File	Doc	Category	Size	Date	Package
MethodGen.java	API Doc	Java SE 6 API	30520	Tue Jun 10 00:22:22 BST 2008	com.sun.org.apache.bcel.internal.generic

MethodGen

• java.lang.Object
  • com.sun.org.apache.bcel.internal.classfile.AccessFlags
    • com.sun.org.apache.bcel.internal.generic.FieldGenOrMethodGen

Fields Summary
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
private ArrayList	line_number_vec
private ArrayList	exception_vec
private ArrayList	throws_vec
private ArrayList	code_attrs_vec
private ArrayList	observers

Constructors Summary
public MethodGen(int access_flags, Type return_type, Type[] arg_types, String[] arg_names, String method_name, String class_name, InstructionList il, ConstantPoolGen cp) 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 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); } } }
public MethodGen(Method m, String class_name, ConstantPoolGen cp) Instantiate from existing method. param m method param class_name class name containing this method param cp constant pool 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 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); }

Methods Summary
public void	addCodeAttribute(com.sun.org.apache.bcel.internal.classfile.Attribute a) 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 code_attrs_vec.add(a);
public void	addException(java.lang.String class_name) Add an exception possibly thrown by this method. param class_name (fully qualified) name of exception throws_vec.add(class_name);
public com.sun.org.apache.bcel.internal.generic.CodeExceptionGen	addExceptionHandler(com.sun.org.apache.bcel.internal.generic.InstructionHandle start_pc, com.sun.org.apache.bcel.internal.generic.InstructionHandle end_pc, com.sun.org.apache.bcel.internal.generic.InstructionHandle handler_pc, com.sun.org.apache.bcel.internal.generic.ObjectType catch_type) 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 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;
public com.sun.org.apache.bcel.internal.generic.LineNumberGen	addLineNumber(com.sun.org.apache.bcel.internal.generic.InstructionHandle ih, int src_line) Give an instruction a line number corresponding to the source code line. param ih instruction to tag return new line number object see LineNumber LineNumberGen l = new LineNumberGen(ih, src_line); line_number_vec.add(l); return l;
public com.sun.org.apache.bcel.internal.generic.LocalVariableGen	addLocalVariable(java.lang.String name, com.sun.org.apache.bcel.internal.generic.Type type, int slot, com.sun.org.apache.bcel.internal.generic.InstructionHandle start, com.sun.org.apache.bcel.internal.generic.InstructionHandle end) 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 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"); }
public com.sun.org.apache.bcel.internal.generic.LocalVariableGen	addLocalVariable(java.lang.String name, com.sun.org.apache.bcel.internal.generic.Type type, com.sun.org.apache.bcel.internal.generic.InstructionHandle start, com.sun.org.apache.bcel.internal.generic.InstructionHandle end) 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 return addLocalVariable(name, type, max_locals, start, end);
public void	addObserver(com.sun.org.apache.bcel.internal.generic.MethodObserver o) Add observer for this object. if(observers == null) observers = new ArrayList(); observers.add(o);
public com.sun.org.apache.bcel.internal.generic.MethodGen	copy(java.lang.String class_name, com.sun.org.apache.bcel.internal.generic.ConstantPoolGen cp) return deep copy of this method 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;
public java.lang.String	getArgumentName(int i) return arg_names[i];
public java.lang.String[]	getArgumentNames() return (String[])arg_names.clone();
public com.sun.org.apache.bcel.internal.generic.Type	getArgumentType(int i) return arg_types[i];
public com.sun.org.apache.bcel.internal.generic.Type[]	getArgumentTypes() return (Type[])arg_types.clone();
public java.lang.String	getClassName() return class that contains this method return class_name;
public com.sun.org.apache.bcel.internal.classfile.Attribute[]	getCodeAttributes() return all attributes of this method. Attribute[] attributes = new Attribute[code_attrs_vec.size()]; code_attrs_vec.toArray(attributes); return attributes;
private com.sun.org.apache.bcel.internal.classfile.CodeException[]	getCodeExceptions() return code exceptions for `Code' attribute 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;
public com.sun.org.apache.bcel.internal.generic.CodeExceptionGen[]	getExceptionHandlers() CodeExceptionGen[] cg = new CodeExceptionGen[exception_vec.size()]; exception_vec.toArray(cg); return cg;
private com.sun.org.apache.bcel.internal.classfile.ExceptionTable	getExceptionTable(com.sun.org.apache.bcel.internal.generic.ConstantPoolGen cp) return `Exceptions' attribute of all the exceptions thrown by this method. 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());
public java.lang.String[]	getExceptions() String[] e = new String[throws_vec.size()]; throws_vec.toArray(e); return e;
public com.sun.org.apache.bcel.internal.generic.InstructionList	getInstructionList() return il;
