NETWORK LAB-SLIDING WINDOW PROTOCOL-SELECTIVE REPEAT N ARQ

               SELECTIVE REPEAT AND ARQ

SENDER SIDE:-

#include<stdio.h>

#include<stdlib.h>

#include<fcntl.h>

#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include<string.h>

int converttoframes(char *n,char data[100][100],int power)

{ FILE *fp;

int k=0,i;

fp=fopen(n,"r");

while(!feof(fp))

{ data[k][0]=k%power+48;

for(i=1;i<9;i++)

data[k][i]=fgetc(fp);

data[k++][i]='\0'; } return (k-1); }

int main(int argc,char **argv)

{ int len,bits,frames,errbit,once;

int sws,lfs,lar;

int sockfd;

int n,l=0,i,j=0,choice=0,k,pre=0;

int flag=-1,count,re=0,ch=0;

struct sockaddr_in servaddr,cliaddr;

char data[100][100],ack[1];

char buff[100][100],buff1[10];

char name[50];

int *recvd,power=1,gla=0;

sockfd=socket(AF_INET,SOCK_STREAM,0);

if(sockfd<0)

perror("Cannot create a socket");

bzero(&servaddr,sizeof(servaddr));

bzero(&buff[0],sizeof(buff[0]));

bzero(&buff1,sizeof(buff1));

servaddr.sin_family=AF_INET;

servaddr.sin_addr.s_addr=inet_addr(argv[1]);

servaddr.sin_port=htons(7995);

connect(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr));

printf("Enter the window size:-");

scanf("%d",&sws);

printf("Enter the file name:-");

scanf("%s",name);

for(i=0;i<sws;i++)

power*=2;

frames=converttoframes(name,data,power);

recvd=(int *)malloc(sizeof(int)*sws);

recvd[-1]=1;

for(i=0;i<sws;i++)

recvd[i]=-1;

while(choice!=6)

{ flag=-1;

count=0;

for(i=0;i<sws;i++)

recvd[i]=-1;

printf("\n\t~~Choose cases~~\n1.Normal\t2.Ack Lost\t3.Data Lost\n4.Delayed Ack\t5.Wrong Data\t6.Exit\tChoice : ");

scanf("%d",&choice);

//printf("\n");

switch(choice)

{ case 1:

for(k=0;k<frames;k++)

{ j=0;

strcpy(buff[k],data[k]);

for(i=1;i<strlen(buff[k]);i++)

{ if(buff[k][i]=='1')

j++; }

if(j%2==0)

buff[k][i++]='0';

else

buff[k][i++]='1';

buff[k][i]='\0';

send(sockfd,buff[k],strlen(buff[k]),0);

recv(sockfd,ack,1,0);

lfs=k%power;

printf("\nLast frame sent:-%d",lfs);

lar=atoi(ack);

recvd[lar]=lar;

if(count==sws-1)

{ printf("\nACK:-");

printf("%d",lar); }

else if(count==sws)

count=0;

count++; }

break;

case 2: lar=0;

for(k=0;k<frames+1;k++)

{ if(k==frames && recvd[count-1]!=-1)

break;

once=0;

j=0;

strcpy(buff[k],data[k]);

for(i=1;i<strlen(buff[k]);i++)

{ if(buff[k][i]=='1')

j++; }

if(j%2==0)

buff[k][i++]='0';

else

buff[k][i++]='1';

buff[k][i]='\0';

if(count<sws)

{ if(flag!=-1)

{ wait(10);

printf("\nTIME OUT!!!"); }

send(sockfd,buff[k],strlen(buff[k]),0);

recv(sockfd,ack,1,0);

lfs=k%power;

printf("\nLast frame sent:-%d",lfs);

if(count==sws-1)

{ printf("\nAck lost?-1/0:-");

scanf("%d",&once); }

if(once==1)

recvd[count]=-1;

else

{ lar=atoi(ack);

recvd[count]=lar; }

if(once!=1 && count==sws-1)

{ if(ack[0]!='n')

{ printf("\nACK:-");

printf("%d",lar); }

else

{ printf("\nNAK:-");

printf("%d",lfs); } }

count++;

if(flag!=-1)

{ k=flag-1;

flag=-1;

count=0; } }

else

{ for(i=0;i<sws;i++)

