import sys try: import ffi except ImportError: print("SKIP") sys.exit() def ffi_open(names): err = None for n in names: try: mod = ffi.open(n) return mod except OSError as e: err = e raise err libc = ffi_open(('libc.so', 'libc.so.0', 'libc.so.6', 'libc.dylib')) qsort = libc.func("v", "qsort", "piip") def cmp(pa, pb): a = ffi.as_bytearray(pa, 1) b = ffi.as_bytearray(pb, 1) #print("cmp:", a, b) return a[0] - b[0] cmp_c = ffi.callback("i", cmp, "pp") s = bytearray(b"foobar") print("org string:", s) qsort(s, len(s), 1, cmp_c) print("qsort'ed:", s)