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

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SPL(Structured Process Language) A programming language specially for structured data computing.
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package com.scudata.dm.cursor;

import java.io.IOException;

import com.scudata.common.RQException;
import com.scudata.dm.BFileReader;
import com.scudata.dm.Context;
import com.scudata.dm.DataStruct;
import com.scudata.dm.Env;
import com.scudata.dm.FileObject;
import com.scudata.dm.Sequence;

/**
 * ???ļ??α?
 * @author
 *
 */
public class BFileCursor extends ICursor {
	private FileObject fileObject; // ?ļ?????
	private String []fields; // ѡ???ֶ?
	
	// ???ڶ??߳?????
	private int segSeq; // ?ֶκ?
	private int segCount; // ?ܶ???
	
	private String opt; // ѡ??
	private int fileBufSize = Env.FILE_BUFSIZE; // ???????ļ?ʱ?Ļ???????С
	private BFileReader reader; // ???ļ???ȡ??
	private boolean isDeleteFile; // ?α?رպ?ɾ??Դ?ļ??????ڼ???????в???????ʱ???ļ?

	// ?Էֶ??????㣬??????????ļ?????ʼλ?úͽ???λ?ã???????ͷȥβ????
	private long startPos = -1;
	private long endPos;
	
	/**
	 * ???????ļ??α?
	 * @param fileObject ?ļ?????
	 * @param fields ѡ???ֶ?
	 * @param opt ѡ??
	 * @param ctx ??????????
	 */
	public BFileCursor(FileObject fileObject, String []fields, String opt, Context ctx) {
		this(fileObject, fields, 1, 1, opt, ctx);
	}

	/**
	 * ???????ļ??α?
	 * @param fileObject ?ļ?????
	 * @param fields ѡ???ֶ?
	 * @param segSeq ??ǰ?α?Ҫ???ĶΣ???1??ʼ????
	 * @param segCount ?ֶ???
	 * @param opt ѡ??
	 * @param ctx ??????????
	 */
	public BFileCursor(FileObject fileObject, String []fields, 
			int segSeq, int segCount, String opt, Context ctx) {
		this.fileObject = fileObject;
		this.fields = fields;
		this.segSeq = segSeq;
		this.segCount = segCount;
		this.opt = opt;
		
		this.ctx = ctx;
		reader = new BFileReader(fileObject, fields, segSeq, segCount, opt);
		if (opt != null) {
			if (opt.indexOf('x') != -1) {
				if (ctx != null) ctx.addResource(this);
				isDeleteFile = true;
			}
		}
	}

	/**
	 * ???ö??ļ?????ʼλ?úͽ???λ??
	 * @param startPos ??ʼλ?ã???????ͷȥβ????
	 * @param endPos ????λ??
	 */
	public void setPosRange(long startPos, long endPos) {
		this.startPos = startPos;
		this.endPos = endPos;
	}
	
	/**
	 * ???ö??ļ?????????С
	 * @param size
	 */
	public void setFileBufferSize(int size) {
		this.fileBufSize = size;
	}

	/**
	 * ??ȡָ???????????ݷ???
	 * @param n ????
	 * @return Sequence
	 */
	protected Sequence get(int n) {
		if (n < 1 || reader == null) {
			return null;
		}
		
		try {
			if (!reader.isOpen()) {
				reader.open(fileBufSize);
				DataStruct ds = reader.getResultSetDataStruct();
				setDataStruct(ds);
				
				if (!isDeleteFile && ctx != null) {
					ctx.addResource(this);
				}
				
				if (startPos > 0) {
					reader.seek(startPos);
					reader.setEndPos(endPos);
				}
			}
			
			Sequence seq = reader.read(n);
			return seq;
		} catch (Exception e) {
			close();
			throw new RQException(e.getMessage(), e);
		}
	}

	/**
	 * ????ָ????????????
	 * @param n ????
	 * @return long ʵ????????????
	 */
	protected long skipOver(long n) {
		if (n < 1 || reader == null) {
			return 0;
		}
		
		try {
			if (!reader.isOpen()) {
				reader.open(fileBufSize);
				DataStruct ds = reader.getResultSetDataStruct();
				setDataStruct(ds);
				
				if (startPos > 0) {
					reader.seek(startPos);
					reader.setEndPos(endPos);
				}
			}
			
			long count = reader.skip(n);
			return count;
		} catch (Exception e) {
			close();
			throw new RQException(e.getMessage(), e);
		}
	}

	/**
	 * ?ر??α?
	 */
	public synchronized void close() {
		super.close();
		
		if (fileObject != null) {
			if (reader != null) {
				if (ctx != null) ctx.removeResource(this);
				try {
					reader.close();
				} catch (IOException e) {
				}
				
				reader = null;
			}

			if (isDeleteFile) {
				fileObject.delete();
				fileObject = null;
			}
		}
	}

	protected void finalize() throws Throwable {
		close();
	}
	
	/**
	 * ?????α?
	 * @return ?????Ƿ?ɹ???true???α???Դ?ͷ????ȡ????false???????Դ?ͷ????ȡ??
	 */
	public boolean reset() {
		close();
		
		if (fileObject != null) {
			reader = new BFileReader(fileObject, fields, segSeq, segCount, opt);
			return true;
		} else {
			return false;
		}
	}
}