Question

I’m trying to copy a file, but whatever I try, the copy seems to be a few bytes short.

_file is an ifstream set to binary mode.

void FileProcessor::send()
{
    //If no file is opened return
    if(!_file.is_open()) return;
    //Reset position to beginning
    _file.seekg(0, ios::beg);

    //Result buffer
    char * buffer;
    char * partBytes = new char[_bufferSize];
    //Packet *p;
    //Read the file and send it over the network

    while(_file.read(partBytes,_bufferSize))
    {
        //buffer = Packet::create(Packet::FILE,std::string(partBytes));
        //p = Packet::create(buffer);
        //cout<< p->getLength() << "\n";
        //writeToFile(p->getData().c_str(),p->getLength());
        writeToFile(partBytes,_bufferSize);
        //delete[] buffer;
    }

    //cout<< *p << "\n";
    delete [] partBytes;
}

_writeFile is the file to be written to.

void FileProcessor::writeToFile(const char *buffer,unsigned int size)
{
    if(_writeFile.is_open())
    {
        _writeFile.write(buffer,size);
        _writeFile.flush();
    }
}

In this case I’m trying to copy a zip file.
But opening both the original and copy in notepad I noticed that while they look identical , It’s different at the end where the copy is missing a few bytes.

Any suggestions?

Answer 1

You are assuming that the file’s size is a multiple of _bufferSize. You have to check what’s left on the buffer after the while:

while(_file.read(partBytes,_bufferSize)) {
  writeToFile(partBytes,_bufferSize);
}
if(_file.gcount())
    writeToFile(partBytes, _file.gcount());