以二进制形式打开文件

Question

I am trying to use C++ to open a file. The file can be of any type. The thing that I am trying to do is to open the file as it is stored in the memory.

Suppose that it is a 1 byte text file and stored in the memory as 10000011 then I want to use C++ to open the file in this format, like how it is stored in the computer.

How to do so?

Answer 1

You can open file in binary format with calling fopen function like:

FILE* f = fopen(filename, "rb");

Now you can't read the file bit by bit, but you'll have to read it at least byte by byte (because byte is the smallest unit you should work with), eg:

unsigned char value;
fread(&value, 1, 1, sizeof(unsigned char));

will read single byte of the file. You can then access single bits by binary and operation (&), printing this value as binary (eg 0s and 1s) could be done like this:

    printf("%d%d%d%d%d%d%d%d\n", 
           value & 0x80 ? 1 : 0, 
           value & 0x40 ? 1 : 0, 
           value & 0x20 ? 1 : 0, 
           value & 0x10 ? 1 : 0, 
           value & 0x8 ? 1 : 0, 
           value & 0x4 ? 1 : 0, 
           value & 0x2 ? 1 : 0, 
           value & 0x1 ? 1 : 0);

Of course these are C standard functions, you can use also C++ ones, for opening use:

  ifstream file (filename, ios::in|ios::binary);

For reading you can use:

  file.read(valueAddress, sizeInBytes);

And you should know how to print the stuff out (with cout).