Thread: interview Q and A i encountered - BOKIBOAZ

hi dudes
had a job interview to implement a transformation protocol between A and B with 5 different massages types, the solution was :

Code:

#include "stateMachine.h"
//#include "stdafx.h"
#include <string.h>
#include <stdlib.h>
#include <stdio.h>

#define VALID 1
#define INVALID 0

#define D_A 0
#define D_B 1

#define ARR_SIZE 25

typedef struct{
	char cmdArr[ARR_SIZE];
	bool AorB;
}cmd_s;

typedef struct{
	char cmdArr[ARR_SIZE];
	int size;
}cmd3_s;


//Global Variables
cmd_s Cmd;
cmd3_s Cmd3;


void fillArr(char destArr[], const char sourceArr[], const int size){
	memset(destArr, 0, ARR_SIZE);
	memcpy(destArr, sourceArr, size);
}

bool isCmd(const char * cmd_t, const int size){
	if(strncmp(Cmd.cmdArr, cmd_t, size) == 0){
		return 1;
	}
	return 0;
}

int checkCmd(bool drction, char * cmd_t, int size, int *statePtr, int dest_state){
	if(Cmd.AorB == drction ){
		if(isCmd(cmd_t, size)){
			*statePtr = dest_state;
			return VALID;
		}
	}

	*statePtr = 1;
	return INVALID;
}

void saveCmd3(const char sourceArr[], const int size){
	fillArr(Cmd3.cmdArr, sourceArr, size);
	Cmd3.size = size - 1; //don't count the '/0'
}

int checkState3(int *statePtr){
	int status = (checkCmd(D_A,"LIST", sizeof("LIST"),statePtr, 4));

	saveCmd3("LIST", sizeof("LIST"));

	// other possible commands ...	

	if(status == INVALID){
		status = (checkCmd(D_A,"EXIT ", sizeof("EXIT "),statePtr, 5));
	}

return status;

}

int getCmdLen(){
	int i=0;
	int cnt=0;

	for(i=0; i<ARR_SIZE; i++){
		if(Cmd.cmdArr[i] != '\0')
			cnt++;
	}

return cnt;
}

int checkCh(char ch){
	if((ch >='a') && (ch <='z'))
		return VALID;

	if((ch >='0') && (ch <='9'))
		return VALID;

return INVALID;

}

int checkState4(int *statePtr){
	int cmdSize = getCmdLen();
	int cmd3Size = Cmd3.size;
	int SecondIdx = cmdSize - cmd3Size;
	int i;

	*statePtr = 1;

	if(cmdSize < cmd3Size*2 + 2)// check if the cmd msg is twice+2 space the cmd3 msg
		return INVALID;

	if(strncmp(&Cmd.cmdArr[0], Cmd3.cmdArr, cmd3Size) != 0)
		return INVALID;

	if(strncmp(&Cmd.cmdArr[SecondIdx], Cmd3.cmdArr, cmd3Size) != 0)
		return INVALID;

	// check the msg
	for(i = cmd3Size+1; i<= SecondIdx-2 ; i++ ){
		if(checkCh(Cmd.cmdArr[i]) == INVALID)
			return INVALID;
	}

	*statePtr = 3;
	return VALID;

}

int handleCmd(){
	static int stat_state = 1;

	switch(stat_state){
		case 1:
			return (checkCmd(D_A,"OPEN_CONNECTION", sizeof("OPEN_CONNECTION"),&stat_state, 2));
		case 2:
			return (checkCmd(D_B,"OPEN_CONNECTION_ACKED", sizeof("OPEN_CONNECTION_ACKED"),&stat_state, 3));
		case 3:
			return (checkState3(&stat_state));
		case 4:
			return (checkState4(&stat_state));
		case 5:
			return (checkCmd(D_B,"EXIT_ACKED", sizeof("EXIT_ACKED"),&stat_state, 1));

		default: 
			return INVALID;

	}
}

int stateMachine::main2(){
	// init

	memset(&Cmd, 0, sizeof(Cmd) );
	memset(&Cmd3, 0, sizeof(Cmd3));

	Cmd.AorB = D_A;
	fillArr(Cmd.cmdArr, "OPEN_CONNECTION", sizeof("OPEN_CONNECTION"));
	handleCmd();

	Cmd.AorB = D_B;
	fillArr(Cmd.cmdArr, "OPEN_CONNECTION_ACKED", sizeof("OPEN_CONNECTION_ACKED"));
	handleCmd();

	Cmd.AorB = D_A;
	fillArr(Cmd.cmdArr, "LIST", sizeof("LIST"));
	handleCmd();

	Cmd.AorB = D_B;
	fillArr(Cmd.cmdArr, "LIST 6575 LIST", sizeof("LIST 6575 LIST"));
	handleCmd();

	printf("YES");
	getchar();
	return 0;
}

hope it will help you if an interviewer asks you about something similar...
cheers!

I don't think this is useful.

hi bokiboaz,
what exactly that "stateMachine.h" file contains?could you give brief information about that header file...
i think this state machine code will be very helpful for me so please...

thanks and regards,
Sri