webit.script.asm.lib.MethodWriter Maven / Gradle / Ivy
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/**
* *
* ASM: a very small and fast Java bytecode manipulation framework Copyright (c)
* 2000,2002,2003 INRIA, France Telecom All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer. 2. Redistributions in
* binary form must reproduce the above copyright notice, this list of
* conditions and the following disclaimer in the documentation and/or other
* materials provided with the distribution. 3. Neither the name of the
* copyright holders nor the names of its contributors may be used to endorse or
* promote products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package webit.script.asm.lib;
/**
* 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.
*
* @author Eric Bruneton
*/
public final class MethodWriter {
private final ClassWriter cw;
private final int name;
private final int desc;
private final int access;
private final int[] exceptions;
/**
* true if the maximum stack size and number of local variables
* must be automatically computed.
*/
private static final boolean computeMaxs = true;
/**
* 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 final ByteBuffer code;
/**
* Number of entries in the catch table of this method.
*/
private int catchCount;
/**
* The catch table of this method.
*/
private ByteBuffer catchTable;
/**
* Number of entries in the LocalVariableTable attribute.
*/
private int localVarCount;
/**
* The LocalVariableTable attribute.
*/
private ByteBuffer localVar;
// /**
// * Indicates if some jump instructions are too small and need to be resized.
// */
// private boolean resize;
/**
* 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 static final 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 MethodWriter 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 MethodWriter 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 MethodWriter).
// --------------------------------------------------------------------------
/**
* The head of the list of {@link Edge Edge} objects used by this {@link
* MethodWriter MethodWriter}. 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
* MethodWriter MethodWriter}. 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.
*/
MethodWriter(final ClassWriter cw,
final int access,
final String name,
final String desc,
final String[] exceptions) {
this.code = new ByteBuffer();
this.cw = cw;
this.access = access;
this.name = cw.newUTF8(name);
this.desc = cw.newUTF8(desc);
if (exceptions != null && exceptions.length > 0) {
int exceptionCount = exceptions.length;
this.exceptions = new int[exceptionCount];
for (int i = 0; i < exceptionCount; ++i) {
this.exceptions[i] = cw.newClass(exceptions[i]);
}
} else {
this.exceptions = ClassWriter.EMPATY_INTS;
}
if (computeMaxs) {
// pushes the first block onto the stack of blocks to be visited
blockStack = currentBlock = new Label();
currentBlock.pushed = true;
// updates maxLocals
int size = getArgumentsAndReturnSizes(desc) >> 2;
if ((access & Constants.ACC_STATIC) != 0) {
--size;
}
if (size > maxLocals) {
maxLocals = size;
}
}
}
public void checkCast(String ownerClass) {
if (!ownerClass.equals("java/lang/Object")) {
visitTypeInsn(Constants.CHECKCAST, ownerClass);
}
}
// public void pushClass(String name) {
// visitLdcInsn(cw.newClassItem(name));
// }
public void push(int value) {
if (value > 0 && value <= 5) {
visitInsn(Constants.ICONST_0 + value);
} else {
visitLdcInsn(value);
}
}
public void invokeStatic(
final String owner,
final String name,
final String desc) {
visitMethodInsn(Constants.INVOKESTATIC, owner, name, desc);
}
public void invokeVirtual(
final String owner,
final String name,
final String desc) {
visitMethodInsn(Constants.INVOKEVIRTUAL, owner, name, desc);
}
public void visitMaxs() {
//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 MethodWriter
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 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.putByte(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.putBS(opcode, operand);
// } else { // BIPUSH or NEWARRAY
// code.putBB(opcode, operand);
// }
// }
public void visitVarInsn(final int opcode, final int var) {
final ByteBuffer code = this.code;
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.putByte(opt);
} else if (var >= 256) {
code.putByte(196 /*WIDE*/).putBS(opcode, var);
} else {
code.putBB(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.putBS(opcode, cw.newClass(desc));
}
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.putBS(opcode, cw.newField(owner, name, desc));
}
public void visitMethodInsn(
final int opcode,
final String owner,
final String name,
final String desc) {
boolean itf = opcode == Constants.INVOKEINTERFACE;
Item i = cw.newMethodItem(owner, name, desc, itf);
int argSize = i.argSize;
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...
