// Copyright (c) 2005, Google Inc.
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// ---
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//
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// A dense hashtable is a particular implementation of
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// a hashtable: one that is meant to minimize memory allocation.
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// It does this by using an array to store all the data. We
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// steal a value from the key space to indicate "empty" array
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// elements (ie indices where no item lives) and another to indicate
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// "deleted" elements.
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//
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// (Note it is possible to change the value of the delete key
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// on the fly; you can even remove it, though after that point
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// the hashtable is insert_only until you set it again. The empty
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// value however can't be changed.)
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//
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// To minimize allocation and pointer overhead, we use internal
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// probing, in which the hashtable is a single table, and collisions
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// are resolved by trying to insert again in another bucket. The
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// most cache-efficient internal probing schemes are linear probing
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// (which suffers, alas, from clumping) and quadratic probing, which
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// is what we implement by default.
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//
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// Type requirements: value_type is required to be Copy Constructible
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// and Default Constructible. It is not required to be (and commonly
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// isn't) Assignable.
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//
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// You probably shouldn't use this code directly. Use dense_hash_map<>
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// or dense_hash_set<> instead.
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// You can change the following below:
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// HT_OCCUPANCY_PCT -- how full before we double size
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// HT_EMPTY_PCT -- how empty before we halve size
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// HT_MIN_BUCKETS -- default smallest bucket size
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//
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// You can also change enlarge_factor (which defaults to
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// HT_OCCUPANCY_PCT), and shrink_factor (which defaults to
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// HT_EMPTY_PCT) with set_resizing_parameters().
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//
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// How to decide what values to use?
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// shrink_factor's default of .4 * OCCUPANCY_PCT, is probably good.
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// HT_MIN_BUCKETS is probably unnecessary since you can specify
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// (indirectly) the starting number of buckets at construct-time.
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// For enlarge_factor, you can use this chart to try to trade-off
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// expected lookup time to the space taken up. By default, this
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// code uses quadratic probing, though you can change it to linear
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// via JUMP_ below if you really want to.
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//
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// From http://www.augustana.ca/~mohrj/courses/1999.fall/csc210/lecture_notes/hashing.html
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// NUMBER OF PROBES / LOOKUP Successful Unsuccessful
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// Quadratic collision resolution 1 - ln(1-L) - L/2 1/(1-L) - L - ln(1-L)
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// Linear collision resolution [1+1/(1-L)]/2 [1+1/(1-L)2]/2
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//
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// -- enlarge_factor -- 0.10 0.50 0.60 0.75 0.80 0.90 0.99
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// QUADRATIC COLLISION RES.
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// probes/successful lookup 1.05 1.44 1.62 2.01 2.21 2.85 5.11
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// probes/unsuccessful lookup 1.11 2.19 2.82 4.64 5.81 11.4 103.6
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// LINEAR COLLISION RES.
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// probes/successful lookup 1.06 1.5 1.75 2.5 3.0 5.5 50.5
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// probes/unsuccessful lookup 1.12 2.5 3.6 8.5 13.0 50.0 5000.0
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#ifndef _DENSEHASHTABLE_H_
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#define _DENSEHASHTABLE_H_
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#include "sparseconfig.h"
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#include <assert.h>
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#include <stdio.h> // for FILE, fwrite, fread
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#include <algorithm> // For swap(), eg
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#include <iterator> // For iterator tags
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#include <limits> // for numeric_limits
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#include <memory> // For uninitialized_fill
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#include <utility> // for pair
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#include "hashtable-common.h"
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#include "libc_allocator_with_realloc.h"
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#include "../type_traits.h"
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#include <stdexcept> // For length_error
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_START_GOOGLE_NAMESPACE_
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namespace base { // just to make google->opensource transition easier
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using GOOGLE_NAMESPACE::true_type;
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using GOOGLE_NAMESPACE::false_type;
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using GOOGLE_NAMESPACE::integral_constant;
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using GOOGLE_NAMESPACE::is_same;
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using GOOGLE_NAMESPACE::remove_const;
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}
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// The probing method
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// Linear probing
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// #define JUMP_(key, num_probes) ( 1 )
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// Quadratic probing
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#define JUMP_(key, num_probes) ( num_probes )
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// Hashtable class, used to implement the hashed associative containers
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// hash_set and hash_map.
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// Value: what is stored in the table (each bucket is a Value).
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// Key: something in a 1-to-1 correspondence to a Value, that can be used
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// to search for a Value in the table (find() takes a Key).
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// HashFcn: Takes a Key and returns an integer, the more unique the better.
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// ExtractKey: given a Value, returns the unique Key associated with it.
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// Must inherit from unary_function, or at least have a
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// result_type enum indicating the return type of operator().
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// SetKey: given a Value* and a Key, modifies the value such that
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// ExtractKey(value) == key. We guarantee this is only called
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// with key == deleted_key or key == empty_key.
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// EqualKey: Given two Keys, says whether they are the same (that is,
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// if they are both associated with the same Value).
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// Alloc: STL allocator to use to allocate memory.
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template <class Value, class Key, class HashFcn,
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class ExtractKey, class SetKey, class EqualKey, class Alloc>
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class dense_hashtable;
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template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
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struct dense_hashtable_iterator;
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template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
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struct dense_hashtable_const_iterator;
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// We're just an array, but we need to skip over empty and deleted elements
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template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
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struct dense_hashtable_iterator {
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private:
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typedef typename A::template rebind<V>::other value_alloc_type;
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public:
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typedef dense_hashtable_iterator<V,K,HF,ExK,SetK,EqK,A> iterator;
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typedef dense_hashtable_const_iterator<V,K,HF,ExK,SetK,EqK,A> const_iterator;
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typedef std::forward_iterator_tag iterator_category; // very little defined!
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typedef V value_type;
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typedef typename value_alloc_type::difference_type difference_type;
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typedef typename value_alloc_type::size_type size_type;
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typedef typename value_alloc_type::reference reference;
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typedef typename value_alloc_type::pointer pointer;
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// "Real" constructor and default constructor
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dense_hashtable_iterator(const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *h,
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pointer it, pointer it_end, bool advance)
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: ht(h), pos(it), end(it_end) {
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if (advance) advance_past_empty_and_deleted();
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}
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dense_hashtable_iterator() { }
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// The default destructor is fine; we don't define one
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// The default operator= is fine; we don't define one
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// Happy dereferencer
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reference operator*() const { return *pos; }
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pointer operator->() const { return &(operator*()); }
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// Arithmetic. The only hard part is making sure that
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// we're not on an empty or marked-deleted array element
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void advance_past_empty_and_deleted() {
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while ( pos != end && (ht->test_empty(*this) || ht->test_deleted(*this)) )
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++pos;
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}
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iterator& operator++() {
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assert(pos != end); ++pos; advance_past_empty_and_deleted(); return *this;
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}
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iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; }
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// Comparison.
