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PktFactory.java
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PktFactory.java
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/**
* PktFactory.java
*
* @author Tigran Hakobyan
* txh7358@rit.edu
*
*/
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
public class PktFactory {
public final byte[] rOpCode = {0,1};
public final byte[] wOpCode = {0,2};
public final byte[] dataOpCode = {0,3};
public final byte[] ackOpCode = {0,4};
// by default our program uses octet mode.
public static String currentMode = "octet";
// termination bit in wrq/rrq packet.
public final byte term = 0;
private int pktLength;
private InetAddress serverAddr;
private int port;
public PktFactory(int pktLength, InetAddress serverAddr, int port) {
this.pktLength = pktLength;
this.serverAddr = serverAddr;
this.port = port;
}
public DatagramPacket createReadRequestPacket(String strFileName){
byte[] filename = strFileName.getBytes();
byte[] mode = currentMode.getBytes();
int len = rOpCode.length + filename.length + mode.length + 2;
ByteArrayOutputStream outputStream = new ByteArrayOutputStream(len);
try {
outputStream.write(rOpCode);
outputStream.write(filename);
outputStream.write(term);
outputStream.write(mode);
outputStream.write(term);
} catch (IOException e) {
e.printStackTrace();
}
byte[] readPacketArray = outputStream.toByteArray();
DatagramPacket readPacket = new DatagramPacket(readPacketArray, readPacketArray.length, serverAddr, port);
return readPacket;
}
public DatagramPacket createAckPacket(byte[] blockNum, int prt){
int len = ackOpCode.length + blockNum.length;
ByteArrayOutputStream outputStream = new ByteArrayOutputStream(len);
try {
outputStream.write(ackOpCode);
outputStream.write(blockNum);
} catch (IOException e) {
e.printStackTrace();
}
byte[] ackPacketArray = outputStream.toByteArray();
DatagramPacket ackPacket = new DatagramPacket(ackPacketArray, ackPacketArray.length, serverAddr, prt);
return ackPacket;
}
public byte[] getOpCode(byte[] data) {
byte[] opCode = new byte[2];
opCode[0] = data[0];
opCode[1] = data[1];
return opCode;
}
public byte[] getBlockNum(byte[] data) {
byte[] blockNum = new byte[2];
blockNum[0] = data[2];
blockNum[1] = data[3];
return blockNum;
}
public byte[] getDataBytes(byte[] data) {
// We sure that data bytes pkt is always 512 bytes.
byte[] dataVal = new byte[pktLength-4];
int j = 0;
for(int i = 4; i < data.length; i++) {
dataVal[j++] = data[i];
}
return dataVal;
}
public String getErrorMessage(byte[] data) {
byte[] errorMsgBytes = new byte[data.length-5];
ByteArrayOutputStream outputStream = new ByteArrayOutputStream(errorMsgBytes.length);
int j = 0;
for(int i = 4; i < data.length - 1; i++) {
errorMsgBytes[j++] = data[i];
}
try {
outputStream.write(errorMsgBytes);
} catch (IOException e) {
e.printStackTrace();
}
return outputStream.toString();
}
}