Question: How do I read a binary file into a `bitset` or `vector<bool>`? The binary file will vary in length. Is there a better container for this? I am new to C++ though experienced as a programmer.

Answer: 
If the file is large, Why should you read once, whole the file into the memory?

You can read a little piece every time. The size is determined with the *size* in this func:

```
file.read(buff, size)

```

When the *buff* is char's array.

I'm sorry, but You can't simplest read/save vector to file. 
for more details [see here](http://www.cplusplus.com/forum/general/11492/) and [here](http://www.daniweb.com/software-development/cpp/threads/132172).

And use Google, It's very helpful...
You didn't give too much context of what you're trying to do in your question. But here's one quick & dirty way to do it:

```
#include <iterator>
#include <fstream>
#include <vector>
#include <assert.h>
using namespace std;

const char *filename = "foo.bar";
int main()
{
  vector<bool> v;
  ifstream binary_file(filename, ios::binary);

  assert(binary_file);
  copy(istream_iterator<unsigned char>(binary_file),
       istream_iterator<unsigned char>(),
       back_insert_iterator< vector<bool> >(v));
}

```

Reading the zero-byte '\0' character into the vector will be false. Any other bytes read in will be treated as true.