Utility.java

package simpledb;

import java.io.*;
import java.util.ArrayList;
import java.util.UUID;

/** Helper methods used for testing and implementing random features. */
public class Utility {
 /**
 * @return a Type array of length len populated with Type.INT_TYPE
 */
 public static Type[] getTypes(int len) {
 Type[] types = new Type[len];
 for (int i = 0; i < len; ++i)
 types[i] = Type.INT_TYPE;
 return types;
 }

 /**
 * @return a String array of length len populated with the (possibly null) strings in val,
 * and an appended increasing integer at the end (val1, val2, etc.).
 */
 public static String[] getStrings(int len, String val) {
 String[] strings = new String[len];
 for (int i = 0; i < len; ++i)
 strings[i] = val + i;
 return strings;
 }

 /**
 * @return a TupleDesc with n fields of type Type.INT_TYPE, each named
 * name + n (name1, name2, etc.).
 */
 public static TupleDesc getTupleDesc(int n, String name) {
 return new TupleDesc(getTypes(n), getStrings(n, name));
 }

 /**
 * @return a TupleDesc with n fields of type Type.INT_TYPE
 */
 public static TupleDesc getTupleDesc(int n) {
 return new TupleDesc(getTypes(n));
 }

 /**
 * @return a Tuple with a single IntField with value n and with
 * RecordId(HeapPageId(1,2), 3)
 */
 public static Tuple getHeapTuple(int n) {
 Tuple tup = new Tuple(getTupleDesc(1));
 tup.setRecordId(new RecordId(new HeapPageId(1, 2), 3));
 tup.setField(0, new IntField(n));
 return tup;
 }

 /**
 * @return a Tuple with an IntField for every element of tupdata
 * and RecordId(HeapPageId(1, 2), 3)
 */
 public static Tuple getHeapTuple(int[] tupdata) {
 Tuple tup = new Tuple(getTupleDesc(tupdata.length));
 tup.setRecordId(new RecordId(new HeapPageId(1, 2), 3));
 for (int i = 0; i < tupdata.length; ++i)
 tup.setField(i, new IntField(tupdata[i]));
 return tup;
 }

 /**
 * @return a Tuple with a 'width' IntFields each with value n and
 * with RecordId(HeapPageId(1, 2), 3)
 */
 public static Tuple getHeapTuple(int n, int width) {
 Tuple tup = new Tuple(getTupleDesc(width));
 tup.setRecordId(new RecordId(new HeapPageId(1, 2), 3));
 for (int i = 0; i < width; ++i)
 tup.setField(i, new IntField(n));
 return tup;
 }

 /**
 * @return a Tuple with a 'width' IntFields with the value tupledata[i]
 * in each field.
 * do not set it's RecordId, hence do not distinguish which
 * sort of file it belongs to.
 */
 public static Tuple getTuple(int[] tupledata, int width) {
 if(tupledata.length != width) {
 System.out.println("get Hash Tuple has the wrong length~");
 System.exit(1);
 }
 Tuple tup = new Tuple(getTupleDesc(width));
 for (int i = 0; i < width; ++i)
 tup.setField(i, new IntField(tupledata[i]));
 return tup;
 }

 /**
 * A utility method to create a new HeapFile with a single empty page,
 * assuming the path does not already exist. If the path exists, the file
 * will be overwritten. The new table will be added to the Catalog with
 * the specified number of columns as IntFields.
 */
 public static HeapFile createEmptyHeapFile(String path, int cols)
 throws IOException {
 File f = new File(path);
 // touch the file
 FileOutputStream fos = new FileOutputStream(f);
 fos.write(new byte[0]);
 fos.close();

 HeapFile hf = openHeapFile(cols, f);
 HeapPageId pid = new HeapPageId(hf.getId(), 0);

 HeapPage page = null;
 try {
 page = new HeapPage(pid, HeapPage.createEmptyPageData());
 } catch (IOException e) {
 // this should never happen for an empty page; bail;
 throw new RuntimeException("failed to create empty page in HeapFile");
 }

 hf.writePage(page);
 return hf;
 }

 /** Opens a HeapFile and adds it to the catalog.
 *
 * @param cols number of columns in the table.
 * @param f location of the file storing the table.
 * @return the opened table.
 */
 public static HeapFile openHeapFile(int cols, File f) {
 // create the HeapFile and add it to the catalog
 	TupleDesc td = getTupleDesc(cols);
 HeapFile hf = new HeapFile(f, td);
 Database.getCatalog().addTable(hf, UUID.randomUUID().toString());
 return hf;
 }
 
 public static HeapFile openHeapFile(int cols, String colPrefix, File f) {
 // create the HeapFile and add it to the catalog
 	TupleDesc td = getTupleDesc(cols, colPrefix);
 HeapFile hf = new HeapFile(f, td);
 Database.getCatalog().addTable(hf, UUID.randomUUID().toString());
 return hf;
 }

 public static String listToString(ArrayList<Integer> list) {
 String out = "";
 for (Integer i : list) {
 if (out.length() > 0) out += "\t";
 out += i;
 }
 return out;
 }
}