public com.sun.org.apache.bcel.internal.classfile.LineNumberTable	getLineNumberTable(com.sun.org.apache.bcel.internal.generic.ConstantPoolGen cp) return `LineNumberTable' attribute of all the local variables of this method. 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());
public com.sun.org.apache.bcel.internal.generic.LineNumberGen[]	getLineNumbers() LineNumberGen[] lg = new LineNumberGen[line_number_vec.size()]; line_number_vec.toArray(lg); return lg;
public com.sun.org.apache.bcel.internal.classfile.LocalVariableTable	getLocalVariableTable(com.sun.org.apache.bcel.internal.generic.ConstantPoolGen cp) return `LocalVariableTable' attribute of all the local variables of this method. 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());
public com.sun.org.apache.bcel.internal.generic.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;
public int	getMaxLocals() return max_locals;
public int	getMaxStack() return max_stack;
public static int	getMaxStack(com.sun.org.apache.bcel.internal.generic.ConstantPoolGen cp, com.sun.org.apache.bcel.internal.generic.InstructionList il, com.sun.org.apache.bcel.internal.generic.CodeExceptionGen[] et) Computes stack usage of an instruction list by performing control flow analysis. return maximum stack depth used by method 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;
public com.sun.org.apache.bcel.internal.classfile.Method	getMethod() 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 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;
public com.sun.org.apache.bcel.internal.generic.Type	getReturnType() return getType();
public java.lang.String	getSignature() return Type.getMethodSignature(type, arg_types);
public void	removeCodeAttribute(com.sun.org.apache.bcel.internal.classfile.Attribute a) Remove a code attribute. code_attrs_vec.remove(a);
public void	removeCodeAttributes() Remove all code attributes. code_attrs_vec.clear();
public void	removeException(java.lang.String c) Remove an exception. throws_vec.remove(c);
public void	removeExceptionHandler(com.sun.org.apache.bcel.internal.generic.CodeExceptionGen c) Remove an exception handler. exception_vec.remove(c);
public void	removeExceptionHandlers() Remove all line numbers. exception_vec.clear();
public void	removeExceptions() Remove all exceptions. throws_vec.clear();
public void	removeLineNumber(com.sun.org.apache.bcel.internal.generic.LineNumberGen l) Remove a line number. line_number_vec.remove(l);
public void	removeLineNumbers() Remove all line numbers. line_number_vec.clear();
public void	removeLocalVariable(com.sun.org.apache.bcel.internal.generic.LocalVariableGen l) Remove a local variable, its slot will not be reused, if you do not use addLocalVariable with an explicit index argument. variable_vec.remove(l);
public void	removeLocalVariables() Remove all local variables. variable_vec.clear();
public void	removeNOPs() 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. 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); } } } } }
public void	removeObserver(com.sun.org.apache.bcel.internal.generic.MethodObserver o) Remove observer for this object. if(observers != null) observers.remove(o);
public void	setArgumentName(int i, java.lang.String name) arg_names[i] = name;
public void	setArgumentNames(java.lang.String[] arg_names) this.arg_names = arg_names;
public void	setArgumentType(int i, com.sun.org.apache.bcel.internal.generic.Type type) arg_types[i] = type;
public void	setArgumentTypes(com.sun.org.apache.bcel.internal.generic.Type[] arg_types) this.arg_types = arg_types;
public void	setClassName(java.lang.String class_name) this.class_name = class_name;
public void	setInstructionList(com.sun.org.apache.bcel.internal.generic.InstructionList il) this.il = il;
public void	setMaxLocals(int m) Set maximum number of local variables. max_locals = m;
public void	setMaxLocals() Compute maximum number of local variables. 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;
public void	setMaxStack(int m) Set maximum stack size for this method. max_stack = m;
public void	setMaxStack() Computes max. stack size by performing control flow analysis. if(il != null) max_stack = getMaxStack(cp, il, getExceptionHandlers()); else max_stack = 0;
public void	setReturnType(com.sun.org.apache.bcel.internal.generic.Type return_type) setType(return_type);
private static final void	sort(com.sun.org.apache.bcel.internal.generic.LocalVariableGen[] vars, int l, int r) Sort local variables by index 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);
public void	stripAttributes(boolean flag) Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O strip_attributes = flag;
public final java.lang.String	toString() Return string representation close to declaration format, `public static void _main(String[]) throws IOException', e.g. return String representation of the method. 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();
public void	update() 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. if(observers != null) for(Iterator e = observers.iterator(); e.hasNext(); ) ((MethodObserver)e.next()).notify(this);