jaxp/src/java.xml/share/classes/com/sun/org/apache/bcel/internal/generic/MethodGen.java
changeset 25868 686eef1e7a79
parent 15346 3f6fd93fec9a
child 27535 872cc59854b0
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jaxp/src/java.xml/share/classes/com/sun/org/apache/bcel/internal/generic/MethodGen.java	Sun Aug 17 15:51:56 2014 +0100
@@ -0,0 +1,995 @@
+/*
+ * reserved comment block
+ * DO NOT REMOVE OR ALTER!
+ */
+package com.sun.org.apache.bcel.internal.generic;
+
+/* ====================================================================
+ * The Apache Software License, Version 1.1
+ *
+ * Copyright (c) 2001 The Apache Software Foundation.  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. The end-user documentation included with the redistribution,
+ *    if any, must include the following acknowledgment:
+ *       "This product includes software developed by the
+ *        Apache Software Foundation (http://www.apache.org/)."
+ *    Alternately, this acknowledgment may appear in the software itself,
+ *    if and wherever such third-party acknowledgments normally appear.
+ *
+ * 4. The names "Apache" and "Apache Software Foundation" and
+ *    "Apache BCEL" must not be used to endorse or promote products
+ *    derived from this software without prior written permission. For
+ *    written permission, please contact apache@apache.org.
+ *
+ * 5. Products derived from this software may not be called "Apache",
+ *    "Apache BCEL", nor may "Apache" appear in their name, without
+ *    prior written permission of the Apache Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
+ * ITS 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.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ */
+
+import com.sun.org.apache.bcel.internal.Constants;
+import com.sun.org.apache.bcel.internal.classfile.*;
+import java.util.*;
+
+/**
+ * Template class for building up a method. This is done by defining exception
+ * handlers, adding thrown exceptions, local variables and attributes, whereas
+ * the `LocalVariableTable' and `LineNumberTable' attributes will be set
+ * automatically for the code. Use stripAttributes() if you don't like this.
+ *
+ * While generating code it may be necessary to insert NOP operations. You can
+ * use the `removeNOPs' method to get rid off them.
+ * The resulting method object can be obtained via the `getMethod()' method.
+ *
+ * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
+ * @author  <A HREF="http://www.vmeng.com/beard">Patrick C. Beard</A> [setMaxStack()]
+ * @see     InstructionList
+ * @see     Method
+ */
+public class MethodGen extends FieldGenOrMethodGen {
+  private String          class_name;
+  private Type[]          arg_types;
+  private String[]        arg_names;
+  private int             max_locals;
+  private int             max_stack;
+  private InstructionList il;
+  private boolean         strip_attributes;
+
+  private ArrayList       variable_vec    = new ArrayList();
+  private ArrayList       line_number_vec = new ArrayList();
+  private ArrayList       exception_vec   = new ArrayList();
+  private ArrayList       throws_vec      = new ArrayList();
+  private ArrayList       code_attrs_vec  = new ArrayList();
+
+  /**
+   * Declare method. If the method is non-static the constructor
+   * automatically declares a local variable `$this' in slot 0. The
+   * actual code is contained in the `il' parameter, which may further
+   * manipulated by the user. But he must take care not to remove any
+   * instruction (handles) that are still referenced from this object.
+   *
+   * For example one may not add a local variable and later remove the
+   * instructions it refers to without causing havoc. It is safe
+   * however if you remove that local variable, too.
