Reading from a text file in C and C++

//=============================================================
// File: IODemo.cpp
// Purpose: Program demonstrates how to open and read lines from
//        simple text files in both C and CPP.  See comments in 
//        the source files for details.
// Author: Dr. Rick Coleman
//=============================================================
// Headers required for file I/O in C
#include <stdio.h>

// Headers required for file I/O in C++
#include <iostream>
#include <fstream>
// Headers required for both C and C++
#include <string>

using namespace std;

#define datafile "IODemo.dat"

// Function Prototypes
void GetNextLine_C(FILE *fp, char *line, int lineLen);
void GetNextLine_CPP(ifstream& inFile, char *line, int lineLen);

int main(int argc, char **argv)
{
    // Vars used in the C I/O demo
    FILE    *fp;            // Pointer to file

    // Vars used in the C++ I/O demo
    ifstream    inFile;        // Input file stream

    // Vars used in both demonstrations
    char    str[128];        // Character array to hold lines read from the file


    //---------------------------------------------
    //     Demonstrate file I/O in Standard C
    //---------------------------------------------
    printf("Demonstrating file I/O in Standard C\n");
    printf("Opening file...\n");
    // Open the file for reading, checking to make sure it was successfully opened
    if((fp = fopen(datafile, "r")) == NULL)
    {
        // fopen() returns NULL if the file could not be found or
        //    if for some other reason the open failed.
        printf("Unable to open file %s\nProgram terminating...\n");
        return 0;
    }

    // File was successfully opened so call the C function to read
    //        all lines from the file.
    printf("Printing lines in file...\n\n");
    while(true)
    {
        GetNextLine_C(fp, str, 128);
        if(strlen(str) == 0)        // End of File reached
            break;                    // terminate the loop
        else
        {
            printf("%s\n", str);    // Print the line
        }

    } // end eternal while() loop
    fclose(fp);                        // Close the data file
    printf("\n\ndone...\n\n");

    //-----------------------------------------------------------------------
    //                   Now we do the same thing in C++
    //-----------------------------------------------------------------------
    cout << "Demonstrating file I/O in C++\n";
    cout << "Opening file...\n";

    // Open the file for reading, checking to make sure it was successfully opened
    inFile.open(datafile, ifstream::in); 
    if(!inFile.is_open())
    {
        // inFile.is_open() returns false if the file could not be found or
        //    if for some other reason the open failed.
        cout << "Unable to open file %s\nProgram terminating...\n";
        return 0;
    }

    // File was successfully opened so call the C++ function to read
    //        all lines from the file.
    cout << "Printing lines in file...\n\n";
    while(true)
    {
        GetNextLine_CPP(inFile, str, strlen(str));
        if(inFile.good())
            cout << str << "\n";    // Print the line
        else
            break;                    // terminate the loop

    } // end eternal while() loop
    fclose(fp);                        // Close the data file
    cout << "\n\ndone...\n\n";

    return 0;
}

/**************************************************************/
/* GetNextLine_C                                              */
/*                                                            */
/* Purpose: Read a line from a data file. Returns void string */
/*          if end of file is reached.                        */
/*  Language: C                                               */
/* Args: fp -- pointer to open file.                          */
/*       line -- Character array to place the line in.        */
/*       lineLen -- Length of the character array line.       */
/* Returns: void                                              */
/**************************************************************/
void GetNextLine_C(FILE *fp, char *line, int lineLen)
{
    int    done = false;
    while(!done)
    {
        if((fgets(line, lineLen, fp)) == NULL)    // Read a line from the file
        {
            strcpy(line, "");    // Return an empty string to flag EOF
            return;
        }
        // Remove the newline character from the end of the line
        // Explanation:  the function fgets() used to read lines from the
        //    file reads all characters up to and including the newline character
        //    at the end of a line in the file.  This character is removed by
        //    overwriting it with a null terminator.  For example: if the first
        //    line in the text file was "testing" it would be read into the 
        //    character array as | t | e | s | t | i | n | g | \n | \0 |...
        //  The previous command overwrites the newline (\n) giving
        //    | t | e | s | t | i | n | g | \0 | \0 |...
        if(strlen(line) > 0) 
            line[strlen(line)-1] = '\0';
        
        if(strlen(line) == 0)  // Skip any blank lines
            continue;
        else if(line[0] == '#')  // Skip any comment lines
            continue;
        else done = true;    // Got a valid data line so return with this line
    }

}

/**************************************************************/
/* GetNextLine_CPP()                                          */
/*                                                            */
/* Purpose: Read a line from a data file.                     */
/*  Language: C                                               */
/* Args: inFile -- istream pointer                            */
/*       line -- Character array to place the line in.        */
/*       lineLen -- Length of the character array line.       */
/* Returns: void                                              */
/**************************************************************/
void GetNextLine_CPP(ifstream& inFile, char *line, int lineLen)
{
    int    done = false;
    while(!done)
    {
        inFile.getline(line, 128);
        
        if(inFile.good())    // If a line was successfully read
        {
            if(strlen(line) == 0)  // Skip any blank lines
                continue;
            else if(line[0] == '#')  // Skip any comment lines
                continue;
            else done = true;    // Got a valid data line so return with this line
        }
        else
        {
            strcpy(line, "");
            return;
        }
    } // end while
}