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The source code
/***
* ASM: a very small and fast Java bytecode manipulation framework
* Copyright (C) 2000 INRIA, France Telecom
* Copyright (C) 2002 France Telecom
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Contact: Eric.Bruneton@rd.francetelecom.com
*
* Author: Eric Bruneton
*/
package org.objectweb.asm;
/**
* A {@link CodeVisitor CodeVisitor} that generates Java bytecode instructions.
* Each visit method of this class appends the bytecode corresponding to the
* visited instruction to a byte vector, in the order these methods are called.
*/
public class CodeWriter implements CodeVisitor {
/**
* true if preconditions must be checked at runtime or not.
*/
final static boolean CHECK = false;
/**
* Next code writer (see {@link ClassWriter#firstMethod firstMethod}).
*/
CodeWriter next;
/**
* The class writer to which this method must be added.
*/
private ClassWriter cw;
/**
* The constant pool item that contains the name of this method.
*/
private Item name;
/**
* The constant pool item that contains the descriptor of this method.
*/
private Item desc;
/**
* Access flags of this method.
*/
private int access;
/**
* Maximum stack size of this method.
*/
private int maxStack;
/**
* Maximum number of local variables for this method.
*/
private int maxLocals;
/**
* The bytecode of this method.
*/
private ByteVector code = new ByteVector();
/**
* Number of entries in the catch table of this method.
*/
private int catchCount;
/**
* The catch table of this method.
*/
private ByteVector catchTable;
/**
* Number of exceptions that can be thrown by this method.
*/
private int exceptionCount;
/**
* The exceptions that can be thrown by this method. More
* precisely, this array contains the indexes of the constant pool items
* that contain the internal names of these exception classes.
*/
private int[] exceptions;
/**
* Number of entries in the LocalVariableTable attribute.
*/
private int localVarCount;
/**
* The LocalVariableTable attribute.
*/
private ByteVector localVar;
/**
* Number of entries in the LineNumberTable attribute.
*/
private int lineNumberCount;
/**
* The LineNumberTable attribute.
*/
private ByteVector lineNumber;
/**
* Indicates if some jump instructions are too small and need to be resized.
*/
private boolean resize;
// --------------------------------------------------------------------------
// Fields for the control flow graph analysis algorithm (used to compute the
// maximum stack size). A control flow graph contains one node per "basic
// block", and one edge per "jump" from one basic block to another. Each node
// (i.e., each basic block) is represented by the Label object that
// corresponds to the first instruction of this basic block. Each node also
// stores the list of its successors in the graph, as a linked list of Edge
// objects.
// --------------------------------------------------------------------------
/**
* true if the maximum stack size and number of local variables must
* be automatically computed.
*/
private final boolean computeMaxs;
/**
* The (relative) stack size after the last visited instruction. This size is
* relative to the beginning of the current basic block, i.e., the true stack
* size after the last visited instruction is equal to the {@link
* Label#beginStackSize beginStackSize} of the current basic block plus
* stackSize.
*/
private int stackSize;
/**
* The (relative) maximum stack size after the last visited instruction. This
* size is relative to the beginning of the current basic block, i.e., the
* true maximum stack size after the last visited instruction is equal to the
* {@link Label#beginStackSize beginStackSize} of the current basic block plus
* stackSize.
*/
private int maxStackSize;
/**
* The current basic block. This block is the basic block to which the next
* instruction to be visited must be added.
*/
private Label currentBlock;
/**
* The basic block stack used by the control flow analysis algorithm. This
* stack is represented by a linked list of {@link Label Label} objects,
* linked to each other by their {@link Label#next} field. This stack must
* not be confused with the JVM stack used to execute the JVM instructions!
*/
private Label blockStack;
/**
* The stack size variation corresponding to each JVM instruction. This stack
* variation is equal to the size of the values produced by an instruction,
* minus the size of the values consumed by this instruction.
*/
private final static int[] SIZE;
// --------------------------------------------------------------------------
// Fields to optimize the creation of {@link Edge Edge} objects by using a
// pool of reusable objects. The (shared) pool is a linked list of Edge
// objects, linked to each other by their {@link Edge#poolNext} field. Each
// time a CodeWriter needs to allocate an Edge, it removes the first Edge
// of the pool and adds it to a private list of Edge objects. After the end
// of the control flow analysis algorithm, the Edge objects in the private
// list of the CodeWriter are added back to the pool (by appending this
// private list to the pool list; in order to do this in constant time, both
// head and tail of the private list are stored in this CodeWriter).
// --------------------------------------------------------------------------
/**
* The head of the list of {@link Edge Edge} objects used by this {@link
* CodeWriter CodeWriter}. These objects, linked to each other by their
* {@link Edge#poolNext} field, are added back to the shared pool at the
* end of the control flow analysis algorithm.
*/
private Edge head;
/**
* The tail of the list of {@link Edge Edge} objects used by this {@link
* CodeWriter CodeWriter}. These objects, linked to each other by their
* {@link Edge#poolNext} field, are added back to the shared pool at the
* end of the control flow analysis algorithm.
*/
private Edge tail;
/**
* The shared pool of {@link Edge Edge} objects. This pool is a linked list
* of Edge objects, linked to each other by their {@link Edge#poolNext} field.
*/
private static Edge pool;
// --------------------------------------------------------------------------
// Static initializer
// --------------------------------------------------------------------------
/**
* Computes the stack size variation corresponding to each JVM instruction.