+   *
+   * @param access_flags access qualifiers
+   * @param return_type  method type
+   * @param arg_types argument types
+   * @param arg_names argument names (if this is null, default names will be provided
+   * for them)
+   * @param method_name name of method
+   * @param class_name class name containing this method (may be null, if you don't care)
+   * @param il instruction list associated with this method, may be null only for
+   * abstract or native methods
+   * @param cp constant pool
+   */
+  public MethodGen(int access_flags, Type return_type, Type[] arg_types,
+                   String[] arg_names, String method_name, String class_name,
+                   InstructionList il, ConstantPoolGen cp) {
+    setAccessFlags(access_flags);
+    setType(return_type);
+    setArgumentTypes(arg_types);
+    setArgumentNames(arg_names);
+    setName(method_name);
+    setClassName(class_name);
+    setInstructionList(il);
+    setConstantPool(cp);
+
+    boolean abstract_ = isAbstract() || isNative();
+    InstructionHandle start = null;
+    InstructionHandle end   = null;
+
+    if(!abstract_) {
+      start = il.getStart();
+      end   = il.getEnd();
+
+      /* Add local variables, namely the implicit `this' and the arguments
+       */
+      if(!isStatic() && (class_name != null)) { // Instance method -> `this' is local var 0
+        addLocalVariable("this", new ObjectType(class_name), start, end);
+      }
+    }
+
+    if(arg_types != null) {
+      int size = arg_types.length;
+
+      for(int i=0; i < size; i++) {
+        if(Type.VOID == arg_types[i]) {
+          throw new ClassGenException("'void' is an illegal argument type for a method");
+        }
+      }
+
+      if(arg_names != null) { // Names for variables provided?
+        if(size != arg_names.length)
+          throw new ClassGenException("Mismatch in argument array lengths: " +
+                                      size + " vs. " + arg_names.length);
+      } else { // Give them dummy names
+        arg_names = new String[size];
+
+        for(int i=0; i < size; i++)
+          arg_names[i] = "arg" + i;
+
+        setArgumentNames(arg_names);
+      }
+
+      if(!abstract_) {
+        for(int i=0; i < size; i++) {
+          addLocalVariable(arg_names[i], arg_types[i], start, end);
+        }
+      }
+    }
+  }
+
+  /**
+   * Instantiate from existing method.
+   *
+   * @param m method
+   * @param class_name class name containing this method
+   * @param cp constant pool
+   */
+  public MethodGen(Method m, String class_name, ConstantPoolGen cp) {
+    this(m.getAccessFlags(), Type.getReturnType(m.getSignature()),
+         Type.getArgumentTypes(m.getSignature()), null /* may be overridden anyway */,
+         m.getName(), class_name,
+         ((m.getAccessFlags() & (Constants.ACC_ABSTRACT | Constants.ACC_NATIVE)) == 0)?
+         new InstructionList(m.getCode().getCode()) : null,
+         cp);
+
+    Attribute[] attributes = m.getAttributes();
+    for(int i=0; i < attributes.length; i++) {
+      Attribute a = attributes[i];
+
+      if(a instanceof Code) {
+        Code c = (Code)a;
+        setMaxStack(c.getMaxStack());
+        setMaxLocals(c.getMaxLocals());
+
+        CodeException[] ces = c.getExceptionTable();
+
+        if(ces != null) {
+          for(int j=0; j < ces.length; j++) {
+            CodeException ce     = ces[j];
+            int           type   = ce.getCatchType();
+            ObjectType    c_type = null;
+
+            if(type > 0) {
+              String cen = m.getConstantPool().getConstantString(type, Constants.CONSTANT_Class);
+              c_type = new ObjectType(cen);
+            }
+
+            int end_pc = ce.getEndPC();
+            int length = m.getCode().getCode().length;
+
+            InstructionHandle end;
+
+            if(length == end_pc) { // May happen, because end_pc is exclusive
+              end = il.getEnd();
+            } else {
+              end = il.findHandle(end_pc);
+              end = end.getPrev(); // Make it inclusive
+            }
+
+            addExceptionHandler(il.findHandle(ce.getStartPC()), end,
+                                il.findHandle(ce.getHandlerPC()), c_type);
+          }
+        }
+
+        Attribute[] c_attributes = c.getAttributes();
+        for(int j=0; j < c_attributes.length; j++) {
+          a = c_attributes[j];
+
+          if(a instanceof LineNumberTable) {