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bool operator==(const iterator& it) const { return pos == it.pos; }
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bool operator!=(const iterator& it) const { return pos != it.pos; }
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// The actual data
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const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht;
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pointer pos, end;
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};
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// Now do it all again, but with const-ness!
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template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
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struct dense_hashtable_const_iterator {
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private:
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typedef typename A::template rebind<V>::other value_alloc_type;
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public:
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typedef dense_hashtable_iterator<V,K,HF,ExK,SetK,EqK,A> iterator;
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typedef dense_hashtable_const_iterator<V,K,HF,ExK,SetK,EqK,A> const_iterator;
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typedef std::forward_iterator_tag iterator_category; // very little defined!
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typedef V value_type;
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typedef typename value_alloc_type::difference_type difference_type;
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typedef typename value_alloc_type::size_type size_type;
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typedef typename value_alloc_type::const_reference reference;
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typedef typename value_alloc_type::const_pointer pointer;
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// "Real" constructor and default constructor
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dense_hashtable_const_iterator(
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const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *h,
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pointer it, pointer it_end, bool advance)
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: ht(h), pos(it), end(it_end) {
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if (advance) advance_past_empty_and_deleted();
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}
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dense_hashtable_const_iterator()
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: ht(NULL), pos(pointer()), end(pointer()) { }
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// This lets us convert regular iterators to const iterators
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dense_hashtable_const_iterator(const iterator &it)
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: ht(it.ht), pos(it.pos), end(it.end) { }
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// The default destructor is fine; we don't define one
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// The default operator= is fine; we don't define one
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// Happy dereferencer
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reference operator*() const { return *pos; }
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pointer operator->() const { return &(operator*()); }
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// Arithmetic. The only hard part is making sure that
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// we're not on an empty or marked-deleted array element
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void advance_past_empty_and_deleted() {
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while ( pos != end && (ht->test_empty(*this) || ht->test_deleted(*this)) )
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++pos;
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}
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const_iterator& operator++() {
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assert(pos != end); ++pos; advance_past_empty_and_deleted(); return *this;
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}
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const_iterator operator++(int) { const_iterator tmp(*this); ++*this; return tmp; }
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// Comparison.
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bool operator==(const const_iterator& it) const { return pos == it.pos; }
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bool operator!=(const const_iterator& it) const { return pos != it.pos; }
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// The actual data
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const dense_hashtable<V,K,HF,ExK,SetK,EqK,A> *ht;
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pointer pos, end;
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};
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template <class Value, class Key, class HashFcn,
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class ExtractKey, class SetKey, class EqualKey, class Alloc>
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class dense_hashtable {
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private:
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typedef typename Alloc::template rebind<Value>::other value_alloc_type;
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public:
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typedef Key key_type;
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typedef Value value_type;
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typedef HashFcn hasher;
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typedef EqualKey key_equal;
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typedef Alloc allocator_type;
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typedef typename value_alloc_type::size_type size_type;
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typedef typename value_alloc_type::difference_type difference_type;
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typedef typename value_alloc_type::reference reference;
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typedef typename value_alloc_type::const_reference const_reference;
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typedef typename value_alloc_type::pointer pointer;
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typedef typename value_alloc_type::const_pointer const_pointer;
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typedef dense_hashtable_iterator<Value, Key, HashFcn,
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ExtractKey, SetKey, EqualKey, Alloc>
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iterator;
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typedef dense_hashtable_const_iterator<Value, Key, HashFcn,
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ExtractKey, SetKey, EqualKey, Alloc>
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const_iterator;
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// These come from tr1. For us they're the same as regular iterators.
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typedef iterator local_iterator;
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typedef const_iterator const_local_iterator;
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// How full we let the table get before we resize, by default.
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// Knuth says .8 is good -- higher causes us to probe too much,
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// though it saves memory.
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static const int HT_OCCUPANCY_PCT; // defined at the bottom of this file
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// How empty we let the table get before we resize lower, by default.
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// (0.0 means never resize lower.)
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// It should be less than OCCUPANCY_PCT / 2 or we thrash resizing
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static const int HT_EMPTY_PCT; // defined at the bottom of this file
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// Minimum size we're willing to let hashtables be.
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// Must be a power of two, and at least 4.
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// Note, however, that for a given hashtable, the initial size is a
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// function of the first constructor arg, and may be >HT_MIN_BUCKETS.
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static const size_type HT_MIN_BUCKETS = 4;
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// By default, if you don't specify a hashtable size at
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// construction-time, we use this size. Must be a power of two, and
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// at least HT_MIN_BUCKETS.
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static const size_type HT_DEFAULT_STARTING_BUCKETS = 32;
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// ITERATOR FUNCTIONS
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iterator begin() { return iterator(this, table,
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table + num_buckets, true); }
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iterator end() { return iterator(this, table + num_buckets,
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table + num_buckets, true); }
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const_iterator begin() const { return const_iterator(this, table,
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table+num_buckets,true);}
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const_iterator end() const { return const_iterator(this, table + num_buckets,
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table+num_buckets,true);}
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// These come from tr1 unordered_map. They iterate over 'bucket' n.
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// We'll just consider bucket n to be the n-th element of the table.
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local_iterator begin(size_type i) {
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return local_iterator(this, table + i, table + i+1, false);
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}
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local_iterator end(size_type i) {
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local_iterator it = begin(i);
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if (!test_empty(i) && !test_deleted(i))
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++it;
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return it;
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}
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const_local_iterator begin(size_type i) const {
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return const_local_iterator(this, table + i, table + i+1, false);
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}
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const_local_iterator end(size_type i) const {
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const_local_iterator it = begin(i);
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if (!test_empty(i) && !test_deleted(i))
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++it;
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return it;
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}
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// ACCESSOR FUNCTIONS for the things we templatize on, basically
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hasher hash_funct() const { return settings; }
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key_equal key_eq() const { return key_info; }
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allocator_type get_allocator() const {
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return allocator_type(val_info);
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}
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// Accessor function for statistics gathering.
