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authorMark Dickinson <dickinsm@gmail.com>2012-12-21 21:52:49 (GMT)
committerMark Dickinson <dickinsm@gmail.com>2012-12-21 21:52:49 (GMT)
commit4cd60175f11e46cb969d822d7e076b0072a9ff0f (patch)
tree5178b0c6c41e5cf8dc647055fcfec3bcb216730d /Modules/_randommodule.c
parent1724bb196a097b5de4a4b8d55e9a2072d6886ebb (diff)
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Simplify random_seed to use _PyLong_AsByteArray. Closes issue #16496.
Diffstat (limited to 'Modules/_randommodule.c')
-rw-r--r--Modules/_randommodule.c99
1 files changed, 35 insertions, 64 deletions
diff --git a/Modules/_randommodule.c b/Modules/_randommodule.c
index 6540ab9..d8927c0 100644
--- a/Modules/_randommodule.c
+++ b/Modules/_randommodule.c
@@ -168,9 +168,9 @@ init_genrand(RandomObject *self, unsigned long s)
/* init_key is the array for initializing keys */
/* key_length is its length */
static PyObject *
-init_by_array(RandomObject *self, unsigned long init_key[], unsigned long key_length)
+init_by_array(RandomObject *self, unsigned long init_key[], size_t key_length)
{
- unsigned int i, j, k; /* was signed in the original code. RDH 12/16/2002 */
+ size_t i, j, k; /* was signed in the original code. RDH 12/16/2002 */
unsigned long *mt;
mt = self->state;
@@ -207,14 +207,11 @@ static PyObject *
random_seed(RandomObject *self, PyObject *args)
{
PyObject *result = NULL; /* guilty until proved innocent */
- PyObject *masklower = NULL;
- PyObject *thirtytwo = NULL;
PyObject *n = NULL;
- unsigned long *new_key, *key = NULL;
- unsigned long keymax; /* # of allocated slots in key */
- unsigned long keyused; /* # of used slots in key */
- int err;
-
+ unsigned long *key = NULL;
+ unsigned char *key_as_bytes = NULL;
+ size_t bits, keyused, i;
+ int res;
PyObject *arg = NULL;
if (!PyArg_UnpackTuple(args, "seed", 0, 1, &arg))
@@ -243,69 +240,43 @@ random_seed(RandomObject *self, PyObject *args)
if (n == NULL)
goto Done;
- /* Now split n into 32-bit chunks, from the right. Each piece is
- * stored into key, which has a capacity of keymax chunks, of which
- * keyused are filled. Alas, the repeated shifting makes this a
- * quadratic-time algorithm; we'd really like to use
- * _PyLong_AsByteArray here, but then we'd have to break into the
- * long representation to figure out how big an array was needed
- * in advance.
- */
- keymax = 8; /* arbitrary; grows later if needed */
- keyused = 0;
- key = (unsigned long *)PyMem_Malloc(keymax * sizeof(*key));
- if (key == NULL)
+ /* Now split n into 32-bit chunks, from the right. */
+ bits = _PyLong_NumBits(n);
+ if (bits == (size_t)-1 && PyErr_Occurred())
goto Done;
- masklower = PyLong_FromUnsignedLong(0xffffffffU);
- if (masklower == NULL)
+ /* Figure out how many 32-bit chunks this gives us. */
+ keyused = bits == 0 ? 1 : (bits - 1) / 32 + 1;
+
+ /* Convert seed to byte sequence. */
+ key_as_bytes = (unsigned char *)PyMem_Malloc((size_t)4 * keyused);
+ if (key_as_bytes == NULL)
goto Done;
- thirtytwo = PyLong_FromLong(32L);
- if (thirtytwo == NULL)
+ res = _PyLong_AsByteArray((PyLongObject *)n,
+ key_as_bytes, keyused * 4,
+ 1, /* little-endian */
+ 0); /* unsigned */
+ if (res == -1) {
+ PyMem_Free(key_as_bytes);
goto Done;
- while ((err=PyObject_IsTrue(n))) {
- PyObject *newn;
- PyObject *pychunk;
- unsigned long chunk;
-
- if (err == -1)
- goto Done;
- pychunk = PyNumber_And(n, masklower);
- if (pychunk == NULL)
- goto Done;
- chunk = PyLong_AsUnsignedLong(pychunk);
- Py_DECREF(pychunk);
- if (chunk == (unsigned long)-1 && PyErr_Occurred())
- goto Done;
- newn = PyNumber_Rshift(n, thirtytwo);
- if (newn == NULL)
- goto Done;
- Py_DECREF(n);
- n = newn;
- if (keyused >= keymax) {
- unsigned long bigger = keymax << 1;
- if ((bigger >> 1) != keymax ||
- bigger > PY_SSIZE_T_MAX / sizeof(*key)) {
- PyErr_NoMemory();
- goto Done;
- }
- new_key = (unsigned long *)PyMem_Realloc(key,
- bigger * sizeof(*key));
- if (new_key == NULL)
- goto Done;
- key = new_key;
- keymax = bigger;
- }
- assert(keyused < keymax);
- key[keyused++] = chunk;
}
- if (keyused == 0)
- key[keyused++] = 0UL;
+ /* Fill array of unsigned longs from byte sequence. */
+ key = (unsigned long *)PyMem_Malloc(sizeof(unsigned long) * keyused);
+ if (key == NULL) {
+ PyMem_Free(key_as_bytes);
+ goto Done;
+ }
+ for (i = 0; i < keyused; i++) {
+ key[i] =
+ ((unsigned long)key_as_bytes[4*i + 0] << 0) +
+ ((unsigned long)key_as_bytes[4*i + 1] << 8) +
+ ((unsigned long)key_as_bytes[4*i + 2] << 16) +
+ ((unsigned long)key_as_bytes[4*i + 3] << 24);
+ }
+ PyMem_Free(key_as_bytes);
result = init_by_array(self, key, keyused);
Done:
- Py_XDECREF(masklower);
- Py_XDECREF(thirtytwo);
Py_XDECREF(n);
PyMem_Free(key);
return result;