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suncertify.db.Data

Seshan Parameswaran
Greenhorn

Joined: Nov 13, 2000
Posts: 10
Hi,
I am posting the code for Suncertify.db.Data
package suncertify.db;
import java.io.*;
import java.util.*;
/**
* This class provides the basic database services. It uses two
* other support classes: DataInfo and FieldInfo.
*
* @version 1.1 17-Nov-1997
*/
public class Data {
private static final byte LIVE_RECORD = 0;
private static final byte DELETED_RECORD = 1;
private static final int MAGIC = 0xC0C0BABE;
private static final String UNEXPECTED =
"Data: Unexpected database access problem";
private FieldInfo [] description;
private int headerLen;
private int recordLen = 1;
private int recordCount;
private RandomAccessFile db,log;
final static char sc = 'A';
/**
* This constructor opens an existing database given the name
* of the disk file containing it.
*
* @param String dbname The name of the database file to open.
* @exception java.io.IOException
*/
public Data(String dbname) throws IOException {
File f = new File(dbname);
if (f.exists() && f.canRead() && f.canWrite()) {
db = new RandomAccessFile(f, "rw");
headerLen = db.readInt();
int nFields= db.readInt();
recordCount = db.readInt();
description = new FieldInfo[nFields];
for (int i=0; i<nFields; i++) {>
description[i] = new FieldInfo(db.readUTF(), db.readInt());
recordLen += description[i].getLength();
}
if (db.readInt() != MAGIC) {
throw new IOException("Data: corrupted database file. " +
"Magic not found in file " + dbname);
}
if (db.getFilePointer() != headerLen) {
throw new IOException("Data: corrupted database file. " +
"Header length incorrect in file " + dbname);
}
} else {
throw new IOException("Data: request to open non-existant or " +
"inaccessible file" + dbname);
}
}
/**
* This constructor creates a new database file, using the name
* provided for the disk file and using the FieldInfo array to
* describe the field names and sizes that should be created.
*
* @param String dbname The name of the database file to open.
* @param FieldInfo[] fields The list of fields for the schema of
* this database.
* @exception IOException Thrown if cannot create database file.
*/
public Data(String dbname, FieldInfo[] fields) throws IOException {
File f = new File(dbname);
File flog = new File("d:\\seshan\\suncertorg\\starting\\scert.log");
if (!f.exists()) {
db = new RandomAccessFile(f, "rw");
log = new RandomAccessFile(flog,"rw");
writeMessage("In Data Constructor");
writeMessage("In File Exists");
db.writeInt(0); // filler for header length
db.writeInt(fields.length);
recordCount = 0;
db.writeInt(recordCount);
for (int i = 0; i < fields.length; i++) {
db.writeUTF(fields[i].getName());
db.writeInt(fields[i].getLength());
recordLen += fields[i].getLength();
writeMessage("Record Len in Constructor " + recordLen);
}
description = fields;
db.writeInt(MAGIC);
headerLen = (int)db.getFilePointer();
writeMessage("HeaderLen in Constructor :" + headerLen);
db.seek(0);
db.writeInt(headerLen);
} else {
//System.err.println("Here"); //seshan
throw new IOException("Data: request to create pre-existing " +
"file" + dbname);
}
}
/**
* This method returns a description of the database schema, as an
* array of FieldInfo objects.
*
* @return FieldInfo[] The array of FieldInfo objects that comprise
* the schema to this database.
*/
public FieldInfo [] getFieldInfo() {
return description;
}
/**
* Gets the number of records stored in the database.
*/
public int getRecordCount() { return recordCount; }
/**
* Gets a requested record from the database based on record number.
* @param recNum The number of the record to read (first record is 1).
* @return DataInfo for the record or null if the record has been marked for
* deletion.
* @exception DatabaseException Thrown if database file cannot be accessed.
*/
public synchronized DataInfo getRecord(int recNum) throws DatabaseException {
try {
if (recNum<1) {
throw new DatabaseException("Record number must be greater than 1");
}
seek(recNum);
String records[] = readRecord();
if (records == null) {
return null;
}
return new DataInfo(recNum, description, records);
} catch(IOException ex) {
throw new DatabaseException(UNEXPECTED);
}
}
/**
* This method searches the database for an entry which has a first
* field which exactly matches the string supplied. If the required
* record cannot be found, this method returns null. For this
* assignment, the key field is the record number field.
*
* @param toMatch The key field value to match upon for
* a successful find.
* @return DataInfo The matching record.
* @exception DatabaseException Thrown when database file could not be accessed.
*/
public synchronized DataInfo find(String toMatch) throws DatabaseException {
writeMessage("In find");
invariant();
try {
seek(1);
DataInfo rv = null;
String [] values = null;
boolean found = false;
int r;
for (r = 1; r <= recordCount; r++) {
values = readRecord();
if ((values != null) && (values[0].equals(toMatch))) {
found = true;
break;
}
}
if (found) {
rv = new DataInfo(r, description, values);
}
return rv;
} catch (IOException e) {
throw new DatabaseException(UNEXPECTED + e);
}
}
/**
* This method adds a new record to the database. The array of
* strings must have exactly the same number of elements as the
* field count of the database schema, otherwise a RuntimeException
* is issued. The first field, the key, must be unique in the
* database or a RuntimeException is thrown.
*
* @param newData The elements of the record to add.
* @exception DatabaseException Attempted to add a duplicate key or
* database file could not be accessed.
*/
public synchronized void add(String [] newData) throws DatabaseException {
invariant();
if (find(newData[0]) != null) {
