1 /*

     2  * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package com.sun.tools.classfile;

    27 

    28 import java.util.Locale;

    29 

    30 /**

    31  * See JVMS, chapter 6.

    32  *

    33  *  <p><b>This is NOT part of any supported API.

    34  *  If you write code that depends on this, you do so at your own risk.

    35  *  This code and its internal interfaces are subject to change or

    36  *  deletion without notice.</b>

    37  *

    38  * @see Code_attribute#getInstructions

    39  */

    40 public class Instruction {

    41     /** The kind of an instruction, as determined by the position, size and

    42      *  types of its operands. */

    43     public static enum Kind {

    44         /** Opcode is not followed by any operands. */

    45         NO_OPERANDS(1),

    46         /** Opcode is followed by a byte indicating a type. */

    47         ATYPE(2),

    48         /** Opcode is followed by a 2-byte branch offset. */

    49         BRANCH(3),

    50         /** Opcode is followed by a 4-byte branch offset. */

    51         BRANCH_W(5),

    52         /** Opcode is followed by a signed byte value. */

    53         BYTE(2),

    54         /** Opcode is followed by a 1-byte index into the constant pool. */

    55         CPREF(2),

    56         /** Opcode is followed by a 2-byte index into the constant pool. */

    57         CPREF_W(3),

    58         /** Opcode is followed by a 2-byte index into the constant pool,

    59          *  an unsigned byte value. */

    60         CPREF_W_UBYTE(4),

    61         /** Opcode is followed by a 2-byte index into the constant pool.,

    62          *  an unsigned byte value, and a zero byte. */

    63         CPREF_W_UBYTE_ZERO(5),

    64         /** Opcode is followed by variable number of operands, depending

    65          * on the instruction.*/

    66         DYNAMIC(-1),

    67         /** Opcode is followed by a 1-byte reference to a local variable. */

    68         LOCAL(2),

    69         /** Opcode is followed by a 1-byte reference to a local variable,

    70          *  and a signed byte value. */

    71         LOCAL_BYTE(3),

    72         /** Opcode is followed by a signed short value. */

    73         SHORT(3),

    74         /** Wide opcode is not followed by any operands. */

    75         WIDE_NO_OPERANDS(2),

    76         /** Wide opcode is followed by a 2-byte index into the local variables array. */

    77         WIDE_LOCAL(4),

    78         /** Wide opcode is followed by a 2-byte index into the constant pool. */

    79         WIDE_CPREF_W(4),

    80         /** Wide opcode is followed by a 2-byte index into the constant pool,

    81          *  and a signed short value. */

    82         WIDE_CPREF_W_SHORT(6),

    83         /** Wide opcode is followed by a 2-byte reference to a local variable,

    84          *  and a signed short value. */

    85         WIDE_LOCAL_SHORT(6),

    86         /** Opcode was not recognized. */

    87         UNKNOWN(1);

    88 

    89         Kind(int length) {

    90             this.length = length;

    91         }

    92 

    93         /** The length, in bytes, of this kind of instruction, or -1 is the

    94          *  length depends on the specific instruction. */

    95         public final int length;

    96     }

    97 

    98     /** A utility visitor to help decode the operands of an instruction.

    99      *  @see Instruction#accept */

   100     public interface KindVisitor<R,P> {

   101         /** See {@link Kind#NO_OPERANDS}, {@link Kind#WIDE_NO_OPERANDS}. */

   102         R visitNoOperands(Instruction instr, P p);

   103         /** See {@link Kind#ATYPE}. */

   104         R visitArrayType(Instruction instr, TypeKind kind, P p);

   105         /** See {@link Kind#BRANCH}, {@link Kind#BRANCH_W}. */

   106         R visitBranch(Instruction instr, int offset, P p);

   107         /** See {@link Kind#CPREF}, {@link Kind#CPREF_W}, {@link Kind#WIDE_CPREF_W}. */

   108         R visitConstantPoolRef(Instruction instr, int index, P p);

   109         /** See {@link Kind#CPREF_W_UBYTE}, {@link Kind#CPREF_W_UBYTE_ZERO}, {@link Kind#WIDE_CPREF_W_SHORT}. */

   110         R visitConstantPoolRefAndValue(Instruction instr, int index, int value, P p);

   111         /** See {@link Kind#LOCAL}, {@link Kind#WIDE_LOCAL}. */

   112         R visitLocal(Instruction instr, int index, P p);

   113         /** See {@link Kind#LOCAL_BYTE}. */

   114         R visitLocalAndValue(Instruction instr, int index, int value, P p);

   115         /** See {@link Kind#DYNAMIC}. */

   116         R visitLookupSwitch(Instruction instr, int default_, int npairs, int[] matches, int[] offsets, P p);

   117         /** See {@link Kind#DYNAMIC}. */

   118         R visitTableSwitch(Instruction instr, int default_, int low, int high, int[] offsets, P p);

   119         /** See {@link Kind#BYTE}, {@link Kind#SHORT}. */

   120         R visitValue(Instruction instr, int value, P p);

   121         /** Instruction is unrecognized. */

   122         R visitUnknown(Instruction instr, P p);

   123 

   124     }

   125 

   126     /** The kind of primitive array type to create.