+            LineNumber[] ln = ((LineNumberTable)a).getLineNumberTable();
+
+            for(int k=0; k < ln.length; k++) {
+              LineNumber l = ln[k];
+              addLineNumber(il.findHandle(l.getStartPC()), l.getLineNumber());
+            }
+          } else if(a instanceof LocalVariableTable) {
+            LocalVariable[] lv = ((LocalVariableTable)a).getLocalVariableTable();
+
+            removeLocalVariables();
+
+            for(int k=0; k < lv.length; k++) {
+              LocalVariable     l     = lv[k];
+              InstructionHandle start = il.findHandle(l.getStartPC());
+              InstructionHandle end   = il.findHandle(l.getStartPC() + l.getLength());
+
+              // Repair malformed handles
+              if(null == start) {
+                start = il.getStart();
+              }
+
+              if(null == end) {
+                end = il.getEnd();
+              }
+
+              addLocalVariable(l.getName(), Type.getType(l.getSignature()),
+                               l.getIndex(), start, end);
+            }
+          } else if (a instanceof LocalVariableTypeTable) {
+             LocalVariable[] lv = ((LocalVariableTypeTable) a).getLocalVariableTypeTable();
+             removeLocalVariables();
+             for (int k = 0; k < lv.length; k++) {
+                 LocalVariable l = lv[k];
+                 InstructionHandle start = il.findHandle(l.getStartPC());
+                 InstructionHandle end = il.findHandle(l.getStartPC() + l.getLength());
+                 // Repair malformed handles
+                 if (null == start) {
+                     start = il.getStart();
+                 }
+                 if (null == end) {
+                     end = il.getEnd();
+                 }
+                 addLocalVariable(l.getName(), Type.getType(l.getSignature()), l
+                         .getIndex(), start, end);
+              }
+          } else
+            addCodeAttribute(a);
+        }
+      } else if(a instanceof ExceptionTable) {
+        String[] names = ((ExceptionTable)a).getExceptionNames();
+        for(int j=0; j < names.length; j++)
+          addException(names[j]);
+      } else
+        addAttribute(a);
+    }
+  }
+
+  /**
+   * Adds a local variable to this method.
+   *
+   * @param name variable name
+   * @param type variable type
+   * @param slot the index of the local variable, if type is long or double, the next available
+   * index is slot+2
+   * @param start from where the variable is valid
+   * @param end until where the variable is valid
+   * @return new local variable object
+   * @see LocalVariable
+   */
+  public LocalVariableGen addLocalVariable(String name, Type type, int slot,
+                                           InstructionHandle start,
+                                           InstructionHandle end) {
+    byte t = type.getType();
+
+    if(t != Constants.T_ADDRESS) {
+      int  add = type.getSize();
+
+      if(slot + add > max_locals)
+        max_locals = slot + add;
+
+      LocalVariableGen l = new LocalVariableGen(slot, name, type, start, end);
+      int i;
+
+      if((i = variable_vec.indexOf(l)) >= 0) // Overwrite if necessary
+        variable_vec.set(i, l);
+      else
+        variable_vec.add(l);
+
+      return l;
+    } else {
+      throw new IllegalArgumentException("Can not use " + type +
+                                         " as type for local variable");
+
+    }
+  }
+
+  /**
+   * Adds a local variable to this method and assigns an index automatically.
+   *
+   * @param name variable name
+   * @param type variable type
+   * @param start from where the variable is valid, if this is null,
+   * it is valid from the start
+   * @param end until where the variable is valid, if this is null,
+   * it is valid to the end
+   * @return new local variable object
+   * @see LocalVariable
+   */
+  public LocalVariableGen addLocalVariable(String name, Type type,
+                                           InstructionHandle start,
+                                           InstructionHandle end) {
+    return addLocalVariable(name, type, max_locals, start, end);
+  }
+
+  /**
+   * Remove a local variable, its slot will not be reused, if you do not use addLocalVariable
+   * with an explicit index argument.
+   */
+  public void removeLocalVariable(LocalVariableGen l) {
+    variable_vec.remove(l);
+  }
+
+  /**
+   * Remove all local variables.
