/**
* Create a HeapPage from a set of bytes of data read from disk. The format of a HeapPage is a set
* of header bytes indicating the slots of the page that are in use, some number of tuple slots.
* Specifically, the number of tuples is equal to:
*
* <p>floor((BufferPool.PAGE_SIZE*8) / (tuple size * 8 + 1))
*
* <p>where tuple size is the size of tuples in this database table, which can be determined via
* {@link Catalog#getTupleDesc}. The number of 8-bit header words is equal to:
*
* <p>ceiling(no. tuple slots / 8)
*
* <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.getTableId());
this.numSlots = getNumTuples();
DataInputStream dis = new DataInputStream(new ByteArrayInputStream(data));
// allocate and read the header slots of this page
header = new byte[getHeaderSize()];
for (int i = 0; i < header.length; i++) header[i] = dis.readByte();
try {
// allocate and read the actual records of this page
tuples = new Tuple[numSlots];
for (int i = 0; i < tuples.length; i++) tuples[i] = readNextTuple(dis, i);
} catch (NoSuchElementException e) {
e.printStackTrace();
}
dis.close();
setBeforeImage();
}
/**
* 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();
}