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int num_table_copies() const { return settings.num_ht_copies(); }
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private:
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// Annoyingly, we can't copy values around, because they might have
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// const components (they're probably pair<const X, Y>). We use
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// explicit destructor invocation and placement new to get around
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// this. Arg.
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void set_value(pointer dst, const_reference src) {
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dst->~value_type(); // delete the old value, if any
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new(dst) value_type(src);
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}
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void destroy_buckets(size_type first, size_type last) {
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for ( ; first != last; ++first)
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table[first].~value_type();
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}
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// DELETE HELPER FUNCTIONS
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// This lets the user describe a key that will indicate deleted
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// table entries. This key should be an "impossible" entry --
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// if you try to insert it for real, you won't be able to retrieve it!
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// (NB: while you pass in an entire value, only the key part is looked
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// at. This is just because I don't know how to assign just a key.)
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private:
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void squash_deleted() { // gets rid of any deleted entries we have
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if ( num_deleted ) { // get rid of deleted before writing
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dense_hashtable tmp(*this); // copying will get rid of deleted
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swap(tmp); // now we are tmp
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}
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assert(num_deleted == 0);
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}
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// Test if the given key is the deleted indicator. Requires
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// num_deleted > 0, for correctness of read(), and because that
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// guarantees that key_info.delkey is valid.
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bool test_deleted_key(const key_type& key) const {
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assert(num_deleted > 0);
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return equals(key_info.delkey, key);
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}
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public:
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void set_deleted_key(const key_type &key) {
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// the empty indicator (if specified) and the deleted indicator
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// must be different
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assert((!settings.use_empty() || !equals(key, get_key(val_info.emptyval)))
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&& "Passed the empty-key to set_deleted_key");
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// It's only safe to change what "deleted" means if we purge deleted guys
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squash_deleted();
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settings.set_use_deleted(true);
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key_info.delkey = key;
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}
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void clear_deleted_key() {
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squash_deleted();
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settings.set_use_deleted(false);
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}
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key_type deleted_key() const {
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assert(settings.use_deleted()
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&& "Must set deleted key before calling deleted_key");
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return key_info.delkey;
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}
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// These are public so the iterators can use them
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// True if the item at position bucknum is "deleted" marker
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bool test_deleted(size_type bucknum) const {
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// Invariant: !use_deleted() implies num_deleted is 0.
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assert(settings.use_deleted() || num_deleted == 0);
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return num_deleted > 0 && test_deleted_key(get_key(table[bucknum]));
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}
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bool test_deleted(const iterator &it) const {
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// Invariant: !use_deleted() implies num_deleted is 0.
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assert(settings.use_deleted() || num_deleted == 0);
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return num_deleted > 0 && test_deleted_key(get_key(*it));
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}
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bool test_deleted(const const_iterator &it) const {
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// Invariant: !use_deleted() implies num_deleted is 0.
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assert(settings.use_deleted() || num_deleted == 0);
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return num_deleted > 0 && test_deleted_key(get_key(*it));
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}
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private:
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void check_use_deleted(const char* caller) {
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(void)caller; // could log it if the assert failed
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assert(settings.use_deleted());
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}
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// Set it so test_deleted is true. true if object didn't used to be deleted.
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bool set_deleted(iterator &it) {
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check_use_deleted("set_deleted()");
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bool retval = !test_deleted(it);
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// &* converts from iterator to value-type.
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set_key(&(*it), key_info.delkey);
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return retval;
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}
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// Set it so test_deleted is false. true if object used to be deleted.
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bool clear_deleted(iterator &it) {
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check_use_deleted("clear_deleted()");
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// Happens automatically when we assign something else in its place.
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return test_deleted(it);
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}
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// We also allow to set/clear the deleted bit on a const iterator.
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// We allow a const_iterator for the same reason you can delete a
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// const pointer: it's convenient, and semantically you can't use
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// 'it' after it's been deleted anyway, so its const-ness doesn't
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// really matter.
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bool set_deleted(const_iterator &it) {
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check_use_deleted("set_deleted()");
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bool retval = !test_deleted(it);
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set_key(const_cast<pointer>(&(*it)), key_info.delkey);
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return retval;
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}
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// Set it so test_deleted is false. true if object used to be deleted.
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bool clear_deleted(const_iterator &it) {
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check_use_deleted("clear_deleted()");
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return test_deleted(it);
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}
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// EMPTY HELPER FUNCTIONS
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// This lets the user describe a key that will indicate empty (unused)
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// table entries. This key should be an "impossible" entry --
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// if you try to insert it for real, you won't be able to retrieve it!
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// (NB: while you pass in an entire value, only the key part is looked
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// at. This is just because I don't know how to assign just a key.)
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public:
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// These are public so the iterators can use them
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// True if the item at position bucknum is "empty" marker
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bool test_empty(size_type bucknum) const {
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assert(settings.use_empty()); // we always need to know what's empty!
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return equals(get_key(val_info.emptyval), get_key(table[bucknum]));
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}
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bool test_empty(const iterator &it) const {
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assert(settings.use_empty()); // we always need to know what's empty!
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return equals(get_key(val_info.emptyval), get_key(*it));
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}
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bool test_empty(const const_iterator &it) const {
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assert(settings.use_empty()); // we always need to know what's empty!
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return equals(get_key(val_info.emptyval), get_key(*it));
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}
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private:
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void fill_range_with_empty(pointer table_start, pointer table_end) {
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std::uninitialized_fill(table_start, table_end, val_info.emptyval);
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}
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public:
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// TODO(csilvers): change all callers of this to pass in a key instead,
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// and take a const key_type instead of const value_type.
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void set_empty_key(const_reference val) {
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// Once you set the empty key, you can't change it
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assert(!settings.use_empty() && "Calling set_empty_key multiple times");
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// The deleted indicator (if specified) and the empty indicator
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// must be different.
