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- /*
- * Javassist, a Java-bytecode translator toolkit.
- * Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. Alternatively, the contents of this file may be used under
- * the terms of the GNU Lesser General Public License Version 2.1 or later,
- * or the Apache License Version 2.0.
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- */
- package javassist.bytecode.analysis;
-
- import java.util.HashMap;
- import java.util.HashSet;
- import java.util.Map;
- import java.util.Set;
-
- import javassist.bytecode.BadBytecode;
- import javassist.bytecode.CodeAttribute;
- import javassist.bytecode.CodeIterator;
- import javassist.bytecode.ExceptionTable;
- import javassist.bytecode.MethodInfo;
- import javassist.bytecode.Opcode;
-
- /**
- * Discovers the subroutines in a method, and tracks all callers.
- *
- * @author Jason T. Greene
- */
- public class SubroutineScanner implements Opcode {
-
- private Subroutine[] subroutines;
- Map subTable = new HashMap();
- Set done = new HashSet();
-
-
- public Subroutine[] scan(MethodInfo method) throws BadBytecode {
- CodeAttribute code = method.getCodeAttribute();
- CodeIterator iter = code.iterator();
-
- subroutines = new Subroutine[code.getCodeLength()];
- subTable.clear();
- done.clear();
-
- scan(0, iter, null);
-
- ExceptionTable exceptions = code.getExceptionTable();
- for (int i = 0; i < exceptions.size(); i++) {
- int handler = exceptions.handlerPc(i);
- // If an exception is thrown in subroutine, the handler
- // is part of the same subroutine.
- scan(handler, iter, subroutines[exceptions.startPc(i)]);
- }
-
- return subroutines;
- }
-
- private void scan(int pos, CodeIterator iter, Subroutine sub) throws BadBytecode {
- // Skip already processed blocks
- if (done.contains(new Integer(pos)))
- return;
-
- done.add(new Integer(pos));
-
- int old = iter.lookAhead();
- iter.move(pos);
-
- boolean next;
- do {
- pos = iter.next();
- next = scanOp(pos, iter, sub) && iter.hasNext();
- } while (next);
-
- iter.move(old);
- }
-
- private boolean scanOp(int pos, CodeIterator iter, Subroutine sub) throws BadBytecode {
- subroutines[pos] = sub;
-
- int opcode = iter.byteAt(pos);
-
- if (opcode == TABLESWITCH) {
- scanTableSwitch(pos, iter, sub);
-
- return false;
- }
-
- if (opcode == LOOKUPSWITCH) {
- scanLookupSwitch(pos, iter, sub);
-
- return false;
- }
-
- // All forms of return and throw end current code flow
- if (Util.isReturn(opcode) || opcode == RET || opcode == ATHROW)
- return false;
-
- if (Util.isJumpInstruction(opcode)) {
- int target = Util.getJumpTarget(pos, iter);
- if (opcode == JSR || opcode == JSR_W) {
- Subroutine s = (Subroutine) subTable.get(new Integer(target));
- if (s == null) {
- s = new Subroutine(target, pos);
- subTable.put(new Integer(target), s);
- scan(target, iter, s);
- } else {
- s.addCaller(pos);
- }
- } else {
- scan(target, iter, sub);
-
- // GOTO ends current code flow
- if (Util.isGoto(opcode))
- return false;
- }
- }
-
- return true;
- }
-
- private void scanLookupSwitch(int pos, CodeIterator iter, Subroutine sub) throws BadBytecode {
- int index = (pos & ~3) + 4;
- // default
- scan(pos + iter.s32bitAt(index), iter, sub);
- int npairs = iter.s32bitAt(index += 4);
- int end = npairs * 8 + (index += 4);
-
- // skip "match"
- for (index += 4; index < end; index += 8) {
- int target = iter.s32bitAt(index) + pos;
- scan(target, iter, sub);
- }
- }
-
- private void scanTableSwitch(int pos, CodeIterator iter, Subroutine sub) throws BadBytecode {
- // Skip 4 byte alignment padding
- int index = (pos & ~3) + 4;
- // default
- scan(pos + iter.s32bitAt(index), iter, sub);
- int low = iter.s32bitAt(index += 4);
- int high = iter.s32bitAt(index += 4);
- int end = (high - low + 1) * 4 + (index += 4);
-
- // Offset table
- for (; index < end; index += 4) {
- int target = iter.s32bitAt(index) + pos;
- scan(target, iter, sub);
- }
- }
-
-
- }
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