Doubt about JavaCard Memory
Posted: Thu Oct 12, 2017 10:27 pm
I made a simple applet to test the speed of adding arrays, depending whether they are saved in EEPROM or RAM. Since working with variables stored in RAM should be faster, I was really surprised when I noticed no difference between them. I would really like to know where I went wrong, but simply cannot figure it out. Could anyone give me some clues on this question?
Code: Select all
package test;
import javacard.framework.APDU;
import javacard.framework.ISO7816;
import javacard.framework.Applet;
import javacard.framework.ISOException;
import javacard.framework.JCSystem;
public class SimpleMemoryTest extends Applet {
private static final short ARRAY_SIZE = 32;
byte[] eeprom_a, eeprom_b, eeprom_c;
byte[] ram_a, ram_b, ram_c;
short[] mem;
private SimpleMemoryTest() {
this.mem = new short[2];
}
public static void install(byte[] bArray, short bOffset, byte bLength) {
new SimpleMemoryTest().register(bArray, (short) (bOffset + 1), bArray[bOffset]);
}
public void process(APDU apdu) {
if (selectingApplet()) return;
byte[] buf = apdu.getBuffer();
switch (buf[ISO7816.OFFSET_INS]) {
case (byte) 0x00: { // Print memory info to verify where arrays are stored
mem[0] = JCSystem.getAvailableMemory(JCSystem.MEMORY_TYPE_PERSISTENT);
mem[1] = JCSystem.getAvailableMemory(JCSystem.MEMORY_TYPE_TRANSIENT_DESELECT);
buf[0] = (byte)(mem[0] / 256);
buf[1] = (byte)(mem[0] % 256);
buf[2] = (byte)(mem[1] / 256);
buf[3] = (byte)(mem[1] % 256);
apdu.setOutgoingAndSend((short)0, (short)4);
break;
}
case (byte) 0x01: { // Put arrays in EEPROM.
this.eeprom_a = new byte[ARRAY_SIZE];
this.eeprom_b = new byte[ARRAY_SIZE];
this.eeprom_c = new byte[ARRAY_SIZE];
break;
}
case (byte) 0x02: { // Put arrays in RAM.
this.ram_a = JCSystem.makeTransientByteArray(ARRAY_SIZE, JCSystem.CLEAR_ON_DESELECT);
this.ram_b = JCSystem.makeTransientByteArray(ARRAY_SIZE, JCSystem.CLEAR_ON_DESELECT);
this.ram_c = JCSystem.makeTransientByteArray(ARRAY_SIZE, JCSystem.CLEAR_ON_DESELECT);
break;
}
case (byte) 0x03: { // Add arrays in EEPROM 100 times
short i, j;
for (i = (short) 0; i < (short) 100; i++) {
for (j = (short) 0; j < (short) ARRAY_SIZE; j++) {
eeprom_c[j] = (byte)(eeprom_a[j] + eeprom_b[j]);
}
}
break;
}
case (byte) 0x04: { // Add arrays in RAM 100 times
short i, j;
for (i = (short) 0; i < (short) 100; i++) {
for (j = (short) 0; j < (short) ARRAY_SIZE; j++) {
ram_c[j] = (byte)(ram_a[j] + ram_b[j]);
}
}
break;
}
default:
ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
}
}
}