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assert((!settings.use_deleted() || !equals(get_key(val), key_info.delkey))
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&& "Setting the empty key the same as the deleted key");
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settings.set_use_empty(true);
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set_value(&val_info.emptyval, val);
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assert(!table); // must set before first use
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// num_buckets was set in constructor even though table was NULL
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table = val_info.allocate(num_buckets);
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assert(table);
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fill_range_with_empty(table, table + num_buckets);
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}
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// TODO(user): return a key_type rather than a value_type
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value_type empty_key() const {
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assert(settings.use_empty());
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return val_info.emptyval;
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}
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// FUNCTIONS CONCERNING SIZE
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public:
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size_type size() const { return num_elements - num_deleted; }
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size_type max_size() const { return val_info.max_size(); }
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bool empty() const { return size() == 0; }
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size_type bucket_count() const { return num_buckets; }
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size_type max_bucket_count() const { return max_size(); }
|
size_type nonempty_bucket_count() const { return num_elements; }
|
// These are tr1 methods. Their idea of 'bucket' doesn't map well to
|
// what we do. We just say every bucket has 0 or 1 items in it.
|
size_type bucket_size(size_type i) const {
|
return begin(i) == end(i) ? 0 : 1;
|
}
|
|
private:
|
// Because of the above, size_type(-1) is never legal; use it for errors
|
static const size_type ILLEGAL_BUCKET = size_type(-1);
|
|
// Used after a string of deletes. Returns true if we actually shrunk.
|
// TODO(csilvers): take a delta so we can take into account inserts
|
// done after shrinking. Maybe make part of the Settings class?
|
bool maybe_shrink() {
|
assert(num_elements >= num_deleted);
|
assert((bucket_count() & (bucket_count()-1)) == 0); // is a power of two
|
assert(bucket_count() >= HT_MIN_BUCKETS);
|
bool retval = false;
|
|
// If you construct a hashtable with < HT_DEFAULT_STARTING_BUCKETS,
|
// we'll never shrink until you get relatively big, and we'll never
|
// shrink below HT_DEFAULT_STARTING_BUCKETS. Otherwise, something
|
// like "dense_hash_set<int> x; x.insert(4); x.erase(4);" will
|
// shrink us down to HT_MIN_BUCKETS buckets, which is too small.
|
const size_type num_remain = num_elements - num_deleted;
|
const size_type shrink_threshold = settings.shrink_threshold();
|
if (shrink_threshold > 0 && num_remain < shrink_threshold &&
|
bucket_count() > HT_DEFAULT_STARTING_BUCKETS) {
|
const float shrink_factor = settings.shrink_factor();
|
size_type sz = bucket_count() / 2; // find how much we should shrink
|
while (sz > HT_DEFAULT_STARTING_BUCKETS &&
|
num_remain < sz * shrink_factor) {
|
sz /= 2; // stay a power of 2
|
}
|
dense_hashtable tmp(*this, sz); // Do the actual resizing
|
swap(tmp); // now we are tmp
|
retval = true;
|
}
|
settings.set_consider_shrink(false); // because we just considered it
|
return retval;
|
}
|
|
// We'll let you resize a hashtable -- though this makes us copy all!
|
// When you resize, you say, "make it big enough for this many more elements"
|
// Returns true if we actually resized, false if size was already ok.
|
bool resize_delta(size_type delta) {
|
bool did_resize = false;
|
if ( settings.consider_shrink() ) { // see if lots of deletes happened
|
if ( maybe_shrink() )
|
did_resize = true;
|
}
|
if (num_elements >=
|
(std::numeric_limits<size_type>::max)() - delta) {
|
assert(false && "resize overflow");
|
exit(-1);
|
}
|
if ( bucket_count() >= HT_MIN_BUCKETS &&
|
(num_elements + delta) <= settings.enlarge_threshold() )
|
return did_resize; // we're ok as we are
|
|
// Sometimes, we need to resize just to get rid of all the
|
// "deleted" buckets that are clogging up the hashtable. So when
|
// deciding whether to resize, count the deleted buckets (which
|
// are currently taking up room). But later, when we decide what
|
// size to resize to, *don't* count deleted buckets, since they
|
// get discarded during the resize.
|
size_type needed_size = settings.min_buckets(num_elements + delta, 0);
|
if ( needed_size <= bucket_count() ) // we have enough buckets
|
return did_resize;
|
|
size_type resize_to =
|
settings.min_buckets(num_elements - num_deleted + delta, bucket_count());
|
|
// When num_deleted is large, we may still grow but we do not want to
|
// over expand. So we reduce needed_size by a portion of num_deleted
|
// (the exact portion does not matter). This is especially helpful
|
// when min_load_factor is zero (no shrink at all) to avoid doubling
|
// the bucket count to infinity. See also test ResizeWithoutShrink.
|
needed_size = settings.min_buckets(num_elements - num_deleted / 4 + delta, 0);
|
if (resize_to < needed_size && // may double resize_to
|
resize_to < (std::numeric_limits<size_type>::max)() / 2) {
|
// This situation means that we have enough deleted elements,
|
// that once we purge them, we won't actually have needed to
|
// grow. But we may want to grow anyway: if we just purge one
|
// element, say, we'll have to grow anyway next time we
|
// insert. Might as well grow now, since we're already going
|
// through the trouble of copying (in order to purge the
|
// deleted elements).
|
const size_type target =
|
static_cast<size_type>(settings.shrink_size(resize_to*2));
|
if (num_elements - num_deleted + delta >= target) {
|
// Good, we won't be below the shrink threshhold even if we double.
|
resize_to *= 2;
|
}
|
}
|
dense_hashtable tmp(*this, resize_to);
|
swap(tmp); // now we are tmp
|
return true;
|
}
|
|
// We require table be not-NULL and empty before calling this.
|
void resize_table(size_type /*old_size*/, size_type new_size,
|
base::true_type) {
|
table = val_info.realloc_or_die(table, new_size);
|
}
|
|
void resize_table(size_type old_size, size_type new_size, base::false_type) {
|
val_info.deallocate(table, old_size);
|
table = val_info.allocate(new_size);
|
}
|
|
// Used to actually do the rehashing when we grow/shrink a hashtable
|
void copy_from(const dense_hashtable &ht, size_type min_buckets_wanted) {
|
clear_to_size(settings.min_buckets(ht.size(), min_buckets_wanted));
|
|
// We use a normal iterator to get non-deleted bcks from ht
|
// We could use insert() here, but since we know there are
|
// no duplicates and no deleted items, we can be more efficient
|
assert((bucket_count() & (bucket_count()-1)) == 0); // a power of two
|
for ( const_iterator it = ht.begin(); it != ht.end(); ++it ) {
|
size_type num_probes = 0; // how many times we've probed
|
size_type bucknum;
|
const size_type bucket_count_minus_one = bucket_count() - 1;
|
for (bucknum = hash(get_key(*it)) & bucket_count_minus_one;
|
!test_empty(bucknum); // not empty
|
bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one) {
|
++num_probes;
|
assert(num_probes < bucket_count()
|
&& "Hashtable is full: an error in key_equal<> or hash<>");
|
}
|
set_value(&table[bucknum], *it); // copies the value to here
|
num_elements++;
|
}
|
settings.inc_num_ht_copies();
|
}
|
|
// Required by the spec for hashed associative container
|
public:
|
// Though the docs say this should be num_buckets, I think it's much
|
// more useful as num_elements. As a special feature, calling with
|
// req_elements==0 will cause us to shrink if we can, saving space.