+   */
+  public void removeLocalVariables() {
+    variable_vec.clear();
+  }
+
+  /**
+   * Sort local variables by index
+   */
+  private static final void sort(LocalVariableGen[] vars, int l, int r) {
+    int i = l, j = r;
+    int m = vars[(l + r) / 2].getIndex();
+    LocalVariableGen h;
+
+    do {
+      while(vars[i].getIndex() < m) i++;
+      while(m < vars[j].getIndex()) j--;
+
+      if(i <= j) {
+        h=vars[i]; vars[i]=vars[j]; vars[j]=h; // Swap elements
+        i++; j--;
+      }
+    } while(i <= j);
+
+    if(l < j) sort(vars, l, j);
+    if(i < r) sort(vars, i, r);
+  }
+
+  /*
+   * If the range of the variable has not been set yet, it will be set to be valid from
+   * the start to the end of the instruction list.
+   *
+   * @return array of declared local variables sorted by index
+   */
+  public LocalVariableGen[] getLocalVariables() {
+    int                size = variable_vec.size();
+    LocalVariableGen[] lg   = new LocalVariableGen[size];
+    variable_vec.toArray(lg);
+
+    for(int i=0; i < size; i++) {
+      if(lg[i].getStart() == null)
+        lg[i].setStart(il.getStart());
+
+      if(lg[i].getEnd() == null)
+        lg[i].setEnd(il.getEnd());
+    }
+
+    if(size > 1)
+      sort(lg, 0, size - 1);
+
+    return lg;
+  }
+
+  /**
+   * @return `LocalVariableTable' attribute of all the local variables of this method.
+   */
+  public LocalVariableTable getLocalVariableTable(ConstantPoolGen cp) {
+    LocalVariableGen[] lg   = getLocalVariables();
+    int                size = lg.length;
+    LocalVariable[]    lv   = new LocalVariable[size];
+
+    for(int i=0; i < size; i++)
+      lv[i] = lg[i].getLocalVariable(cp);
+
+    return new LocalVariableTable(cp.addUtf8("LocalVariableTable"),
+                                  2 + lv.length * 10, lv, cp.getConstantPool());
+  }
+
+  /**
+   * Give an instruction a line number corresponding to the source code line.
+   *
+   * @param ih instruction to tag
+   * @return new line number object
+   * @see LineNumber
+   */
+  public LineNumberGen addLineNumber(InstructionHandle ih, int src_line) {
+    LineNumberGen l = new LineNumberGen(ih, src_line);
+    line_number_vec.add(l);
+    return l;
+  }
+
+  /**
+   * Remove a line number.
+   */
+  public void removeLineNumber(LineNumberGen l) {
+    line_number_vec.remove(l);
+  }
+
+  /**
+   * Remove all line numbers.
+   */
+  public void removeLineNumbers() {
+    line_number_vec.clear();
+  }
+
+  /*
+   * @return array of line numbers
+   */
+  public LineNumberGen[] getLineNumbers() {
+    LineNumberGen[] lg = new LineNumberGen[line_number_vec.size()];
+    line_number_vec.toArray(lg);
+    return lg;
+  }
+
+  /**
+   * @return `LineNumberTable' attribute of all the local variables of this method.
+   */
+  public LineNumberTable getLineNumberTable(ConstantPoolGen cp) {
+    int          size = line_number_vec.size();
+    LineNumber[] ln   = new LineNumber[size];
+
+    try {
+      for(int i=0; i < size; i++)
+        ln[i] = ((LineNumberGen)line_number_vec.get(i)).getLineNumber();
+    } catch(ArrayIndexOutOfBoundsException e) {} // Never occurs
+
+    return new LineNumberTable(cp.addUtf8("LineNumberTable"),
+                               2 + ln.length * 4, ln, cp.getConstantPool());
+  }
+
+  /**
+   * Add an exception handler, i.e., specify region where a handler is active and an
+   * instruction where the actual handling is done.
+   *
+   * @param start_pc Start of region (inclusive)
+   * @param end_pc End of region (inclusive)
+   * @param handler_pc Where handling is done
+   * @param catch_type class type of handled exception or null if any
+   * exception is handled
+   * @return new exception handler object
+   */
+  public CodeExceptionGen addExceptionHandler(InstructionHandle start_pc,
+                                              InstructionHandle end_pc,
+                                              InstructionHandle handler_pc,
+                                              ObjectType catch_type) {
+    if((start_pc == null) || (end_pc == null) || (handler_pc == null))
+      throw new ClassGenException("Exception handler target is null instruction");
+
+    CodeExceptionGen c = new CodeExceptionGen(start_pc, end_pc,
+                                              handler_pc, catch_type);
+    exception_vec.add(c);
+    return c;
+  }
+
+  /**
+   * Remove an exception handler.
