/** Suck up tuples from the source file. */
private Tuple readNextTuple(DataInputStream dis, int slotId) throws NoSuchElementException {
// if associated bit is not set, read forward to the next tuple, and
// return null.
if (!getSlot(slotId)) {
for (int i = 0; i < td.getSize(); i++) {
try {
dis.readByte();
} catch (IOException e) {
throw new NoSuchElementException("error reading empty tuple");
}
}
return null;
}
// read fields in the tuple
Tuple t = new Tuple(td);
RecordID rid = new RecordID(pid, slotId);
t.setRecordID(rid);
try {
for (int j = 0; j < td.numFields(); j++) {
Field f = td.getType(j).parse(dis);
t.setField(j, f);
}
} catch (java.text.ParseException e) {
// e.printStackTrace();
throw new NoSuchElementException("parsing error!");
}
return t;
}
/**
* Generates a byte array representing the contents of this page. Used to serialize this page to
* disk.
*
* <p>The invariant here is that it should be possible to pass the byte array generated by
* getPageData to the HeapPage constructor and have it produce an identical HeapPage object.
*
* @see #HeapPage
* @return A byte array correspond to the bytes of this page.
*/
public byte[] getPageData() {
// int len = header.length*4 + BufferPool.PAGE_SIZE;
int len = BufferPool.PAGE_SIZE;
ByteArrayOutputStream baos = new ByteArrayOutputStream(len);
DataOutputStream dos = new DataOutputStream(baos);
// create the header of the page
try {
dos.write(header.getHeader());
} catch (IOException e) {
// this really shouldn't happen
e.printStackTrace();
}
// create the tuples
for (int i = 0; i < numSlots; i++) {
// empty slot
if (!getSlot(i)) {
for (int j = 0; j < td.getSize(); j++) {
try {
dos.writeByte(0);
} catch (IOException e) {
e.printStackTrace();
}
}
continue;
}
// non-empty slot
for (int j = 0; j < td.numFields(); j++) {
Field f = tuples[i].getField(j);
try {
f.serialize(dos);
} catch (IOException e) {
e.printStackTrace();
}
}
}
// padding
int zerolen = BufferPool.PAGE_SIZE - numSlots * td.getSize() - header.length();
byte[] zeroes = new byte[zerolen];
try {
dos.write(zeroes, 0, zerolen);
} catch (IOException e) {
e.printStackTrace();
}
try {
dos.flush();
} catch (IOException e) {
e.printStackTrace();
}
return baos.toByteArray();
}
public Tuple getNext() throws NoSuchElementException, TransactionAbortedException {
try {
Tuple tuple = new Tuple(td);
for (int i = 0; i < td.numFields(); i++) {
IntField intf = IntField.createIntField(in.readInt());
tuple.setField(i, intf);
}
return tuple;
} catch (EOFException eof) {
throw new NoSuchElementException(eof.getMessage());
} catch (Exception e) {
e.printStackTrace();
BufferPool.Instance().abortTransaction(tid);
closeConnection();
throw new TransactionAbortedException(e);
}
}
/**
* Adds the specified tuple to the page; the tuple should be updated to reflect that it is now
* stored on this page.
*
* @throws DbException if the page is full (no empty slots) or tupledesc is mismatch.
* @param t The tuple to add.
*/
public void insertTuple(Tuple t) throws DbException {
// some code goes here
// not necessary for lab1
RecordId targetrid = t.getRecordId();
if (getNumEmptySlots() == 0 || !td.equals(t.getTupleDesc())) {
throw new DbException("Either page is full or tuple desc doesn't match");
}
for (int i = 0; i < getNumTuples(); i++) {
if (!isSlotUsed(i)) {
markSlotUsed(i, true);
RecordId rid = new RecordId(pid, i);
t.setRecordId(rid);
tuples[i] = t;
return;
}
}
}
/**
* Helper constructor to create a heap page to be used as buffer.
*
* @param data - Data to be put in tmp page
* @param td - Tuple description for the corresponding table.
* @throws IOException
*/
private HeapPage(byte[] data, TupleDesc td) throws IOException {
this.pid =
null; // No need of a pid here as this page serves as a dummy buffer page and is meant to be
// used independent of BufferManager.
this.td = td;
this.numSlots = (BufferPool.PAGE_SIZE * 8) / ((td.getSize() * 8) + 1);
DataInputStream dis = new DataInputStream(new ByteArrayInputStream(data));
this.header = new Header(dis);
try {
// allocate and read the actual records of this page
tuples = new Tuple[numSlots];
for (int i = 0; i < numSlots; i++) {
tuples[i] = readNextTuple(dis, i);
}
} catch (NoSuchElementException e) {
e.printStackTrace();
}
dis.close();
}
/**
* Create a HeapPage from a set of bytes of data read from disk. The format of a HeapPage is a set
* of 32-bit header words indicating the slots of the page that are in use, plus
* (BufferPool.PAGE_SIZE/tuple size) tuple slots, where tuple size is the size of tuples in this
* database table, which can be determined via {@link Catalog#getTupleDesc}.
*
* <p>The number of 32-bit header words is equal to:
*
* <p>(no. tuple slots / 32) + 1
*
* <p>
*
* @see Database#getCatalog
* @see Catalog#getTupleDesc
* @see BufferPool#PAGE_SIZE
*/
public HeapPage(HeapPageId id, byte[] data) throws IOException {
this.pid = id;
this.td = Database.getCatalog().getTupleDesc(id.tableid());
// this.numSlots = (BufferPool.PAGE_SIZE) / (td.getSize());
this.numSlots = (BufferPool.PAGE_SIZE * 8) / ((td.getSize() * 8) + 1);
// System.out.println(this.numSlots);
DataInputStream dis = new DataInputStream(new ByteArrayInputStream(data));
// allocate and read the header slots of this page
header = new Header(dis);
try {
// allocate and read the actual records of this page
tuples = new Tuple[numSlots];
for (int i = 0; i < numSlots; i++) {
tuples[i] = readNextTuple(dis, i);
}
} catch (NoSuchElementException e) {
// e.printStackTrace();
}
dis.close();
}
/**
* Retrieve the number of tuples on this page.
*
* @return the number of tuples on this page
*/
private int getNumTuples() {
// some code goes here
int tupsPerPage = (BufferPool.PAGE_SIZE * 8) / ((td.getSize() * 8) + 1); // default to be floor
return tupsPerPage;
}
/**
* Retrieve the number of tuples on this page.
*
* @return the number of tuples on this page
*/
private int getNumTuples() {
// hdj
return BufferPool.PAGE_SIZE * 8 / (td.getSize() * 8 + 1);
}