"Switch Case" 和 "If...else.." 区别 Java/Java 卡片

Question

请看下面的Java卡片程序。它们在逻辑上似乎是相等的，但在实践中有不同的输出：

使用 switch ... case 的简单传入 APDU 命令分析器：

package testPack;

import javacard.framework.APDU;
import javacard.framework.Applet;
import javacard.framework.ISO7816;
import javacard.framework.ISOException;

public class TestApp extends Applet {

    private TestApp() {
    }

    public static void install(byte bArray[], short bOffset, byte bLength) throws ISOException {
        new TestApp().register();
    }

    public void process(APDU arg0) throws ISOException {
        if (selectingApplet()) {
            return;
        }

        byte[] buffer = arg0.getBuffer();
        byte ins = buffer[ISO7816.OFFSET_INS];

        switch (ins) {
        case (byte) 0x80:
            ISOException.throwIt((short) 0x6901);
            break;
        default:
            ISOException.throwIt((short) 0x6902);
            break;
        }
    }
}

使用 if ... else ... 的相同程序：

package testPack;

import javacard.framework.APDU;
import javacard.framework.Applet;
import javacard.framework.ISO7816;
import javacard.framework.ISOException;

public class TestApp extends Applet {

    private TestApp() {
    }

    public static void install(byte bArray[], short bOffset, byte bLength) throws ISOException {
        new TestApp().register();
    }

    public void process(APDU arg0) throws ISOException {
        if (selectingApplet()) {
            return;
        }

        byte[] buffer = arg0.getBuffer();
        byte ins = buffer[ISO7816.OFFSET_INS];

        if (ins == (byte) 0x80) {
            ISOException.throwIt((short) 0x6901);
        } else {
            ISOException.throwIt((short) 0x6902);
        }
    }
}

我们知道，在Java Card中，APDU缓冲区头字段被认为是带符号的字节。所以我认为为了响应 00 80 00 00 00 APDU 命令，我必须为上述两个程序接收 69 02。

但这是结果：

第一个节目：

Download Cap begin...
Download Cap successful.
Install Applet begin...
Install Applet successful.
Select Applet begin...
Select Applet successful.
Send: 00 80 00 00 00
Recv: 69 01

第二个节目：

Download Cap begin...
Download Cap successful.
Install Applet begin...
Install Applet successful.
Select Applet begin...
Select Applet successful.
Send: 00 80 00 00 00
Recv: 69 02

为什么响应不同？

Answer 1

java没有问题。此代码：

byte ins = (byte) 0x80;

switch (ins) {
    case (byte) 0x80:
        System.out.println("switch matched");
        break;
    default:
        System.out.println("switch missed");
}

if (ins == (byte) 0x80) {
    System.out.println("if matched");
} else {
    System.out.println("if missed");
}

产生：

switch matched
if matched

问题出在其他地方。

可能值得注意的是 (byte) 0x80 结果是 -128。

"Switch Case" 和 "If...else.." 区别 Java/Java 卡片

"Switch Case" and "If...else.." difference in Java/Java Card

java

javacard