read binary file

This is a discussion on read binary file within the C++ Programming forums, part of the General Programming Boards category; Hello, Why does not this work Code: ifstream dtmfile (filename, ios::in|ios::binary|ios::ate); when filename is declared as a string and read ...

  1. #1
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    read binary file

    Hello,
    Why does not this work
    Code:
    ifstream dtmfile (filename, ios::in|ios::binary|ios::ate);
    when filename is declared as a string and read with getline (file,filename); when this works
    Code:
    ifstream dtmfile ("dem.bin", ios::in|ios::binary|ios::ate);
    string filename is holding "dem.bin", still it does not work.. what do I miss?
    cheers

  2. #2
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    maybe I should have included my compilation error..
    error C2664: '__thiscall std::basic_ifstream<char,struct std::char_traits<char> >::std::basic_ifstream<char,struct std::char_traits<char> >(const char *,int)' : cannot convert
    parameter 1 from 'class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >' to 'const char *'
    No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

  3. #3
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    Since the std::string came in relatively late in the standard library.

    So, the iostream open interface takes a C-style string, not a std::string. Use std::string::c_str().

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  4. #4
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    Thanks for your reply. How can I use a std::string::c_str()? I declared it as string filename.
    Would you recommend reading a mixed text and number file in another way? Say fgets or something.
    Cheers

  5. #5
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    I was talking about the binary file of course, and thinking about another thing. forget the last part with mixed number and text

  6. #6
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    So, filename.c_str() will give you a C style string (const variant, so you can't change it - but that is fine for opening a file).

    Since you haven't posted what your file-reading code actually does, I can't comment on how you go about reading (or writing).

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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