+   */
+  public void removeExceptionHandler(CodeExceptionGen c) {
+    exception_vec.remove(c);
+  }
+
+  /**
+   * Remove all line numbers.
+   */
+  public void removeExceptionHandlers() {
+    exception_vec.clear();
+  }
+
+  /*
+   * @return array of declared exception handlers
+   */
+  public CodeExceptionGen[] getExceptionHandlers() {
+    CodeExceptionGen[] cg   = new CodeExceptionGen[exception_vec.size()];
+    exception_vec.toArray(cg);
+    return cg;
+  }
+
+  /**
+   * @return code exceptions for `Code' attribute
+   */
+  private CodeException[] getCodeExceptions() {
+    int             size  = exception_vec.size();
+    CodeException[] c_exc = new CodeException[size];
+
+    try {
+      for(int i=0; i < size; i++) {
+        CodeExceptionGen c = (CodeExceptionGen)exception_vec.get(i);
+        c_exc[i] = c.getCodeException(cp);
+      }
+    } catch(ArrayIndexOutOfBoundsException e) {}
+
+    return c_exc;
+  }
+
+  /**
+   * Add an exception possibly thrown by this method.
+   *
+   * @param class_name (fully qualified) name of exception
+   */
+  public void addException(String class_name) {
+    throws_vec.add(class_name);
+  }
+
+  /**
+   * Remove an exception.
+   */
+  public void removeException(String c) {
+    throws_vec.remove(c);
+  }
+
+  /**
+   * Remove all exceptions.
+   */
+  public void removeExceptions() {
+    throws_vec.clear();
+  }
+
+  /*
+   * @return array of thrown exceptions
+   */
+  public String[] getExceptions() {
+    String[] e = new String[throws_vec.size()];
+    throws_vec.toArray(e);
+    return e;
+  }
+
+  /**
+   * @return `Exceptions' attribute of all the exceptions thrown by this method.
+   */
+  private ExceptionTable getExceptionTable(ConstantPoolGen cp) {
+    int   size = throws_vec.size();
+    int[] ex   = new int[size];
+
+    try {
+      for(int i=0; i < size; i++)
+        ex[i] = cp.addClass((String)throws_vec.get(i));
+    } catch(ArrayIndexOutOfBoundsException e) {}
+
+    return new ExceptionTable(cp.addUtf8("Exceptions"),
+                              2 + 2 * size, ex, cp.getConstantPool());
+  }
+
+  /**
+   * Add an attribute to the code. Currently, the JVM knows about the
+   * LineNumberTable, LocalVariableTable and StackMap attributes,
+   * where the former two will be generated automatically and the
+   * latter is used for the MIDP only. Other attributes will be
+   * ignored by the JVM but do no harm.
+   *
+   * @param a attribute to be added
+   */
+  public void addCodeAttribute(Attribute a) { code_attrs_vec.add(a); }
+
+  /**
+   * Remove a code attribute.
+   */
+  public void removeCodeAttribute(Attribute a) { code_attrs_vec.remove(a); }
+
+  /**
+   * Remove all code attributes.
+   */
+  public void removeCodeAttributes() {
+    code_attrs_vec.clear();
+  }
+
+  /**
+   * @return all attributes of this method.
+   */
+  public Attribute[] getCodeAttributes() {
+    Attribute[] attributes = new Attribute[code_attrs_vec.size()];
+    code_attrs_vec.toArray(attributes);
+    return attributes;
+  }
+
+  /**
+   * Get method object. Never forget to call setMaxStack() or setMaxStack(max), respectively,
+   * before calling this method (the same applies for max locals).
