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//----------------------------------------------------------------------------
//
// Module: LogExtent.java
//
// Description: Log extent file interface.
//
// Product: com.sun.jts.CosTransactions
//
// Author: Simon Holdsworth
//
// Date: March, 1997
//
// Copyright (c): 1995-1997 IBM Corp.
//
// The source code for this program is not published or otherwise divested
// of its trade secrets, irrespective of what has been deposited with the
// U.S. Copyright Office.
//
// This software contains confidential and proprietary information of
// IBM Corp.
//----------------------------------------------------------------------------
package com.sun.jts.CosTransactions;
// Import required definitions.
import java.io.*;
//------------------------------------------------------------------------------
// LogExtent class
//------------------------------------------------------------------------------
/**A structure containing information for an open log file extent.
*
* @version 0.01
*
* @author Simon Holdsworth, IBM Corporation
*
* @see
*/
//----------------------------------------------------------------------------
// CHANGE HISTORY
//
// Version By Change Description
// 0.01 SAJH Initial implementation.
//-----------------------------------------------------------------------------
class LogExtent extends Object {
// The type of access last made to an extent file is stored in the extent
// descriptor block. This is used to save doing uneccessary fseeks.
/**Type of last access is unknown (forces fseek to required cursor pos'n)
*/
final static int ACCESSTYPE_UNKNOWN = 0;
/**Last access was for reading
*/
final static int ACCESSTYPE_READ = 1;
/**Last access was for writing
*/
final static int ACCESSTYPE_WRITE = 2;
/**The radix used to convert extent numbers to strings.
*/
final static int EXTENT_RADIX = 36;
/**The maximum number of extent files that can be allocated to a single
* log at any one time. Extent names are made up of <logfilename>.nnn
* Hence this value is restricted by the .nnn extension (3 characters
* only, to support the FAT file system.
*/
final static int MAX_NO_OF_EXTENTS = EXTENT_RADIX*EXTENT_RADIX*EXTENT_RADIX;
/**This value is used to validate the LogExtent object.
*/
LogExtent blockValid = null;
/**The extent number.
*/
int extentNumber = -1;
/**The file handle for the log extent file.
*/
LogFileHandle fileHandle = null;
/**The file for the log extent file.
*/
File file = null;
/**Indicates whether any information has been written since the last force.
*/
boolean writtenSinceLastForce = false;
/**The cursor position in the log extent.
*/
int cursorPosition = 0;
/**The last type of access to the extent.
*/
int lastAccess = ACCESSTYPE_UNKNOWN;
/**LogExtent constructor
*
* @param extent The number of the extent.
* @param extentFH The handle of the extent file.
*
* @return
*
* @see
*/
LogExtent( int extent,
LogFileHandle extentFH,
File extentFile ) {
extentNumber = extent;
fileHandle = extentFH;
file = extentFile;
}
/**Default LogExtent destructor.
*
* @param
*
* @return
*
* @see
*/
public void doFinalize() {
try {
fileHandle.destroy();
} catch( Throwable e ) {};
blockValid = null;
file = null;
}
/**Modulates the extent number using the maximum extent number.
*
* @param ext The extent number
*
* @return The modulated extent number.
*
* @see
*/
final static int modExtent( int ext ) {
return (ext % MAX_NO_OF_EXTENTS);
}
}