Question

I am working on an assignment for my GUI programming class, in which we are to make a windows program that displays the contents of a file in hexadecimal. I have a class that holds the text and creates the hex in string format.

I’m attempting to create an array of character arrays to store each line for output. However, when I use new to create the array of character pointers, I get an access violation error.

I’ve done some searching, but haven’t had any luck finding the answer.

The class has these member variables:

char* fileText;   
char** Lines;
int numChars;  
int numLines;  
bool fileCopied;

My constructor:

Text::Text(char* fileName){  //load and copy file.
   fileText = NULL;
   Lines = NULL;
   fileCopied = ExtractText(fileName);
   if ( fileCopied ) {
      CreateHex();
   }//endif
}//end constructor 

ExtractText loads the file given to the constructor, and copies it into a large string.

bool Text::ExtractText(char fileName[]){
   char buffer = '/0';    //buffer for text transfer
   numChars = 0;              //initialize numLines
   ifstream fin( fileName, ios::in|ios::out );  //load file stream
   if ( !fin ) {     //return false if the file fails to load
      return false;
   }//endif

   while ( !fin.eof() ) {      //count the lines in the file
      fin.get(buffer);
      numChars++;
   }//endwh

   fileText = new char[numLines];  //create an array of strings, one for each line in the file.

   fin.clear();           //clear the eof flag
   fin.seekg(0, ios::beg); //move the get pointer back to the start of the file.

   for ( int i = 0; i < numChars; i++ ) { //copy the text from the file into the string array.
      fin.get(fileText[i]);
   }//endfr
   fileText[numChars-1] = '\0';
   fin.close();
   numLines = (numChars % 16 == 0) ? (numChars/16) : (numChars/16 + 1);
   return true;
}//end fun ExtractText

Then comes the problem code. In the CreateHex function, the first line is where try to create the array of character pointers.

void Text::CreateHex(){
    Lines = new char*[numLines];

As soon as the program runs that line of code, that’s when I get the access violation. I’m not really sure what the problem is, because I’ve used that exact same method before in a previous program. The only difference was the name of pointer. I’m using Borland C++ 5.02 if that makes any difference. It’s not my first choice in compilers, but its what our teacher wants us to use.

Answer 1

When you execute the line

fileText = new char[numLines]

The variable numLines has not yet been initialized. As a member variable, it’s initialized to 0, so you are allocating an empty array for fileText.