{ if(recvd[i]==-1)

{ flag=k;

if(k>sws)

k=i-1+sws;

else

k=i-1;

count=count-1; } }

if(flag==-1)

{ for(i=0;i<sws;i++)

recvd[i]=-1;

count=0;

k=k-1; } }

bzero(&buff[k+1],sizeof(buff[k+1])); }

//bzero(&recvd,sizeof(recvd));

break;

case 3:

lar=0;

count=0;

for(k=0;k<frames+1;k++)

{

j=0;

if(k==frames && recvd[count-1]!=-1 && recvd[count-2]!=-1)

break;

strcpy(buff[k],data[k]);

for(i=1;i<strlen(buff[k]);i++)

{

if(buff[k][i]=='1')

j++;

}

if(j%2==0)

buff[k][i++]='0';

else

buff[k][i++]='1';

buff[k][i]='\0';

if(count<sws)

{

send(sockfd,buff[k],strlen(buff[k]),0);

recv(sockfd,ack,1,0);

lfs=k%power;

printf("\nLast frame sent:-%d",lfs);

if(ack[0]!='n')

{

lar=atoi(ack);

recvd[count]=lar;

}

else

recvd[count]=-1;

if(ack[0]!='n' && count==sws-1 && recvd[gla]!=-1)

{

printf("\nACK:-");

if(lar<frames-1)

printf("%d",lar+1);

else

printf("%d",lar);

}

else if(count==sws-1)

{

printf("\nNAK:-");

if(recvd[gla]==-1)

printf("%d",lfs-1);

else if(recvd[count]==-1)

printf("%d",lfs);

}

count++;

if(flag!=-1)

{

k=flag-1;

flag=-1;

count=0;

gla=0;

}

}

else

{

for(i=0;i<sws;i++)

{

if(recvd[i]==-1)

{

flag=k;

if(k>sws)

k=i-1+sws;

else

k=i-1;

if(i==0)

gla=1;

count=count-1;

}

}

if(flag==-1)

{ for(i=0;i<sws;i++)

recvd[i]=-1;

count=0;

k=k-1; } }

bzero(&buff[k+1],sizeof(buff[k+1])); }

//bzero(&recvd,sizeof(recvd));

break;

case 4:

lar=0;

for(k=0;k<frames+1;k++)

{ j=0;

once=0;

if(k==frames && recvd[count-1]!=-1)

break;

strcpy(buff[k],data[k]);

for(i=1;i<strlen(buff[k]);i++)

{ if(buff[k][i]=='1')

j++; }

if(j%2==0)

buff[k][i++]='0';

else

buff[k][i++]='1';

buff[k][i]='\0';

if(count<sws)

{ if(flag!=-1)

{ wait(10);

printf("\nTIME OUT!!!"); }

send(sockfd,buff[k],strlen(buff[k]),0);

recv(sockfd,ack,1,0);

if(count==sws-1)

{printf("\nAck delayed?-1/0:-");

scanf("%d",&once); }

if(once==1)

recvd[count]=-1;

else

{ lar=atoi(ack);

recvd[count]=lar; }

if(once!=1 && count==sws-1)

{ if(ack[0]!='n')

{ printf("\nACK : ");

printf("%d",lar); }

else

{ printf("\nNAK:-");

printf("%d",lfs); } }

count++;

if(flag!=-1)

{

k=flag-1;

flag=-1;

count=0; } }

else

{ for(i=0;i<sws;i++)

{ if(recvd[i]==-1)

{ flag=k;

if(k>sws)

k=i-1+sws;

else

k=i-1;

count=count-1; } }

if(flag==-1)

{ for(i=0;i<sws;i++)

recvd[i]=-1;

count=0;

k=k-1; } }

bzero(&buff[k+1],sizeof(buff[k+1])); }

//bzero(&recvd,sizeof(recvd));

break;

case 5:

count=0;

lar=0;

flag=0;

for(k=0;k<frames;k++)

{ j=0;

strcpy(buff1,data[k]);

for(i=1;i<strlen(buff1);i++)

{ if(buff1[i]=='1')

j++; }

if(j%2==0)

buff1[i++]='0';

else

buff1[i++]='1';

buff1[i]='\0';

printf("\nWanna introduce Error?-yes/no:-");

scanf("%d",&ch);

if(ch==1)