*/
static {
int i;
int[] b = new int[202];
String s =
"EFFFFFFFFGGFFFGGFFFEEFGFGFEEEEEEEEEEEEEEEEEEEEDEDEDDDDDCDCDEEEEEEEEE" +
"EEEEEEEEEEEBABABBBBDCFFFGGGEDCDCDCDCDCDCDCDCDCDCEEEEDDDDDDDCDCDCEFEF" +
"DDEEFFDEDEEEBDDBBDDDDDDCCCCCCCCEFEDDDCDCDEEEEEEEEEEFEEEEEEDDEEDDEE";
for (i = 0; i < b.length; ++i) {
b[i] = s.charAt(i) - 'E';
}
SIZE = b;
/* code to generate the above string
int NA = 0; // not applicable (unused opcode or variable size opcode)
b = new int[] {
0, //NOP, // visitInsn
1, //ACONST_NULL, // -
1, //ICONST_M1, // -
1, //ICONST_0, // -
1, //ICONST_1, // -
1, //ICONST_2, // -
1, //ICONST_3, // -
1, //ICONST_4, // -
1, //ICONST_5, // -
2, //LCONST_0, // -
2, //LCONST_1, // -
1, //FCONST_0, // -
1, //FCONST_1, // -
1, //FCONST_2, // -
2, //DCONST_0, // -
2, //DCONST_1, // -
1, //BIPUSH, // visitIntInsn
1, //SIPUSH, // -
1, //LDC, // visitLdcInsn
NA, //LDC_W, // -
NA, //LDC2_W, // -
1, //ILOAD, // visitVarInsn
2, //LLOAD, // -
1, //FLOAD, // -
2, //DLOAD, // -
1, //ALOAD, // -
NA, //ILOAD_0, // -
NA, //ILOAD_1, // -
NA, //ILOAD_2, // -
NA, //ILOAD_3, // -
NA, //LLOAD_0, // -
NA, //LLOAD_1, // -
NA, //LLOAD_2, // -
NA, //LLOAD_3, // -
NA, //FLOAD_0, // -
NA, //FLOAD_1, // -
NA, //FLOAD_2, // -
NA, //FLOAD_3, // -
NA, //DLOAD_0, // -
NA, //DLOAD_1, // -
NA, //DLOAD_2, // -
NA, //DLOAD_3, // -
NA, //ALOAD_0, // -
NA, //ALOAD_1, // -
NA, //ALOAD_2, // -
NA, //ALOAD_3, // -
-1, //IALOAD, // visitInsn
0, //LALOAD, // -
-1, //FALOAD, // -
0, //DALOAD, // -
-1, //AALOAD, // -
-1, //BALOAD, // -
-1, //CALOAD, // -
-1, //SALOAD, // -
-1, //ISTORE, // visitVarInsn
-2, //LSTORE, // -
-1, //FSTORE, // -
-2, //DSTORE, // -
-1, //ASTORE, // -
NA, //ISTORE_0, // -
NA, //ISTORE_1, // -
NA, //ISTORE_2, // -
NA, //ISTORE_3, // -
NA, //LSTORE_0, // -
NA, //LSTORE_1, // -
NA, //LSTORE_2, // -
NA, //LSTORE_3, // -
NA, //FSTORE_0, // -
NA, //FSTORE_1, // -
NA, //FSTORE_2, // -
NA, //FSTORE_3, // -
NA, //DSTORE_0, // -
NA, //DSTORE_1, // -
NA, //DSTORE_2, // -
NA, //DSTORE_3, // -
NA, //ASTORE_0, // -
NA, //ASTORE_1, // -
NA, //ASTORE_2, // -
NA, //ASTORE_3, // -
-3, //IASTORE, // visitInsn
-4, //LASTORE, // -
-3, //FASTORE, // -
-4, //DASTORE, // -
-3, //AASTORE, // -
-3, //BASTORE, // -
-3, //CASTORE, // -
-3, //SASTORE, // -
-1, //POP, // -
-2, //POP2, // -
1, //DUP, // -
1, //DUP_X1, // -
1, //DUP_X2, // -
2, //DUP2, // -
2, //DUP2_X1, // -
2, //DUP2_X2, // -
0, //SWAP, // -
-1, //IADD, // -
-2, //LADD, // -
-1, //FADD, // -
-2, //DADD, // -
-1, //ISUB, // -
-2, //LSUB, // -
-1, //FSUB, // -
-2, //DSUB, // -
-1, //IMUL, // -
-2, //LMUL, // -
-1, //FMUL, // -
-2, //DMUL, // -
-1, //IDIV, // -
-2, //LDIV, // -
-1, //FDIV, // -
-2, //DDIV, // -
-1, //IREM, // -
-2, //LREM, // -
-1, //FREM, // -
-2, //DREM, // -
0, //INEG, // -
0, //LNEG, // -
0, //FNEG, // -
0, //DNEG, // -
-1, //ISHL, // -
-1, //LSHL, // -
-1, //ISHR, // -
-1, //LSHR, // -
-1, //IUSHR, // -
-1, //LUSHR, // -
-1, //IAND, // -
-2, //LAND, // -
-1, //IOR, // -
-2, //LOR, // -
-1, //IXOR, // -
-2, //LXOR, // -
0, //IINC, // visitIincInsn
1, //I2L, // visitInsn
0, //I2F, // -
1, //I2D, // -
-1, //L2I, // -
-1, //L2F, // -
0, //L2D, // -
0, //F2I, // -
1, //F2L, // -
1, //F2D, // -
-1, //D2I, // -
0, //D2L, // -
-1, //D2F, // -
0, //I2B, // -
0, //I2C, // -
0, //I2S, // -
-3, //LCMP, // -
-1, //FCMPL, // -
-1, //FCMPG, // -
-3, //DCMPL, // -
-3, //DCMPG, // -
-1, //IFEQ, // visitJumpInsn
-1, //IFNE, // -
-1, //IFLT, // -
-1, //IFGE, // -
-1, //IFGT, // -
-1, //IFLE, // -
-2, //IF_ICMPEQ, // -
-2, //IF_ICMPNE, // -
-2, //IF_ICMPLT, // -
-2, //IF_ICMPGE, // -
-2, //IF_ICMPGT, // -
-2, //IF_ICMPLE, // -
-2, //IF_ACMPEQ, // -
-2, //IF_ACMPNE, // -
0, //GOTO, // -
1, //JSR, // -
0, //RET, // visitVarInsn
-1, //TABLESWITCH, // visiTableSwitchInsn
-1, //LOOKUPSWITCH, // visitLookupSwitch
-1, //IRETURN, // visitInsn
-2, //LRETURN, // -
-1, //FRETURN, // -
-2, //DRETURN, // -
-1, //ARETURN, // -
0, //RETURN, // -
NA, //GETSTATIC, // visitFieldInsn
NA, //PUTSTATIC, // -
NA, //GETFIELD, // -
NA, //PUTFIELD, // -
NA, //INVOKEVIRTUAL, // visitMethodInsn
NA, //INVOKESPECIAL, // -
NA, //INVOKESTATIC, // -
NA, //INVOKEINTERFACE, // -
NA, //UNUSED, // NOT VISITED
1, //NEW, // visitTypeInsn
0, //NEWARRAY, // visitIntInsn
0, //ANEWARRAY, // visitTypeInsn
0, //ARRAYLENGTH, // visitInsn
NA, //ATHROW, // -
0, //CHECKCAST, // visitTypeInsn
0, //INSTANCEOF, // -
-1, //MONITORENTER, // visitInsn
-1, //MONITOREXIT, // -
NA, //WIDE, // NOT VISITED
NA, //MULTIANEWARRAY, // visitMultiANewArrayInsn
-1, //IFNULL, // visitJumpInsn
-1, //IFNONNULL, // -
NA, //GOTO_W, // -
NA, //JSR_W, // -
};
for (i = 0; i < b.length; ++i) {
System.err.print((char)('E' + b[i]));
}
System.err.println();
*/
}
// --------------------------------------------------------------------------
// Constructor
// --------------------------------------------------------------------------
/**
* Constructs a CodeWriter.
