com.scudata.dm.cursor.ConjxCursor Maven / Gradle / Ivy

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SPL(Structured Process Language) A programming language specially for structured data computing.

There is a newer version: 20240823

package com.scudata.dm.cursor;

import com.scudata.dm.Context;
import com.scudata.dm.Sequence;

/**
 * ?Ѷ???α?????????һ???α꣬ȡ??ʱ?????α???ÿ???αֱ꣬?????һ???α?ȡ??????
 * ?ṹ?Ե?һ???α?Ϊ׼
 * @author 
 *
 */
public class ConjxCursor extends ICursor {
	private ICursor []cursors; // ?α?????
	private int curIndex = 0; // ??ǰ???ڶ??????α?????

	/**
	 * ?????????????α????
	 * @param cursors
	 */
	public ConjxCursor(ICursor []cursors) {
		this.cursors = cursors;
		setDataStruct(cursors[0].getDataStruct());
	}
	
	// ???м???ʱ??Ҫ?ı???????
	// ?̳???????õ??˱???ʽ????Ҫ?????????????½???????ʽ
	public void resetContext(Context ctx) {
		if (this.ctx != ctx) {
			for (ICursor cursor : cursors) {
				cursor.resetContext(ctx);
			}
			
			super.resetContext(ctx);
		}
	}

	/**
	 * ??ȡָ???????????ݷ???
	 * @param n ????
	 * @return Sequence
	 */
	protected Sequence get(int n) {
		if (cursors.length == curIndex || n < 1) return null;
		Sequence table = cursors[curIndex].fetch(n);
		if (table == null || table.length() < n) {
			curIndex++;
			if (curIndex < cursors.length) {
				if (table == null) {
					return get(n);
				} else {
					Sequence rest;
					if (n == MAXSIZE) {
						rest = get(n);
					} else {
						rest = get(n - table.length());
					}
					
					table = append(table, rest);
				}
			}
		}

		return table;
	}

	/**
	 * ????ָ????????????
	 * @param n ????
	 * @return long ʵ????????????
	 */
	protected long skipOver(long n) {
		if (cursors.length == curIndex || n < 1) return 0;

		long count = cursors[curIndex].skip(n);
		if (count < n) {
			curIndex++;
			if (curIndex < cursors.length) {
				count += skipOver(n - count);
			}
		}

		return count;
	}

	/**
	 * ?ر??α?
	 */
	public synchronized void close() {
		super.close();
		
		for (int i = 0, count = cursors.length; i < count; ++i) {
			cursors[i].close();
		}
	}
	
	/**
	 * ?????α?
	 * @return ?????Ƿ?ɹ???true???α???Դ?ͷ????ȡ????false???????Դ?ͷ????ȡ??
	 */
	public boolean reset() {
		curIndex = 0;
		for (int i = 0, count = cursors.length; i < count; ++i) {
			if (!cursors[i].reset()) {
				return false;
			}
		}
		
		return true;
	}
	
	public ICursor[] getCursors() {
		return cursors;
	}
}