|
void resize(size_type req_elements) { // resize to this or larger
|
if ( settings.consider_shrink() || req_elements == 0 )
|
maybe_shrink();
|
if ( req_elements > num_elements )
|
resize_delta(req_elements - num_elements);
|
}
|
|
// Get and change the value of shrink_factor and enlarge_factor. The
|
// description at the beginning of this file explains how to choose
|
// the values. Setting the shrink parameter to 0.0 ensures that the
|
// table never shrinks.
|
void get_resizing_parameters(float* shrink, float* grow) const {
|
*shrink = settings.shrink_factor();
|
*grow = settings.enlarge_factor();
|
}
|
void set_resizing_parameters(float shrink, float grow) {
|
settings.set_resizing_parameters(shrink, grow);
|
settings.reset_thresholds(bucket_count());
|
}
|
|
// CONSTRUCTORS -- as required by the specs, we take a size,
|
// but also let you specify a hashfunction, key comparator,
|
// and key extractor. We also define a copy constructor and =.
|
// DESTRUCTOR -- needs to free the table
|
explicit dense_hashtable(size_type expected_max_items_in_table = 0,
|
const HashFcn& hf = HashFcn(),
|
const EqualKey& eql = EqualKey(),
|
const ExtractKey& ext = ExtractKey(),
|
const SetKey& set = SetKey(),
|
const Alloc& alloc = Alloc())
|
: settings(hf),
|
key_info(ext, set, eql),
|
num_deleted(0),
|
num_elements(0),
|
num_buckets(expected_max_items_in_table == 0
|
? HT_DEFAULT_STARTING_BUCKETS
|
: settings.min_buckets(expected_max_items_in_table, 0)),
|
val_info(alloc_impl<value_alloc_type>(alloc)),
|
table(NULL) {
|
// table is NULL until emptyval is set. However, we set num_buckets
|
// here so we know how much space to allocate once emptyval is set
|
settings.reset_thresholds(bucket_count());
|
}
|
|
// As a convenience for resize(), we allow an optional second argument
|
// which lets you make this new hashtable a different size than ht
|
dense_hashtable(const dense_hashtable& ht,
|
size_type min_buckets_wanted = HT_DEFAULT_STARTING_BUCKETS)
|
: settings(ht.settings),
|
key_info(ht.key_info),
|
num_deleted(0),
|
num_elements(0),
|
num_buckets(0),
|
val_info(ht.val_info),
|
table(NULL) {
|
if (!ht.settings.use_empty()) {
|
// If use_empty isn't set, copy_from will crash, so we do our own copying.
|
assert(ht.empty());
|
num_buckets = settings.min_buckets(ht.size(), min_buckets_wanted);
|
settings.reset_thresholds(bucket_count());
|
return;
|
}
|
settings.reset_thresholds(bucket_count());
|
copy_from(ht, min_buckets_wanted); // copy_from() ignores deleted entries
|
}
|
|
dense_hashtable& operator= (const dense_hashtable& ht) {
|
if (&ht == this) return *this; // don't copy onto ourselves
|
if (!ht.settings.use_empty()) {
|
assert(ht.empty());
|
dense_hashtable empty_table(ht); // empty table with ht's thresholds
|
this->swap(empty_table);
|
return *this;
|
}
|
settings = ht.settings;
|
key_info = ht.key_info;
|
set_value(&val_info.emptyval, ht.val_info.emptyval);
|
// copy_from() calls clear and sets num_deleted to 0 too
|
copy_from(ht, HT_MIN_BUCKETS);
|
// we purposefully don't copy the allocator, which may not be copyable
|
return *this;
|
}
|
|
~dense_hashtable() {
|
if (table) {
|
destroy_buckets(0, num_buckets);
|
val_info.deallocate(table, num_buckets);
|
}
|
}
|
|
// Many STL algorithms use swap instead of copy constructors
|
void swap(dense_hashtable& ht) {
|
std::swap(settings, ht.settings);
|
std::swap(key_info, ht.key_info);
|
std::swap(num_deleted, ht.num_deleted);
|
std::swap(num_elements, ht.num_elements);
|
std::swap(num_buckets, ht.num_buckets);
|
{ value_type tmp; // for annoying reasons, swap() doesn't work
|
set_value(&tmp, val_info.emptyval);
|
set_value(&val_info.emptyval, ht.val_info.emptyval);
|
set_value(&ht.val_info.emptyval, tmp);
|
}
|
std::swap(table, ht.table);
|
settings.reset_thresholds(bucket_count()); // also resets consider_shrink
|
ht.settings.reset_thresholds(ht.bucket_count());
|
// we purposefully don't swap the allocator, which may not be swap-able
|
}
|
|
private:
|
void clear_to_size(size_type new_num_buckets) {
|
if (!table) {
|
table = val_info.allocate(new_num_buckets);
|
} else {
|
destroy_buckets(0, num_buckets);
|
if (new_num_buckets != num_buckets) { // resize, if necessary
|
typedef base::integral_constant<bool,
|
base::is_same<value_alloc_type,
|
libc_allocator_with_realloc<value_type> >::value>
|
realloc_ok;
|
resize_table(num_buckets, new_num_buckets, realloc_ok());
|
}
|
}
|
assert(table);
|
fill_range_with_empty(table, table + new_num_buckets);
|
num_elements = 0;
|
num_deleted = 0;
|
num_buckets = new_num_buckets; // our new size
|
settings.reset_thresholds(bucket_count());
|
}
|
|
public:
|
// It's always nice to be able to clear a table without deallocating it
|
void clear() {
|
// If the table is already empty, and the number of buckets is
|
// already as we desire, there's nothing to do.
|
const size_type new_num_buckets = settings.min_buckets(0, 0);
|
if (num_elements == 0 && new_num_buckets == num_buckets) {
|
return;
|
}
|
clear_to_size(new_num_buckets);
|
}
|
|
// Clear the table without resizing it.
