/**
* creates a new send-frame.
*
* @param requestRecord, the data to be sent to the reader.
* @return the composed frame ready for sending to the reader.
* @throws IOException if the send frame is longer then 65535 bytes.
*/
static byte[] composeReaderSendFrame(RequestRecord requestRecord) throws IOException {
byte[] frame;
// calculating LENGTH (Advanced Protocol-Length)
int dataLen;
if (requestRecord.data != null) dataLen = requestRecord.data.length;
else dataLen = 0;
// STX + ALENGTH + COM-ADR + CONTROLBYTE + DATA + CRC16
int length = 1 + 2 + 1 + 1 + dataLen + 2;
if (length > 65535) {
throw new IOException("Protocol send frame too long. (>65535)");
}
byte[] len = ByteBlock.numberToByteArray(length);
// constructing send-frame
frame = new byte[length];
frame[0] = STX;
frame[1] = len[2];
frame[2] = len[3];
frame[3] = requestRecord.comAdr;
frame[4] = requestRecord.controlByte;
for (int i = 0; i < dataLen; i++) {
frame[5 + i] = requestRecord.data[i];
}
// calculating crc16-checksum
byte[] temp = new byte[length - 2];
for (int i = 0; i < length - 2; i++) temp[i] = frame[i];
byte[] cs = CRC16.crc16(temp);
frame[length - 2] = cs[0];
frame[length - 1] = cs[1];
return frame;
}
/**
* This method gets the answer from the reader and creates a responseRecord which is returned to
* the caller
*/
private synchronized ResponseRecord getResponse() throws IOException {
byte[] buf = null;
// receiving data...
// wait for at least 3 bytes of response
long t0 = System.currentTimeMillis();
long time = 0;
while (in.available() < 3) {
try {
Thread.sleep(10);
} catch (InterruptedException ie) {
}
time = System.currentTimeMillis() - t0;
if (time >= timeout) {
throw new IOException("Timeout occured, no response for " + timeout + "ms.");
}
}
// read first three byte
byte[] firstthree = new byte[3];
int stat = in.read(firstthree, 0, 3);
if (stat != 3) {
throw new IOException("No data available.");
}
// check STX
if (firstthree[0] != STX) {
throw new IOException(
"Received Data not of type 'Protocol Frame: " + "Advanced Protocol-Length'.");
}
// get length of response frame
int msb = ByteBlock.byteToNumber(firstthree[1]);
int lsb = ByteBlock.byteToNumber(firstthree[2]);
int len = (msb << 8) + lsb;
// wait for len - 3 bytes (rest of response)
while (in.available() < (len - 3)) {
try {
Thread.sleep(10);
} catch (InterruptedException ie) {
}
time = System.currentTimeMillis() - t0;
if (time >= timeout) {
throw new IOException(
"Timeout occured, response not completely " + "arrived for " + timeout + "ms.");
}
}
// read len - 3 bytes
buf = new byte[len - 3];
stat = in.read(buf, 0, len - 3);
if (stat != (len - 3)) {
throw new IOException("No data available.");
}
// if more available, frame is too long
if (in.available() > 0) {
throw new IOException("Protocol response frame too long.");
}
// verify checksum
byte[] frame = new byte[len];
for (int i = 0; i < 3; i++) frame[i] = firstthree[i];
for (int i = 3; i < len; i++) frame[i] = buf[i - 3];
byte[] cs = CRC16.crc16(frame);
if ((cs[0] != 0) || (cs[1] != 0)) {
throw new IOException("Protocol response frame checksum error.");
}
// create responseRecord
ResponseRecord responseRecord = new ResponseRecord();
// Reader ISO responses
responseRecord.status = buf[2];
byte[] data = new byte[buf.length - 5];
for (int i = 3, j = 0; i < buf.length - 2; i++) {
data[j++] = buf[i];
}
responseRecord.data = data;
// for debugging only...
// System.out.println(" buf: (without length) " +
// ByteBlock.byteArrayToHexString(buf));
// System.out.println();
return responseRecord;
}