+   *
+   * @return method object
+   */
+  public Method getMethod() {
+    String signature       = getSignature();
+    int    name_index      = cp.addUtf8(name);
+    int    signature_index = cp.addUtf8(signature);
+
+    /* Also updates positions of instructions, i.e., their indices
+     */
+    byte[] byte_code = null;
+
+    if(il != null)
+      byte_code = il.getByteCode();
+
+    LineNumberTable    lnt = null;
+    LocalVariableTable lvt = null;
+
+    /* Create LocalVariableTable and LineNumberTable attributes (for debuggers, e.g.)
+     */
+    if((variable_vec.size() > 0) && !strip_attributes)
+      addCodeAttribute(lvt = getLocalVariableTable(cp));
+
+    if((line_number_vec.size() > 0) && !strip_attributes)
+      addCodeAttribute(lnt = getLineNumberTable(cp));
+
+    Attribute[] code_attrs = getCodeAttributes();
+
+    /* Each attribute causes 6 additional header bytes
+     */
+    int                attrs_len  = 0;
+    for(int i=0; i < code_attrs.length; i++)
+      attrs_len += (code_attrs[i].getLength() + 6);
+
+    CodeException[] c_exc   = getCodeExceptions();
+    int             exc_len = c_exc.length * 8; // Every entry takes 8 bytes
+
+    Code code = null;
+
+    if((il != null) && !isAbstract()) {
+      // Remove any stale code attribute
+      Attribute[] attributes = getAttributes();
+      for(int i=0; i < attributes.length; i++) {
+        Attribute a = attributes[i];
+
+        if(a instanceof Code)
+          removeAttribute(a);
+      }
+
+      code = new Code(cp.addUtf8("Code"),
+                      8 + byte_code.length + // prologue byte code
+                      2 + exc_len +          // exceptions
+                      2 + attrs_len,         // attributes
+                      max_stack, max_locals,
+                      byte_code, c_exc,
+                      code_attrs,
+                      cp.getConstantPool());
+
+      addAttribute(code);
+    }
+
+    ExceptionTable et = null;
+
+    if(throws_vec.size() > 0)
+      addAttribute(et = getExceptionTable(cp)); // Add `Exceptions' if there are "throws" clauses
+
+    Method m = new Method(access_flags, name_index, signature_index,
+                          getAttributes(), cp.getConstantPool());
+
+    // Undo effects of adding attributes
+    if(lvt != null)  removeCodeAttribute(lvt);
+    if(lnt != null)  removeCodeAttribute(lnt);
+    if(code != null) removeAttribute(code);
+    if(et != null)   removeAttribute(et);
+
+    return m;
+  }
+
+  /**
+   * Remove all NOPs from the instruction list (if possible) and update every
+   * object refering to them, i.e., branch instructions, local variables and
+   * exception handlers.
+   */
+  public void removeNOPs() {
+    if(il != null) {
+      InstructionHandle next;
+      /* Check branch instructions.
+       */
+      for(InstructionHandle ih = il.getStart(); ih != null; ih = next) {
+        next = ih.next;
+
+        if((next != null) && (ih.getInstruction() instanceof NOP)) {
+          try {
+            il.delete(ih);
+          } catch(TargetLostException e) {
+            InstructionHandle[] targets = e.getTargets();
+
+            for(int i=0; i < targets.length; i++) {
+              InstructionTargeter[] targeters = targets[i].getTargeters();
+
+              for(int j=0; j < targeters.length; j++)
+                targeters[j].updateTarget(targets[i], next);
+            }
+          }
+        }
+      }
+    }
+  }
+
+  /**
+   * Set maximum number of local variables.
+   */
+  public void   setMaxLocals(int m)  { max_locals = m; }
+  public int    getMaxLocals()       { return max_locals; }
+
+  /**
+   * Set maximum stack size for this method.