|
// Mimicks the stl_hashtable's behaviour when clear()-ing in that it
|
// does not modify the bucket count
|
void clear_no_resize() {
|
if (num_elements > 0) {
|
assert(table);
|
destroy_buckets(0, num_buckets);
|
fill_range_with_empty(table, table + num_buckets);
|
}
|
// don't consider to shrink before another erase()
|
settings.reset_thresholds(bucket_count());
|
num_elements = 0;
|
num_deleted = 0;
|
}
|
|
// LOOKUP ROUTINES
|
private:
|
// Returns a pair of positions: 1st where the object is, 2nd where
|
// it would go if you wanted to insert it. 1st is ILLEGAL_BUCKET
|
// if object is not found; 2nd is ILLEGAL_BUCKET if it is.
|
// Note: because of deletions where-to-insert is not trivial: it's the
|
// first deleted bucket we see, as long as we don't find the key later
|
std::pair<size_type, size_type> find_position(const key_type &key) const {
|
size_type num_probes = 0; // how many times we've probed
|
const size_type bucket_count_minus_one = bucket_count() - 1;
|
size_type bucknum = hash(key) & bucket_count_minus_one;
|
size_type insert_pos = ILLEGAL_BUCKET; // where we would insert
|
while ( 1 ) { // probe until something happens
|
if ( test_empty(bucknum) ) { // bucket is empty
|
if ( insert_pos == ILLEGAL_BUCKET ) // found no prior place to insert
|
return std::pair<size_type,size_type>(ILLEGAL_BUCKET, bucknum);
|
else
|
return std::pair<size_type,size_type>(ILLEGAL_BUCKET, insert_pos);
|
|
} else if ( test_deleted(bucknum) ) {// keep searching, but mark to insert
|
if ( insert_pos == ILLEGAL_BUCKET )
|
insert_pos = bucknum;
|
|
} else if ( equals(key, get_key(table[bucknum])) ) {
|
return std::pair<size_type,size_type>(bucknum, ILLEGAL_BUCKET);
|
}
|
++num_probes; // we're doing another probe
|
bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one;
|
assert(num_probes < bucket_count()
|
&& "Hashtable is full: an error in key_equal<> or hash<>");
|
}
|
}
|
|
public:
|
|
iterator find(const key_type& key) {
|
if ( size() == 0 ) return end();
|
std::pair<size_type, size_type> pos = find_position(key);
|
if ( pos.first == ILLEGAL_BUCKET ) // alas, not there
|
return end();
|
else
|
return iterator(this, table + pos.first, table + num_buckets, false);
|
}
|
|
const_iterator find(const key_type& key) const {
|
if ( size() == 0 ) return end();
|
std::pair<size_type, size_type> pos = find_position(key);
|
if ( pos.first == ILLEGAL_BUCKET ) // alas, not there
|
return end();
|
else
|
return const_iterator(this, table + pos.first, table+num_buckets, false);
|
}
|
|
// This is a tr1 method: the bucket a given key is in, or what bucket
|
// it would be put in, if it were to be inserted. Shrug.
|
size_type bucket(const key_type& key) const {
|
std::pair<size_type, size_type> pos = find_position(key);
|
return pos.first == ILLEGAL_BUCKET ? pos.second : pos.first;
|
}
|
|
// Counts how many elements have key key. For maps, it's either 0 or 1.
|
size_type count(const key_type &key) const {
|
std::pair<size_type, size_type> pos = find_position(key);
|
return pos.first == ILLEGAL_BUCKET ? 0 : 1;
|
}
|
|
// Likewise, equal_range doesn't really make sense for us. Oh well.
|
std::pair<iterator,iterator> equal_range(const key_type& key) {
|
iterator pos = find(key); // either an iterator or end
|
if (pos == end()) {
|
return std::pair<iterator,iterator>(pos, pos);
|
} else {
|
const iterator startpos = pos++;
|
return std::pair<iterator,iterator>(startpos, pos);
|
}
|
}
|
std::pair<const_iterator,const_iterator> equal_range(const key_type& key)
|
const {
|
const_iterator pos = find(key); // either an iterator or end
|
if (pos == end()) {
|
return std::pair<const_iterator,const_iterator>(pos, pos);
|
} else {
|
const const_iterator startpos = pos++;
|
return std::pair<const_iterator,const_iterator>(startpos, pos);
|
}
|
}
|
|
|
// INSERTION ROUTINES
|
private:
|
// Private method used by insert_noresize and find_or_insert.
|
iterator insert_at(const_reference obj, size_type pos) {
|
if (size() >= max_size()) {
|
assert(false && "insert overflow");
|
exit(-1);
|
}
|
if ( test_deleted(pos) ) { // just replace if it's been del.
|
// shrug: shouldn't need to be const.
|
const_iterator delpos(this, table + pos, table + num_buckets, false);
|
clear_deleted(delpos);
|
assert( num_deleted > 0);
|
--num_deleted; // used to be, now it isn't
|
} else {
|
++num_elements; // replacing an empty bucket
|
}
|
set_value(&table[pos], obj);
|
return iterator(this, table + pos, table + num_buckets, false);
|
}
|
|
// If you know *this is big enough to hold obj, use this routine
|
std::pair<iterator, bool> insert_noresize(const_reference obj) {
|
// First, double-check we're not inserting delkey or emptyval
|
assert((!settings.use_empty() || !equals(get_key(obj),
|
get_key(val_info.emptyval)))
|
&& "Inserting the empty key");
|
assert((!settings.use_deleted() || !equals(get_key(obj), key_info.delkey))
|
&& "Inserting the deleted key");
|
const std::pair<size_type,size_type> pos = find_position(get_key(obj));
|
if ( pos.first != ILLEGAL_BUCKET) { // object was already there
|
return std::pair<iterator,bool>(iterator(this, table + pos.first,
|
table + num_buckets, false),
|
false); // false: we didn't insert
|
} else { // pos.second says where to put it
|
return std::pair<iterator,bool>(insert_at(obj, pos.second), true);
|
}
|
}
|
|
// Specializations of insert(it, it) depending on the power of the iterator:
|
// (1) Iterator supports operator-, resize before inserting
|
template <class ForwardIterator>
|
void insert(ForwardIterator f, ForwardIterator l, std::forward_iterator_tag) {
|
size_t dist = std::distance(f, l);
|
if (dist >= (std::numeric_limits<size_type>::max)()) {
|
assert(false && "insert-range overflow");
|
exit(-1);
|
}
|
resize_delta(static_cast<size_type>(dist));
|
for ( ; dist > 0; --dist, ++f) {
|
insert_noresize(*f);
|
}
|
}
|
|
// (2) Arbitrary iterator, can't tell how much to resize
|
template <class InputIterator>
|
void insert(InputIterator f, InputIterator l, std::input_iterator_tag) {
|
for ( ; f != l; ++f)
|
insert(*f);
|
}
|
|
public:
|
// This is the normal insert routine, used by the outside world
|
std::pair<iterator, bool> insert(const_reference obj) {
|
resize_delta(1); // adding an object, grow if need be
|
return insert_noresize(obj);
|
}
|
|
// When inserting a lot at a time, we specialize on the type of iterator
|
template <class InputIterator>
|
void insert(InputIterator f, InputIterator l) {
|
// specializes on iterator type
|
insert(f, l,
|
typename std::iterator_traits<InputIterator>::iterator_category());
|
}
|
|
// DefaultValue is a functor that takes a key and returns a value_type
|
// representing the default value to be inserted if none is found.
