Function module_random

python/stringzilla.c:1450–1527

    "If alphabet is provided, each byte is mapped to alphabet[b % len(alphabet)].";

static PyObject *module_random(PyObject *self, PyObject *const *args, Py_ssize_t positional_args_count,
                               PyObject *args_names_tuple) {
    (void)self;
    if (positional_args_count < 1 || positional_args_count > 2) {
        PyErr_SetString(PyExc_TypeError, "random() expects 1 or 2 positional arguments");
        return NULL;
    }
    PyObject *length_obj = args[0];
    PyObject *nonce_obj = positional_args_count > 1 ? args[1] : NULL;
    PyObject *alphabet_obj = NULL;

    if (args_names_tuple) {
        Py_ssize_t kw_count = PyTuple_GET_SIZE(args_names_tuple);
        for (Py_ssize_t i = 0; i < kw_count; ++i) {
            PyObject *key = PyTuple_GET_ITEM(args_names_tuple, i);
            PyObject *value = args[positional_args_count + i];
            if (PyUnicode_CompareWithASCIIString(key, "nonce") == 0 && !nonce_obj) nonce_obj = value;
            else if (PyUnicode_CompareWithASCIIString(key, "alphabet") == 0 && !alphabet_obj)
                alphabet_obj = value;
            else {
                PyErr_Format(PyExc_TypeError, "unexpected keyword argument: %S", key);
                return NULL;
            }
        }
    }

    if (!PyLong_Check(length_obj)) {
        PyErr_SetString(PyExc_TypeError, "length must be an integer");
        return NULL;
    }
    Py_ssize_t signed_length = PyLong_AsSsize_t(length_obj);
    if (signed_length == -1 && PyErr_Occurred()) return NULL;
    if (signed_length < 0) {
        PyErr_SetString(PyExc_ValueError, "length must be non-negative");
        return NULL;
    }
    sz_size_t length = (sz_size_t)signed_length;

    sz_u64_t nonce = 0;
    if (nonce_obj) {
        if (!PyLong_Check(nonce_obj)) {
            PyErr_SetString(PyExc_TypeError, "nonce must be an integer");
            return NULL;
        }
        nonce = PyLong_AsUnsignedLongLong(nonce_obj);
        if (PyErr_Occurred()) return NULL;
    }

    PyObject *bytes_obj = PyBytes_FromStringAndSize(NULL, (Py_ssize_t)length);
    if (!bytes_obj) {
        PyErr_SetString(PyExc_MemoryError, "Unable to allocate random bytes");
        return NULL;
    }
    if (length > 0) {
        sz_ptr_t buffer = (sz_ptr_t)PyBytes_AS_STRING(bytes_obj);
        sz_fill_random(buffer, length, nonce);
    }