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CyclicFile.javaAPI DocJava Card3601Wed Mar 22 21:07:24 GMT 2006package com.sun.javacard.samples.JavaPurse

CyclicFile

public class CyclicFile extends Object
Class CyclicFile implements ISO 7816 CyclicFile. This class always allocates one more record than the maximum number of allowed records in CyclicFile. Method getNewLogRecord returns a new record without affecting contents of CyclicFile. Method updateNewLogRecord updates the internal record pointers, so the new record becomes the current record(record number one) and the oldest record becomes the next new record.
author
Zhiqun Chen (zhiqun.chen@sun.com)

Fields Summary
private byte
num_record
private byte
current_record
private byte
next_record
private Record[]
records
Constructors Summary
CyclicFile(byte max_record, byte record_length)
Constructor

param
max_record maximum number of record in CyclicFile
param
record_length record length


                         
        

      // allocate one more record than the maximum number
      // of allowed records in CyclicFile
      num_record = ++max_record;

      records = new Record[num_record];

      for ( byte i = 0; i < num_record; i++) {
        records[i] = new Record(record_length);
      }
Methods Summary
bytefindRecord(byte firstByte)
Find the record.

param
firstByte if non-0, the record's first byte must match this value; if 0, any value of the record's first byte matches.
return
the record number, or 0 if the record is not found


		byte eRecNum = num_record--; //max record
		byte currentRecNumber = 1;
		byte thisRec[];

		while (true) {

			thisRec = getRecord(currentRecNumber);

			if ( firstByte == 0) {
				return currentRecNumber;
			}

			if ( thisRec[0] == firstByte) {
				return currentRecNumber;
			}

			if ( currentRecNumber == eRecNum )
				return 0;
			currentRecNumber++;
		}
byte[]getNewLogRecord()
Get a new record

return
the new record


		byte[] record = records[next_record].record;
		return record;
byte[]getRecord(byte recordNum)
Get a record with the specified record number

param
recordNum record number
return
the specified record


      // check if the record number is in the range of 1..maximum record number
      if ( ( recordNum < 1 ) || ( recordNum > (byte)(num_record - 1 ) ) )
         ISOException.throwIt(ISO7816.SW_RECORD_NOT_FOUND);

      if ((recordNum = (byte) (current_record - recordNum + 1)) < 0 )
        recordNum += num_record;

      return records[recordNum].record;
voidupdateNewLogRecord()
Update internal record pointers, so the new record becomes the current record and the oldest record in CyclicFile becomes the next new record

see
getNewLogRecord


      // update current record pointer and next record pointer
      if (++current_record == num_record)
        current_record = 0;

      if (++next_record == num_record)
        next_record = 0;