+   */
+  public void   setMaxStack(int m)  { max_stack = m; }
+  public int    getMaxStack()       { return max_stack; }
+
+  /** @return class that contains this method
+   */
+  public String getClassName()                     { return class_name; }
+  public void   setClassName(String class_name)    { this.class_name = class_name; }
+
+  public void   setReturnType(Type return_type)    { setType(return_type); }
+  public Type   getReturnType()                    { return getType(); }
+
+  public void   setArgumentTypes(Type[] arg_types)  { this.arg_types = arg_types; }
+  public Type[] getArgumentTypes()                  { return (Type[])arg_types.clone(); }
+  public void   setArgumentType(int i, Type type)       { arg_types[i] = type; }
+  public Type   getArgumentType(int i)                  { return arg_types[i]; }
+
+  public void     setArgumentNames(String[] arg_names) { this.arg_names = arg_names; }
+  public String[] getArgumentNames()                   { return (String[])arg_names.clone(); }
+  public void     setArgumentName(int i, String name)     { arg_names[i] = name; }
+  public String   getArgumentName(int i)                  { return arg_names[i]; }
+
+  public InstructionList getInstructionList()                    { return il; }
+  public void            setInstructionList(InstructionList il)  { this.il = il; }
+
+  public String getSignature() {
+    return Type.getMethodSignature(type, arg_types);
+  }
+
+  /**
+   * Computes max. stack size by performing control flow analysis.
+   */
+  public void setMaxStack() {
+    if(il != null)
+      max_stack = getMaxStack(cp, il, getExceptionHandlers());
+    else
+      max_stack = 0;
+  }
+
+  /**
+   * Compute maximum number of local variables.
+   */
+  public void setMaxLocals() {
+    if(il != null) {
+      int max = isStatic()? 0 : 1;
+
+      if(arg_types != null)
+        for(int i=0; i < arg_types.length; i++)
+          max += arg_types[i].getSize();
+
+      for(InstructionHandle ih = il.getStart(); ih != null; ih = ih.getNext()) {
+        Instruction ins = ih.getInstruction();
+
+        if((ins instanceof LocalVariableInstruction) ||
+           (ins instanceof RET) || (ins instanceof IINC))
+        {
+          int index = ((IndexedInstruction)ins).getIndex() +
+            ((TypedInstruction)ins).getType(cp).getSize();
+
+          if(index > max)
+            max = index;
+        }
+      }
+
+      max_locals = max;
+    } else
+      max_locals = 0;
+  }
+
+  /** Do not/Do produce attributes code attributesLineNumberTable and
+   * LocalVariableTable, like javac -O
+   */
+  public void stripAttributes(boolean flag) { strip_attributes = flag; }
+
+  static final class BranchTarget {
+    InstructionHandle target;
+    int               stackDepth;
+
+    BranchTarget(InstructionHandle target, int stackDepth) {
+      this.target = target;
+      this.stackDepth = stackDepth;
+    }
+  }
+
+  static final class BranchStack {
+    Stack     branchTargets  = new Stack();
+    Hashtable visitedTargets = new Hashtable();
+
+    public void push(InstructionHandle target, int stackDepth) {
+      if(visited(target))
+        return;
+
+      branchTargets.push(visit(target, stackDepth));
+    }
+
+    public BranchTarget pop() {
+      if(!branchTargets.empty()) {
+        BranchTarget bt = (BranchTarget) branchTargets.pop();
+        return bt;
+      }
+
+      return null;
+    }
+
+    private final BranchTarget visit(InstructionHandle target, int stackDepth) {
+      BranchTarget bt = new BranchTarget(target, stackDepth);
+      visitedTargets.put(target, bt);
+
+      return bt;
+    }
+
+    private final boolean visited(InstructionHandle target) {
+      return (visitedTargets.get(target) != null);
+    }
+  }
+
+  /**
+   * Computes stack usage of an instruction list by performing control flow analysis.
+   *
+   * @return maximum stack depth used by method
+   */
+  public static int getMaxStack(ConstantPoolGen cp, InstructionList il, CodeExceptionGen[] et) {
+    BranchStack branchTargets = new BranchStack();
+
+    /* Initially, populate the branch stack with the exception
+     * handlers, because these aren't (necessarily) branched to
+     * explicitly. in each case, the stack will have depth 1,
+     * containing the exception object.
