我想为实现路由协议的网络分配计算1字节校验和 因为我是全新的，请通过向我提供1字节校验和的源代码来帮助我
这是我的simPhy.java类。
import java.util.*;
import java.net.*;
import java.io.*;
/**
* the IpAddress class handles ip address including functionalities such as whether two ip addresses are in the same network
*/
class IpAddress{
/**
* contains the ip address in byte format
*/
byte[] ipAddr=new byte[4];
/**
* receives an ip address in string format and stores it in instance variable ipAddr
*
* @param ipString ip address in String format
*/
public IpAddress(String ipString){
StringTokenizer strTok=new StringTokenizer(ipString,".",false);
int i=0;
String octet;
while(strTok.hasMoreTokens()){
octet=strTok.nextToken();
ipAddr[i++]=(byte)Integer.valueOf(octet,10).intValue();
}
}
/**
* receives an ip address in array of bytes format and stores in instance variable ipAddr
*
* @param ip ip address in the array of bytes formats
*/
public IpAddress(byte[] ip){
System.arraycopy(ip, 0, ipAddr, 0, 4);
}
/**
* returns ip address in array of bytes format
*
* @return ip address in array of bytes format
*/
public byte[] getBytes(){return ipAddr;}
/**
* return ip address in String format
*
* @return ip address in String format
*/
public String getString(){return new String((int)(ipAddr[0]& 0xFF)+"."+(int)(ipAddr[1]& 0xFF)+"."+(int)(ipAddr[2]& 0xFF)+"."+(int)(ipAddr[3]& 0xFF));}
/**
* calculates the network address of the ip address from supplied subnet mask
*
* @param mask subnet mask
* @return IpAddress class having ip address set to the network address
*/
public IpAddress getNetworkAddress(int mask){
byte[] netMask=new byte[4];
//find mask
int j=0;
int tMask=128;
for(int i=0;i<32;i++){
if(i<mask){
tMask=(tMask>>1)|128;
}
if((i+1)%8==0){
netMask[j++]=(byte)tMask;
tMask=0;
}
}
//find network address
byte[] netAddr=new byte[4];
for(int i=0;i<4;i++){
netAddr[i]=(byte)(ipAddr[i] & netMask[i]);
}
return new IpAddress(netAddr);
}
/**
* checks whether the supplied instance of IpAddress has ip address which is in the the same network as that of the invoking instance
*
* @param ip instance of IpAddress
* @param mask subnet mask
* @return true if the supplied instance of IpAddress has ip address which is in the the same network as that of the invoking instance and false otherwise
*/
public boolean sameSubnet(IpAddress ip, int mask){
IpAddress network1=getNetworkAddress(mask);
IpAddress network2=ip.getNetworkAddress(mask);
return network1.sameIp(network2);
}
/**
* checks whether the supplied instance of IpAddress has the same ip address as that of the invoking instance
*
* @param ip instance of IpAddress class
* @return true if the supplied instance of IpAddress has the same ip address as that of the invoking instance and false otherwise
*/
public boolean sameIp(IpAddress ip){
byte[] other=ip.getBytes();
for (int i=0; i<4; i++) {
if(ipAddr[i]!=other[i]){
return false;
}
}
return true;
}
}
/**
* the Packet class defines the structure of packets in network layer
*/
class Packet{
/**
* ip address of the source encapsulated in an instance if IpAddress
*/
IpAddress src;
/**
* ip address of the destination encapsulated in an instance if IpAddress
*/
IpAddress dst;
/**
* actual data of the packet in array of bytes format
*/
byte payload[];
/**
* initializes instance variables corresponding to source ip, destination ip, and payload
*
* @param an array of bytes containing source ip in first four slots, destination ip in second four slots, and the payload in rest
*/
Packet(byte[] a){
byte[] srcIp=new byte[4];
byte[] dstIp=new byte[4];
payload=new byte[a.length-8];
System.arraycopy(a, 0, srcIp, 0, 4);
System.arraycopy(a, 4, dstIp, 0, 4);
System.arraycopy(a, 8, payload, 0, a.length-8);
src=new IpAddress(srcIp);
dst=new IpAddress(dstIp);
}
/**
* initializes instance variables corresponding to source ip, destination ip, and payload
*
* @param s source ip address encapsulated in an instance of IpAddress
* @param d destination ip address encapsulated in an instance of IpAddress
* @param a array of bytes containing the payload
*/
Packet(IpAddress s, IpAddress d, byte[] a){
payload=new byte[a.length];
System.arraycopy(a, 0, payload, 0, a.length);
src=s;
dst=d;
}
/**
* returns the ip address of the source encapsulated in an instance of IpAddress
*