{ printf("\nIn which position to introduce error? ");

scanf("%d",&errbit);

if(buff1[errbit]=='1')

buff1[errbit]='0';

else

buff1[errbit]='1';

flag=buff1[0]-48;

if(flag<0)

flag+=48; }

send(sockfd,buff1,strlen(buff1),0);

recv(sockfd,ack,1,0);

lfs=k%power;

if(count==sws-1)

{ if(ack[0]!='n' && flag==0 && lar!=0)

{ printf("\nACK:-");

printf("%d",lar); }

else

{ printf("\nNAK:-");

printf("%d",flag);

flag=0; }

count=-1; }

else

if(ack[0]!='n')

flag=1;

count++;

lar=ack[0]-48;

if(lar<0)

lar+=48;

bzero(&buff1,sizeof(buff1)); }

l=0;

break;

case 6:

buff[0][1]='!';

send(sockfd,buff[0],1,0);

break; } }

shutdown(sockfd,SHUT_RDWR);

return 0; }

RECEIVER SIDE:-

#include<stdio.h>

#include<stdlib.h>

#include<fcntl.h>

#include<unistd.h>

#include<sys/types.h>

#include<sys/socket.h>

#include<netinet/in.h>

#include<string.h>

int main(int argc,char **argv)

{ int sockfd,newfd,len,count=0;

struct sockaddr_in servaddr,cliaddr;

int i,j=0,n,once=0;

int *recvd;

char s[10],ack[1];

int rws,lfr=0,mult;

sockfd=socket(AF_INET,SOCK_STREAM,0);

if(sockfd<0)

perror("Cannot create socket");

bzero(&servaddr,sizeof(servaddr));

bzero(&s,sizeof(s));

servaddr.sin_family=AF_INET;

servaddr.sin_port=htons(7995);

servaddr.sin_addr.s_addr=inet_addr(argv[1]);

if(bind(sockfd,(struct sockaddr*)&servaddr,sizeof(servaddr))<0)

perror("Bind error");

listen(sockfd,2);

len=sizeof(&cliaddr);

newfd=accept(sockfd,(struct sockaddr*)&cliaddr,&len);

bzero(&s,sizeof(s));

printf("Enter the window size:-");

scanf("%d",&rws);

mult=rws*2;

recvd=(int *)malloc(sizeof(int)*mult);

printf("Expecting frame:-%d",lfr);

recv(newfd,s,sizeof(s),0);

while(strcmp(s,"!"))

{ printf("\n");

j=0;

printf("\nData:-%s",s);

recvd[lfr]=lfr;

for(i=1;i<strlen(s);i++)

{ if(s[i]=='1')

j=j+1; }

if(j%2==0)

ack[0]=lfr+48;

else

ack[0]='n';

printf("\nData lost?-1/0:-");

scanf("%d",&once);

if(once==1)

ack[0]='n';

send(newfd,ack,1,0);

bzero(&s,sizeof(s));

recv(newfd,s,sizeof(s),0);

lfr=s[0]-48;

if(lfr<0)

lfr+=48;

printf("Expecting frame:-%d",lfr); }

shutdown(sockfd,SHUT_RDWR);

shutdown(newfd,SHUT_RDWR);

return 0; }

INPUT FILE:-

11110000111100000000111100001111

SYSTEM SOFTWARE LAB-SIMULATION OF PASS-2 OF A 2-PASS ASSEMBLER

                      
                SIMULATION OF PASS-2 OF A 2-PASS ASSEMBLER
PROGRAM CODE:-
MAIN FILE:-

#include "PASSONE.h"
#include <math.h>


struct HeaderRecord
{
char programname[6];
int startingaddress;
int lengthofcode;
};


struct TextRecord
{
int startingaddress;
int lengthofcode;
char *objectcode;
};


void writetextrecord(FILE *file,struct TextRecord* text)
{
int i=0;
fprintf(file,"T^%06X^%02X",text->startingaddress,text->lengthofcode);
for(;i<text->lengthofcode*2;i++)
{
if((i%6) == 0 && i!=text->lengthofcode*2-1)
fprintf(file,"^");
fprintf(file,"%c",text->objectcode[i]);
}
fprintf(file,"\n");
}


