Answered: Write a C program, called msg.c, that…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

Write a C program, called msg.c, that reads messages from an input file (or stdin) and verifies whether the messages are valid or not.

We developed a protocol for reading messages from a device. There are different length messages. Each message has rules, described below. Messages are separated by a newline..
Each message is followed by a description, some examples, and a Deterministic Finite State Automaton (DFA) which recognizes the message. Before input is read, we are in state 1. We transition states on each character read. If, at the end of input, we are in an accepting state (double circle), then the message is valid.

foo:

Starts with an E followed by a string of digits 0 1 or 2 followed by an F . E.g.:

E201022011101F

eep:

Starts with a P, followed by arbitrary number of BC (including none). E.g.:

P
PBCBCBC

op:

Starts with a Q . Followed by a string of 6 and 7 , where the number of 7 s must be odd. E.g.:

Q7
Q66666676666
Q76767

ork:

Starts with an M, followed by a foo or an eep. E.g.:

ME2010201F
MPBC

Following is the code for 1st and 3rd case. Please complete the code for 2nd and 4th which are highlighted in the code.

#include <stdio.h>

#include<string.h>

#include<stdbool.h>

bool foo(char msg[120]);

bool eep(char msg[120]);

bool op(char msg[120]);

bool ork(char msg[120]);

void main()

{

char fname[30],lyne[120];

FILE *filehandle;

char *item;

char rule[100],msg[120];

printf("Enter the filename: ");

scanf("%s",fname);

filehandle = fopen(fname, "r");

if (filehandle == NULL)

{

printf("Error Could not open");

return;

}

while (fgets(lyne,120,filehandle)) {

//printf("%s",lyne);

item = strtok(lyne,":");

strcpy( rule,item);

//printf("%s",rule);

item = strtok(NULL,":");

strcpy( msg,item);

if(strcmp(rule,"foo")==0)

{

printf("\nMessage: %s",msg);

if(foo(msg))

{

//strcat(msg," OK");

printf("OK");

}

else

{

//strcat(msg," FAIL");

printf("FAIL");

}

/* if(strcmp(rule,"eep")==0)

{

if(eep(msg))

{

printf("OK\n");

}

else

{

printf("FAIL\n");

}

}*/

if(strcmp(rule,"op")==0)

{

printf("\nMessage: %s",msg);

if(op(msg))

{

//strcat(msg," OK");

printf("OK");

}

else

{

//strcat(msg," FAIL");

printf("FAIL");

}

if(strcmp(rule,"ork")==0)

{

if(ork(msg))

{

printf("OK\n");

}

else

{

printf("FAIL\n");

}

}*/

// printf("msg: %s",msg);

}

bool foo(char msg[120])

{

int len;

len=strlen(msg);

int valid1=0,valid2=0;

int i;

// printf("%c last %c",msg[0],msg[(len-3)]);

// printf("%d",len);

// for(i=0;i<len;i++)

// {

// printf("%c",msg[i]);

//}

if(msg[0]=='E' && msg[len-3]=='F') // please check the correct character position and take

{

valid1=1;

}

for(i=1;i<=len-4;i++)

{

if(msg[i]=='0'||msg[i]=='1'||msg[i]=='2')

{

valid2=1;

}

else

{

valid2=0;

}

// printf("\n%d %c",i,msg[i]);

}

if(valid1==1 && valid2==1)

{

return true;

}

//printf("%d%d",valid1,valid2);

return false;

}

bool eep(char msg[120])

{

bool v1=false;

if(msg[0]=='P')

{

v1=true;

}

return false;

}

bool op(char msg[120])

{

int l;

bool v1=false,v2=false,v3=true;

int i;

int c=0;

l=strlen(msg);

// printf("%d",l);

if(msg[0]=='Q')

{

v1=true;

}

for(int i=1;i<l-2;i++)

{

if(msg[i]=='6'||msg[i]=='7')

{

v2=true;

}

else

{

v2=false;

}

if(msg[i]=='7')

{

c++;

}

if(c%2==1)

{

v3=true;

}

if(v1=true && v2==true && v3==true)

{

return true;

}

return false;

}

bool ork(char msg[120])

{

return false;

}

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