* @return ip address of the source encapsulated in an instance of IpAddress
*/
IpAddress getSrcIp(){return src;}
/**
* returns the ip address of the destination encapsulated in an instance of IpAddress
*
* @return ip address of the destination encapsulated in an instance of IpAddress
*/
IpAddress getDstIp(){return dst;}
/**
* returns the payload as array of bytes
*
* @return payload as array of bytes
*/
byte[] getPayload(){return payload;}
/**
* returns an array of bytes with embedded source ip address in first four slots, destination ip address in second four slots, and the rest containing payload
*
* @return array of bytes having source ip in first four slots, destination ip in second four slots and payload in the rest
*/
byte [] getBytes(){
byte[] packet=new byte[payload.length+8];
try{
System.arraycopy(src.getBytes(), 0, packet, 0, 4);
System.arraycopy(dst.getBytes(), 0, packet, 4, 4);
System.arraycopy(payload, 0, packet, 8, payload.length);
return packet;
}
catch(Exception e){
e.printStackTrace();
}
return null;
}
/**
* returns a string informing source ip address, destination ip address and payload
*
* @return string informing source ip address, destination ip address and payload
*/
String getString(){
return new String("SrcIP="+src.getString()+ " | DestIP="+dst.getString()+" | Payload="+new String(payload));
}
}
/**
* the Frame class defines the structure of frames in data link layer
*/
class Frame{
/**
* byte representing the source mac address
*/
byte srcMac;
/**
* byte representing the destination mac address
*/
byte dstMac;
/**
* array of bytes representing the payload
*/
byte payload[];
/**
* checksum byte for error checking
*/
byte checksum;
/**
* initializes instance variables corresponding to source mac address, destination mac address and payload
*
* @param a array of bytes containing source and destination mac address in first two slots respectively and payload in the rest
*/
Frame(byte[] a){
srcMac=a[0];
dstMac=a[1];
payload=new byte[a.length-3];
try{
System.arraycopy(a, 2, payload, 0, payload.length);
checksum=a[a.length-1];
}
catch(Exception e){
e.printStackTrace();
}
}
/**
* initializes instance variables corresponding to source mac address, destination mac address and payload
*
* @param s source mac address in integer format
* @param d destination mac address in integer format
* @param a payload in array of bytes
*/
Frame(int s, int d, byte[] a){
srcMac=(byte)s;
dstMac=(byte)d;
payload=new byte[a.length];
try{
System.arraycopy(a, 0, payload, 0, a.length);
checksum=calculateChecksum();
}
catch(Exception e){
e.printStackTrace();
}
}
/**
* initializes instance variables corresponding to source mac address, destination mac address, payload initialized to zero
*
* @param s source mac address in integer format
* @param d destination mac address in integer format
*/
Frame(int s, int d){
srcMac=(byte)s;
dstMac=(byte)d;
payload=new byte[0];
checksum=calculateChecksum();
}
/**
* returns source mac address in byte
*
* @return source mac address in byte
*/
byte getSrcMac(){
return srcMac;
}
/**
* returns destination mac address in byte
*
* @return destination mac address in byte
*/
byte getDstMac(){
return dstMac;
}
/**
* returns value in the checksum field
*
* @return value in the checksum field
*/
byte getChecksum(){
return checksum;
}
/**
* returns payload in array of bytes
*
* @return payload in array of bytes
*/
byte [] getPayload(){
return payload;
}
/**
* returns an array of bytes with embedded mac address in first slot, destination mac address in second slot, and payload in the rest
*
* @return array of bytes having source mac address in first slot, destination mac address in second slot, and payload in the rest
*/
byte [] getBytes(){
byte[] frame=new byte[payload.length+3];
frame[0]=srcMac;
frame[1]=dstMac;
try{
System.arraycopy(payload, 0, frame, 2, payload.length);
frame[payload.length+2]=checksum;
return frame;
}
catch(Exception e){
e.printStackTrace();
}
return null;
}
/**
* Calculate one byte checksum for the frame
*
* @return checksum value
*/
byte calculateChecksum(){
/*Replace the following code with checksum generation algorithm to calculate checksum on src MAC, dst MAC and payload*/
return 1;
}
/**
* checks whether the frame has any checksum error
