Dev-C++ error?
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Thread: Dev-C++ error?

  1. #1
    Join Date
    Feb 2006
    Posts
    15

    Dev-C++ error?

    Hi!

    I noticed a very strange behaviour of Dev-C++ compiler. I have a function which transforms a binary file (containing positive and negative integers as records) by moving all the integers one position (4 bytes) to the left (so the first record in the file is left `empty`). I have written a function like this:

    Code:
    void moveRecords(fstream & f) {
     f.seekg(0,ios::beg);
     int x=0,y=0;
     f.read((char *)&x,sizeof(int));
     if (f) {
      f.read((char *)&y,sizeof(int));
      while (f) {
       f.seekp(-4,ios::cur);
       f.write((char *)&x,sizeof(int));
       x=y;
       f.tellp();
       f.read((char *)&y,sizeof(int));
      }
     }
     f.clear();
     f.seekp(0,ios::end);
     f.write((char *)&x,sizeof(int));
     f.clear();
    }
    It works fine! Now, if I delete or comment the line `f.tellp();`, nothing works fine anymore - just some first integers are moved and after that a while loop is finished (so I guess some error occurs). And the funny part is that it happens only in Dev-C++ compiler - if compiled with Borland, I don't have to write this useless line of `tellp`.. Why is that and how to get rid of it? Because in the situation, I must use the Dev-C++.

  2. #2
    Join Date
    Jul 2002
    Location
    Portsmouth. United Kingdom
    Posts
    2,725

    Re: Dev-C++ error?

    Is it a large file?
    Can you read it all into a container and then write it out again?

    Code:
    void moveRecords(fstream & f) 
    {
        std::deque<int> value_list;
    
        int value;
    
        // Read it all in.
        while (f.read((char *)&value, sizeof(int)))
        {
            value_list.push_back(value);
        }
    
        // Remove the first.
        value_list.pop_front();
    
        // Write them back.
        std::copy(value_list.begin(), value_list.end(),  std::ostream_iterator<int>(f, ""));
    }
    (Untested)
    "It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong."
    Richard P. Feynman

  3. #3
    Join Date
    Feb 2006
    Posts
    15

    Re: Dev-C++ error?

    No, it is not a large file - I tested the function on file having only 10 records in it.. But the thing is I have to demonstrate the operations within the file itself and I am not allowed to put all the contents of the file in the memory and then to forget about the file..

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