//////////////////////////////////////////////////////////////////
// strFunctions.cpp : Lab 8
// Today's date - 2/11/99
//
// Name:  Your name here
// Class:  C 647 Introduction to Programming with C++ (CHS)
// Class:  CP 107 Introduction to Programming with C++ (NHTI)
/////////////////////////////////////////////////////////////////
// Description
// Describe what you program is doing.....
// 
/////////////////////////////////////////////////////////////////
// Program Output
// output can be attached at the end of the program.
//
/////////////////////////////////////////////////////////////////
#include <iostream>
using namespace std;
//#include <cstring>   //needed for string manipulation functions

const char TAB = '\t';
void DisplayMenu();

int mystrcmp(char a[], char b[]);
char * myStrcat(char *a, const char *b);

void main()
{
    const int STRING_LENGTH = 80;
	int iMenuItem = -1;
	int len ;									// number of actual chars in the array
	
	char szDestString[STRING_LENGTH*2] = {0};	// source string
	char szSrcString[STRING_LENGTH] = {0};		//array to receive input chars
	char szFirstString[STRING_LENGTH],			// arrays for receiving chars
		szSecondString[STRING_LENGTH] ;
	char *pTmpChr;								// temporary pointer used for receiving a string

	while ( 1 )
	{
		DisplayMenu();
		iMenuItem = cin.get();					//need to flush enter key out of buffer
		cin.get();								// must do this to get the enter key
		
		switch(iMenuItem)
		{
	   		case '1':		//strlen
				cout << endl 
					 << "Please enter a line of characters terminated with enter key" 
				     << endl ;
				cout << endl;
			
				cin.getline( szSrcString , STRING_LENGTH, '\n' ) ; // reads up to 79 chars or until
										//enter key detected or ctrlz
				cout << endl << "You just entered the following:" << endl ;
				cout << szSrcString << endl ;
				len = strlen ( szSrcString ) ;
				cout << "number of characters returned from strlen is " << len << endl ;
			break;
	   
		   case '2':
				//  strcpy
				cout << endl
				<< "Enter source string for strcpy test " << endl;
				cin.getline( szSrcString, STRING_LENGTH ) ;
				strcpy ( szDestString, szSrcString );
				cout << endl << "destination string is " << endl 
					<< szDestString << endl;
			break;
		   
		   case '3':
				// strcmp
				cout << endl << "Enter first string for strcmp" << endl;
				cin.getline(szFirstString, STRING_LENGTH) ;
				
				cout << endl << "Enter second string for strcmp" << endl;
				cin.getline(szSecondString, STRING_LENGTH) ;
				
				int iReturnValue;
				//iReturnValue = strcmp ( szFirstString,szSecondString) ;
				iReturnValue = mystrcmp ( szFirstString,szSecondString) ;
				cout << endl << "iReturnValue is " << iReturnValue << endl ;
				if ( iReturnValue == 0 )
				{
					cout << endl << "strings are equal" << endl ;
				}
				else if ( iReturnValue < 0 )
				{
					cout << endl 
					<< "first string is less than second" << endl;
				}
				else
				{
					cout << endl
					<< "first string is greater than second" << endl;
				}
			break;
		   
			case '4':
				//strcat
				// Make sure that the first string has enough space
				// to hold the additional characters placed at the end
				cout << "Enter first string" << endl;
				cin.getline(szDestString, STRING_LENGTH);
				//cin >> szSrcString;
				
				// get the string that will be concatenated.
				cout << "Enter string that will be appended to the first string" << endl;
				cin.getline(szSrcString, STRING_LENGTH);

				pTmpChr = myStrcat(szDestString, szSrcString);
				cout << "New string after concatenation is ";
				cout << szDestString << endl ;
				cout << "New string after concatenation is using return value ";
				cout << pTmpChr << endl << endl << endl;


			break;
			
			case '5':
			default:
				cout << "BYE....." << endl;
				//cout << "You have entered " << iMenuItem << " which is not a valid number, enter [1 to 4]" << endl;
			   return;
	   }//end of switch case

	}//end of while loop

}

void DisplayMenu()
{

	cout << TAB << "Please make the following menu choice" << endl;
	cout << TAB << TAB << "1.  strlen example" << endl << TAB << TAB << "2.  strcpy example" << endl ;
	cout << TAB << TAB << "3.  strcmp example" << endl << TAB << TAB << "4.  strcat example" << endl ;
	cout << TAB << TAB << "5.  quit the program" << endl ;
	
	return;
}

int mystrlen(char a[])
{
	int len = 0 ;
	int i = 0;
	while (a[i] != '\0')
	{	
		len++;
		i++;
	}
	return len;
}

void mystrcpy(char a[], char b[])
{
	int i = 0;
	while (b[i] != '\0')
	{
		a[i] = b[i];
		i++ ;
	}
	a[i] = '\0' ;
}

int mystrcmp(char a[], char b[])
{
	int i = 0;
	int iRetVal = -1;

	while (a[i] != '\0' && b[i] != '\0')
	{
		if(a[i] < b[i])
			return -1 ;
		
		if (a[i] > b[i] )
			return 1;
		i++;
	}

	if (a[i] == b[i])
	{
		iRetVal = 0;
	}
	else if(a[i] < b[i])
	{
		iRetVal = -1 ;
	}
	else //(a[i] > b[i])
	{
		iRetVal = 1;
	}

	return iRetVal;
}

//////////////////////////////////////////////////////////////////
// Function myStrcat
/////////////////////////////////////////////////////////////////
// Description:
//	Take two strings arguments and concatenates 
//  the second string at the end of the first string.
/////////////////////////////////////////////////////////////////
// INPUTS:
// char *	szDestination string (where second string will be 
//			concatenated.
// char *	String that will be attached to the first string
// char *	Same as first argument, concatenated string 
/////////////////////////////////////////////////////////////////
char * myStrcat(char *a, const char *b)
{
	// save the starting location of the first
	// string. This is what we will return.
	char *retString = a;
	
	// go to the end of the first string
	while ( *a != '\0')
		a++;
	
	// we are using b + i notation just incase
	// the second argument was an array (constant
	// pointer).
	int i = 0;			// used for traversing the string
	while ( *(b + i) != '\0')
	{
		*(a++) = *(b + i);	// attach char from str b to str a
		 i++ ;				// point to next character
	}
	*a = '\0' ;				// we pointer after the last char, add a null
	return retString;		// return the concanated string.
}

//////////////////////////////////////////////////////////////////
// Function myStrcat
/////////////////////////////////////////////////////////////////
// Description:
//	Take two strings arguments and concatenates 
//  the second string at the end of the first string.
/////////////////////////////////////////////////////////////////
// INPUTS:
// char []	szDestination string (where second string will be 
//			concatenated.
// char []	String that will be attached to the first string
// char *	Same as first argument, concatenated string 
/////////////////////////////////////////////////////////////////
void myStrcatA(char a[], char b [])
{
	// go to the end of the first array
	int i = 0;
	while ( a[i] != '\0')
		i++;

	// Start adding characters to the end 
	// of the first string
	int j = 0;
	while ( b[j] != '\0')
	{
		a[i] = b[j];
		j++; i++ ;
	}

	// Add a null character at the end of the array
	a[i] = '\0' ;
}