throw new DatabaseException("Attempt to add a duplicate key");
}
try {
seek(++recordCount);
//for(int i = 0;i<newData.length;i++)>
// writeMessage(newData[i]);
writeRecord(newData);
db.seek(8);
db.writeInt(recordCount);
}
catch (IOException e) {
throw new DatabaseException(UNEXPECTED + e);
}
}
/**
* This method updates the record specified by the record number
* field in the DataInfo argument. The fields are all modified
* to reflect the values in that argument. If the key field
* specified in the argument matches any record other than the
* one indicated by the record number of the argument, then a
* RuntimeException is thrown.
*
* @param newData The updated record to modify.
* @exception DatabaseException Thrown if attempting to add a duplicate
* key.
*/
public synchronized void modify(DataInfo newData) throws DatabaseException {
invariant();
DataInfo test = find((newData.getValues())[0]);
if ((test != null) &&
(test.getRecordNumber()!=newData.getRecordNumber()))
{
throw new DatabaseException("Attempt to create a "+
"duplicate key by modification");
}
try {
seek(newData.getRecordNumber());
writeRecord(newData.getValues());
} catch (IOException e) {
throw new DatabaseException(UNEXPECTED + e);
}
}
/**
* This method deletes the record referred to by the record
* number in the DataInfo argument.
*
* @param DataInfo newData The record to delete.
* @exception DatabaseException Thrown if database cannot be accessed.
*/
public synchronized void delete(DataInfo toDelete) throws DatabaseException {
invariant();
try {
seek(toDelete.getRecordNumber());
db.write(DELETED_RECORD);
} catch (IOException e) {
throw new DatabaseException(UNEXPECTED + e);
}
}
/**
* This method closes the database, flushing any outstanding
* writes at the same time. Any attempt to access the
* database after this results in a IOException.
*/
public synchronized void close() {
try {
db.close();
} catch (IOException e) {}
db = null;
}
protected void finalize() {
if (db != null) {
close();
}
}
/**
* Reads a record from the current cursor position of the underlying random
* access file.
* @return The array of strings that make up a database record.
* @exception IOException Generated if the RandomAccessFile cannot read from
* the database file.
*/
private synchronized String[] readRecord() throws IOException {
int offset = 1;
String [] rv = null;
byte [] buffer = new byte[recordLen];
db.read(buffer);
if (buffer[0] == LIVE_RECORD) {
rv = new String[description.length];
for (int i = 0; i < description.length; i++) {
//rv[i] = new String(buffer, 0, offset, description[i].getLength());
rv[i] = new String(buffer,offset,description[i].getLength ());
offset += description[i].getLength();
}
}
return rv;
}
/**
* Writes a new record to the database using the current location of the
* underlying random access file.
* @param newData An array of strings in the database specified order.
* @exception IOException Generated if the RandomAccessFile cannot write to
* the file or the wrong number of fields are specified.
*/
private void writeRecord(String[] newData) throws IOException {
writeMessage("In writeReocrd");
if (newData.length != description.length) {
throw new IOException("Data: Wrong number of fields in writeRecord() " +
newData.length + " given, " +
description.length + " required");
}
int size, space, toCopy;
byte [] buffer = new byte[recordLen];
buffer[0] = LIVE_RECORD;
int offset = 1;
for(int j = 0; j< newData.length; j++)
writeMessage("writeRecord " + newData[j]) ;
for (int i = 0; i < description.length; i++) {
space = description[i].getLength();
size = newData[i].length();
toCopy = (size <= space) ? size : space;
String s = new String(newData[i].substring(0,toCopy));
buffer = s.getBytes ();
//newData[i].getBytes(0, toCopy, buffer, offset);
//offset += space;
}
db.write(buffer);
writeMessage("Written Record") ;
}
/**
* Moves the current database record pointer to the specified record.
* @param recno The record number to position the cursor.
* @exception IOException If the record position is invalid.
*/
private synchronized void seek(int recno) throws IOException {
writeMessage("In Seek");
db.seek(headerLen + (recordLen * (recno - 1)));
}
/**
* Lock the requested record. If the argument is -1, lock the whole
* database. This method blocks until the lock succeeds. No timeouts
* are defined for this.
* @param recno The record number to lock.
* @exception IOException If the record position is invalid.
*/
public void lock(int record) throws IOException {
}
/**
* Unlock the requested record. Ignored if the caller does not have
* a current lock on the requested record.
*/
public void unlock(int record) {
}
private void writeMessage(String message)
{
try{
System.out.println(message);
log.writeChars(new String(message + "\n"));
}
catch(IOException ioex)
{
ioex.printStackTrace();
}
}
public DataInfo[] criteriaFind(String criteria) throws DatabaseException
{
//Add the code to read the database from find
invariant();
try{
StringBuffer bufCrit = new StringBuffer(1);
Hashtable table = new HashTable();
StringTokenizer tokens = new StringTokenizer(criteria,",");
while ( tokens.hasMoreTokens() )
{
String critTemp = new String(format(tokens.nextToken()));
bufCrit.setLength(bufCrit.length() + critTemp.length());
bufCrit.append(critTemp);
}
System.out.println(bufCrit);
seek(1);
DataInfo[] rv = null;
String [] values = null;
boolean found = false;
int r,c=1;
for (r = 1; r <= recordCount; r++) {
values = readRecord();
//Boolean b = new Boolean((values != null) && (bufCrit));
if ((values != null) && new Boolean(bufCrit.toString())) {
rv[c] = new DataInfo(r,description,values);
c++;
}
}
return rv;
}
catch (IOException e) {
throw new DatabaseException(UNEXPECTED + e);
}
}