*
* @param cw the class writer in which the method must be added.
* @param computeMaxs true if the maximum stack size and number of
* local variables must be automatically computed.
*/
protected CodeWriter (final ClassWriter cw, final boolean computeMaxs) {
if (cw.firstMethod == null) {
cw.firstMethod = this;
cw.lastMethod = this;
} else {
cw.lastMethod.next = this;
cw.lastMethod = this;
}
this.cw = cw;
this.computeMaxs = computeMaxs;
if (computeMaxs) {
// pushes the first block onto the stack of blocks to be visited
currentBlock = new Label();
currentBlock.pushed = true;
blockStack = currentBlock;
}
}
/**
* Initializes this CodeWriter to define the bytecode of the specified method.
*
* @param access the method's access flags (see {@link Constants}).
* @param name the method's name.
* @param desc the method's descriptor (see {@link Type Type}).
* @param exceptions the internal names of the method's exceptions. May be
* null.
*/
protected void init (
final int access,
final String name,
final String desc,
final String[] exceptions)
{
this.access = access;
this.name = cw.newUTF8(name);
this.desc = cw.newUTF8(desc);
if (exceptions != null && exceptions.length > 0) {
exceptionCount = exceptions.length;
this.exceptions = new int[exceptionCount];
for (int i = 0; i < exceptionCount; ++i) {
this.exceptions[i] = cw.newClass(exceptions[i]).index;
}
}
if (computeMaxs) {
// updates maxLocals
int size = getArgumentsAndReturnSizes(desc) >> 2;
if ((access & Constants.ACC_STATIC) != 0) {
--size;
}
if (size > maxLocals) {
maxLocals = size;
}
}
}
// --------------------------------------------------------------------------
// Implementation of the CodeVisitor interface
// --------------------------------------------------------------------------
public void visitInsn (final int opcode) {
if (computeMaxs) {
// updates current and max stack sizes
int size = stackSize + SIZE[opcode];
if (size > maxStackSize) {
maxStackSize = size;
}
stackSize = size;
// if opcode == ATHROW or xRETURN, ends current block (no successor)
if ((opcode >= Constants.IRETURN && opcode <= Constants.RETURN) ||
opcode == Constants.ATHROW)
{
if (currentBlock != null) {
currentBlock.maxStackSize = maxStackSize;
currentBlock = null;
}
}
}
// adds the instruction to the bytecode of the method
code.put1(opcode);
}
public void visitIntInsn (final int opcode, final int operand) {
if (computeMaxs && opcode != Constants.NEWARRAY) {
// updates current and max stack sizes only if opcode == NEWARRAY
// (stack size variation = 0 for BIPUSH or SIPUSH)
int size = stackSize + 1;
if (size > maxStackSize) {
maxStackSize = size;
}
stackSize = size;
}
// adds the instruction to the bytecode of the method
if (opcode == Constants.SIPUSH) {
code.put12(opcode, operand);
} else { // BIPUSH or NEWARRAY
code.put11(opcode, operand);
}
}
public void visitVarInsn (final int opcode, final int var) {
if (computeMaxs) {
// updates current and max stack sizes
if (opcode == Constants.RET) {
// no stack change, but end of current block (no successor)
if (currentBlock != null) {
currentBlock.maxStackSize = maxStackSize;
currentBlock = null;
}
} else { // xLOAD or xSTORE
int size = stackSize + SIZE[opcode];
if (size > maxStackSize) {
maxStackSize = size;
}
stackSize = size;
}
// updates max locals
int n;
if (opcode == Constants.LLOAD || opcode == Constants.DLOAD ||
opcode == Constants.LSTORE || opcode == Constants.DSTORE)
{
n = var + 2;
} else {
n = var + 1;
}
if (n > maxLocals) {
maxLocals = n;
}
}
// adds the instruction to the bytecode of the method
if (var < 4 && opcode != Constants.RET) {
int opt;
if (opcode < Constants.ISTORE) {
opt = 26 /*ILOAD_0*/ + ((opcode - Constants.ILOAD) << 2) + var;
} else {
opt = 59 /*ISTORE_0*/ + ((opcode - Constants.ISTORE) << 2) + var;
}
code.put1(opt);
} else if (var >= 256) {
code.put1(196 /*WIDE*/).put12(opcode, var);
} else {
code.put11(opcode, var);
}
}
public void visitTypeInsn (final int opcode, final String desc) {
if (computeMaxs && opcode == Constants.NEW) {
// updates current and max stack sizes only if opcode == NEW
// (stack size variation = 0 for ANEWARRAY, CHECKCAST, INSTANCEOF)
int size = stackSize + 1;
if (size > maxStackSize) {
maxStackSize = size;
}
stackSize = size;
}
// adds the instruction to the bytecode of the method
code.put12(opcode, cw.newClass(desc).index);
}
public void visitFieldInsn (
final int opcode,
final String owner,
final String name,
final String desc)
{
if (computeMaxs) {
int size;
// computes the stack size variation
char c = desc.charAt(0);
switch (opcode) {
case Constants.GETSTATIC:
size = stackSize + (c == 'D' || c == 'J' ? 2 : 1);
break;
case Constants.PUTSTATIC:
size = stackSize + (c == 'D' || c == 'J' ? -2 : -1);
break;
case Constants.GETFIELD:
size = stackSize + (c == 'D' || c == 'J' ? 1 : 0);
break;
//case Constants.PUTFIELD:
default:
size = stackSize + (c == 'D' || c == 'J' ? -3 : -2);
break;
}
// updates current and max stack sizes
if (size > maxStackSize) {
maxStackSize = size;
}
stackSize = size;
}
// adds the instruction to the bytecode of the method
code.put12(opcode, cw.newField(owner, name, desc).index);
}
public void visitMethodInsn (
final int opcode,
final String owner,
final String name,
final String desc)
{
Item i;
if (opcode == Constants.INVOKEINTERFACE) {
i = cw.newItfMethod(owner, name, desc);
} else {
i = cw.newMethod(owner, name, desc);
}
int argSize = i.intVal;
if (computeMaxs) {
// computes the stack size variation. In order not to recompute several
// times this variation for the same Item, we use the intVal field of
// this item to store this variation, once it has been computed. More
// precisely this intVal field stores the sizes of the arguments and of
// the return value corresponding to desc.
