Syntax for file.read() using std::bitset??

Hi all,
I'm trying to read-in some binary data from a file, into a bitset. I was doing this:

Code:

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bitset<FLAG_SIZE>  flags;
file.read((char *) &flags, FLAG_SIZE);

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but found my stack was getting corrupted when I was doing the read(). It seemed to work most of the time, but not all of the time.

I've tried other syntax with no luck. Any ideas?? Can I read binary data from a file directly into a bitset? (STL newbie)

Thanks for any pointers. :)

On my machine, a bitset<N> takes up 4 bytes for 1 < N <= 32 and 8 bytes for 32 < N <= 64 so you can see that it grows by basically the size of my machines basic int data type. If FLAG_SIZE happens to 16 for instance, then you are trying to read 16 bytes worth of data and stuff it into a 4 byte area of memory. What do you think is going to happen here?

Code:

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bitset<32> bits32;
bitset<33> bits33;
bitset<64> bits64;
bitset<65> bits65;
cout << sizeof(bits32) << endl;  // outputs 4
cout << sizeof(bits33) << endl;  // outputs 8
cout << sizeof(bits64) << endl;  // outputs 8
cout << sizeof(bits65) << endl;  // outputs 12

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NEVER try to directly read/write non-POD classes!

bitset has methods for conversion from/to string and long, use these.

hk_mp5kpw> Thanks!! That fixed it!

CornedBee> Thanks for the tip. I tried different syntax for the to_string method. The book I'm using suggests

flags.template to_string<char>()

however /usr/include/c++/3.2.2/bitset
gives the example of

flags.to_string<char,char_traits<char>,allocator<c har> >()

and neither of them work ("no matching function....."), so I went with the (char *). I'll keep muddling with the syntax though, thanks.

:)

Something like this might work.

Code:

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char buffer[FLAG_SIZE];
file.read((char *) &buffer, FLAG_SIZE);
string input(buffer,FLAG_SIZE); // Convert char array into string
bitset<FLAG_SIZE>  flags(input);  // Convert string into bitset

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Actually bitset overloads the stream operators.

Code:

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bitset<27> bs; // Fill it
ofstream ofs("bs.dat");
ofs << bs << endl;
ofs.close();
ifstream ifs("bs.dat");
ifs >> bs;

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