   127      *  See JVMS chapter 6, newarray. */

   128     public static enum TypeKind {

   129         T_BOOLEAN(4, "boolean"),

   130         T_CHAR(5, "char"),

   131         T_FLOAT(6, "float"),

   132         T_DOUBLE(7, "double"),

   133         T_BYTE(8, "byte"),

   134         T_SHORT(9, "short"),

   135         T_INT (10, "int"),

   136         T_LONG (11, "long");

   137         TypeKind(int value, String name) {

   138             this.value = value;

   139             this.name = name;

   140         }

   141 

   142         public static TypeKind get(int value) {

   143             switch (value) {

   144                 case  4: return T_BOOLEAN;

   145                 case  5: return T_CHAR;

   146                 case  6: return T_FLOAT;

   147                 case  7: return T_DOUBLE;

   148                 case  8: return T_BYTE;

   149                 case  9: return T_SHORT;

   150                 case  10: return T_INT;

   151                 case  11: return T_LONG;

   152                 default: return null;

   153             }

   154         }

   155 

   156         public final int value;

   157         public final String name;

   158     }

   159 

   160     /** An instruction is defined by its position in a bytecode array. */

   161     public Instruction(byte[] bytes, int pc) {

   162         this.bytes = bytes;

   163         this.pc = pc;

   164     }

   165 

   166     /** Get the position of the instruction within the bytecode array. */

   167     public int getPC() {

   168         return pc;

   169     }

   170 

   171     /** Get a byte value, relative to the start of this instruction. */

   172     public int getByte(int offset) {

   173         return bytes[pc + offset];

   174     }

   175 

   176     /** Get an unsigned byte value, relative to the start of this instruction. */

   177     public int getUnsignedByte(int offset) {

   178         return getByte(offset) & 0xff;

   179     }

   180 

   181     /** Get a 2-byte value, relative to the start of this instruction. */

   182     public int getShort(int offset) {

   183         return (getByte(offset) << 8) | getUnsignedByte(offset + 1);

   184     }

   185 

   186     /** Get a unsigned 2-byte value, relative to the start of this instruction. */

   187     public int getUnsignedShort(int offset) {

   188         return getShort(offset) & 0xFFFF;

   189     }

   190 

   191     /** Get a 4-byte value, relative to the start of this instruction. */

   192     public int getInt(int offset) {

   193         return (getShort(offset) << 16) | (getUnsignedShort(offset + 2));

   194     }

   195 

   196     /** Get the Opcode for this instruction, or null if the instruction is

   197      * unrecognized. */

   198     public Opcode getOpcode() {

   199         int b = getUnsignedByte(0);

   200         switch (b) {

   201             case Opcode.NONPRIV:

   202             case Opcode.PRIV:

   203             case Opcode.WIDE:

   204                 return Opcode.get(b, getUnsignedByte(1));

   205         }

   206         return Opcode.get(b);

   207     }

   208 

   209     /** Get the mnemonic for this instruction, or a default string if the

   210      * instruction is unrecognized. */

   211     public String getMnemonic() {

   212         Opcode opcode = getOpcode();

   213         if (opcode == null)

   214             return "bytecode " + getUnsignedByte(0);

   215         else

   216             return opcode.toString().toLowerCase(Locale.US);

   217     }

   218 

   219     /** Get the length, in bytes, of this instruction, including the opcode

   220      * and all its operands. */

   221     public int length() {

   222         Opcode opcode = getOpcode();

   223         if (opcode == null)

   224             return 1;

   225 

   226         switch (opcode) {

   227             case TABLESWITCH: {

   228                 int pad = align(pc + 1) - pc;

   229                 int low = getInt(pad + 4);

   230                 int high = getInt(pad + 8);

   231                 return pad + 12 + 4 * (high - low + 1);

   232             }

   233             case LOOKUPSWITCH: {

   234                 int pad = align(pc + 1) - pc;