i.argSize = argSize = getArgumentsAndReturnSizes(desc);
}
int size = stackSize - (argSize >> 2) + (argSize & 0x03);
if (opcode == Constants.INVOKESTATIC) {
size += 1;
}
// updates current and max stack sizes
if (size > maxStackSize) {
maxStackSize = size;
}
stackSize = size;
}
// adds the instruction to the bytecode of the method
final ByteBuffer code = this.code;
if (itf) {
if (!computeMaxs) {
if (argSize == 0) {
argSize = getArgumentsAndReturnSizes(desc);
i.argSize = argSize;
}
}
code.putBS(Constants.INVOKEINTERFACE, i.index).putBB(argSize >> 2, 0);
} else {
code.putBS(opcode, i.index);
}
}
public void visitJumpInsn(final int opcode, final Label label) {
final ByteBuffer code = this.code;
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.putByte(200); // GOTO_W
} else if (opcode == Constants.JSR) {
code.putByte(201); // JSR_W
} else {
code.putByte(opcode <= 166 ? ((opcode + 1) ^ 1) - 1 : opcode ^ 1)
.putShort(8) // jump offset
.putByte(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.putByte(opcode);
label.put(this, code, code.length - 1, false);
}
}
public void visitLabel(final Label label) {
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.newConstItem(cst);
if (computeMaxs) {
int size;
// computes the stack size variation
size = stackSize = stackSize + ((i.type == ClassWriter.LONG || i.type == ClassWriter.DOUBLE) ? 2 : 1);
// updates current and max stack sizes
if (size > maxStackSize) {
maxStackSize = size;
}
}
// adds the instruction to the bytecode of the method
final ByteBuffer code = this.code;
int index = i.index;
if (i.type == ClassWriter.LONG || i.type == ClassWriter.DOUBLE) {
code.putBS(20 /*LDC2_W*/, index);
} else if (index >= 256) {
code.putBS(19 /*LDC_W*/, index);
} else {
code.putBB(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.putByte(196 /*WIDE*/).putBS(Constants.IINC, var).putShort(increment);
// } else {
// code.putByte(Constants.IINC).putBB(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.putByte(Constants.TABLESWITCH);
// while (code.length % 4 != 0) {
// code.putByte(0);
// }
// dflt.put(this, code, source, true);
// code.putInt(min).putInt(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;
}
}
final ByteBuffer code = this.code;
// adds the instruction to the bytecode of the method
int source = code.length;
code.putByte(Constants.LOOKUPSWITCH);
while (code.length % 4 != 0) {
code.putByte(0);
}
dflt.put(this, code, source, true);
code.putInt(labels.length);
for (int i = 0; i < labels.length; ++i) {
code.putInt(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
// code.putBS(Constants.MULTIANEWARRAY, cw.newClass(desc)).putByte(dims);
// }
// public void visitTryCatchBlock(
// final Label start,
// final Label end,
// final Label handler,
// final String type) {
// 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 ByteBuffer();
// }
// catchTable.putShort(start.position)
// .putShort(end.position)
// .putShort(handler.position)
// .putShort(type != null ? cw.newClass(type) : 0);
// }
// public void visitLocalVariable(
// final String name,
// final String desc,
// final Label start,
// final Label end,
// final int index) {
// if (localVar == null) {
// cw.newUTF8("LocalVariableTable");
// localVar = new ByteBuffer();
// }
// ++localVarCount;
// localVar.putShort(start.position)
// .putShort(end.position - start.position)
// .putShort(cw.newUTF8(name))
// .putShort(cw.newUTF8(desc))
// .putShort(index);
// }
// --------------------------------------------------------------------------
// 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;
for (;;) {
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 MethodWriter
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(ClassWriter.EMPATY_INTS, ClassWriter.EMPATY_INTS, 0);
// }
int size = 8;
if (code.length > 0) {
cw.newUTF8("Code");
size += 18 + code.length + 8 * catchCount;
if (localVar != null) {
size += 8 + localVar.length;
}
}
int exceptionCount = exceptions.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 renderTo(final ByteBuffer out) {
final ByteBuffer code = this.code;
out.putShort(access).putShort(name).putShort(desc);
int attributeCount = 0;
if (code.length > 0) {
++attributeCount;
}
int exceptionCount = exceptions.length;
if (exceptionCount > 0) {
++attributeCount;
}
// if ((access & Constants.ACC_SYNTHETIC) != 0) {
// ++attributeCount;
// }
// if ((access & Constants.ACC_DEPRECATED) != 0) {
// ++attributeCount;
// }
out.putShort(attributeCount);
if (code.length > 0) {
int size = 12 + code.length + 8 * catchCount;
if (localVar != null) {
size += 8 + localVar.length;
}
out.putShort(cw.newUTF8("Code")).putInt(size)
.putShort(maxStack).putShort(maxLocals)
.putInt(code.length).put(code)
.putShort(catchCount);
if (catchCount > 0) {
out.put(catchTable);
}
attributeCount = 0;
if (localVar != null) {
++attributeCount;
}
out.putShort(attributeCount);
if (localVar != null) {
out.putShort(cw.newUTF8("LocalVariableTable"))
.putInt(localVar.length + 2).putShort(localVarCount)
.put(localVar);
}
}
if (exceptionCount > 0) {
out.putShort(cw.newUTF8("Exceptions")).putInt(2 * exceptionCount + 2)
.putShort(exceptionCount);
for (int i = 0; i < exceptionCount; ++i) {
out.putShort(exceptions[i]);
}
}
// if ((access & Constants.ACC_SYNTHETIC) != 0) {
// out.putShort(cw.newUTF8("Synthetic")).putInt(0);
// }
// if ((access & Constants.ACC_DEPRECATED) != 0) {
// out.putShort(cw.newUTF8("Deprecated")).putInt(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.
