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Fixups to the hash function for frozensets. 

* Non-zero initial value so that hash(frozenset()) != hash(0).
* Final permutation to differentiate nested sets.
* Add logic to make sure that -1 is not a possible hash value.
This commit is contained in:
Raymond Hettinger 2004-06-10 21:38:41 +00:00
parent 57c2d930f6
commit 27e403ebe9
1 changed files with 4 additions and 1 deletions
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5
Objects/setobject.c
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@ -663,7 +663,7 @@ frozenset_hash(PyObject *self)
PySetObject *so = (PySetObject *)self;
PyObject *key, *value;
int pos = 0;
long hash = 0;
long hash = 1905176217L;
if (so->hash != -1)
return so->hash;
@ -676,6 +676,9 @@ frozenset_hash(PyObject *self)
collapse to only a handful of distinct hash values. */
hash ^= PyObject_Hash(key) * 3644798167u;
}
hash *= 69069L;
if (hash == -1)
hash = 590923713L;
so->hash = hash;
return hash;
}