. */
jjg@255:         R visitConstantPoolRefAndValue(Instruction instr, int index, int value, P p);
jjg@255:         /** See {@link Kind#LOCAL}. */
jjg@255:         R visitLocal(Instruction instr, int index, P p);
jjg@255:         /** See {@link Kind#LOCAL_UBYTE}. */
jjg@255:         R visitLocalAndValue(Instruction instr, int index, int value, P p);
jjg@255:         /** See {@link Kind#DYNAMIC}. */
jjg@437:         R visitLookupSwitch(Instruction instr, int default_, int npairs, int[] matches, int[] offsets, P p);
jjg@255:         /** See {@link Kind#DYNAMIC}. */
jjg@437:         R visitTableSwitch(Instruction instr, int default_, int low, int high, int[] offsets, P p);
jjg@255:         /** See {@link Kind#BYTE}, {@link Kind#SHORT}. */
jjg@255:         R visitValue(Instruction instr, int value, P p);
jjg@255:         /** Instruction is unrecognized. */
jjg@255:         R visitUnknown(Instruction instr, P p);
jjg@255: 
jjg@255:     }
jjg@255: 
jjg@255:     /** The kind of primitive array type to create.
jjg@255:      *  See JVMS chapter 6, newarray. */
jjg@255:     public static enum TypeKind {
jjg@255:         T_BOOLEAN(4, "boolean"),
jjg@255:         T_CHAR(5, "char"),
jjg@255:         T_FLOAT(6, "float"),
jjg@255:         T_DOUBLE(7, "double"),
jjg@255:         T_BYTE(8, "byte"),
jjg@255:         T_SHORT(9, "short"),
jjg@255:         T_INT (10, "int"),
jjg@255:         T_LONG (11, "long");
jjg@255:         TypeKind(int value, String name) {
jjg@255:             this.value = value;
jjg@255:             this.name = name;
jjg@255:         }
jjg@255: 
jjg@255:         public static TypeKind get(int value) {
jjg@255:             switch (value) {
jjg@255:                 case  4: return T_BOOLEAN;
jjg@255:                 case  5: return T_CHAR;
jjg@255:                 case  6: return T_FLOAT;
jjg@255:                 case  7: return T_DOUBLE;
jjg@255:                 case  8: return T_BYTE;
jjg@255:                 case  9: return T_SHORT;
jjg@255:                 case  10: return T_INT;
jjg@255:                 case  11: return T_LONG;
jjg@255:                 default: return null;
jjg@255:             }
jjg@255:         }
jjg@255: 
jjg@255:         public final int value;
jjg@255:         public final String name;
jjg@255:     }
jjg@255: 
jjg@255:     /** An instruction is defined by its position in a bytecode array. */
jjg@255:     public Instruction(byte[] bytes, int pc) {
jjg@255:         this.bytes = bytes;
jjg@255:         this.pc = pc;
jjg@255:     }
jjg@255: 
jjg@255:     /** Get the position of the instruction within the bytecode array. */
jjg@255:     public int getPC() {
jjg@255:         return pc;
jjg@255:     }
jjg@255: 
jjg@255:     /** Get a byte value, relative to the start of this instruction. */
jjg@255:     public int getByte(int offset) {
jjg@255:         return bytes[pc + offset];
jjg@255:     }
jjg@255: 
jjg@255:     /** Get an unsigned byte value, relative to the start of this instruction. */
jjg@255:     public int getUnsignedByte(int offset) {
jjg@255:         return getByte(offset) & 0xff;
jjg@255:     }
jjg@255: 
jjg@255:     /** Get a 2-byte value, relative to the start of this instruction. */
jjg@255:     public int getShort(int offset) {
jjg@255:         return (getByte(offset) << 8) | getUnsignedByte(offset + 1);
jjg@255:     }
jjg@255: 
jjg@255:     /** Get a unsigned 2-byte value, relative to the start of this instruction. */
jjg@255:     public int getUnsignedShort(int offset) {
jjg@255:         return getShort(offset) & 0xFFFF;
jjg@255:     }
jjg@255: 
jjg@255:     /** Get a 4-byte value, relative to the start of this instruction. */
jjg@255:     public int getInt(int offset) {
jjg@255:         return (getShort(offset) << 16) | (getUnsignedShort(offset + 2));
jjg@255:     }
jjg@255: 
jjg@255:     /** Get the Opcode for this instruction, or null if the instruction is
jjg@255:      * unrecognized. */
jjg@255:     public Opcode getOpcode() {
jjg@255:         int b = getUnsignedByte(0);
jjg@255:         switch (b) {
jjg@255:             case Opcode.NONPRIV:
jjg@255:             case Opcode.PRIV:
jjg@255:             case Opcode.WIDE:
jjg@255:                 return Opcode.get(b, getUnsignedByte(1));
jjg@255:         }
jjg@255:         return Opcode.get(b);
jjg@255:     }
jjg@255: 
jjg@255:     /** Get the mnemonic for this instruction, or a default string if the
jjg@255:      * instruction is unrecognized. */
jjg@255:     public String getMnemonic() {
jjg@255:         Opcode opcode = getOpcode();
jjg@255:         if (opcode == null)
jjg@255:             return "bytecode " + getUnsignedByte(0);
jjg@255:         else
jjg@255:             return opcode.toString().toLowerCase();
jjg@255:     }
jjg@255: 
jjg@255:     /** Get the length, in bytes, of this instruction, including the opcode
jjg@255:      * and all its operands. */
jjg@255:     public int length() {
jjg@255:         Opcode opcode = getOpcode();
jjg@255:         if (opcode == null)
jjg@255:             return 1;
jjg@255: 
jjg@255:         switch (opcode) {
jjg@255:             case TABLESWITCH: {
jjg@255:                 int pad = align(pc + 1) - pc;
jjg@255:                 int low = getInt(pad + 4);
jjg@255:                 int high = getInt(pad + 8);
