org.objectweb.asm.commons.TryCatchBlockSorter Maven / Gradle / Ivy
package org.objectweb.asm.commons;
import java.util.Collections;
import java.util.Comparator;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.TryCatchBlockNode;
/**
* Sorts the exception handlers in a method innermost-to-outermost. This allows
* the programmer to add handlers without worrying about ordering them correctly
* with respect to existing, in-code handlers.
*
* Behavior is only defined for properly-nested handlers. If any "try" blocks
* overlap (something that isn't possible in Java code) then this may not do
* what you want. In fact, this adapter just sorts by the length of the "try"
* block, taking advantage of the fact that a given try block must be larger
* than any block it contains).
*
* @author Adrian Sampson
*/
public class TryCatchBlockSorter extends MethodNode {
private final MethodVisitor mv;
public TryCatchBlockSorter(
final MethodVisitor mv,
final int access,
final String name,
final String desc,
final String signature,
final String[] exceptions)
{
super(access, name, desc, signature, exceptions);
this.mv = mv;
}
public void visitEnd() {
// Compares TryCatchBlockNodes by the length of their "try" block.
Comparator comp = new Comparator() {
public int compare(Object o1, Object o2) {
int len1 = blockLength((TryCatchBlockNode) o1);
int len2 = blockLength((TryCatchBlockNode) o2);
return len1 - len2;
}
private int blockLength(TryCatchBlockNode block) {
int startidx = instructions.indexOf(block.start);
int endidx = instructions.indexOf(block.end);
return endidx - startidx;
}
};
Collections.sort(tryCatchBlocks, comp);
if (mv != null) {
accept(mv);
}
}
}