I am trying to write a program with a menu that reads from a text file a few different ways. I'm just working on menu option #2 still (reading backwards from the end of the file), but I can't wrap my head around what I'm doing wrong. I've been at this for a few days now and just can't find any good resources to help on this. Any help would be appreciated.
#include <iostream>
#include <string>
#include <iomanip>
#include <istream>
#include <math.h>
#include <fstream>
using namespace std;
const int SIZE = 20;
typedef char String[SIZE];
//prototypes
void Menu(int &);
void ReadFile(ifstream &);
void BackwardFile(ifstream &,long &);
long CountFile(ifstream &,long &);
int main()
{
char filename[]= "grades.txt";
int choice;
long numBytes;
ifstream InList;
InList.open(filename);
if(InList.good())
{
do
{
Menu(choice);
switch(choice)
{
case 1:
ReadFile(InList);
break;
case 2:
CountFile(InList,numBytes);
BackwardFile(InList,numBytes);
break;
case 3:
cout << "Pick a start position between 0 - " << numBytes << endl;
break;
/*case 4:*/
case 5:
cout << "\n GOOD BYE." << endl << endl;
break;
}
}while (choice != 5);
}
else
cout << "File did not open successfully." << endl << endl;
system("PAUSE");
return EXIT_SUCCESS;
}
void Menu(int &choice)
{
cout << "\n Choose an option:";
cout << "\n...................................";
cout << "\n 1- Display All Contents of the File";
cout << "\n 2- Display Content in Reverse Order";
cout << "\n 3- Display from Point A to Point B";
cout << "\n 4- Display from Point B to Point A";
cout << "\n 5- Exit";
cout << "\n\n Enter your choice: ";
cin >> choice;
}
void ReadFile(ifstream& inFile)
{
char byte;
inFile.clear();
cout<< "\nReading contents from the file:" <<endl;
if(inFile)
{
inFile.get(byte);
while(inFile.good())
{
cout << byte;
inFile.get(byte);
}
}
inFile.close();
}
void BackwardFile(ifstream& inFile, long& numBytes)
{
char byte;
inFile.clear();
cout<< "\nReading contents backwards from the file:" <<endl;
inFile.seekg(numBytes, ios::end);
while(inFile)
{
inFile.get(byte);
cout << byte;
numBytes--;
inFile.seekg(numBytes);
}
inFile.close();
}
long CountFile(ifstream& inFile, long& numBytes)
{
inFile.seekg(0L, ios::end);
numBytes = inFile.tellg();
return numBytes;
}
The following is my solution to the question. When open the file, I use ios::ate to set the file position to the end of the file and use seekg method to read back. I am not sure whether there is a more efficient way to solve this question.
void readFile(char *fileName){
char c;
std::ifstream myFile(fileName,std::ios::ate);
std::streampos size = myFile.tellg();
for(int i=1;i<=size;i++){
myFile.seekg(-i,std::ios::end);
myFile.get(c);
printf("%c\n",c);
}
}