module runtime

#include <sys/sysctl.h>
#include <uvm/uvmexp.h>

struct C.uvmexp {
    pagesize int
    free     int
}

fn free_memory_impl() !usize {
    $if cross ? {
        return error('free_memory: not implemented')
    }
    $if !cross ? {
        $if openbsd {
            mib := [C.CTL_VM, C.VM_UVMEXP]!
            mut uvm := C.uvmexp{0, 0}
            mut len := usize(sizeof(C.uvmexp))
            retval := unsafe { C.sysctl(&mib[0], mib.len, &uvm, &len, C.NULL, 0) }
            c_errno := C.errno
            if retval == -1 {
                return error('free_memory: `C.sysctl()` return error code = ${c_errno}')
            }
            return usize(uvm.pagesize) * usize(uvm.free)
        }
    }
    return error('free_memory: not implemented')
}