+     */
+    for (int i = 0; i < et.length; i++) {
+      InstructionHandle handler_pc = et[i].getHandlerPC();
+      if (handler_pc != null)
+        branchTargets.push(handler_pc, 1);
+    }
+
+    int               stackDepth = 0, maxStackDepth = 0;
+    InstructionHandle ih         = il.getStart();
+
+    while(ih != null) {
+      Instruction instruction = ih.getInstruction();
+      short opcode = instruction.getOpcode();
+      int delta = instruction.produceStack(cp) - instruction.consumeStack(cp);
+
+      stackDepth += delta;
+      if(stackDepth > maxStackDepth)
+        maxStackDepth = stackDepth;
+
+      // choose the next instruction based on whether current is a branch.
+      if(instruction instanceof BranchInstruction) {
+        BranchInstruction branch = (BranchInstruction) instruction;
+        if(instruction instanceof Select) {
+          // explore all of the select's targets. the default target is handled below.
+          Select select = (Select) branch;
+          InstructionHandle[] targets = select.getTargets();
+          for (int i = 0; i < targets.length; i++)
+            branchTargets.push(targets[i], stackDepth);
+          // nothing to fall through to.
+          ih = null;
+        } else if(!(branch instanceof IfInstruction)) {
+          // if an instruction that comes back to following PC,
+          // push next instruction, with stack depth reduced by 1.
+          if(opcode == Constants.JSR || opcode == Constants.JSR_W)
+            branchTargets.push(ih.getNext(), stackDepth - 1);
+          ih = null;
+        }
+        // for all branches, the target of the branch is pushed on the branch stack.
+        // conditional branches have a fall through case, selects don't, and
+        // jsr/jsr_w return to the next instruction.
+        branchTargets.push(branch.getTarget(), stackDepth);
+      } else {
+        // check for instructions that terminate the method.
+        if(opcode == Constants.ATHROW || opcode == Constants.RET ||
+           (opcode >= Constants.IRETURN && opcode <= Constants.RETURN))
+          ih = null;
+      }
+      // normal case, go to the next instruction.
+      if(ih != null)
+        ih = ih.getNext();
+      // if we have no more instructions, see if there are any deferred branches to explore.
+      if(ih == null) {
+        BranchTarget bt = branchTargets.pop();
+        if (bt != null) {
+          ih = bt.target;
+          stackDepth = bt.stackDepth;
+        }
+      }
+    }
+
+    return maxStackDepth;
+  }
+
+  private ArrayList observers;
+
+  /** Add observer for this object.
+   */
+  public void addObserver(MethodObserver o) {
+    if(observers == null)
+      observers = new ArrayList();
+
+    observers.add(o);
+  }
+
+  /** Remove observer for this object.
+   */
+  public void removeObserver(MethodObserver o) {
+    if(observers != null)
+      observers.remove(o);
+  }
+
+  /** Call notify() method on all observers. This method is not called
+   * automatically whenever the state has changed, but has to be
+   * called by the user after he has finished editing the object.
+   */
+  public void update() {
+    if(observers != null)
+      for(Iterator e = observers.iterator(); e.hasNext(); )
+        ((MethodObserver)e.next()).notify(this);
+  }
+
+  /**
+   * Return string representation close to declaration format,
+   * `public static void _main(String[]) throws IOException', e.g.
+   *
+   * @return String representation of the method.
+   */
+  public final String toString() {
+    String access    = Utility.accessToString(access_flags);
+    String signature = Type.getMethodSignature(type, arg_types);
+
+    signature = Utility.methodSignatureToString(signature, name, access,
+                                                true, getLocalVariableTable(cp));
+
+    StringBuffer buf = new StringBuffer(signature);
+
+    if(throws_vec.size() > 0) {
+      for(Iterator e = throws_vec.iterator(); e.hasNext(); )
+        buf.append("\n\t\tthrows " + e.next());
+    }
+
+    return buf.toString();
+  }
+
+  /** @return deep copy of this method
+   */
+  public MethodGen copy(String class_name, ConstantPoolGen cp) {
+    Method    m  = ((MethodGen)clone()).getMethod();
+    MethodGen mg = new MethodGen(m, class_name, this.cp);
+
+    if(this.cp != cp) {
+      mg.setConstantPool(cp);
+      mg.getInstructionList().replaceConstantPool(this.cp, cp);
+    }
+
+    return mg;
+  }
+}