/**
* 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();
}
/**
* Serializa el registro escribiéndolo en un stream de salida.
*
* @param stream Stream de salida.
* @return Cantidad de bytes escrito.
* @throws RecordSerializationException
*/
public long serialize(OutputStream stream) throws RecordSerializationException {
long byteCount = 0;
byte hash = 0;
try {
for (Field field : this.getFields()) {
byte[] serialize = field.serialize();
stream.write(serialize);
byteCount += serialize.length;
// modifica el hash actual con los datos de la serialización del campo
hash = calculateHash(hash, serialize);
}
// graba el hash al final
stream.write(new byte[] {hash});
} catch (IOException e) {
throw new RecordSerializationException();
}
return byteCount;
}
/**
* Deserializa el registro a partir de un stream de entrada.
*
* @param stream Stream de entrada.
* @return Cantidad de bytes leido.
* @throws RecordSerializationException
*/
public long deserialize(InputStream stream) throws RecordSerializationException {
long byteCount = 0;
byte calculatedHash = 0;
byte deserializedHash = 0;
try {
for (Field field : this.getFields()) {
byteCount += field.deserialize(stream);
// agrega al hash actual el hash del campo
calculatedHash = calculateHash(calculatedHash, field.serialize());
}
// carga el hash serializado
deserializedHash = (byte) stream.read();
} catch (IOException e) {
throw new RecordSerializationException(e);
}
if (deserializedHash != calculatedHash) {
throw new RecordSerializationCorruptDataException("Record", deserializedHash, calculatedHash);
}
return byteCount;
}
