forked from mirrors/gecko-dev
6ca25ecbe6
And thus massively speed up ascii-case-insensitive atom comparisons when both atoms are lowercase (which is the common case by far). This removes almost all the slow selector-matching in this page, and it seems an easier fix than storing the lowercased version of all class-names in quirks mode in elements and selectors... Differential Revision: https://phabricator.services.mozilla.com/D10945 --HG-- extra : moz-landing-system : lando
64 lines
1.9 KiB
Python
64 lines
1.9 KiB
Python
# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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class Atom():
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def __init__(self, ident, string, ty="nsStaticAtom"):
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self.ident = ident
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self.string = string
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self.ty = ty
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self.atom_type = self.__class__.__name__
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self.hash = hash_string(string)
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self.is_ascii_lowercase = is_ascii_lowercase(string)
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class PseudoElementAtom(Atom):
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def __init__(self, ident, string):
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Atom.__init__(self, ident, string, ty="nsCSSPseudoElementStaticAtom")
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class AnonBoxAtom(Atom):
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def __init__(self, ident, string):
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Atom.__init__(self, ident, string, ty="nsCSSAnonBoxPseudoStaticAtom")
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class NonInheritingAnonBoxAtom(AnonBoxAtom):
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def __init__(self, ident, string):
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AnonBoxAtom.__init__(self, ident, string)
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class InheritingAnonBoxAtom(AnonBoxAtom):
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def __init__(self, ident, string):
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AnonBoxAtom.__init__(self, ident, string)
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GOLDEN_RATIO_U32 = 0x9E3779B9
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def rotate_left_5(value):
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return ((value << 5) | (value >> 27)) & 0xFFFFFFFF
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def wrapping_multiply(x, y):
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return (x * y) & 0xFFFFFFFF
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# Calculate the precomputed hash of the static atom. This is a port of
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# mozilla::HashString(const char16_t*), which is what we use for atomizing
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# strings. An assertion in nsAtomTable::RegisterStaticAtoms ensures that
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# the value we compute here matches what HashString() would produce.
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def hash_string(s):
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h = 0
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for c in s:
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h = wrapping_multiply(GOLDEN_RATIO_U32, rotate_left_5(h) ^ ord(c))
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return h
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# Returns true if lowercasing this string in an ascii-case-insensitive way
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# would leave the string unchanged.
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def is_ascii_lowercase(s):
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for c in s:
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if c >= 'A' and c <= 'Z':
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return False
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return True
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