com.jd.blockchain.utils.AbstractSkippingIterator Maven / Gradle / Ivy
package com.jd.blockchain.utils;
/**
* {@link AbstractSkippingIterator} 提供了对 {@link SkippingIterator} 的基础实现；
*
*
*
* 遍历的结果是得到一个数据差集：包含在新数据默克尔树中，但不包含在比较基准默克尔树中的数据集合；
*
* @author huanghaiquan
*
* @param
*/
public abstract class AbstractSkippingIterator implements SkippingIterator {
// TODO: seal the access of cursor;
protected long cursor = -1;
public long getCursor() {
return cursor;
}
@Override
public boolean hasNext() {
return cursor + 1 < getTotalCount();
}
@Override
public long skip(long skippingCount) {
if (skippingCount < 0) {
throw new IllegalArgumentException("The specified count is out of bound!");
}
if (skippingCount == 0) {
return 0;
}
long count = getTotalCount();
if (cursor + skippingCount < count) {
cursor += skippingCount;
return skippingCount;
}
long skipped = count - cursor - 1;
cursor = count - 1;
return skipped;
}
@Override
public T next() {
if (!hasNext()) {
return null;
}
T v = get(cursor + 1);
cursor++;
return v;
}
/**
* 返回指定游标位置的元素；
*
* @param cursor 游标位置；取值范围大于等于 0 ， 小于 {@link #getTotalCount()};
* @return
*/
protected T get(long cursor) {
throw new UnsupportedOperationException();
}
}