void writeheaderrecord(FILE *file,struct HeaderRecord *header)
{
fprintf(file,"H^%s^%06X^%06X\n",header->programname,header->startingaddress,header->lengthofcode);
}


void writeendrecord(FILE *file,int startingaddress)
{
fprintf(file,"E^%06X\n",startingaddress);
}


void performpasstwo(struct OPTAB *optab,struct SYMTAB *symtab,char *interfilename,char *outputfilename,char *listingfilename,int lengthofcode,int startaddress)
{
FILE *interfile = fopen(interfilename,"r"),*outputfile = fopen(outputfilename,"w"),*listingfile = fopen(listingfilename,"w");
char *line,objectcode[20],word1[20],word2[20],word3[20],word4[20],record[10000],buffer[20];
int i,numberofwords,j,createnewrecord=0,opcode;
struct HeaderRecord *header = (struct HeaderRecord *)malloc(sizeof(struct HeaderRecord));
struct TextRecord *textrecord;
line = getlinefromfile(interfile);
sscanf(line,"%s",word1);
if(strcasecmp(word1,"START") == 0)
sprintf(header->programname,"NONAME");
else
sprintf(header->programname,"%s",word1);
header->startingaddress =  startaddress;
header->lengthofcode = lengthofcode;
writeheaderrecord(outputfile,header);

textrecord = (struct TextRecord*)malloc(sizeof(struct TextRecord));
textrecord->startingaddress = startaddress;
textrecord->lengthofcode = 0;

while((line=getlinefromfile(interfile))!=NULL)
{
objectcode[0]='\0';
sscanf(line,"%s %s",word1,word2);
if(textrecord->startingaddress == -1)
textrecord->startingaddress = strtol(word1,NULL,16);


numberofwords=1;
for(j=0;line[j]!='\0';j++)
if(line[j] == ' ')
numberofwords++;


if(numberofwords == 2)
{
if(getopcode(optab,word2) >= 0)
{
sprintf(objectcode,"%02X0000",getopcode(optab,word2));
textrecord->lengthofcode+=6;
}
}
else if(numberofwords == 3)
{
sscanf(line,"%s %s %s",word1,word2,word3);
if(getopcode(optab,word2) == -1)
{
if(getopcode(optab,word3) >=0)
{
sprintf(objectcode,"%02X0000",getopcode(optab,word3));
textrecord->lengthofcode+=6;
}
}
else
{
opcode = getopcode(optab,word2);
if(strchr(word3,',') == NULL)
sprintf(objectcode,"%02X%04X",opcode,getaddress(symtab,word3));
else
{
j=0;
while(word3[j]!=',')
{
buffer[j] = word3[j];
j++;
}
buffer[j]='\0';
sprintf(objectcode,"%02X%04X",opcode,getaddress(symtab,buffer)|0x8000);
}
textrecord->lengthofcode+=6;
}
}
else if(numberofwords == 4)
{
sscanf(line,"%s %s %s %s",word1,word2,word3,word4);
if(getopcode(optab,word3) ==-1)
{
if(strcasecmp(word3,"RESW") == 0)
createnewrecord = 1;
else if(strcasecmp(word3,"RESB") ==0)
createnewrecord = 1;
else if(strcasecmp(word3,"WORD") == 0)
{
sprintf(objectcode,"%06X",(unsigned int)strtol(word4,NULL,16));
textrecord->lengthofcode+=6;
}
else if(strcasecmp(word3,"BYTE") == 0)
{
j = strlen(word4);
if(word4[0] == 'X' || word4[0] == 'x')
{
for(i=2;i<j-1;i++)
buffer[i-2] = word4[i];
buffer[i-2]='\0';
if(strlen(buffer)%2 != 0)
{
i=strlen(buffer);
buffer[i] = buffer[i-1];
buffer[i+1]='\0';
buffer[i-1] = '0';
}
strcat(objectcode,buffer);
textrecord->lengthofcode+= strlen(buffer);
}
else
{
for(i=2;i<j-1;i++)
sprintf(objectcode,"%s%02X",objectcode,word4[i]);
textrecord->lengthofcode+=(j-3)*2;
}
}
}
else
{
opcode = getopcode(optab,word3);
if(strchr(word4,',') == NULL)
sprintf(objectcode,"%02X%04X",opcode,getaddress(symtab,word4));
else
{
j=0;
while(word4[j]!=',')
{
buffer[j] = word4[j];
j++;
}
buffer[j]='\0';
sprintf(objectcode,"%02X%04X",opcode,getaddress(symtab,buffer)|0x8000);
}
textrecord->lengthofcode+=6;
}
}
fprintf(listingfile,"%s %s\n",line,objectcode);
if(createnewrecord == 0)
strcat(record,objectcode);
else
{
record[textrecord->lengthofcode]='\0';
textrecord->objectcode = (char *)malloc(sizeof(char)*(textrecord->lengthofcode+1));
strcpy(textrecord->objectcode,record);
textrecord->lengthofcode /= 2;
if(strlen(textrecord->objectcode) > 0)
writetextrecord(outputfile,textrecord);
textrecord->lengthofcode = 0;
textrecord->startingaddress = -1;
free(textrecord->objectcode);
createnewrecord = 0;
record[0] = '\0';
}
}
writeendrecord(outputfile,startaddress);
fclose(outputfile);
fclose(interfile);
fclose(listingfile);
}