if (argSize == 0) {
// the above sizes have not been computed yet, so we compute them...
argSize = getArgumentsAndReturnSizes(desc);
// ... and we save them in order not to recompute them in the future
i.intVal = argSize;
}
int size;
if (opcode == Constants.INVOKESTATIC) {
size = stackSize - (argSize >> 2) + (argSize & 0x03) + 1;
} else {
size = stackSize - (argSize >> 2) + (argSize & 0x03);
}
// updates current and max stack sizes
if (size > maxStackSize) {
maxStackSize = size;
}
stackSize = size;
}
// adds the instruction to the bytecode of the method
if (opcode == Constants.INVOKEINTERFACE) {
if (!computeMaxs) {
if (argSize == 0) {
argSize = getArgumentsAndReturnSizes(desc);
i.intVal = argSize;
}
}
code.put12(Constants.INVOKEINTERFACE, i.index).put11(argSize >> 2, 0);
} else {
code.put12(opcode, i.index);
}
}
public void visitJumpInsn (final int opcode, final Label label) {
if (CHECK) {
if (label.owner == null) {
label.owner = this;
} else if (label.owner != this) {
throw new IllegalArgumentException();
}
}
if (computeMaxs) {
if (opcode == Constants.GOTO) {
// no stack change, but end of current block (with one new successor)
if (currentBlock != null) {
currentBlock.maxStackSize = maxStackSize;
addSuccessor(stackSize, label);
currentBlock = null;
}
} else if (opcode == Constants.JSR) {
if (currentBlock != null) {
addSuccessor(stackSize + 1, label);
}
} else {
// updates current stack size (max stack size unchanged because stack
// size variation always negative in this case)
stackSize += SIZE[opcode];
if (currentBlock != null) {
addSuccessor(stackSize, label);
}
}
}
// adds the instruction to the bytecode of the method
if (label.resolved && label.position - code.length < Short.MIN_VALUE) {
// case of a backward jump with an offset < -32768. In this case we
// automatically replace GOTO with GOTO_W, JSR with JSR_W and IFxxx
// with IFNOTxxx GOTO_W , where IFNOTxxx is the "opposite" opcode
// of IFxxx (i.e., IFNE for IFEQ) and where designates the
// instruction just after the GOTO_W.
if (opcode == Constants.GOTO) {
code.put1(200); // GOTO_W
} else if (opcode == Constants.JSR) {
code.put1(201); // JSR_W
} else {
code.put1(opcode <= 166 ? ((opcode + 1) ^ 1) - 1 : opcode ^ 1);
code.put2(8); // jump offset
code.put1(200); // GOTO_W
}
label.put(this, code, code.length - 1, true);
} else {
// case of a backward jump with an offset >= -32768, or of a forward jump
// with, of course, an unknown offset. In these cases we store the offset
// in 2 bytes (which will be increased in resizeInstructions, if needed).
code.put1(opcode);
label.put(this, code, code.length - 1, false);
}
}
public void visitLabel (final Label label) {
if (CHECK) {
if (label.owner == null) {
label.owner = this;
} else if (label.owner != this) {
throw new IllegalArgumentException();
}
}
if (computeMaxs) {
if (currentBlock != null) {
// ends current block (with one new successor)
currentBlock.maxStackSize = maxStackSize;
addSuccessor(stackSize, label);
}
// begins a new current block,
// resets the relative current and max stack sizes
currentBlock = label;
stackSize = 0;
maxStackSize = 0;
}
// resolves previous forward references to label, if any
resize |= label.resolve(this, code.length, code.data);
}
public void visitLdcInsn (final Object cst) {
Item i = cw.newCst(cst);
if (computeMaxs) {
int size;
// computes the stack size variation
if (i.type == ClassWriter.LONG || i.type == ClassWriter.DOUBLE) {
size = stackSize + 2;
} else {
size = stackSize + 1;
}
// updates current and max stack sizes
if (size > maxStackSize) {
maxStackSize = size;
}
stackSize = size;
}
// adds the instruction to the bytecode of the method
int index = i.index;
if (i.type == ClassWriter.LONG || i.type == ClassWriter.DOUBLE) {
code.put12(20 /*LDC2_W*/, index);
} else if (index >= 256) {
code.put12(19 /*LDC_W*/, index);
} else {
code.put11(Constants.LDC, index);
}
}
public void visitIincInsn (final int var, final int increment) {
if (computeMaxs) {
// updates max locals only (no stack change)
int n = var + 1;
if (n > maxLocals) {
maxLocals = n;
}
}
// adds the instruction to the bytecode of the method
if ((var > 255) || (increment > 127) || (increment < -128)) {
code.put1(196 /*WIDE*/).put12(Constants.IINC, var).put2(increment);
} else {
code.put1(Constants.IINC).put11(var, increment);
}
}
public void visitTableSwitchInsn (
final int min,
final int max,
final Label dflt,
final Label labels[])
{
if (computeMaxs) {
// updates current stack size (max stack size unchanged)
--stackSize;
// ends current block (with many new successors)
if (currentBlock != null) {
currentBlock.maxStackSize = maxStackSize;
addSuccessor(stackSize, dflt);
for (int i = 0; i < labels.length; ++i) {
addSuccessor(stackSize, labels[i]);
}
currentBlock = null;
}
}
// adds the instruction to the bytecode of the method
int source = code.length;
code.put1(Constants.TABLESWITCH);
while (code.length % 4 != 0) {
code.put1(0);
}
dflt.put(this, code, source, true);
code.put4(min).put4(max);
for (int i = 0; i < labels.length; ++i) {
labels[i].put(this, code, source, true);
}
}
public void visitLookupSwitchInsn (
final Label dflt,
final int keys[],
final Label labels[])
{
if (computeMaxs) {
// updates current stack size (max stack size unchanged)
--stackSize;
// ends current block (with many new successors)
if (currentBlock != null) {
currentBlock.maxStackSize = maxStackSize;
addSuccessor(stackSize, dflt);
for (int i = 0; i < labels.length; ++i) {
addSuccessor(stackSize, labels[i]);
}
currentBlock = null;
}
}
// adds the instruction to the bytecode of the method
int source = code.length;
code.put1(Constants.LOOKUPSWITCH);
while (code.length % 4 != 0) {
code.put1(0);
}
dflt.put(this, code, source, true);
code.put4(labels.length);
for (int i = 0; i < labels.length; ++i) {
code.put4(keys[i]);
labels[i].put(this, code, source, true);
}
}
public void visitMultiANewArrayInsn (final String desc, final int dims) {
if (computeMaxs) {
// updates current stack size (max stack size unchanged because stack
// size variation always negative or null)
stackSize += 1 - dims;
}
// adds the instruction to the bytecode of the method
Item classItem = cw.newClass(desc);
code.put12(Constants.MULTIANEWARRAY, classItem.index).put1(dims);
}
public void visitTryCatchBlock (
final Label start,
final Label end,
final Label handler,
final String type)
{
if (CHECK) {
if (start.owner != this || end.owner != this || handler.owner != this) {
throw new IllegalArgumentException();
}
if (!start.resolved || !end.resolved || !handler.resolved) {
throw new IllegalArgumentException();
}
}
if (computeMaxs) {
// pushes handler block onto the stack of blocks to be visited
if (!handler.pushed) {
handler.beginStackSize = 1;
handler.pushed = true;
handler.next = blockStack;
blockStack = handler;
}
}
++catchCount;
if (catchTable == null) {
catchTable = new ByteVector();
}
catchTable.put2(start.position);
catchTable.put2(end.position);
catchTable.put2(handler.position);
catchTable.put2(type != null ? cw.newClass(type).index : 0);
}
public void visitMaxs (final int maxStack, final int maxLocals) {
if (computeMaxs) {
// true (non relative) max stack size
int max = 0;
// control flow analysis algorithm: while the block stack is not empty,
// pop a block from this stack, update the max stack size, compute
// the true (non relative) begin stack size of the successors of this
// block, and push these successors onto the stack (unless they have
// already been pushed onto the stack). Note: by hypothesis, the {@link
// Label#beginStackSize} of the blocks in the block stack are the true
// (non relative) beginning stack sizes of these blocks.
