soot.jimple.spark.ondemand.genericutil.FIFOQueue Maven / Gradle / Ivy
package soot.jimple.spark.ondemand.genericutil;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 2007 Manu Sridharan
* %%
* This program 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 program 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 Lesser Public License for more details.
*
* You should have received a copy of the GNU General Lesser Public
* License along with this program. If not, see
* .
* #L%
*/
/**
* A FIFO queue of objects, implemented as a circular buffer. NOTE: elements stored in the buffer should be non-null; this is
* not checked for performance reasons.
*
* @author Manu Sridharan
*/
public final class FIFOQueue {
/**
* the buffer.
*/
private Object[] _buf;
/**
* pointer to current top of buffer
*/
private int _top;
/**
* point to current bottom of buffer, where things will be added invariant: after call to add / remove, should always point
* to an empty slot in the buffer
*/
private int _bottom;
/**
* @param initialSize_
* the initial size of the queue
*/
public FIFOQueue(int initialSize_) {
_buf = new Object[initialSize_];
}
public FIFOQueue() {
this(10);
}
public boolean push(Object obj_) {
return add(obj_);
}
/**
* add an element to the bottom of the queue
*/
public boolean add(Object obj_) {
// Assert.chk(obj_ != null);
// add the element
_buf[_bottom] = obj_;
// increment bottom, wrapping around if necessary
_bottom = (_bottom == _buf.length - 1) ? 0 : _bottom + 1;
// see if we need to increase the queue size
if (_bottom == _top) {
// allocate a new array and copy
int oldLen = _buf.length;
int newLen = oldLen * 2;
// System.out.println("growing buffer to size " + newLen);
Object[] newBuf = new Object[newLen];
int topToEnd = oldLen - _top;
int newTop = newLen - topToEnd;
// copy from 0 to _top to beginning of new buffer,
// _top to _buf.length to the end of the new buffer
System.arraycopy(_buf, 0, newBuf, 0, _top);
System.arraycopy(_buf, _top, newBuf, newTop, topToEnd);
_buf = newBuf;
_top = newTop;
return true;
}
return false;
}
public Object pop() {
return remove();
}
/**
* remove the top element from the buffer
*/
public Object remove() {
// check if buffer is empty
if (_bottom == _top) {
return null;
}
Object ret = _buf[_top];
// increment top, wrapping if necessary
_top = (_top == _buf.length - 1) ? 0 : _top + 1;
return ret;
}
public boolean isEmpty() {
return _bottom == _top;
}
public String toString() {
return _bottom + " " + _top;
}
public void clear() {
_bottom = 0;
_top = 0;
}
}