diff options
Diffstat (limited to 'Modules')
| -rw-r--r-- | Modules/_randommodule.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/Modules/_randommodule.c b/Modules/_randommodule.c index 4a87a8e..1189036 100644 --- a/Modules/_randommodule.c +++ b/Modules/_randommodule.c @@ -435,6 +435,47 @@ random_jumpahead(RandomObject *self, PyObject *n) } static PyObject * +random_getrandbits(RandomObject *self, PyObject *args) +{ + int k, i, bytes; + unsigned long r; + unsigned char *bytearray; + PyObject *result; + + if (!PyArg_ParseTuple(args, "i:getrandbits", &k)) + return NULL; + + if (k <= 0) { + PyErr_SetString(PyExc_ValueError, + "number of bits must be greater than zero"); + return NULL; + } + + bytes = ((k - 1) / 32 + 1) * 4; + bytearray = (unsigned char *)PyMem_Malloc(bytes); + if (bytearray == NULL) { + PyErr_NoMemory(); + return NULL; + } + + /* Fill-out whole words, byte-by-byte to avoid endianness issues */ + for (i=0 ; i<bytes ; i+=4, k-=32) { + r = genrand_int32(self); + if (k < 32) + r >>= (32 - k); + bytearray[i+0] = (unsigned char)r; + bytearray[i+1] = (unsigned char)(r >> 8); + bytearray[i+2] = (unsigned char)(r >> 16); + bytearray[i+3] = (unsigned char)(r >> 24); + } + + /* little endian order to match bytearray assignment order */ + result = _PyLong_FromByteArray(bytearray, bytes, 1, 0); + PyMem_Free(bytearray); + return result; +} + +static PyObject * random_new(PyTypeObject *type, PyObject *args, PyObject *kwds) { RandomObject *self; @@ -464,6 +505,9 @@ static PyMethodDef random_methods[] = { {"jumpahead", (PyCFunction)random_jumpahead, METH_O, PyDoc_STR("jumpahead(int) -> None. Create new state from " "existing state and integer.")}, + {"getrandbits", (PyCFunction)random_getrandbits, METH_VARARGS, + PyDoc_STR("getrandbits(k) -> x. Generates a long int with " + "k random bits.")}, {NULL, NULL} /* sentinel */ }; |