org.apache.xbean.asm7.tree.analysis.Subroutine Maven / Gradle / Ivy
// ASM: a very small and fast Java bytecode manipulation framework
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package org.objectweb.asm.tree.analysis;
import java.util.ArrayList;
import java.util.List;
import org.objectweb.asm.tree.JumpInsnNode;
import org.objectweb.asm.tree.LabelNode;
/**
* A method subroutine (corresponds to a JSR instruction).
*
* @author Eric Bruneton
*/
final class Subroutine {
/** The start of this subroutine. */
final LabelNode start;
/**
* The local variables that are read or written by this subroutine. The i-th element is true if
* and only if the local variable at index i is read or written by this subroutine.
*/
final boolean[] localsUsed;
/** The JSR instructions that jump to this subroutine. */
final List callers;
/**
* Constructs a new {@link Subroutine}.
*
* @param start the start of this subroutine.
* @param maxLocals the local variables that are read or written by this subroutine.
* @param caller a JSR instruction that jump to this subroutine.
*/
Subroutine(final LabelNode start, final int maxLocals, final JumpInsnNode caller) {
this.start = start;
this.localsUsed = new boolean[maxLocals];
this.callers = new ArrayList();
callers.add(caller);
}
/**
* Constructs a copy of the given {@link Subroutine}.
*
* @param subroutine the subroutine to copy.
*/
Subroutine(final Subroutine subroutine) {
this.start = subroutine.start;
this.localsUsed = new boolean[subroutine.localsUsed.length];
this.callers = new ArrayList(subroutine.callers);
System.arraycopy(subroutine.localsUsed, 0, this.localsUsed, 0, subroutine.localsUsed.length);
}
/**
* Merges the given subroutine into this subroutine. The local variables read or written by the
* given subroutine are marked as read or written by this one, and the callers of the given
* subroutine are added as callers of this one (if both have the same start).
*
* @param subroutine another subroutine. This subroutine is left unchanged by this method.
* @return whether this subroutine has been modified by this method.
*/
public boolean merge(final Subroutine subroutine) {
boolean changed = false;
for (int i = 0; i < localsUsed.length; ++i) {
if (subroutine.localsUsed[i] && !localsUsed[i]) {
localsUsed[i] = true;
changed = true;
}
}
if (subroutine.start == start) {
for (int i = 0; i < subroutine.callers.size(); ++i) {
JumpInsnNode caller = subroutine.callers.get(i);
if (!callers.contains(caller)) {
callers.add(caller);
changed = true;
}
}
}
return changed;
}
}