LineByteStreamCreator.java

/*******************************************************************************
 * Copyright (c) 2011 The Board of Trustees of the Leland Stanford Junior University
 * as Operator of the SLAC National Accelerator Laboratory.
 * Copyright (c) 2011 Brookhaven National Laboratory.
 * EPICS archiver appliance is distributed subject to a Software License Agreement found
 * in file LICENSE that is included with this distribution.
 *******************************************************************************/
package edu.stanford.slac.archiverappliance.PlainPB;

import java.io.IOException;
import java.nio.file.Path;

import org.epics.archiverappliance.config.ArchDBRTypes;

import edu.stanford.slac.archiverappliance.PB.utils.LineByteStream;

/**
 * When using a MultiFileEventStream on a HOUR granularity, we could potentially run into "too many open files" issues. 
 * So we add a level of indirection for this case.
 * @author mshankar
 *
 */
public class LineByteStreamCreator {
	LineByteStream lis;
	Path path;
	String pvName;
	ArchDBRTypes type;
	
	/**
	 * In this case we get a correctly positioned LIS
	 * @param lis The line bytes stream
	 * @param pvName the PV name
	 * @param type  Enum ArchDBRTypes
	 */
	public LineByteStreamCreator(LineByteStream lis, String pvName, ArchDBRTypes type) {
		this.lis = lis;
		this.pvName = pvName;
		this.type = type;
	}
	
	/**
	 * In this case, we get a whole file 
	 * We need to position the lis past the header before returning.
	 * @param path Path
	 * @param pvName The PV name
	 * @param type  Enum ArchDBRTypes
	 */
	public LineByteStreamCreator(Path path, String pvName, ArchDBRTypes type) {
		this.path = path;
		this.pvName = pvName;
		this.type = type;
	}
	

	public LineByteStream getLineByteStream() throws IOException {
		if(lis != null) return lis;
		
		lis = new LineByteStream(path);
		// Position the lis after the header.
		PBFileInfo.checkPayloadInfo(lis, pvName, type);
		return lis;
	}
	
	public void safeClose() {
		if(lis != null) {
			lis.safeClose();
		}
	}
	
}