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bpo-40286: Remove C implementation of Random.randbytes() (GH-19797) 

Remove _random.Random.randbytes(): the C implementation of
randbytes(). Implement the method in Python to ease subclassing:
randbytes() now directly reuses getrandbits().
This commit is contained in:
Victor Stinner 2020-04-29 18:49:00 +02:00 committed by GitHub
parent e3dfb9b967
commit 2d8757758d
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GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 10 additions and 87 deletions
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6
Lib/random.py
View File

@ -192,6 +192,12 @@ class Random(_random.Random):
## ---- Methods below this point do not need to be overridden when
## ---- subclassing for the purpose of using a different core generator.
## -------------------- bytes methods ---------------------
def randbytes(self, n):
"""Generate n random bytes."""
return self.getrandbits(n * 8).to_bytes(n, 'little')
## -------------------- pickle support -------------------
# Issue 17489: Since __reduce__ was defined to fix #759889 this is no

3
Misc/NEWS.d/next/Library/2020-04-29-18-02-16.bpo-40286.txbQNx.rst Normal file
View File

@ -0,0 +1,3 @@
Remove ``_random.Random.randbytes()``: the C implementation of
``randbytes()``. Implement the method in Python to ease subclassing:
``randbytes()`` now directly reuses ``getrandbits()``.

45
Modules/_randommodule.c
View File

@ -513,50 +513,6 @@ _random_Random_getrandbits_impl(RandomObject *self, int k)
return result;
}
/*[clinic input]
_random.Random.randbytes
self: self(type="RandomObject *")
n: Py_ssize_t
/
Generate n random bytes.
[clinic start generated code]*/
static PyObject *
_random_Random_randbytes_impl(RandomObject *self, Py_ssize_t n)
/*[clinic end generated code: output=67a28548079a17ea input=7ba658a24150d233]*/
{
if (n < 0) {
PyErr_SetString(PyExc_ValueError,
"number of bytes must be non-negative");
return NULL;
}
PyObject *bytes = PyBytes_FromStringAndSize(NULL, n);
if (bytes == NULL) {
return NULL;
}
uint8_t *ptr = (uint8_t *)PyBytes_AS_STRING(bytes);
for (; n; ptr += 4, n -= 4) {
uint32_t word = genrand_uint32(self);
#if PY_BIG_ENDIAN
/* Convert to little endian */
word = _Py_bswap32(word);
#endif
if (n < 4) {
/* Drop least significant bits */
memcpy(ptr, (uint8_t *)&word + (4 - n), n);
break;
}
memcpy(ptr, &word, 4);
}
return bytes;
}
static PyObject *
random_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
@ -586,7 +542,6 @@ static PyMethodDef random_methods[] = {
_RANDOM_RANDOM_GETSTATE_METHODDEF
_RANDOM_RANDOM_SETSTATE_METHODDEF
_RANDOM_RANDOM_GETRANDBITS_METHODDEF
_RANDOM_RANDOM_RANDBYTES_METHODDEF
{NULL, NULL} /* sentinel */
};

43
Modules/clinic/_randommodule.c.h generated
View File

@ -114,45 +114,4 @@ _random_Random_getrandbits(RandomObject *self, PyObject *arg)
exit:
return return_value;
}
PyDoc_STRVAR(_random_Random_randbytes__doc__,
"randbytes($self, n, /)\n"
"--\n"
"\n"
"Generate n random bytes.");
#define _RANDOM_RANDOM_RANDBYTES_METHODDEF \
{"randbytes", (PyCFunction)_random_Random_randbytes, METH_O, _random_Random_randbytes__doc__},
static PyObject *
_random_Random_randbytes_impl(RandomObject *self, Py_ssize_t n);
static PyObject *
_random_Random_randbytes(RandomObject *self, PyObject *arg)
{
PyObject *return_value = NULL;
Py_ssize_t n;
if (PyFloat_Check(arg)) {
PyErr_SetString(PyExc_TypeError,
"integer argument expected, got float" );
goto exit;
}
{
Py_ssize_t ival = -1;
PyObject *iobj = PyNumber_Index(arg);
if (iobj != NULL) {
ival = PyLong_AsSsize_t(iobj);
Py_DECREF(iobj);
}
if (ival == -1 && PyErr_Occurred()) {
goto exit;
}
n = ival;
}
return_value = _random_Random_randbytes_impl(self, n);
exit:
return return_value;
}
/*[clinic end generated code: output=e515c651860c4001 input=a9049054013a1b77]*/
/*[clinic end generated code: output=a7feb0c9c8d1b627 input=a9049054013a1b77]*/