jjg@255:                 return pad + 12 + 4 * (high - low + 1);
jjg@255:             }
jjg@255:             case LOOKUPSWITCH: {
jjg@255:                 int pad = align(pc + 1) - pc;
jjg@255:                 int npairs = getInt(pad + 4);
jjg@255:                 return pad + 8 + 8 * npairs;
jjg@255: 
jjg@255:             }
jjg@255:             default:
jjg@255:                 return opcode.kind.length;
jjg@255:         }
jjg@255:     }
jjg@255: 
jjg@255:     /** Get the {@link Kind} of this instruction. */
jjg@255:     public Kind getKind() {
jjg@255:         Opcode opcode = getOpcode();
jjg@255:         return (opcode != null ? opcode.kind : Kind.UNKNOWN);
jjg@255:     }
jjg@255: 
jjg@255:     /** Invoke a method on the visitor according to the kind of this
jjg@255:      * instruction, passing in the decoded operands for the instruction. */
jjg@255:     public <R,P> R accept(KindVisitor<R,P> visitor, P p) {
jjg@255:         switch (getKind()) {
jjg@255:             case NO_OPERANDS:
jjg@255:                 return visitor.visitNoOperands(this, p);
jjg@255: 
jjg@255:             case ATYPE:
jjg@255:                 return visitor.visitArrayType(
jjg@255:                         this, TypeKind.get(getUnsignedByte(1)), p);
jjg@255: 
jjg@255:             case BRANCH:
jjg@255:                 return visitor.visitBranch(this, getShort(1), p);
jjg@255: 
jjg@255:             case BRANCH_W:
jjg@255:                 return visitor.visitBranch(this, getInt(1), p);
jjg@255: 
jjg@255:             case BYTE:
jjg@255:                 return visitor.visitValue(this, getByte(1), p);
jjg@255: 
jjg@255:             case CPREF:
jjg@255:                 return visitor.visitConstantPoolRef(this, getUnsignedByte(1), p);
jjg@255: 
jjg@255:             case CPREF_W:
jjg@255:                 return visitor.visitConstantPoolRef(this, getUnsignedShort(1), p);
jjg@255: 
jjg@255:             case CPREF_W_UBYTE:
jjg@255:             case CPREF_W_UBYTE_ZERO:
jjg@255:                 return visitor.visitConstantPoolRefAndValue(
jjg@255:                         this, getUnsignedShort(1), getUnsignedByte(3), p);
jjg@255: 
jjg@255:             case DYNAMIC: {
jjg@255:                 switch (getOpcode()) {
jjg@255:                     case TABLESWITCH: {
jjg@255:                         int pad = align(pc + 1) - pc;
jjg@255:                         int default_ = getInt(pad);
jjg@255:                         int low = getInt(pad + 4);
jjg@255:                         int high = getInt(pad + 8);
jjg@255:                         int[] values = new int[high - low + 1];
jjg@255:                         for (int i = 0; i < values.length; i++)
jjg@255:                             values[i] = getInt(pad + 12 + 4 * i);
jjg@255:                         return visitor.visitTableSwitch(
jjg@437:                                 this, default_, low, high, values, p);
jjg@255:                     }
jjg@255:                     case LOOKUPSWITCH: {
jjg@255:                         int pad = align(pc + 1) - pc;
jjg@255:                         int default_ = getInt(pad);
jjg@255:                         int npairs = getInt(pad + 4);
jjg@255:                         int[] matches = new int[npairs];
jjg@255:                         int[] offsets = new int[npairs];
jjg@255:                         for (int i = 0; i < npairs; i++) {
jjg@255:                             matches[i] = getInt(pad +  8 + i * 8);
jjg@255:                             offsets[i] = getInt(pad + 12 + i * 8);
jjg@255:                         }
jjg@255:                         return visitor.visitLookupSwitch(
jjg@437:                                 this, default_, npairs, matches, offsets, p);
jjg@255:                     }
jjg@255:                     default:
jjg@255:                         throw new IllegalStateException();
jjg@255:                 }
jjg@255:             }
jjg@255: 
jjg@255:             case LOCAL:
jjg@255:                 return visitor.visitLocal(this, getUnsignedByte(1), p);
jjg@255: 
jjg@255:             case LOCAL_BYTE:
jjg@255:                 return visitor.visitLocalAndValue(
jjg@255:                         this, getUnsignedByte(1), getByte(2), p);
jjg@255: 
jjg@255:             case SHORT:
jjg@255:                 return visitor.visitValue(this, getShort(1), p);
jjg@255: 
jjg@255:             case WIDE_NO_OPERANDS:
jjg@255:                 return visitor.visitNoOperands(this, p);
jjg@255: 
jjg@255:             case WIDE_CPREF_W:
jjg@255:                 return visitor.visitConstantPoolRef(this, getUnsignedShort(2), p);
jjg@255: 
jjg@255:             case WIDE_CPREF_W_SHORT:
jjg@255:                 return visitor.visitConstantPoolRefAndValue(
jjg@255:                         this, getUnsignedShort(2), getUnsignedByte(4), p);
jjg@255: 
jjg@255:             case UNKNOWN:
jjg@255:                 return visitor.visitUnknown(this, p);
jjg@255: 
jjg@255:             default:
jjg@255:                 throw new IllegalStateException();
jjg@255:         }
jjg@255:     }
jjg@255: 
jjg@255:     private static int align(int n) {
jjg@255:         return (n + 3) & ~3;
jjg@255:     }
jjg@255: 
jjg@255:     private byte[] bytes;
jjg@255:     private int pc;
jjg@255: }