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# Copyright (C) 2009 Canonical Ltd
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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"""Interface definition of a class like PySet but without caching the hash.
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This is generally useful when you want to 'intern' objects, etc. Note that this
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differs from Set in that we:
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1) Don't have all of the .intersection, .difference, etc functions
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2) Do return the object from the set via queries
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eg. SimpleSet.add(key) => saved_key and SimpleSet[key] => saved_key
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cdef extern from "Python.h":
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ctypedef struct PyObject:
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cdef public api class SimpleSet [object SimpleSetObject, type SimpleSet_Type]:
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"""A class similar to PySet, but with simpler implementation.
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The main advantage is that this class uses only 2N memory to store N
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objects rather than 4N memory. The main trade-off is that we do not cache
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the hash value of saved objects. As such, it is assumed that computing the
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hash will be cheap (such as strings or tuples of strings, etc.)
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This also differs in that you can get back the objects that are stored
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(like a dict), but we also don't implement the complete list of 'set'
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operations (difference, intersection, etc).
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# Data structure definition:
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# This is a basic hash table using open addressing.
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# http://en.wikipedia.org/wiki/Open_addressing
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# Basically that means we keep an array of pointers to Python objects
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# (called a table). Each location in the array is called a 'slot'.
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# An empty slot holds a NULL pointer, a slot where there was an item
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# which was then deleted will hold a pointer to _dummy, and a filled slot
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# points at the actual object which fills that slot.
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# The table is always a power of two, and the default location where an
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# object is inserted is at hash(object) & (table_size - 1)
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# If there is a collision, then we search for another location. The
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# specific algorithm is in _lookup. We search until we:
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# find an equivalent object (by tp_richcompare(obj1, obj2, Py_EQ))
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# When an object is deleted, we set its slot to _dummy. this way we don't
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# have to track whether there was a collision, and find the corresponding
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# keys. (The collision resolution algorithm makes that nearly impossible
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# anyway, because it depends on the upper bits of the hash.)
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# The main effect of this, is that if we find _dummy, then we can insert
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# an object there, but we have to keep searching until we find NULL to
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# know that the object is not present elsewhere.
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cdef Py_ssize_t _used # active
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cdef Py_ssize_t _fill # active + dummy
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cdef Py_ssize_t _mask # Table contains (mask+1) slots, a power of 2
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cdef PyObject **_table # Pyrex/Cython doesn't support arrays to 'object'
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# so we manage it manually
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cdef PyObject *_get(self, object key) except? NULL
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cdef object _add(self, key)
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cdef int _discard(self, key) except -1
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cdef int _insert_clean(self, PyObject *key) except -1
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cdef Py_ssize_t _resize(self, Py_ssize_t min_unused) except -1
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# TODO: might want to export the C api here, though it is all available from
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cdef api SimpleSet SimpleSet_New()
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cdef api object SimpleSet_Add(object self, object key)
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cdef api int SimpleSet_Contains(object self, object key) except -1
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cdef api int SimpleSet_Discard(object self, object key) except -1
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cdef api PyObject *SimpleSet_Get(SimpleSet self, object key) except? NULL
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cdef api Py_ssize_t SimpleSet_Size(object self) except -1
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cdef api int SimpleSet_Next(object self, Py_ssize_t *pos, PyObject **key) except -1
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bzrlib/_simple_set_pyx.pxd
