/*
* Bytecode Analysis Framework
* Copyright (C) 2003,2004 University of Maryland
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package edu.umd.cs.findbugs.ba.bcp;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.InstructionHandle;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.Edge;
import edu.umd.cs.findbugs.ba.vna.ValueNumberFrame;
/**
* A PatternElement is an element of a ByteCodePattern.
* It potentially matches some number of bytecode instructions.
*/
public abstract class PatternElement {
private static final boolean DEBUG = SystemProperties.getBoolean("bcp.debug");
private PatternElement next;
private String label;
private String dominatedBy;
private int index;
private boolean allowTrailingEdges = true;
/**
* Get the next PatternElement.
*/
public PatternElement getNext() {
return next;
}
/**
* Set the next PatternElement.
*/
public void setNext(PatternElement patternElement) {
this.next = patternElement;
}
/**
* Set a label for this PatternElement.
*
* @param label the label
* @return this object
*/
public PatternElement label(String label) {
this.label = label;
return this;
}
/**
* Get the label of this PatternElement.
*
* @return the label, or null if the PatternElement is not labeled
*/
public String getLabel() {
return label;
}
/**
* Set the label of another pattern element whose first
* matched instruction must dominate the instruction(s) matched
* by this element.
*/
public PatternElement dominatedBy(String dominatedBy) {
this.dominatedBy = dominatedBy;
return this;
}
/**
* Get the label of the pattern element whose first
* matched instruction must dominate the instruction(s) matched
* by this element.
*/
public String getDominatedBy() {
return dominatedBy;
}
/**
* Set the index. This is just for debugging.
*/
public void setIndex(int index) {
this.index = index;
}
/**
* Set whether or not this PatternElement allows trailing edges to be matched.
* By default, trailing edges may be matched. When this value is set
* to false, it ensures that the successor instruction must be in the
* same basic block.
*
* @param allowTrailingEdges true if trailing edges may be matched,
* false if trailing edges will never be matched
*/
public PatternElement setAllowTrailingEdges(boolean allowTrailingEdges) {
this.allowTrailingEdges = allowTrailingEdges;
return this;
}
/**
* Return whether or not this PatternElement may match trailing edges.
*/
public boolean allowTrailingEdges() {
return allowTrailingEdges;
}
/**
* Look up a variable definition in given BindingSet.
*
* @param varName the name of the variable
* @param bindingSet the BindingSet to look in
* @return the Variable, or null if no Variable is bound to the name
*/
public static Variable lookup(String varName, BindingSet bindingSet) {
if (bindingSet == null)
return null;
Binding binding = bindingSet.lookup(varName);
return (binding != null) ? binding.getVariable() : null;
}
/**
* Return whether or not this element matches the given
* instruction with the given Bindings in effect.
*
* @param handle the instruction
* @param cpg the ConstantPoolGen from the method
* @param before the ValueNumberFrame representing values in the Java stack frame
* just before the execution of the instruction
* @param after the ValueNumberFrame representing values in the Java stack frame
* just after the execution of the instruction
* @param bindingSet the set of Bindings
* @return if the match is successful, returns a MatchResult with the PatternElement
* and BindingSet; if the match is not successful, returns null
*/
public abstract MatchResult match(InstructionHandle handle, ConstantPoolGen cpg,
ValueNumberFrame before, ValueNumberFrame after, BindingSet bindingSet) throws DataflowAnalysisException;
/**
* Return whether or not it is acceptable to take the given branch.
*
* @param edge the Edge representing the branch
* @param source the source instruction of the branch
* @return true if the Edge is acceptable, false if not
*/
public abstract boolean acceptBranch(Edge edge, InstructionHandle source);
/**
* Return the minimum number of instructions this PatternElement
* must match in the ByteCodePattern.
*/
public abstract int minOccur();
/**
* Return the maximum number of instructions this PatternElement
* must match in the ByteCodePattern.
*/
public abstract int maxOccur();
/**
* Add a variable definition to the given BindingSet, or if
* there is an existing definition, make sure it is consistent with
* the new definition.
*
* @param varName the name of the variable
* @param variable the Variable which should be added or checked for consistency
* @param bindingSet the existing set of bindings
* @return the updated BindingSet (if the variable is consistent with the
* previous bindings), or null if the new variable is inconsistent with
* the previous bindings
*/
protected static BindingSet addOrCheckDefinition(String varName, Variable variable, BindingSet bindingSet) {
Variable existingVariable = lookup(varName, bindingSet);
if (existingVariable == null) {
bindingSet = new BindingSet(new Binding(varName, variable), bindingSet);
} else {
if (!existingVariable.sameAs(variable)) {
if (DEBUG) System.out.println("\tConflicting variable " + varName + ": " + variable + " != " + existingVariable);
return null;
}
}
return bindingSet;
}
@Override
public String toString() {
StringBuilder buf = new StringBuilder();
String className = this.getClass().getName();
buf.append(className.substring(className.lastIndexOf('.') + 1));
buf.append('(');
buf.append(index);
buf.append(')');
return buf.toString();
}
}
// vim:ts=4