// ByteBuffer newCode = new ByteBuffer(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.put(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.putByte(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 (resize[u]) {
// // 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.putByte(200); // GOTO_W
// } else if (opcode == Constants.JSR) {
// newCode.putByte(201); // JSR_W
// } else {
// newCode.putByte(opcode <= 166 ? ((opcode + 1) ^ 1) - 1 : opcode ^ 1)
// .putShort(8) // jump offset
// .putByte(200); // GOTO_W
// newOffset -= 3; // newOffset now computed from start of GOTO_W
// }
// newCode.putInt(newOffset);
// } else {
// newCode.putByte(opcode);
// newCode.putShort(newOffset);
// }
// u += 3;
// break;
// case ClassWriter.LABELW_INSN:
// label = u + readInt(b, u + 1);
// newOffset = getNewOffset(allIndexes, allSizes, u, label);
// newCode.putByte(opcode);
// newCode.putInt(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
//// newCode.putByte(Constants.TABLESWITCH);
//// while (newCode.length % 4 != 0) {
//// newCode.putByte(0);
//// }
//// label = v + readInt(b, u);
//// u += 4;
//// newOffset = getNewOffset(allIndexes, allSizes, v, label);
//// newCode.putInt(newOffset);
//// j = readInt(b, u);
//// u += 4;
//// newCode.putInt(j);
//// j = readInt(b, u) - j + 1;
//// u += 4;
//// newCode.putInt(readInt(b, u - 4));
//// for (; j > 0; --j) {
//// label = v + readInt(b, u);
//// u += 4;
//// newOffset = getNewOffset(allIndexes, allSizes, v, label);
//// newCode.putInt(newOffset);
//// }
//// break;
// case ClassWriter.LOOK_INSN:
// // skips 0 to 3 padding bytes
// v = u;
// u = u + 4 - (v & 3);
// // reads and copies instruction
// newCode.putByte(Constants.LOOKUPSWITCH);
// while (newCode.length % 4 != 0) {
// newCode.putByte(0);
// }
// label = v + readInt(b, u);
// u += 4;
// newOffset = getNewOffset(allIndexes, allSizes, v, label);
// newCode.putInt(newOffset);
// j = readInt(b, u);
// u += 4;
// newCode.putInt(j);
// for (; j > 0; --j) {
// newCode.putInt(readInt(b, u));
// u += 4;
// label = v + readInt(b, u);
// u += 4;
// newOffset = getNewOffset(allIndexes, allSizes, v, label);
// newCode.putInt(newOffset);
// }
// break;
// case ClassWriter.WIDE_INSN:
// opcode = b[u + 1] & 0xFF;
// if (opcode == Constants.IINC) {
// newCode.put(b, u, 6);
// u += 6;
// } else {
// newCode.put(b, u, 4);
// u += 4;
// }
// break;
// case ClassWriter.VAR_INSN:
// case ClassWriter.SBYTE_INSN:
// case ClassWriter.LDC_INSN:
// newCode.put(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.put(b, u, 3);
// u += 3;
// break;
// case ClassWriter.ITFMETH_INSN:
// newCode.put(b, u, 5);
// u += 5;
// break;
// // case MANA_INSN:
// default:
// newCode.put(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 + 2, newOffset);
// u += 10;
// }
// }
//
// // 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;
// }
}