How to get extended attributes of a file(UNIX/C)?

When I type ls -l in the command line, sometimes an @ or + symbol comes up alongside the file permissions(btw, I am on OS X), as shown below:

-rw-r-----@  1 john  staff      6731 Sep 28 01:10 mutations.txt
drwxr-xr-x+ 71 john  staff      2414 Mar 25 18:16 ..

I know how to get the permission bits using the stat structure, but I don't think these extended permission values are there. Can someone point me in the right direction as to how to obtain these values via a C or POSIX API?

EDIT:

I attempted the following:

#include <sys/types.h>
#include <sys/xattr.h>
#include <sys/types.h>

int main () {
    char  l[1024];
    listxattr("/Users/john/desktop/mutations.txt", l, 1024,  XATTR_SHOWCOMPRESSION);

    printf("%s\n", l);
}

and got as output:

com.apple.metadata:kMDItemWhereFroms

Still trying to understand how to convert this to an @ or +?