D binding around magic number recognition library.
See man 3 libmagic for more info.
import magic;
auto m = new Magic(MAGIC_MIME_TYPE | MAGIC_NO_CHECK_BUILTIN);
m.load(null);
ubyte[] rar = [
0x52, 0x61, 0x72, 0x21, 0x1a, 0x07, 0x00, 0xcf,
0x90, 0x73, 0x00, 0x00, 0x0d, 0x00, 0x00, 0x00,
];
assert(m.buffer(rar) == "application/x-rar");