> 4gb文件的文件大小？

Question

In MSVC I ran the following code. a gives me -1, b gives me EINVAL and c gives me 0. When the path is a file that can fit in a 32bit value this function works fine. How do I get the length of a file >4gb?

f = fopen(path.c_str(), "r+b");
printf("f=%X\n", f);
auto a = fseek(f, 0, SEEK_END);
auto b = errno;
auto c = ftell(f);

Answer 1

MSVC has 64 bit variants of most C stdlib file functions which allow you to work with files larger that 4GB, in your case, see _ftelli64 . There is also _filelengthi64 for descriptors (which you can get using _fileno ).

Answer 2

The POSIX API uses lseek which takes a off_t argument.

Windows API uses SetFilePointerEx which takes a LARGE_INTEGER argument.

And @Necrolis told you the clib MSVC extension...

Answer 3

boost::file_size returns the largest available integer type, so at least 64 bits. Works on all major platforms.