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import java.io.RandomAccessFile;
import java.io.IOException;
/**
* <p>Provides functionality to decode a pdb formatted file into
* a <code>PalmDB</code> object given a file input stream</p>
*
* <p>Sample usage:</p>
*
* <p><blockquote><pre>
* PDBDecoder decoder = new PDBDecoder("sample.pdb");
* PalmDB palmDB = decoder.parse();
* </pre></blockquote></p>
*
* <p>Refer to the
* <a href="http://starlite.eng/zensync/eng/converters/palmfileformats.pdf">
* Palm file format specification</a> for details on the pdb format.</p>
*
* <p>This decoder has the following assumptions on the pdb file ...</p>
* <ol>
* <li><p>There is only one RecordList section in the pdb.</p></li>
* <li><p>The record indices in the RecordList are sorted in order, i.e. the
* first record index refers to record 0, and so forth.</p></li>
* <li><p>The raw records in the record section are sorted as well in order,
* i.e. first record comes ahead of second record, etc.</p></li>
* </ol>
*
* Other decoders assume these as well.
*
* @author Herbie Ong
* @see PalmDB
* @see PDBHeader
*
* @author Herbie Ong
*/
public final class PDBDecoder {
/**
* <p>This method decodes a pdb file into a PalmDB object.</p>
*
* <p>First, read in the header data using <code>PDBHeader</code>'s
* <code>read</code> method</p>. Next, read in the record list
* section. Store the record offsets for use when parsing the records.
* Based on these offsets, read in each record's bytes and store
* each in a <code>Record</code> object. Lastly, create a
* <code>PalmDB</code> object with the read in <code>Record</code>s.
*
* @param fileName pdb file name
* @throws IOException if I/O error occurs
*/
public PalmDB parse(String fileName) throws IOException {
RandomAccessFile file = new RandomAccessFile(fileName, "r");
// read the pdb header
PDBHeader header = new PDBHeader();
header.read(file);
Record recArray[] = new Record[header.numRecords];
if (header.numRecords != 0) {
// read in the record indices + offsets
int recOffset[] = new int[header.numRecords];
for (int i = 0; i < header.numRecords; i++) {
recOffset[i] = file.readInt();
int attr = file.readInt(); // read in attribute.
}
// read the records
int len = 0;
byte[] bytes = null;
int lastIndex = header.numRecords - 1;
for (int i = 0; i < lastIndex; i++) {
file.seek(recOffset[i]);
len = recOffset[i+1] - recOffset[i];
bytes = new byte[len];
file.readFully(bytes);
recArray[i] = new Record(bytes);
}
// last record
file.seek(recOffset[lastIndex]);
len = (int) file.length() - recOffset[lastIndex];
bytes = new byte[len];
file.readFully(bytes);
recArray[lastIndex] = new Record(bytes);
}
file.close();
// create PalmDB and return it
PalmDB pdb = new PalmDB(header.pdbName, recArray);
return pdb;
}
}