CharBufferSpliterator.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package java.nio;

import java.util.Spliterator;
import java.util.function.IntConsumer;

/**
 * A Spliterator.OfInt for sources that traverse and split elements maintained in a CharBuffer.
 *
 * @implNote The implementation is based on the code for the Array-based spliterators.
 */
// 字符序列的流迭代器
class CharBufferSpliterator implements Spliterator.OfInt {
    private final CharBuffer buffer;    // 字符缓冲区
    private int index;                  // 当前元素的游标，会被advance/split改变
    private final int limit;            // 游标上限
    
    CharBufferSpliterator(CharBuffer buffer) {
        this(buffer, buffer.position(), buffer.limit());
    }
    
    CharBufferSpliterator(CharBuffer buffer, int origin, int limit) {
        assert origin<=limit;
        this.buffer = buffer;
        this.index = Math.min(origin, limit);
        this.limit = limit;
    }
    
    /*
     * 返回子Spliterator，该子Spliterator内持有原Spliterator的部分数据。
     *
     * 注1：该操作可能会引起内部游标的变化
     * 注2：子Spliterator的参数可能发生改变
     */
    @Override
    public OfInt trySplit() {
        int lo = index, mid = (lo + limit) >>> 1;
        if(lo >= mid) {
            return null;
        }
        
        return new CharBufferSpliterator(buffer, lo, index = mid);
    }
    
    /*
     * 尝试用action消费当前流迭代器中下一个元素。
     * 返回值指示是否找到了下一个元素。
     *
     * 注1：该操作可能会引起内部游标的变化
     * 注2：该操作可能会顺着sink链向下游传播
     */
    @Override
    public boolean tryAdvance(IntConsumer action) {
        if(action == null) {
            throw new NullPointerException();
        }
        
        if(index<0 || index >= limit) {
            return false;
        }
        
        action.accept(buffer.getUnchecked(index++));
        
        return true;
    }
    
    /*
     * 尝试用action逐个消费当前流迭代器中所有剩余元素。
     *
     * 注1：该操作可能会引起内部游标的变化
     * 注2：该操作可能会顺着sink链向下游传播
     */
    @Override
    public void forEachRemaining(IntConsumer action) {
        if(action == null) {
            throw new NullPointerException();
        }
        
        CharBuffer cb = buffer;
        int i = index;
        int hi = limit;
        index = hi;
        while(i<hi) {
            action.accept(cb.getUnchecked(i++));
        }
    }
    
    // 返回元素数量
    @Override
    public long estimateSize() {
        return (long) (limit - index);
    }
    
    // 返回流迭代器的参数
    @Override
    public int characteristics() {
        return Buffer.SPLITERATOR_CHARACTERISTICS;
    }
    
}