int main (int argc, char *argv[])
{
char filename[256];
char interfilename[256];
char objectprogramfilename[256];
char listingfilename[256];
int lengthofcode=-1,startingaddress;
struct SYMTAB *symtab;
struct OPTAB *optable = getoptable();
printf("\nEnter the name of the file to be assembled: ");
scanf("%s",filename);
printf("\nEnter name for intermediate file: ");
scanf("%s",interfilename);
printf("\nEnter name for Object Program: ");
scanf("%s",objectprogramfilename);
printf("\nEnter name for Listing File: ");
scanf("%s",listingfilename);
symtab = performpassone(filename,interfilename,&lengthofcode,&startingaddress);
if(symtab != NULL)
{
displaysymboltable(symtab);
printf("\nPerforming Pass two ...\n");
performpasstwo(optable,symtab,interfilename,objectprogramfilename,listingfilename,lengthofcode,startingaddress);
printf("\nProgram Assembled.\nOutput File: %s\n",objectprogramfilename);
}
return 0;
}

<PASSONE.h> FILE:-

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <math.h>

struct OPTABentry

{

char mnemonic[5];

int opcode;

};

struct OPTAB

{

struct OPTABentry *entries;

int numberofentries;

};

struct SYMTABentry

{

char symbolname[15];

int address;

};

struct SYMTAB

{

struct SYMTABentry entries[1000];

int numberofentries;

};

int getopcode(struct OPTAB *optable,char *mnemonic)

{

int i;

for(i=0;i<optable->numberofentries;i++)

{

if(strcasecmp(optable->entries[i].mnemonic,mnemonic) == 0)

return optable->entries[i].opcode;

}

return -1;

}

int getaddress(struct SYMTAB *symtab,char *symbolname)

{

int i;

for(i=0;i<symtab->numberofentries;i++)

{

if(strcasecmp(symtab->entries[i].symbolname,symbolname) == 0)

return symtab->entries[i].address;

}

return -1;

}

int insertintosymboltable(struct SYMTAB *symtab,char *symbolname,int address)

{

if(getaddress(symtab,symbolname) > 0)

return -1;

strcpy(symtab->entries[symtab->numberofentries].symbolname,symbolname);

symtab->entries[symtab->numberofentries].address = address;

symtab->numberofentries++;

return 1;

}

struct OPTAB* createoptable(char mnemonics[][6],int opcode[],int n)

{

int i;

struct OPTAB* optable = (struct OPTAB*)malloc(sizeof(struct OPTAB));

optable->entries = (struct OPTABentry*)malloc(sizeof(struct OPTABentry)*n);

optable->numberofentries = n;

for(i=0;i<n;i++)

{

strcpy(optable->entries[i].mnemonic,mnemonics[i]);

optable->entries[i].opcode = opcode[i];

}

return optable;

}

struct OPTAB* getoptable()

