ok = base64_decode_alloc_ctx (&ctx, "JjZGVmZ2", 8, &p, &len);
ASSERT (ok);
ASSERT (len == 6);
ASSERT (memcmp (p, "abcdef", len) == 0);
ok = base64_decode_alloc_ctx (&ctx, "JjZGVmZ2", 8, &p, &len);
ASSERT (ok);
ASSERT (len == 6);
ASSERT (memcmp (p, "abcdef", len) == 0);