   235                 int npairs = getInt(pad + 4);

   236                 return pad + 8 + 8 * npairs;

   237 

   238             }

   239             default:

   240                 return opcode.kind.length;

   241         }

   242     }

   243 

   244     /** Get the {@link Kind} of this instruction. */

   245     public Kind getKind() {

   246         Opcode opcode = getOpcode();

   247         return (opcode != null ? opcode.kind : Kind.UNKNOWN);

   248     }

   249 

   250     /** Invoke a method on the visitor according to the kind of this

   251      * instruction, passing in the decoded operands for the instruction. */

   252     public <R,P> R accept(KindVisitor<R,P> visitor, P p) {

   253         switch (getKind()) {

   254             case NO_OPERANDS:

   255                 return visitor.visitNoOperands(this, p);

   256 

   257             case ATYPE:

   258                 return visitor.visitArrayType(

   259                         this, TypeKind.get(getUnsignedByte(1)), p);

   260 

   261             case BRANCH:

   262                 return visitor.visitBranch(this, getShort(1), p);

   263 

   264             case BRANCH_W:

   265                 return visitor.visitBranch(this, getInt(1), p);

   266 

   267             case BYTE:

   268                 return visitor.visitValue(this, getByte(1), p);

   269 

   270             case CPREF:

   271                 return visitor.visitConstantPoolRef(this, getUnsignedByte(1), p);

   272 

   273             case CPREF_W:

   274                 return visitor.visitConstantPoolRef(this, getUnsignedShort(1), p);

   275 

   276             case CPREF_W_UBYTE:

   277             case CPREF_W_UBYTE_ZERO:

   278                 return visitor.visitConstantPoolRefAndValue(

   279                         this, getUnsignedShort(1), getUnsignedByte(3), p);

   280 

   281             case DYNAMIC: {

   282                 switch (getOpcode()) {

   283                     case TABLESWITCH: {

   284                         int pad = align(pc + 1) - pc;

   285                         int default_ = getInt(pad);

   286                         int low = getInt(pad + 4);

   287                         int high = getInt(pad + 8);

   288                         int[] values = new int[high - low + 1];

   289                         for (int i = 0; i < values.length; i++)

   290                             values[i] = getInt(pad + 12 + 4 * i);

   291                         return visitor.visitTableSwitch(

   292                                 this, default_, low, high, values, p);

   293                     }

   294                     case LOOKUPSWITCH: {

   295                         int pad = align(pc + 1) - pc;

   296                         int default_ = getInt(pad);

   297                         int npairs = getInt(pad + 4);

   298                         int[] matches = new int[npairs];

   299                         int[] offsets = new int[npairs];

   300                         for (int i = 0; i < npairs; i++) {

   301                             matches[i] = getInt(pad +  8 + i * 8);

   302                             offsets[i] = getInt(pad + 12 + i * 8);

   303                         }

   304                         return visitor.visitLookupSwitch(

   305                                 this, default_, npairs, matches, offsets, p);

   306                     }

   307                     default:

   308                         throw new IllegalStateException();

   309                 }

   310             }

   311 

   312             case LOCAL:

   313                 return visitor.visitLocal(this, getUnsignedByte(1), p);

   314 

   315             case LOCAL_BYTE:

   316                 return visitor.visitLocalAndValue(

   317                         this, getUnsignedByte(1), getByte(2), p);

   318 

   319             case SHORT:

   320                 return visitor.visitValue(this, getShort(1), p);

   321 

   322             case WIDE_NO_OPERANDS:

   323                 return visitor.visitNoOperands(this, p);

   324 

   325             case WIDE_LOCAL:

   326                 return visitor.visitLocal(this, getUnsignedShort(2), p);

   327 

   328             case WIDE_CPREF_W:

   329                 return visitor.visitConstantPoolRef(this, getUnsignedShort(2), p);

   330 

   331             case WIDE_CPREF_W_SHORT:

   332                 return visitor.visitConstantPoolRefAndValue(

   333                         this, getUnsignedShort(2), getUnsignedByte(4), p);

   334 

   335             case WIDE_LOCAL_SHORT:

   336                 return visitor.visitLocalAndValue(

   337                         this, getUnsignedShort(2), getShort(4), p);

   338 

   339             case UNKNOWN:

   340                 return visitor.visitUnknown(this, p);

   341 

   342             default:

   343                 throw new IllegalStateException();

   344         }

   345     }

   346 

   347     private static int align(int n) {

   348         return (n + 3) & ~3;

   349     }

   350 

   351     private byte[] bytes;

   352     private int pc;

   353 }