{

char mnemonics[][6] = {"ADD\0","AND\0","COMP\0","DIV\0","J\0","JEQ\0","JGT\0","JLT\0","JSUB\0","LDA\0","LDCH\0","LDL\0","LDX\0","MUL\0","OR\0","RD\0","RSUB\0","STA\0","STCH\0","STL\0","STSW\0","STX\0","SUB\0","TD\0","TIX\0","WD\0"};

int opcode[] = {0x18,0x40,0x28,0x24,0x3C,0x30,0x34,0x38,0x48,0x00,0x50,0x08,0x04,0x20,0x44,0xD8,0x4C,0x0C,0x54,0x14,0xE8,0x10,0x1C,0xE0,0x2C,0xDC};

return createoptable(mnemonics,opcode,26);

}

struct SYMTAB* getsymboltable()

{

struct SYMTAB *newtab = (struct SYMTAB*)malloc(sizeof(struct SYMTAB));

newtab->numberofentries = 0;

return newtab;

}

//returns -1 for invalid mnemonic

//returns -2 for duplicate label

//returns -3 for invalid label name, label name is a mnemonic

//returns -4 for comments or empty lines

//returns -5 for redundant START instructions

//returns 0 on successful scan

int standardscanner(struct OPTAB *optab,struct SYMTAB *symtab,char *line,int address,int *startaddress)

{

int position=0,i,numberofwords=1;

char buffer[20],temp[20],temp2[20];

if(line[0] == '.' || line[0]=='\0')

return -4;

for(i=0;line[i] != '\0';i++)

{

if(line[i] == ' ' || line[i] == '\t')

numberofwords++;

}

if(numberofwords == 1)

{

if(strcasecmp(line,"RSUB") == 0)

return 0;

else

return -1;

}

if(numberofwords == 2)

{

i=0;

position =0 ;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

strcpy(temp,buffer);

i=0;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

if(strcasecmp(temp,"START") == 0)

{

if(*startaddress >= 0)

return -5;

*startaddress = strtol(buffer,NULL,16);

return 0;

}

if(getopcode(optab,temp) >= 0)

{

if(getopcode(optab,buffer) >= 0)

return -3;

else

return 0;

}

else

{

if(strcasecmp(buffer,"RSUB") == 0 && *startaddress >= 0)

return insertintosymboltable(symtab,temp,address)>0?0:-2;

else if(strcasecmp(buffer,"START") == 0)

{

if(*startaddress > 0)

return -5;

*startaddress = 0;

return 0;

}

else

return -1;

}

}

if(numberofwords == 3)

{

i=0;

position =0 ;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

strcpy(temp,buffer);

i=0;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

strcpy(temp2,buffer);

i=0;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

if(getopcode(optab,temp) == -1)

{

if(strcasecmp(temp2,"START") == 0)

{

if(*startaddress > 0)

return -5;

*startaddress = strtol(buffer,NULL,16);

return 0;

}

if(getopcode(optab,temp2) >= 0)

if(getopcode(optab,buffer) == -1 && *startaddress > 0)

return insertintosymboltable(symtab,temp,address)>0?0:-2;

return -3;

}

else

return -1;

}

return -1;

}

int directivescanner(struct SYMTAB *symtab,char *line,int address)

{

int position=0,i,numberofwords=1,tempaddress;

char buffer[20],temp[20];

if(line[0] == '.' || line[0]=='\0')

return 0;

for(i=0;line[i] != '\0';i++)

{

if(line[i] == ' ' || line[i] == '\t')

numberofwords++;

}

if(numberofwords == 3)

{

i=0;

position =0;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

strcpy(temp,buffer);

i=0;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

if(strcasecmp(buffer,"RESW") ==0)

{

i=0;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

insertintosymboltable(symtab,temp,address);

return (address+(atoi(buffer)*3));

}

else if(strcasecmp(buffer,"RESB") == 0)

{

i=0;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

insertintosymboltable(symtab,temp,address);

return (address+atoi(buffer));

}

else if(strcasecmp(buffer,"WORD") == 0)

{

insertintosymboltable(symtab,temp,address);

return (address+3);

}

else if(strcasecmp(buffer,"BYTE") == 0)