Label stack = blockStack;
while (stack != null) {
// pops a block from the stack
Label l = stack;
stack = stack.next;
// computes the true (non relative) max stack size of this block
int start = l.beginStackSize;
int blockMax = start + l.maxStackSize;
// updates the global max stack size
if (blockMax > max) {
max = blockMax;
}
// analyses the successors of the block
Edge b = l.successors;
while (b != null) {
l = b.successor;
// if this successor has not already been pushed onto the stack...
if (!l.pushed) {
// computes the true beginning stack size of this successor block
l.beginStackSize = start + b.stackSize;
// pushes this successor onto the stack
l.pushed = true;
l.next = stack;
stack = l;
}
b = b.next;
}
}
this.maxStack = max;
// releases all the Edge objects used by this CodeWriter
synchronized (SIZE) {
// appends the [head ... tail] list at the beginning of the pool list
if (tail != null) {
tail.poolNext = pool;
pool = head;
}
}
} else {
this.maxStack = maxStack;
this.maxLocals = maxLocals;
}
}
public void visitLocalVariable (
final String name,
final String desc,
final Label start,
final Label end,
final int index)
{
if (CHECK) {
if (start.owner != this || !start.resolved) {
throw new IllegalArgumentException();
}
if (end.owner != this || !end.resolved) {
throw new IllegalArgumentException();
}
}
if (localVar == null) {
cw.newUTF8("LocalVariableTable");
localVar = new ByteVector();
}
++localVarCount;
localVar.put2(start.position);
localVar.put2(end.position - start.position);
localVar.put2(cw.newUTF8(name).index);
localVar.put2(cw.newUTF8(desc).index);
localVar.put2(index);
}
public void visitLineNumber (final int line, final Label start) {
if (CHECK) {
if (start.owner != this || !start.resolved) {
throw new IllegalArgumentException();
}
}
if (lineNumber == null) {
cw.newUTF8("LineNumberTable");
lineNumber = new ByteVector();
}
++lineNumberCount;
lineNumber.put2(start.position);
lineNumber.put2(line);
}
// --------------------------------------------------------------------------
// Utility methods: control flow analysis algorithm
// --------------------------------------------------------------------------
/**
* Computes the size of the arguments and of the return value of a method.
*
* @param desc the descriptor of a method.
* @return the size of the arguments of the method (plus one for the implicit
* this argument), argSize, and the size of its return value, retSize,
* packed into a single int i = (argSize << 2) | retSize
* (argSize is therefore equal to i >> 2, and retSize to
* i & 0x03).
*/
private static int getArgumentsAndReturnSizes (final String desc) {
int n = 1;
int c = 1;
while (true) {
char car = desc.charAt(c++);
if (car == ')') {
car = desc.charAt(c);
return n << 2 | (car == 'V' ? 0 : (car == 'D' || car == 'J' ? 2 : 1));
} else if (car == 'L') {
while (desc.charAt(c++) != ';') {
}
n += 1;
} else if (car == '[') {
while ((car = desc.charAt(c)) == '[') {
++c;
}
if (car == 'D' || car == 'J') {
n -= 1;
}
} else if (car == 'D' || car == 'J') {
n += 2;
} else {
n += 1;
}
}
}
/**
* Adds a successor to the {@link #currentBlock currentBlock} block.
*
* @param stackSize the current (relative) stack size in the current block.
* @param successor the successor block to be added to the current block.
*/
private void addSuccessor (final int stackSize, final Label successor) {
Edge b;
// creates a new Edge object or reuses one from the shared pool
synchronized (SIZE) {
if (pool == null) {
b = new Edge();
} else {
b = pool;
// removes b from the pool
pool = pool.poolNext;
}
}
// adds the previous Edge to the list of Edges used by this CodeWriter
if (tail == null) {
tail = b;
}
b.poolNext = head;
head = b;
// initializes the previous Edge object...
b.stackSize = stackSize;
b.successor = successor;
// ...and adds it to the successor list of the currentBlock block
b.next = currentBlock.successors;
currentBlock.successors = b;
}
// --------------------------------------------------------------------------
// Utility methods: dump bytecode array
// --------------------------------------------------------------------------
/**
* Returns the size of the bytecode of this method.
*
* @return the size of the bytecode of this method.
*/
final int getSize () {
if (resize) {
// replaces the temporary jump opcodes introduced by Label.resolve.
resizeInstructions(new int[0], new int[0], 0);
}
int size = 8;
if (code.length > 0) {
cw.newUTF8("Code");
size += 18 + code.length + 8 * catchCount;
if (localVar != null) {
size += 8 + localVar.length;
}
if (lineNumber != null) {
size += 8 + lineNumber.length;
}
}
if (exceptionCount > 0) {
cw.newUTF8("Exceptions");
size += 8 + 2 * exceptionCount;
}
if ((access & Constants.ACC_SYNTHETIC) != 0) {
cw.newUTF8("Synthetic");
size += 6;
}
if ((access & Constants.ACC_DEPRECATED) != 0) {
cw.newUTF8("Deprecated");
size += 6;
}
return size;
}
/**
* Puts the bytecode of this method in the given byte vector.
