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

import com.scudata.common.ISessionFactory;
import com.scudata.dm.Context;
import com.scudata.dm.Env;
import com.scudata.dm.JobSpace;
import com.scudata.dm.Param;
import com.scudata.dm.Sequence;

/**
 * ??????صĹ?????
 * @author RunQian
 *
 */
public class EnvUtil {
	//private static final long G = 1024 * 1024 * 1024; // 1G?Ĵ?С
	private static final int FIELDSIZE = 50; // ?????ڴ?ʱÿ???ֶ?ռ?õĿռ??С
	private static final int MAXRECORDCOUNT = 20000000; // ?ڴ??б????????¼????
	private static double MAX_USEDMEMORY_PERCENT = 0.4;
	
	public static void setMaxUsedMemoryPercent(double d) {
		MAX_USEDMEMORY_PERCENT = d;
	}
	
	public static double getMaxUsedMemoryPercent() {
		return MAX_USEDMEMORY_PERCENT;
	}
	
	// ȡ??ǰ?????ڴ???Դ?Լ?????ɶ???????¼
	/**
	 * ȡ??ǰ?????ڴ??Լ???Դ?Ŷ???????¼
	 * @param fcount ?ֶ???
	 * @return ??¼????
	 */
	public static int getCapacity(int fcount) {
		Runtime rt = Runtime.getRuntime();
		runGC(rt);
	
		long freeMemory = rt.maxMemory() - rt.totalMemory() + rt.freeMemory();
		long recordCount = freeMemory / fcount / FIELDSIZE / 3;
		if (recordCount > MAXRECORDCOUNT) {
			return MAXRECORDCOUNT;
		} else {
			return (int)recordCount;
		}
	}
	
	/**
	 * ?????Ƿ??п????ڴ???????α????
	 * @param rt Runtime
	 * @param table ?Ѷ???????
	 * @param readSize ÿ?ζ???????ռ???ڴ??С????׼ȷ??
	 * @return true?????Լ???????false?????????ٶ???
	 */
	public static boolean memoryTest(Runtime rt, Sequence table, long readSize) {
		int len = table.length();
		if (len >= MAXRECORDCOUNT) return false;
		
		long maxUseMemory = (long)(rt.maxMemory() * MAX_USEDMEMORY_PERCENT);
		long usedMemory = rt.totalMemory() - rt.freeMemory();
		
		if (usedMemory > maxUseMemory || usedMemory + readSize > maxUseMemory) {
			return false;
		} else {
			return true;
		}
	}
	
	/**
	 * ִ???????ռ?
	 * @param rt Runtime
	 */
	public static void runGC(Runtime rt) {
		for (int i = 0; i < 2; ++i) {
			//rt.runFinalization();
			rt.gc();
			Thread.yield();
		}
	}

	/**
	 * ???ұ????????????????еı?????????Session?еģ??????Env?е?ȫ?ֱ?????
	 * @param varName String ??????
	 * @param ctx Context ??????????
	 * @return Param
	 */
	public static Param getParam(String varName, Context ctx) {
		if (ctx != null) {
			Param p = ctx.getParam(varName);
			if (p != null)return p;

			JobSpace js = ctx.getJobSpace();
			if (js != null) {
				p = js.getParam(varName);
				if (p != null)return p;
			}
		}

		return Env.getParam(varName);
	}

	/**
	 * ɾ??????
	 * @param varName ??????
	 * @param ctx ??????????
	 * @return Param ɾ???ı?????û?ҵ??򷵻ؿ?
	 */
	public static Param removeParam(String varName, Context ctx) {
		if (ctx != null) {
			Param p = ctx.removeParam(varName);
			if (p != null) {
				return p;
			}

			JobSpace js = ctx.getJobSpace();
			if (js != null) {
				p = js.removeParam(varName);
				if (p != null) {
					return p;
				}
			}
		}

		return Env.removeParam(varName);
	}

	/**
	 * ȡ???ݿ????ӹ???
	 * @param dbName ???ݿ???
	 * @param ctx ??????????
	 * @return ISessionFactory
	 */
	public static ISessionFactory getDBSessionFactory(String dbName, Context ctx) {
		if (ctx == null) {
			return Env.getDBSessionFactory(dbName);
		} else {
			ISessionFactory dbsf = ctx.getDBSessionFactory(dbName);
			return dbsf == null ? Env.getDBSessionFactory(dbName) : dbsf;
		}
	}
}