Reading variable length strings from a binary file / dynamic array issue

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C++

stream

Good day,

I have a block of code that reads structures and related character strings from a binary file. The length of the character string is defined within the structure read immediately prior.

Currently, I am reading the string one character at a time but I am positive that something better with dynamic character arrays.

The structures are pretty basic, a few numbers and the length of the string being one.

ifstream in_file("(path)\\zTEST.dat", ios::binary);
if ( !in_file.is_open() ) {
     MessageBox::Show("File failed to open.");
  } else {
     sst = "";

     SFE_structure r;
     in_file.read(reinterpret_cast<char*>(&r), sizeof(SFE_structure));
     char coop;
     MessageBox::Show("numEntries=" + r.numEntries,"length of string");
     for (i=0;i<r.numEntries;i++){
          coop = in_file.get();
          sst = sst + coop;
     }
    this->textParentID->Text = gcnew String(sst.c_str());
 (***)
}

This works to read the characters in. It just seems that it might be inefficient, so I thought I would look at doing a dynamic array:

in_file.read(reinterpret_cast<char*>(&r), sizeof(SFE_structure));
                    sst = "";

                    MessageBox::Show("numEntries=" + r.numEntries,"length of string");
                    char * tmpDynamicArray = new char[r.numEntries];
                    in_file.read(tmpDynamicArray, r.numEntries);
                    sst = tmpDynamicArray;
                    delete [] tmpDynamicArray;
                    this->textSelfID->Text = gcnew String(sst.c_str());

(***)
}

It works but there are trailing characters on the character array. One instance, for example, is a two character pairing. When I dimension the array tmpDynamicArray based upon the r.numEntries (2), I get

"x>x>S"

(there are some of the block / boxy characters that aren't showing in the <pre> code area)

When it reads the dynamic array, it does take the two proper characters but the remaining characters remain. (Size becomes 9 in debug mode, in release mode it looks longer but I cannot tell...)

If I do a "sizeof(tmpDynamicArray)" it shows 4 in release and debug.


Coming from a Pascal / VB (not even .NET) background, so the string conversions are a real treat... trying to learn.