*
* @return true if checksum error is detected and false otherwise
*/
boolean hasCheckSumError(){
/*replace the following code with checksum verification*/
return false;
}
/**
* returns a string informing source mac address, destination mac address and payload
*
* @return string informing source mac address, destination mac address and payload
*/
String getString(){
return new String("Src Mac="+(int)(srcMac& 0xFF)+ " | Dst Mac="+(int)(dstMac& 0xFF));
}
}
/**
* class ByteArray is a custom method to manipulate array of bytes
*/
class ByteArray{
/**
* array of bytes to be manipulated
*/
byte[] bArray;
/**
* instantiates instance variable corresponding to array of bytes
*
* @param size size of the array
*/
ByteArray(int size){
bArray=new byte[size];
}
/**
* initializes instance variable with the supplied array of bytes
*
* @param b array of bytes
*/
ByteArray(byte[] b){
bArray=new byte[b.length];
System.arraycopy(b, 0, bArray, 0, b.length);
}
/**
* stores value of supplied array of bytes b in instance variable bArray, starting from an specified index of bArray
*
* @param index index of instance variable bArray from where the copy should start
* @param b array of bytes to be stored in instance variable bArray
*/
void setAt(int index, byte[] b){
System.arraycopy(b, 0, bArray, index, b.length);
}
/**
* returns byte value at specified index of instance variable bArray
*
* @param index index of instance variable bArray from which byte value should be retrieved
* @return byte value at specified index of instance variable bArray
*/
byte getByteVal(int index){return bArray[index];}
/**
* stores byte value at specified index of instance variable bArray
*
* @param index index of instance variable bArray to which byte value should be stored
*/
void setByteVal(int index, byte b){bArray[index]=b;}
/**
* returns a portion of instance variable bArray according to supplied index from which copy should start, along with number of bytes to be copied
*
* @param index index of bArray from which copy should start
* @param length number of bytes to be copied
* @return array of bytes containing portion of instance variable bArray as specified through parameters
*/
byte[] getAt(int index, int length){
byte[] temp=new byte[length];
System.arraycopy(bArray, index, temp, 0, length);
return temp;
}
/**
* returns array of bytes containing value of instance variable bArray
*
* @return array of bytes containing value of instance variable bArray
*/
byte[] getBytes(){return bArray;}
/**
* returns size of instance variable bArray
*
* @return size of instance variable bArray
*/
int getSize(){return bArray.length;}
}
/**
* class Buffer<T> acts as a generic storage class
*/
class Buffer<T>{
/**
* array of supplied type
*/
T data[];
/**
* size of the buffer
*/
int size;
/**
* index of the start of the buffer
*/
int head;
/**
* index of the end of the buffer
*/
int tail;
/**
* name of the buffer
*/
String name;
/**
* initializes name and size of buffer
*
* @param n String denoting name of the buffer
* @param sz integer denoting size of the buffer
*/
Buffer(String n, int sz){
name=n;
size=sz+1;
data=(T[])new Object[size];
head=0;
tail=0;
}
/**
* checks whether buffer is empty
*
* @return true if buffer is empty and false otherwise
*/
synchronized boolean empty(){
if (head==tail) return true;
else return false;
}
/**
* checks whether buffer is full
*
* @return true if buffer is full and false otherwise
*/
synchronized boolean full(){
if((tail+1)%size==head) return true;
else return false;
}
/**
* stores a single item in buffer if space is available and dropped otherwise
*
* @param t element of type T that should be stored
* @return true of storage was successful and false otherwise
*/
synchronized boolean store(T t){
if(full()){
System.out.println(name+" Buffer Full. Dropping Packet ...");
return false;
}
else{
tail=(tail+1)%size;
data[tail]=t;
return true;
}
}
/**
* returns a single item from head of the buffer if buffer is not empty and null otherwise
*
* @return a single item from head of the buffer if buffer is not empty and null otherwise
*/
synchronized T get(){
if(empty()){
System.out.println(name+" Buffer Empty.");
return null;
}
else {
head=(head+1)%size;
return data[head];
}
}
}