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Get rid of the superstitious "~" in dict hashing's "i = (~hash) & mask".
The comment following used to say: /* We use ~hash instead of hash, as degenerate hash functions, such as for ints <sigh>, can have lots of leading zeros. It's not really a performance risk, but better safe than sorry. 12-Dec-00 tim: so ~hash produces lots of leading ones instead -- what's the gain? */ That is, there was never a good reason for doing it. And to the contrary, as explained on Python-Dev last December, it tended to make the *sum* (i + incr) & mask (which is the first table index examined in case of collison) the same "too often" across distinct hashes. Changing to the simpler "i = hash & mask" reduced the number of string-dict collisions (== # number of times we go around the lookup for-loop) from about 6 million to 5 million during a full run of the test suite (these are approximate because the test suite does some random stuff from run to run). The number of collisions in non-string dicts also decreased, but not as dramatically. Note that this may, for a given dict, change the order (wrt previous releases) of entries exposed by .keys(), .values() and .items(). A number of std tests suffered bogus failures as a result. For dicts keyed by small ints, or (less so) by characters, the order is much more likely to be in increasing order of key now; e.g., >>> d = {} >>> for i in range(10): ... d[i] = i ... >>> d {0: 0, 1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 6: 6, 7: 7, 8: 8, 9: 9} >>> Unfortunately. people may latch on to that in small examples and draw a bogus conclusion. test_support.py Moved test_extcall's sortdict() into test_support, made it stronger, and imported sortdict into other std tests that needed it. test_unicode.py Excluced cp875 from the "roundtrip over range(128)" test, because cp875 doesn't have a well-defined inverse for unicode("?", "cp875"). See Python-Dev for excruciating details. Cookie.py Chaged various output functions to sort dicts before building strings from them. test_extcall Fiddled the expected-result file. This remains sensitive to native dict ordering, because, e.g., if there are multiple errors in a keyword-arg dict (and test_extcall sets up many cases like that), the specific error Python complains about first depends on native dict ordering.
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11 changed files with 64 additions and 46 deletions
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@ -70,8 +70,8 @@ a dictionary.
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>>> C["fig"] = "newton"
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>>> C["sugar"] = "wafer"
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>>> print C
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Set-Cookie: sugar=wafer;
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Set-Cookie: fig=newton;
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Set-Cookie: sugar=wafer;
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Notice that the printable representation of a Cookie is the
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appropriate format for a Set-Cookie: header. This is the
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@ -93,8 +93,8 @@ HTTP_COOKIE environment variable.
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>>> C = Cookie.SmartCookie()
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>>> C.load("chips=ahoy; vienna=finger")
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>>> print C
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Set-Cookie: vienna=finger;
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Set-Cookie: chips=ahoy;
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Set-Cookie: vienna=finger;
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The load() method is darn-tootin smart about identifying cookies
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within a string. Escaped quotation marks, nested semicolons, and other
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@ -493,7 +493,9 @@ class Morsel(UserDict):
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# Now add any defined attributes
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if attrs is None:
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attrs = self._reserved_keys
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for K,V in self.items():
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items = self.items()
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items.sort()
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for K,V in items:
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if V == "": continue
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if K not in attrs: continue
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if K == "expires" and type(V) == type(1):
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@ -586,7 +588,9 @@ class BaseCookie(UserDict):
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def output(self, attrs=None, header="Set-Cookie:", sep="\n"):
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"""Return a string suitable for HTTP."""
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result = []
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for K,V in self.items():
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items = self.items()
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items.sort()
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for K,V in items:
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result.append( V.output(attrs, header) )
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return string.join(result, sep)
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# end output
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@ -595,14 +599,18 @@ class BaseCookie(UserDict):
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def __repr__(self):
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L = []
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for K,V in self.items():
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items = self.items()
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items.sort()
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for K,V in items:
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L.append( '%s=%s' % (K,repr(V.value) ) )
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return '<%s: %s>' % (self.__class__.__name__, string.join(L))
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def js_output(self, attrs=None):
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"""Return a string suitable for JavaScript."""
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result = []
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for K,V in self.items():
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items = self.items()
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items.sort()
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for K,V in items:
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result.append( V.js_output(attrs) )
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return string.join(result, "")
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# end js_output
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