1 files changed, 64 insertions, 0 deletions
diff --git a/xpcom/ds/Atom.py b/xpcom/ds/Atom.py
new file mode 100644
index 0000000000..1399ba840a
--- /dev/null
+++ b/xpcom/ds/Atom.py
@@ -0,0 +1,64 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+class Atom:
+    def __init__(self, ident, string, ty="nsStaticAtom"):
+        self.ident = ident
+        self.string = string
+        self.ty = ty
+        self.atom_type = self.__class__.__name__
+        self.hash = hash_string(string)
+        self.is_ascii_lowercase = is_ascii_lowercase(string)
+
+
+class PseudoElementAtom(Atom):
+    def __init__(self, ident, string):
+        Atom.__init__(self, ident, string, ty="nsCSSPseudoElementStaticAtom")
+
+
+class AnonBoxAtom(Atom):
+    def __init__(self, ident, string):
+        Atom.__init__(self, ident, string, ty="nsCSSAnonBoxPseudoStaticAtom")
+
+
+class NonInheritingAnonBoxAtom(AnonBoxAtom):
+    def __init__(self, ident, string):
+        AnonBoxAtom.__init__(self, ident, string)
+
+
+class InheritingAnonBoxAtom(AnonBoxAtom):
+    def __init__(self, ident, string):
+        AnonBoxAtom.__init__(self, ident, string)
+
+
+GOLDEN_RATIO_U32 = 0x9E3779B9
+
+
+def rotate_left_5(value):
+    return ((value << 5) | (value >> 27)) & 0xFFFFFFFF
+
+
+def wrapping_multiply(x, y):
+    return (x * y) & 0xFFFFFFFF
+
+
+# Calculate the precomputed hash of the static atom. This is a port of
+# mozilla::HashString(const char16_t*), which is what we use for atomizing
+# strings. An assertion in nsAtomTable::RegisterStaticAtoms ensures that
+# the value we compute here matches what HashString() would produce.
+def hash_string(s):
+    h = 0
+    for c in s:
+        h = wrapping_multiply(GOLDEN_RATIO_U32, rotate_left_5(h) ^ ord(c))
+    return h
+
+
+# Returns true if lowercasing this string in an ascii-case-insensitive way
+# would leave the string unchanged.
+def is_ascii_lowercase(s):
+    for c in s:
+        if c >= "A" and c <= "Z":
+            return False
+    return True