*
* @param out the byte vector into which the bytecode of this method must be
* copied.
*/
final void put (final ByteVector out) {
out.put2(access).put2(name.index).put2(desc.index);
int attributeCount = 0;
if (code.length > 0) {
++attributeCount;
}
if (exceptionCount > 0) {
++attributeCount;
}
if ((access & Constants.ACC_SYNTHETIC) != 0) {
++attributeCount;
}
if ((access & Constants.ACC_DEPRECATED) != 0) {
++attributeCount;
}
out.put2(attributeCount);
if (code.length > 0) {
int size = 12 + code.length + 8 * catchCount;
if (localVar != null) {
size += 8 + localVar.length;
}
if (lineNumber != null) {
size += 8 + lineNumber.length;
}
out.put2(cw.newUTF8("Code").index).put4(size);
out.put2(maxStack).put2(maxLocals);
out.put4(code.length).putByteArray(code.data, 0, code.length);
out.put2(catchCount);
if (catchCount > 0) {
out.putByteArray(catchTable.data, 0, catchTable.length);
}
attributeCount = 0;
if (localVar != null) {
++attributeCount;
}
if (lineNumber != null) {
++attributeCount;
}
out.put2(attributeCount);
if (localVar != null) {
out.put2(cw.newUTF8("LocalVariableTable").index);
out.put4(localVar.length + 2).put2(localVarCount);
out.putByteArray(localVar.data, 0, localVar.length);
}
if (lineNumber != null) {
out.put2(cw.newUTF8("LineNumberTable").index);
out.put4(lineNumber.length + 2).put2(lineNumberCount);
out.putByteArray(lineNumber.data, 0, lineNumber.length);
}
}
if (exceptionCount > 0) {
out.put2(cw.newUTF8("Exceptions").index).put4(2 * exceptionCount + 2);
out.put2(exceptionCount);
for (int i = 0; i < exceptionCount; ++i) {
out.put2(exceptions[i]);
}
}
if ((access & Constants.ACC_SYNTHETIC) != 0) {
out.put2(cw.newUTF8("Synthetic").index).put4(0);
}
if ((access & Constants.ACC_DEPRECATED) != 0) {
out.put2(cw.newUTF8("Deprecated").index).put4(0);
}
}
// --------------------------------------------------------------------------
// Utility methods: instruction resizing (used to handle GOTO_W and JSR_W)
// --------------------------------------------------------------------------
/**
* Resizes the designated instructions, while keeping jump offsets and
* instruction addresses consistent. This may require to resize other existing
* instructions, or even to introduce new instructions: for example,
* increasing the size of an instruction by 2 at the middle of a method can
* increases the offset of an IFEQ instruction from 32766 to 32768, in which
* case IFEQ 32766 must be replaced with IFNEQ 8 GOTO_W 32765. This, in turn,
* may require to increase the size of another jump instruction, and so on...
* All these operations are handled automatically by this method.
*
* This method must be called after all the method that is being built has
* been visited. In particular, the {@link Label Label} objects used to
* construct the method are no longer valid after this method has been called.
*
* @param indexes current positions of the instructions to be resized. Each
* instruction must be designated by the index of its last byte,
* plus one (or, in other words, by the index of the first byte of
* the next instruction).
* @param sizes the number of bytes to be added to the above
* instructions. More precisely, for each i < len,
* sizes[i] bytes will be added at the end of the instruction
* designated by indexes[i] or, if sizes[i] is
* negative, the last |sizes[i]| bytes of the instruction
* will be removed (the instruction size must not become negative
* or null). The gaps introduced by this method must be filled in
* "manually" in the array returned by the {@link #getCode getCode}
* method.
* @param len the number of instruction to be resized. Must be smaller than or
* equal to indexes.length and sizes.length.
* @return the indexes array, which now contains the new positions of
* the resized instructions (designated as above).
*/
protected int[] resizeInstructions (
final int[] indexes,
final int[] sizes,
final int len)
{
byte[] b = code.data; // bytecode of the method
int u, v, label; // indexes in b
int i, j; // loop indexes
// 1st step:
// As explained above, resizing an instruction may require to resize another
// one, which may require to resize yet another one, and so on. The first
// step of the algorithm consists in finding all the instructions that
// need to be resized, without modifying the code. This is done by the
// following "fix point" algorithm:
// - parse the code to find the jump instructions whose offset will need
// more than 2 bytes to be stored (the future offset is computed from the
// current offset and from the number of bytes that will be inserted or
// removed between the source and target instructions). For each such
// instruction, adds an entry in (a copy of) the indexes and sizes arrays
// (if this has not already been done in a previous iteration!)
// - if at least one entry has been added during the previous step, go back
// to the beginning, otherwise stop.
// In fact the real algorithm is complicated by the fact that the size of
// TABLESWITCH and LOOKUPSWITCH instructions depends on their position in
// the bytecode (because of padding). In order to ensure the convergence of
// the algorithm, the number of bytes to be added or removed from these
// instructions is over estimated during the previous loop, and computed
// exactly only after the loop is finished (this requires another pass to
// parse the bytecode of the method).
int[] allIndexes = new int[len]; // copy of indexes
int[] allSizes = new int[len]; // copy of sizes
boolean[] resize; // instructions to be resized
int newOffset; // future offset of a jump instruction
System.arraycopy(indexes, 0, allIndexes, 0, len);
System.arraycopy(sizes, 0, allSizes, 0, len);
resize = new boolean[code.length];
int state = 3; // 3 = loop again, 2 = loop ended, 1 = last pass, 0 = done
do {
if (state == 3) {
state = 2;
}
u = 0;
while (u < b.length) {
int opcode = b[u] & 0xFF; // opcode of current instruction
int insert = 0; // bytes to be added after this instruction
switch (ClassWriter.TYPE[opcode]) {
case ClassWriter.NOARG_INSN:
case ClassWriter.IMPLVAR_INSN:
u += 1;
break;
case ClassWriter.LABEL_INSN:
if (opcode > 201) {
// converts temporary opcodes 202 to 217 (inclusive), 218 and 219
// to IFEQ ... JSR (inclusive), IFNULL and IFNONNULL
opcode = opcode < 218 ? opcode - 49 : opcode - 20;
label = u + readUnsignedShort(b, u + 1);
} else {
label = u + readShort(b, u + 1);
}
newOffset = getNewOffset(allIndexes, allSizes, u, label);
if (newOffset < Short.MIN_VALUE || newOffset > Short.MAX_VALUE) {
if (!resize[u]) {
if (opcode == Constants.GOTO || opcode == Constants.JSR) {
// two additional bytes will be required to replace this
// GOTO or JSR instruction with a GOTO_W or a JSR_W
insert = 2;
} else {
// five additional bytes will be required to replace this
// IFxxx instruction with IFNOTxxx GOTO_W , where
// IFNOTxxx is the "opposite" opcode of IFxxx (i.e., IFNE for
// IFEQ) and where designates the instruction just after
// the GOTO_W.