|
template <class DefaultValue>
|
value_type& find_or_insert(const key_type& key) {
|
// First, double-check we're not inserting emptykey or delkey
|
assert((!settings.use_empty() || !equals(key, get_key(val_info.emptyval)))
|
&& "Inserting the empty key");
|
assert((!settings.use_deleted() || !equals(key, key_info.delkey))
|
&& "Inserting the deleted key");
|
const std::pair<size_type,size_type> pos = find_position(key);
|
DefaultValue default_value;
|
if ( pos.first != ILLEGAL_BUCKET) { // object was already there
|
return table[pos.first];
|
} else if (resize_delta(1)) { // needed to rehash to make room
|
// Since we resized, we can't use pos, so recalculate where to insert.
|
return *insert_noresize(default_value(key)).first;
|
} else { // no need to rehash, insert right here
|
return *insert_at(default_value(key), pos.second);
|
}
|
}
|
|
|
// DELETION ROUTINES
|
size_type erase(const key_type& key) {
|
// First, double-check we're not trying to erase delkey or emptyval.
|
assert((!settings.use_empty() || !equals(key, get_key(val_info.emptyval)))
|
&& "Erasing the empty key");
|
assert((!settings.use_deleted() || !equals(key, key_info.delkey))
|
&& "Erasing the deleted key");
|
const_iterator pos = find(key); // shrug: shouldn't need to be const
|
if ( pos != end() ) {
|
assert(!test_deleted(pos)); // or find() shouldn't have returned it
|
set_deleted(pos);
|
++num_deleted;
|
settings.set_consider_shrink(true); // will think about shrink after next insert
|
return 1; // because we deleted one thing
|
} else {
|
return 0; // because we deleted nothing
|
}
|
}
|
|
// We return the iterator past the deleted item.
|
void erase(iterator pos) {
|
if ( pos == end() ) return; // sanity check
|
if ( set_deleted(pos) ) { // true if object has been newly deleted
|
++num_deleted;
|
settings.set_consider_shrink(true); // will think about shrink after next insert
|
}
|
}
|
|
void erase(iterator f, iterator l) {
|
for ( ; f != l; ++f) {
|
if ( set_deleted(f) ) // should always be true
|
++num_deleted;
|
}
|
settings.set_consider_shrink(true); // will think about shrink after next insert
|
}
|
|
// We allow you to erase a const_iterator just like we allow you to
|
// erase an iterator. This is in parallel to 'delete': you can delete
|
// a const pointer just like a non-const pointer. The logic is that
|
// you can't use the object after it's erased anyway, so it doesn't matter
|
// if it's const or not.
|
void erase(const_iterator pos) {
|
if ( pos == end() ) return; // sanity check
|
if ( set_deleted(pos) ) { // true if object has been newly deleted
|
++num_deleted;
|
settings.set_consider_shrink(true); // will think about shrink after next insert
|
}
|
}
|
void erase(const_iterator f, const_iterator l) {
|
for ( ; f != l; ++f) {
|
if ( set_deleted(f) ) // should always be true
|
++num_deleted;
|
}
|
settings.set_consider_shrink(true); // will think about shrink after next insert
|
}
|
|
|
// COMPARISON
|
bool operator==(const dense_hashtable& ht) const {
|
if (size() != ht.size()) {
|
return false;
|
} else if (this == &ht) {
|
return true;
|
} else {
|
// Iterate through the elements in "this" and see if the
|
// corresponding element is in ht
|
for ( const_iterator it = begin(); it != end(); ++it ) {
|
const_iterator it2 = ht.find(get_key(*it));
|
if ((it2 == ht.end()) || (*it != *it2)) {
|
return false;
|
}
|
}
|
return true;
|
}
|
}
|
bool operator!=(const dense_hashtable& ht) const {
|
return !(*this == ht);
|
}
|
|
|
// I/O
|
// We support reading and writing hashtables to disk. Alas, since
|
// I don't know how to write a hasher or key_equal, you have to make
|
// sure everything but the table is the same. We compact before writing.
|
private:
|
// Every time the disk format changes, this should probably change too
|
typedef unsigned long MagicNumberType;
|
static const MagicNumberType MAGIC_NUMBER = 0x13578642;
|
|
public:
|
// I/O -- this is an add-on for writing hash table to disk
|
//
|
// INPUT and OUTPUT must be either a FILE, *or* a C++ stream
|
// (istream, ostream, etc) *or* a class providing
|
// Read(void*, size_t) and Write(const void*, size_t)
|
// (respectively), which writes a buffer into a stream
|
// (which the INPUT/OUTPUT instance presumably owns).
|
|
typedef sparsehash_internal::pod_serializer<value_type> NopointerSerializer;
|
|
// ValueSerializer: a functor. operator()(OUTPUT*, const value_type&)
|
template <typename ValueSerializer, typename OUTPUT>
|
bool serialize(ValueSerializer serializer, OUTPUT *fp) {
|
squash_deleted(); // so we don't have to worry about delkey
|
if ( !sparsehash_internal::write_bigendian_number(fp, MAGIC_NUMBER, 4) )
|
return false;
|
if ( !sparsehash_internal::write_bigendian_number(fp, num_buckets, 8) )
|
return false;
|
if ( !sparsehash_internal::write_bigendian_number(fp, num_elements, 8) )
|
return false;
|
// Now write a bitmap of non-empty buckets.
|
for ( size_type i = 0; i < num_buckets; i += 8 ) {
|
unsigned char bits = 0;
|
for ( int bit = 0; bit < 8; ++bit ) {
|
if ( i + bit < num_buckets && !test_empty(i + bit) )
|
bits |= (1 << bit);
|
}
|
if ( !sparsehash_internal::write_data(fp, &bits, sizeof(bits)) )
|
return false;
|
for ( int bit = 0; bit < 8; ++bit ) {
|
if ( bits & (1 << bit) ) {
|
if ( !serializer(fp, table[i + bit]) ) return false;
|
}
|
}
|
}
|
return true;
|
}
|
|
// INPUT: anything we've written an overload of read_data() for.
