GeezerVison is showing github.com — gh-111545: Add Py_HashDouble() function by vstinner · Pull Request #112449 · python/cpython
gh-111545: Add Py_HashDouble() function
#112449
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@@ -5,12 +5,16 @@ PyHash API
See also the :c:member:`PyTypeObject.tp_hash` member.
Types
^^^^^
.. c:type:: Py_hash_t
Hash value type: signed integer.
.. versionadded:: 3.2
.. c:type:: Py_uhash_t
Hash value type: unsigned integer.
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@@ -41,6 +45,27 @@ See also the :c:member:`PyTypeObject.tp_hash` member.
.. versionadded:: 3.4
Functions
^^^^^^^^^
.. c:function:: int Py_HashDouble(double value, Py_hash_t *result)
Hash a C double number.
* Set *\*result* to the hash value and return ``1`` on success.
* Set *\*result* to ``0`` and return ``0`` if the hash value cannot be
calculated. For example, if *value* is not-a-number (NaN).
*result* must not be ``NULL``.
.. note::
Only rely on the function return value to distinguish the "not-a-number"
case. *\*result* can be ``0`` if *value* is finite. For example,
``Py_HashDouble(0.0, &result)`` sets *\*result* to 0.
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.. versionadded:: 3.13
.. c:function:: PyHash_FuncDef* PyHash_GetFuncDef(void)
Get the hash function definition.
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@@ -1274,6 +1274,21 @@ New Features
* Add :c:func:`Py_HashPointer` function to hash a pointer.
(Contributed by Victor Stinner in :gh:`111545`.)
* Add :c:func:`Py_HashDouble` function to hash a C double number. Existing code
using the private ``_Py_HashDouble()`` function can be updated to::
Py_hash_t
hash_double(PyObject *obj, double value)
{
Py_hash_t hash;
if (Py_HashDouble(value, &hash) == 0) {
hash = Py_HashPointer(obj);
}
return hash;
}
(Contributed by Victor Stinner in :gh:`111545`.)
Porting to Python 3.13
----------------------
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@@ -37,3 +37,4 @@ typedef struct {
PyAPI_FUNC(PyHash_FuncDef*) PyHash_GetFuncDef(void);
PyAPI_FUNC(Py_hash_t) Py_HashPointer(const void *ptr);
PyAPI_FUNC(int) Py_HashDouble(double value, Py_hash_t *result);
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@@ -1,3 +1,4 @@
import math
import sys
import unittest
from test.support import import_helper
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@@ -77,3 +78,46 @@ def python_hash_pointer(x):
# Py_HashPointer((void*)(uintptr_t)-1) doesn't return -1 but -2
VOID_P_MAX = -1 & (2 ** (8 * SIZEOF_VOID_P) - 1)
self.assertEqual(hash_pointer(VOID_P_MAX), -2)
def test_hash_double(self):
# Test Py_HashDouble()
hash_double = _testcapi.hash_double
def check_number(value, expected):
self.assertEqual(hash_double(value), (1, expected))
# test some integers
integers = [
*range(1, 30),
2**30 - 1,
2 ** 233,
int(sys.float_info.max),
]
for x in integers:
with self.subTest(x=x):
check_number(float(x), hash(x))
check_number(float(-x), hash(-x))
# test positive and negative zeros
check_number(float(0.0), 0)
check_number(float(-0.0), 0)
# test +inf and -inf
inf = float("inf")
check_number(inf, sys.hash_info.inf)
check_number(-inf, -sys.hash_info.inf)
# special float values: compare with Python hash() function
special_values = (
math.nextafter(0.0, 1.0), # smallest positive subnormal number
sys.float_info.min, # smallest positive normal number
sys.float_info.epsilon,
sys.float_info.max, # largest positive finite number
)
for x in special_values:
with self.subTest(x=x):
check_number(x, hash(x))
check_number(-x, hash(-x))
# test not-a-number (NaN)
self.assertEqual(hash_double(float('nan')), (0, 0))
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@@ -0,0 +1,2 @@
Add :c:func:`Py_HashDouble` function to hash a C double number. Patch by
Victor Stinner.
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@@ -1,6 +1,17 @@
#include "parts.h"
#include "util.h"
static PyObject *
long_from_hash(Py_hash_t hash)
{
assert(hash != -1);
Py_BUILD_ASSERT(sizeof(long long) >= sizeof(hash));
return PyLong_FromLongLong(hash);
}
static PyObject *
hash_getfuncdef(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
{
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@@ -54,14 +65,28 @@ hash_pointer(PyObject *Py_UNUSED(module), PyObject *arg)
}
Py_hash_t hash = Py_HashPointer(ptr);
Py_BUILD_ASSERT(sizeof(long long) >= sizeof(hash));
return PyLong_FromLongLong(hash);
return long_from_hash(hash);
}
static PyObject *
hash_double(PyObject *Py_UNUSED(module), PyObject *args)
{
double value;
if (!PyArg_ParseTuple(args, "d", &value)) {
return NULL;
}
Py_hash_t hash;
int res = Py_HashDouble(value, &hash);
return Py_BuildValue("iN", res, long_from_hash(hash));
}
static PyMethodDef test_methods[] = {
{"hash_getfuncdef", hash_getfuncdef, METH_NOARGS},
{"hash_pointer", hash_pointer, METH_O},
{"hash_double", hash_double, METH_VARARGS},
{NULL},
};
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@@ -83,18 +83,23 @@ static Py_ssize_t hashstats[Py_HASH_STATS_MAX + 1] = {0};
*/
Py_hash_t
_Py_HashDouble(PyObject *inst, double v )
int
Py_HashDouble(double v, Py_hash_t *result )
{
int e, sign;
double m;
Py_uhash_t x, y;
if (!Py_IS_FINITE(v)) {
if (Py_IS_INFINITY(v))
return v > 0 ? _PyHASH_INF : -_PyHASH_INF;
else
return _Py_HashPointer(inst);
if (Py_IS_INFINITY(v)) {
*result = (v > 0 ? _PyHASH_INF : -_PyHASH_INF);
return 1;
}
else {
assert(Py_IS_NAN(v));
*result = 0;
return 0;
}
}
m = frexp(v, &e);
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@@ -126,7 +131,20 @@ _Py_HashDouble(PyObject *inst, double v)
x = x * sign;
if (x == (Py_uhash_t)-1)
x = (Py_uhash_t)-2;
return (Py_hash_t)x;
*result = (Py_hash_t)x;
return 1;
}
Py_hash_t
_Py_HashDouble(PyObject *obj, double value)
{
assert(obj != NULL);
Py_hash_t hash;
if (Py_HashDouble(value, &hash) == 0) {
hash = Py_HashPointer(obj);
}
return hash;
}
Py_hash_t
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