{

i=0;

while(line[position]!= ' ' && line[position]!='\t' && line[position] != '\0')

buffer[i++] = line[position++];

buffer[i] = '\0';

position++;

tempaddress = address;

if(buffer[0] == 'C' || buffer[0] =='c')

address = address + (i-3);

else if(buffer[0] == 'X' || buffer[0] =='x')

address = address + (int)ceil((double)(i-3.0)/2.0);

else

return -1;

insertintosymboltable(symtab,temp,tempaddress);

return (address);

}

else

return -1;

}

else

return -1;

}

char* getlinefromfile(FILE *file)

{

char ch='\0';

char previouschar='\0';

int position=0;

int stringstart=0;

char *buffer=(char*)malloc(sizeof(char)*1000);

while(ch != '\n')

{

if((ch = fgetc(file)) != EOF)

{

if(ch == '\'')

{

if(stringstart == 0)

stringstart=1;

else 

if(stringstart == 1)

stringstart = 0;

}

if(ch == '\n')

{

if(previouschar ==' ' || previouschar =='\t')

position--;

}

else

if(!(position == 0 && (ch==' '|| ch=='\t')))

if(!((previouschar == ' ' || previouschar == '\t') && (ch == ' ' || ch =='\t')) || stringstart==1)

{

if(ch == '\t')

ch = ' ';

previouschar = ch;

buffer[position++]=ch;

}

}

else

return NULL;

}

buffer[position]='\0';

return buffer;

}

struct SYMTAB* performpassone(char *filename,char *intermediatefilename,int *lengthofcode,int *startingaddress)

{

FILE *fd = fopen(filename,"r");

FILE *interfd = fopen(intermediatefilename,"w");

int LOCCTR = -1;

char *line;

int start = 0, end = 0, error = 0,status;

struct OPTAB *optable = getoptable();

struct SYMTAB *symtab = getsymboltable();

if(fd < 0 )

printf("\n error: file %s could not be opened\n",filename);

else if(interfd < 0)

printf("\n error: file %s could not be created or opened\n",intermediatefilename);

else

{

line = getlinefromfile(fd);

while(line!=NULL && end!=1)

{

if((line[0]=='E' || line[0] == 'e') && (line[1]=='N' || line[1] == 'n') && (line[2]=='D' || line[2] == 'd') && (line[3]=='\0' || line[3] == '\t' || line[3] == ' '))

{

fprintf(interfd,"%s\n",line);

end = 1;

}

else

{

status = standardscanner(optable,symtab,line,LOCCTR,&LOCCTR);

if(status != 0)

{

if(status == -2)

{

printf("error:\t%s\n\tduplicate label\n",line);

error=end = 1;

}

else if(status == -1)

{

printf("error:\t%s\n\tnot an instruction\n",line);

error=end = 1;

}

else if(status == -3)

{

status = directivescanner(symtab,line,LOCCTR);

if(status > 0)

{

fprintf(interfd,"%0X %s\n",LOCCTR,line);

LOCCTR = status;

}

else

{

printf("\nerror :\t%s\n\t\tunable to assemble line\n",line);

error=end = 1;

}

}

else if(status == -5)

{

printf("\n%s\n",line);

printf("\nStart Instruction already encountered\n");

end = 1;

}

}

else

{

if(start == 0 && LOCCTR >0)

{

start = 1;

*startingaddress = LOCCTR;

fprintf(interfd,"%s\n",line);

}

else

{

fprintf(interfd,"%0X %s\n",LOCCTR,line);

LOCCTR = LOCCTR + 0x3;

}

}

}

line = getlinefromfile(fd);

}

fclose(fd);

fclose(interfd);

*lengthofcode = LOCCTR-*startingaddress;

if(error == 0)

return symtab;

}

return NULL;

}

void displaysymboltable(struct SYMTAB *symtable)

{

int i=0;

printf("\nSymbol Table:\n");

printf("\tSymbol\t\tAddress\n");

for(;i<symtable->numberofentries;i++)

{

printf("\t%s\t\t%0X\n",symtable->entries[i].symbolname,symtable->entries[i].address);

}

}

INPUT-FILE:-

MOVE START 1000

FIRST LDA FIVE

STA UNO

UNO LDCH CHARZ

STCH C1,x

.LABEL LDA

ALPHA RESW 1

BETA RESB 2

FIVE WORD 5

CHARZ BYTE C'F1'

C2 BYTE       X'F1'

C1 RESB 1

END MOVE