com.scudata.dm.cursor.GroupxnCursor 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 com.scudata.dm.Context;
import com.scudata.dm.DataStruct;
import com.scudata.dm.FileObject;
import com.scudata.dm.Sequence;
import com.scudata.dm.op.IGroupsResult;
import com.scudata.expression.Expression;
import com.scudata.expression.Node;

/**
 * ??????????cs.groupx@n()??cs.groupx@g()?Ķ??η???
 * groupx??@n??@gѡ??ʱ??ͬһ????м????ݻ??ŵ?ͬһ????ʱ?ļ???????ֻ???ÿ????ʱ?ļ????????¶??η?????ܵõ????յķ?????
 * @author RunQian
 *
 */
public class GroupxnCursor extends ICursor {
	private FileObject []files; // ?״η??????????ʱ???ļ?
	private int fileIndex = -1; // ??ǰҪ??????ʱ?ļ?????
	private Expression[] exps; // ???????ʽ????
	private String[] names; // ?????ֶ???????
	private Expression[] calcExps; // ???ܱ???ʽ????
	private String[] calcNames; // ?????ֶ???????
	
	private MemoryCursor cursor; // ?ڴ??α꣬???ڱ??浱ǰ??ʱ?ļ??Ķ??η?????
	
	/**
	 * ??????????Ķ??λ????α?
	 * @param files ?״η??????????ʱ???ļ?????
	 * @param exps ???????ʽ????
	 * @param names ?????ֶ???????
	 * @param calcExps ???ܱ???ʽ????
	 * @param calcNames ?????ֶ???????
	 * @param ctx ??????????
	 */
	public GroupxnCursor(FileObject []files, Expression[] exps, String[] names, 
			Expression[] calcExps, String[] calcNames, Context ctx) {
		this.files = files;
		this.names = names;
		this.calcNames = calcNames;
		this.ctx = ctx;
		
		int keyCount = exps.length;
		int valCount = calcExps == null ? 0 : calcExps.length;
		String[] colNames = new String[keyCount + valCount];
		System.arraycopy(names, 0, colNames, 0, keyCount);
		if (this.calcNames != null) {
			System.arraycopy(this.calcNames, 0, colNames, keyCount, valCount);
		}

		DataStruct ds = new DataStruct(colNames);
		ds.setPrimary(names);
		setDataStruct(ds);
		
		// ȡ???ξۺ???Ҫ?õı???ʽ
		Node[] gathers = Sequence.prepareGatherMethods(calcExps, ctx);
		Expression []keyExps = new Expression[keyCount];
		for (int i = 0, q = 1; i < keyCount; ++i, ++q) {
			keyExps[i] = new Expression(ctx, "#" + q);
		}
		
		Expression []valExps = new Expression[valCount];
		for (int i = 0, q = keyCount + 1; i < valCount; ++i, ++q) {
			valExps[i] = gathers[i].getRegatherExpression(q);
		}
		
		this.exps = keyExps;
		this.calcExps = valExps;
	}
	
	// ???м???ʱ??Ҫ?ı???????
	// ?̳???????õ??˱???ʽ????Ҫ?????????????½???????ʽ
	public void resetContext(Context ctx) {
		this.ctx = ctx;
	}

	/**
	 * ??ȡָ???????????ݷ???
	 * @param n ????
	 * @return Sequence
	 */
	protected Sequence get(int n) {
		if (files == null || n < 1) return null;
		
		if (fileIndex == -1) {
			fileIndex++;
			BFileCursor cs = new BFileCursor(files[0], null, "x", ctx);
			DataStruct ds = cs.getDataStruct();
			IGroupsResult groups = IGroupsResult.instance(exps, names, calcExps, calcNames, ds, "", ctx);
			groups.push(cs);
			Sequence seq = groups.getResultTable();
			cursor = new MemoryCursor(seq);
		}
		
		Sequence table = cursor.fetch(n);
		if (table == null || table.length() < n) {
			fileIndex++;
			if (fileIndex < files.length) {
				BFileCursor cs = new BFileCursor(files[fileIndex], null, "x", ctx);
				DataStruct ds = cs.getDataStruct();
				IGroupsResult groups = IGroupsResult.instance(exps, names, calcExps, calcNames, ds, "", ctx);
				groups.push(cs);
				Sequence seq = groups.getResultTable();
				cursor = new MemoryCursor(seq);
				
				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);
				}
			} else {
				files = null;
				cursor = null;
			}
		}

		return table;
	}

	/**
	 * ????ָ????????????
	 * @param n ????
	 * @return long ʵ????????????
	 */
	protected long skipOver(long n) {
		if (files == null || n < 1) return 0;
		
		if (fileIndex == -1) {
			fileIndex++;
			BFileCursor cs = new BFileCursor(files[0], null, "x", ctx);
			DataStruct ds = cs.getDataStruct();
			IGroupsResult groups = IGroupsResult.instance(exps, names, calcExps, calcNames, ds, "", ctx);
			groups.push(cs);
			Sequence seq = groups.getResultTable();
			cursor = new MemoryCursor(seq);
		}

		long count = cursor.skip(n);
		if (count < n) {
			fileIndex++;
			if (fileIndex < files.length) {
				BFileCursor cs = new BFileCursor(files[fileIndex], null, "x", ctx);
				DataStruct ds = cs.getDataStruct();
				IGroupsResult groups = IGroupsResult.instance(exps, names, calcExps, calcNames, ds, "", ctx);
				groups.push(cs);
				Sequence seq = groups.getResultTable();
				cursor = new MemoryCursor(seq);
				
				count += skipOver(n - count);
			}
		}

		return count;
	}

	/**
	 * ?ر??α?
	 */
	public synchronized void close() {
		super.close();
		
		if (files != null) {
			for (FileObject file : files) {
				if (file != null) {
					file.delete();
				}
			}
			
			files = null;
			cursor = null;
		}
	}
}