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- changed hash calculation for unicode strings. the new

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value is calculated from the character values, in a way
  that makes sure an 8-bit ASCII string and a unicode string
  with the same contents get the same hash value.

  (as a side effect, this also works for ISO Latin 1 strings).

  for more details, see the python-dev discussion.
This commit is contained in:
Fredrik Lundh 2000-07-10 18:27:47 +00:00
parent 417c489def
commit dde6164402
1 changed files with 19 additions and 17 deletions
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36
Objects/unicodeobject.c
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@ -3471,26 +3471,28 @@ unicode_getitem(PyUnicodeObject *self, int index)
static long
unicode_hash(PyUnicodeObject *self)
{
long hash;
PyObject *utf8;
/* Since Unicode objects compare equal to their ASCII string
counterparts, they should use the individual character values
as basis for their hash value. This is needed to assure that
strings and Unicode objects behave in the same way as
dictionary keys. */
register int len;
register Py_UNICODE *p;
register long x;
/* Since Unicode objects compare equal to their UTF-8 string
counterparts, they should also use the UTF-8 strings as basis
for their hash value. This is needed to assure that strings and
Unicode objects behave in the same way as dictionary
keys. Unfortunately, this costs some performance and also some
memory if the cached UTF-8 representation is not used later
on. */
if (self->hash != -1)
return self->hash;
utf8 = _PyUnicode_AsUTF8String((PyObject *)self, NULL);
if (utf8 == NULL)
return -1;
hash = PyObject_Hash(utf8);
if (hash == -1)
return -1;
self->hash = hash;
return hash;
len = PyUnicode_GET_SIZE(self);
p = PyUnicode_AS_UNICODE(self);
x = *p << 7;
while (--len >= 0)
x = (1000003*x) ^ *p++;
x ^= PyUnicode_GET_SIZE(self);
if (x == -1)
x = -2;
self->hash = x;
return x;
}
static char index__doc__[] =