/* This file is part of the db4o object database http://www.db4o.com
Copyright (C) 2004 - 2011 Versant Corporation http://www.versant.com
db4o is free software; you can redistribute it and/or modify it under
the terms of version 3 of the GNU General Public License as published
by the Free Software Foundation.
db4o is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License along
with this program. If not, see http://www.gnu.org/licenses/. */
package EDU.purdue.cs.bloat.cfg;
import java.io.*;
import java.util.*;
import EDU.purdue.cs.bloat.editor.*;
import EDU.purdue.cs.bloat.tree.*;
/**
* Subroutine represents a subroutine (target of a <i>jsr</i> instruction) in
* java bytecode. Subroutines are used to implement the finally part of a
* try-catch-finally block.
* <p>
* Each Subroutine belongs in a control flow graph, has an entry and exit block,
* and has a local variable that contains its return address. Additionally, it
* maintains a list of paths from blocks in which the subroutine is called to
* block that is executed after the subroutine returns.
* <p>
* Note that it is assumed that each subroutine ends with a <i>ret</i>. While
* this is true for bytecode generated by javac, it is not required.
*
* @see AddressStoreStmt
* @see Block
*/
// Important: I assume there is a ret statement for each jsr.
// This is true for javac code, but not in general.
public class Subroutine {
FlowGraph graph; // CFG containing this Subroutine
Block entry; // Basic Block at beginning of code
Block exit; // Basic Block ending code
ArrayList paths;
LocalVariable returnAddress; // This Subroutine's return address
/**
* Constructor.
*
* @param graph
* The CFG containing the block.
*/
public Subroutine(final FlowGraph graph) {
this.graph = graph;
this.entry = null;
this.exit = null;
this.paths = new ArrayList();
this.returnAddress = null;
}
/**
* Returns the local variable containing the return address of this
* subroutine.
*/
public LocalVariable returnAddress() {
return returnAddress;
}
/**
* Sets the address (stored in a LocalVariable) to which this subroutine
* will return once it is finished.
*
* @param returnAddress
* Local variable that stores the address to which the subroutine
* returns when it is completed.
*
* @see Tree#visit_astore
*/
public void setReturnAddress(final LocalVariable returnAddress) {
this.returnAddress = returnAddress;
}
/**
* Returns the number of places that this subroutine is called.
*/
public int numPaths() {
return paths.size();
}
/**
* Returns the paths (a Collection of two-element arrays of Blocks) that
* represent the Blocks that end in a call to this subroutine and the block
* that begin with the return address from this subroutine.
*/
public Collection paths() {
return paths;
}
/**
* Returns the CFG that contains this subroutine.
*/
public FlowGraph graph() {
return graph;
}
/**
* Removes all paths involving block regardless of whether it is a calling
* (source) block or a returning (target) block.
*/
public void removePathsContaining(final Block block) {
for (int i = paths.size() - 1; i >= 0; i--) {
final Block[] path = (Block[]) paths.get(i);
if ((path[0] == block) || (path[1] == block)) {
if (FlowGraph.DEBUG) {
System.out.println("removing path " + path[0] + " -> "
+ path[1]);
}
paths.remove(i);
}
}
}
/**
* Removes a path between a caller Block and a return Block.
*/
public void removePath(final Block callerBlock, final Block returnBlock) {
for (int i = 0; i < paths.size(); i++) {
final Block[] path = (Block[]) paths.get(i);
if ((path[0] == callerBlock) && (path[1] == returnBlock)) {
if (FlowGraph.DEBUG) {
System.out.println("removing path " + path[0] + " -> "
+ path[1]);
}
paths.remove(i);
return;
}
}
}
/**
* Removes all caller-return paths.
*/
public void removeAllPaths() {
paths = new ArrayList();
}
/**
* Adds a path from the block before a Subroutine is called to a block after
* the subroutine is called. If the callerBlock is already associated with a
* returnBlock, the old returnBlock is replaced.
*
* @param callerBlock
* The block in which the subroutine is called. This Block ends
* with a <i>jsr</i> to this subroutine.
* @param returnBlock
* The block to which the subroutine returns. This Block begins
* at the return address of this subroutine.
*/
public void addPath(final Block callerBlock, final Block returnBlock) {
for (int i = 0; i < paths.size(); i++) {
final Block[] path = (Block[]) paths.get(i);
if (path[0] == callerBlock) {
path[1] = returnBlock;
return;
}
}
paths.add(new Block[] { callerBlock, returnBlock });
}
/**
* Returns the "return block" for a given "caller block".
*/
public Block pathTarget(final Block block) {
for (int i = 0; i < paths.size(); i++) {
final Block[] path = (Block[]) paths.get(i);
if (path[0] == block) {
return path[1];
}
}
return null;
}
/**
* Returns the "caller block" for a given "return block".
*/
public Block pathSource(final Block block) {
for (int i = 0; i < paths.size(); i++) {
final Block[] path = (Block[]) paths.get(i);
if (path[1] == block) {
return path[0];
}
}
return null;
}
/**
* Sets the entry Block for this Subroutine.
*/
public void setEntry(final Block entry) {
this.entry = entry;
}
/**
* Sets the exit Block for this Subroutine.
*/
public void setExit(final Block exit) {
this.exit = exit;
}
/**
* Returns the first Block in the subroutine.
*/
public Block entry() {
return entry;
}
/**
* Returns the last Block in the subroutine.
*/
public Block exit() {
return exit;
}
/**
* Prints a textual representation of this Subroutine.
*
* @param out
* The PrintStream to which to print.
*/
public void print(final PrintStream out) {
out.println(" " + entry);
final Iterator e = paths().iterator();
while (e.hasNext()) {
final Block[] path = (Block[]) e.next();
out.println(" path: " + path[0] + " -> " + path[1]);
}
}
public String toString() {
return "sub " + entry;
}
}