insert = 5;
}
resize[u] = true;
}
}
u += 3;
break;
case ClassWriter.LABELW_INSN:
u += 5;
break;
case ClassWriter.TABL_INSN:
if (state == 1) {
// true number of bytes to be added (or removed) from this
// instruction = (future number of padding bytes - current number
// of padding byte) - previously over estimated variation =
// = ((3 - newOffset%4) - (3 - u%4)) - u%4
// = (-newOffset%4 + u%4) - u%4
// = -(newOffset & 3)
newOffset = getNewOffset(allIndexes, allSizes, 0, u);
insert = -(newOffset & 3);
} else if (!resize[u]) {
// over estimation of the number of bytes to be added to this
// instruction = 3 - current number of padding bytes = 3 - (3 -
// u%4) = u%4 = u & 3
insert = u & 3;
resize[u] = true;
}
// skips instruction
u = u + 4 - (u & 3);
u += 4*(readInt(b, u + 8) - readInt(b, u + 4) + 1) + 12;
break;
case ClassWriter.LOOK_INSN:
if (state == 1) {
// like TABL_INSN
newOffset = getNewOffset(allIndexes, allSizes, 0, u);
insert = -(newOffset & 3);
} else if (!resize[u]) {
// like TABL_INSN
insert = u & 3;
resize[u] = true;
}
// skips instruction
u = u + 4 - (u & 3);
u += 8*readInt(b, u + 4) + 8;
break;
case ClassWriter.WIDE_INSN:
opcode = b[u + 1] & 0xFF;
if (opcode == Constants.IINC) {
u += 6;
} else {
u += 4;
}
break;
case ClassWriter.VAR_INSN:
case ClassWriter.SBYTE_INSN:
case ClassWriter.LDC_INSN:
u += 2;
break;
case ClassWriter.SHORT_INSN:
case ClassWriter.LDCW_INSN:
case ClassWriter.FIELDORMETH_INSN:
case ClassWriter.TYPE_INSN:
case ClassWriter.IINC_INSN:
u += 3;
break;
case ClassWriter.ITFMETH_INSN:
u += 5;
break;
// case ClassWriter.MANA_INSN:
default:
u += 4;
break;
}
if (insert != 0) {
// adds a new (u, insert) entry in the allIndexes and allSizes arrays
int[] newIndexes = new int[allIndexes.length + 1];
int[] newSizes = new int[allSizes.length + 1];
System.arraycopy(allIndexes, 0, newIndexes, 0, allIndexes.length);
System.arraycopy(allSizes, 0, newSizes, 0, allSizes.length);
newIndexes[allIndexes.length] = u;
newSizes[allSizes.length] = insert;
allIndexes = newIndexes;
allSizes = newSizes;
if (insert > 0) {
state = 3;
}
}
}
if (state < 3) {
--state;
}
} while (state != 0);
// 2nd step:
// copies the bytecode of the method into a new bytevector, updates the
// offsets, and inserts (or removes) bytes as requested.
ByteVector newCode = new ByteVector(code.length);
u = 0;
while (u < code.length) {
for (i = allIndexes.length - 1; i >= 0; --i) {
if (allIndexes[i] == u) {
if (i < len) {
if (sizes[i] > 0) {
newCode.putByteArray(null, 0, sizes[i]);
} else {
newCode.length += sizes[i];
}
indexes[i] = newCode.length;
}
}
}
int opcode = b[u] & 0xFF;
switch (ClassWriter.TYPE[opcode]) {
case ClassWriter.NOARG_INSN:
case ClassWriter.IMPLVAR_INSN:
newCode.put1(opcode);
u += 1;
break;
case ClassWriter.LABEL_INSN:
if (opcode > 201) {
// changes temporary opcodes 202 to 217 (inclusive), 218 and 219
// to IFEQ ... JSR (inclusive), IFNULL and IFNONNULL
opcode = opcode < 218 ? opcode - 49 : opcode - 20;
label = u + readUnsignedShort(b, u + 1);
} else {
label = u + readShort(b, u + 1);
}
newOffset = getNewOffset(allIndexes, allSizes, u, label);
if (newOffset < Short.MIN_VALUE || newOffset > Short.MAX_VALUE) {
// replaces GOTO with GOTO_W, JSR with JSR_W and IFxxx with
// IFNOTxxx GOTO_W , where IFNOTxxx is the "opposite" opcode
// of IFxxx (i.e., IFNE for IFEQ) and where designates the
// instruction just after the GOTO_W.