private String format(String stringToFormat)
{
String tmpField = new String(),tmpData = new String();
if (stringToFormat.startsWith("\""))
{
tmpField = stringToFormat.substring(1,stringToFormat.indexOf("="));
tmpData = stringToFormat.substring(stringToFormat.indexOf("=")+1,stringToFormat.lastIndexOf("'"));
}
if (stringToFormat.endsWith("\""))
{
tmpField = stringToFormat.substring(0,stringToFormat.indexOf("="));
tmpData = stringToFormat.substring(stringToFormat.indexOf("=")+1,stringToFormat.indexOf("\""));
}
for(int i = 0;i<description.length;i++)>
{
if (tmpField.equalsIgnoreCase(description[i].getName()))
{
tmpField = "values[" + i + "]";
break;
}
}
return new String(tmpField + ".equals(" + tmpData + ") &&");
}
/**
* Ensures that the database structure is valid.
* @exception RuntimeException If structure has become corrupted.
*/
protected final synchronized void invariant() {
writeMessage("In invariant()");
boolean ok = false;
try {
writeMessage("DBlen :" + db.length());
writeMessage("HeaderLen :" + headerLen);
writeMessage("RecLen :" + recordLen);
writeMessage("Reccnt :" + recordCount);
// writeMessage(headerLen + (recordLen * recordCount));
if (db.length() == headerLen + (recordLen * recordCount)) {
ok = true;
}
} catch (Exception e) {
throw new RuntimeException(UNEXPECTED + e);
}
if (!ok) {
writeMessage("Not Ok!");
throw new RuntimeException("Data: Internal error");
}
}
}
Frank Carver
Sheriff

Joined: Jan 07, 1999
Posts: 6920
why?


Read about me at frankcarver.me ~ Raspberry Alpha Omega ~ Frank's Punchbarrel Blog
Carl Trusiak
Sheriff

Joined: Jun 13, 2000
Posts: 3340
You are throwing the error that you are seeing (A previous post of his Frank). What is the full output from
In invariant()
until
Data: Internal error
?


I Hope This Helps
Carl Trusiak, SCJP2, SCWCD
 
I agree. Here's the link: http://aspose.com/file-tools
 
subject: suncertify.db.Data