if (opcode == Constants.GOTO) {
newCode.put1(200); // GOTO_W
} else if (opcode == Constants.JSR) {
newCode.put1(201); // JSR_W
} else {
newCode.put1(opcode <= 166 ? ((opcode + 1) ^ 1) - 1 : opcode ^ 1);
newCode.put2(8); // jump offset
newCode.put1(200); // GOTO_W
newOffset -= 3; // newOffset now computed from start of GOTO_W
}
newCode.put4(newOffset);
} else {
newCode.put1(opcode);
newCode.put2(newOffset);
}
u += 3;
break;
case ClassWriter.LABELW_INSN:
label = u + readInt(b, u + 1);
newOffset = getNewOffset(allIndexes, allSizes, u, label);
newCode.put1(opcode);
newCode.put4(newOffset);
u += 5;
break;
case ClassWriter.TABL_INSN:
// skips 0 to 3 padding bytes
v = u;
u = u + 4 - (v & 3);
// reads and copies instruction
int source = newCode.length;
newCode.put1(Constants.TABLESWITCH);
while (newCode.length % 4 != 0) {
newCode.put1(0);
}
label = v + readInt(b, u); u += 4;
newOffset = getNewOffset(allIndexes, allSizes, v, label);
newCode.put4(newOffset);
j = readInt(b, u); u += 4;
newCode.put4(j);
j = readInt(b, u) - j + 1; u += 4;
newCode.put4(readInt(b, u - 4));
for ( ; j > 0; --j) {
label = v + readInt(b, u); u += 4;
newOffset = getNewOffset(allIndexes, allSizes, v, label);
newCode.put4(newOffset);
}
break;
case ClassWriter.LOOK_INSN:
// skips 0 to 3 padding bytes
v = u;
u = u + 4 - (v & 3);
// reads and copies instruction
source = newCode.length;
newCode.put1(Constants.LOOKUPSWITCH);
while (newCode.length % 4 != 0) {
newCode.put1(0);
}
label = v + readInt(b, u); u += 4;
newOffset = getNewOffset(allIndexes, allSizes, v, label);
newCode.put4(newOffset);
j = readInt(b, u); u += 4;
newCode.put4(j);
for ( ; j > 0; --j) {
newCode.put4(readInt(b, u)); u += 4;
label = v + readInt(b, u); u += 4;
newOffset = getNewOffset(allIndexes, allSizes, v, label);
newCode.put4(newOffset);
}
break;
case ClassWriter.WIDE_INSN:
opcode = b[u + 1] & 0xFF;
if (opcode == Constants.IINC) {
newCode.putByteArray(b, u, 6);
u += 6;
} else {
newCode.putByteArray(b, u, 4);
u += 4;
}
break;
case ClassWriter.VAR_INSN:
case ClassWriter.SBYTE_INSN:
case ClassWriter.LDC_INSN:
newCode.putByteArray(b, u, 2);
u += 2;
break;
case ClassWriter.SHORT_INSN:
case ClassWriter.LDCW_INSN:
case ClassWriter.FIELDORMETH_INSN:
case ClassWriter.TYPE_INSN:
case ClassWriter.IINC_INSN:
newCode.putByteArray(b, u, 3);
u += 3;
break;
case ClassWriter.ITFMETH_INSN:
newCode.putByteArray(b, u, 5);
u += 5;
break;
// case MANA_INSN:
default:
newCode.putByteArray(b, u, 4);
u += 4;
break;
}
}
// updates the instructions addresses in the
// catch, local var and line number tables
if (catchTable != null) {
b = catchTable.data;
u = 0;
while (u < catchTable.length) {
writeShort(b, u, getNewOffset(
allIndexes, allSizes, 0, readUnsignedShort(b, u)));
writeShort(b, u + 2, getNewOffset(
allIndexes, allSizes, 0, readUnsignedShort(b, u + 2)));
writeShort(b, u + 4, getNewOffset(
allIndexes, allSizes, 0, readUnsignedShort(b, u + 4)));
u += 8;
}
}
if (localVar != null) {
b = localVar.data;
u = 0;
while (u < localVar.length) {
label = readUnsignedShort(b, u);
newOffset = getNewOffset(allIndexes, allSizes, 0, label);
writeShort(b, u, newOffset);
label += readUnsignedShort(b, u + 2);
newOffset = getNewOffset(allIndexes, allSizes, 0, label) - newOffset;
writeShort(b, u, newOffset);
u += 10;
}
}
if (lineNumber != null) {
b = lineNumber.data;
u = 0;
while (u < lineNumber.length) {
writeShort(b, u, getNewOffset(
allIndexes, allSizes, 0, readUnsignedShort(b, u)));
u += 4;
}
}
// replaces old bytecodes with new ones
code = newCode;
// returns the positions of the resized instructions
return indexes;
}
/**
* Reads an unsigned short value in the given byte array.
*
* @param b a byte array.
* @param index the start index of the value to be read.
* @return the read value.
*/
static int readUnsignedShort (final byte[] b, final int index) {
return ((b[index] & 0xFF) << 8) | (b[index + 1] & 0xFF);
}
/**
* Reads a signed short value in the given byte array.
*
* @param b a byte array.
* @param index the start index of the value to be read.
* @return the read value.
*/
static short readShort (final byte[] b, final int index) {
return (short)(((b[index] & 0xFF) << 8) | (b[index + 1] & 0xFF));
}
/**
* Reads a signed int value in the given byte array.
*
* @param b a byte array.
* @param index the start index of the value to be read.
* @return the read value.
*/
static int readInt (final byte[] b, final int index) {
return ((b[index] & 0xFF) << 24) |
((b[index + 1] & 0xFF) << 16) |
((b[index + 2] & 0xFF) << 8) |
(b[index + 3] & 0xFF);
}
/**
* Writes a short value in the given byte array.
*
* @param b a byte array.
* @param index where the first byte of the short value must be written.
* @param s the value to be written in the given byte array.
*/
static void writeShort (final byte[] b, final int index, final int s) {
b[index] = (byte)(s >>> 8);
b[index + 1] = (byte)s;
}
/**
* Computes the future value of a bytecode offset.
*
* Note: it is possible to have several entries for the same instruction
* in the indexes and sizes: two entries (index=a,size=b)
* and (index=a,size=b') are equivalent to a single entry (index=a,size=b+b').
*
* @param indexes current positions of the instructions to be resized. Each
* instruction must be designated by the index of its last byte,
* plus one (or, in other words, by the index of the first byte of
* the next instruction).
* @param sizes the number of bytes to be added to the above
* instructions. More precisely, for each i < len,
* sizes[i] bytes will be added at the end of the instruction
* designated by indexes[i] or, if sizes[i] is
* negative, the last |sizes[i]| bytes of the instruction
* will be removed (the instruction size must not become negative
* or null).
* @param begin index of the first byte of the source instruction.
* @param end index of the first byte of the target instruction.
* @return the future value of the given bytecode offset.
*/
static int getNewOffset (
final int[] indexes,
final int[] sizes,
final int begin,
final int end)
{
int offset = end - begin;
for (int i = 0; i < indexes.length; ++i) {
if (begin < indexes[i] && indexes[i] <= end) { // forward jump
offset += sizes[i];
} else if (end < indexes[i] && indexes[i] <= begin) { // backward jump
offset -= sizes[i];
}
}
return offset;
}
/**
* Returns the current size of the bytecode of this method. This size just
* includes the size of the bytecode instructions: it does not include the
* size of the Exceptions, LocalVariableTable, LineNumberTable, Synthetic
* and Deprecated attributes, if present.
*
* @return the current size of the bytecode of this method.
*/
protected int getCodeSize () {
return code.length;
}
/**
* Returns the current bytecode of this method. This bytecode only contains
* the instructions: it does not include the Exceptions, LocalVariableTable,
* LineNumberTable, Synthetic and Deprecated attributes, if present.
*
* @return the current bytecode of this method. The bytecode is contained
* between the index 0 (inclusive) and the index {@link #getCodeSize
* getCodeSize} (exclusive).
*/
protected byte[] getCode () {
return code.data;
}
}
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