|
// ValueSerializer: a functor. operator()(INPUT*, value_type*)
|
template <typename ValueSerializer, typename INPUT>
|
bool unserialize(ValueSerializer serializer, INPUT *fp) {
|
assert(settings.use_empty() && "empty_key not set for read");
|
|
clear(); // just to be consistent
|
MagicNumberType magic_read;
|
if ( !sparsehash_internal::read_bigendian_number(fp, &magic_read, 4) )
|
return false;
|
if ( magic_read != MAGIC_NUMBER ) {
|
return false;
|
}
|
size_type new_num_buckets;
|
if ( !sparsehash_internal::read_bigendian_number(fp, &new_num_buckets, 8) )
|
return false;
|
clear_to_size(new_num_buckets);
|
if ( !sparsehash_internal::read_bigendian_number(fp, &num_elements, 8) )
|
return false;
|
|
// Read the bitmap of non-empty buckets.
|
for (size_type i = 0; i < num_buckets; i += 8) {
|
unsigned char bits;
|
if ( !sparsehash_internal::read_data(fp, &bits, sizeof(bits)) )
|
return false;
|
for ( int bit = 0; bit < 8; ++bit ) {
|
if ( i + bit < num_buckets && (bits & (1 << bit)) ) { // not empty
|
if ( !serializer(fp, &table[i + bit]) ) return false;
|
}
|
}
|
}
|
return true;
|
}
|
|
private:
|
template <class A>
|
class alloc_impl : public A {
|
public:
|
typedef typename A::pointer pointer;
|
typedef typename A::size_type size_type;
|
|
// Convert a normal allocator to one that has realloc_or_die()
|
alloc_impl(const A& a) : A(a) { }
|
|
// realloc_or_die should only be used when using the default
|
// allocator (libc_allocator_with_realloc).
|
pointer realloc_or_die(pointer /*ptr*/, size_type /*n*/) {
|
fprintf(stderr, "realloc_or_die is only supported for "
|
"libc_allocator_with_realloc\n");
|
exit(1);
|
return NULL;
|
}
|
};
|
|
// A template specialization of alloc_impl for
|
// libc_allocator_with_realloc that can handle realloc_or_die.
|
template <class A>
|
class alloc_impl<libc_allocator_with_realloc<A> >
|
: public libc_allocator_with_realloc<A> {
|
public:
|
typedef typename libc_allocator_with_realloc<A>::pointer pointer;
|
typedef typename libc_allocator_with_realloc<A>::size_type size_type;
|
|
alloc_impl(const libc_allocator_with_realloc<A>& a)
|
: libc_allocator_with_realloc<A>(a) { }
|
|
pointer realloc_or_die(pointer ptr, size_type n) {
|
pointer retval = this->reallocate(ptr, n);
|
if (retval == NULL) {
|
fprintf(stderr,
|
"sparsehash: FATAL ERROR: failed to reallocate "
|
"%lu elements for ptr %p",
|
static_cast<unsigned long>(n), static_cast<void*>(ptr));
|
exit(1);
|
}
|
return retval;
|
}
|
};
|
|
// Package allocator with emptyval to eliminate memory needed for
|
// the zero-size allocator.
|
// If new fields are added to this class, we should add them to
|
// operator= and swap.
|
class ValInfo : public alloc_impl<value_alloc_type> {
|
public:
|
typedef typename alloc_impl<value_alloc_type>::value_type value_type;
|
|
ValInfo(const alloc_impl<value_alloc_type>& a)
|
: alloc_impl<value_alloc_type>(a), emptyval() { }
|
ValInfo(const ValInfo& v)
|
: alloc_impl<value_alloc_type>(v), emptyval(v.emptyval) { }
|
|
value_type emptyval; // which key marks unused entries
|
};
|
|
|
// Package functors with another class to eliminate memory needed for
|
// zero-size functors. Since ExtractKey and hasher's operator() might
|
// have the same function signature, they must be packaged in
|
// different classes.
|
struct Settings :
|
sparsehash_internal::sh_hashtable_settings<key_type, hasher,
|
size_type, HT_MIN_BUCKETS> {
|
explicit Settings(const hasher& hf)
|
: sparsehash_internal::sh_hashtable_settings<key_type, hasher,
|
size_type, HT_MIN_BUCKETS>(
|
hf, HT_OCCUPANCY_PCT / 100.0f, HT_EMPTY_PCT / 100.0f) {}
|
};
|
|
// Packages ExtractKey and SetKey functors.
|
class KeyInfo : public ExtractKey, public SetKey, public EqualKey {
|
public:
|
KeyInfo(const ExtractKey& ek, const SetKey& sk, const EqualKey& eq)
|
: ExtractKey(ek),
|
SetKey(sk),
|
EqualKey(eq) {
|
}
|
|
// We want to return the exact same type as ExtractKey: Key or const Key&
|
typename ExtractKey::result_type get_key(const_reference v) const {
|
return ExtractKey::operator()(v);
|
}
|
void set_key(pointer v, const key_type& k) const {
|
SetKey::operator()(v, k);
|
}
|
bool equals(const key_type& a, const key_type& b) const {
|
return EqualKey::operator()(a, b);
|
}
|
|
// Which key marks deleted entries.
|
// TODO(csilvers): make a pointer, and get rid of use_deleted (benchmark!)
|
typename base::remove_const<key_type>::type delkey;
|
};
|
|
// Utility functions to access the templated operators
|
size_type hash(const key_type& v) const {
|
return settings.hash(v);
|
}
|
bool equals(const key_type& a, const key_type& b) const {
|
return key_info.equals(a, b);
|
}
|
typename ExtractKey::result_type get_key(const_reference v) const {
|
return key_info.get_key(v);
|
}
|
void set_key(pointer v, const key_type& k) const {
|
key_info.set_key(v, k);
|
}
|
|
private:
|
// Actual data
|
Settings settings;
|
KeyInfo key_info;
|
|
size_type num_deleted; // how many occupied buckets are marked deleted
|
size_type num_elements;
|
size_type num_buckets;
|
ValInfo val_info; // holds emptyval, and also the allocator
|
pointer table;
|
};
|
|
|
// We need a global swap as well
|
template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
|
inline void swap(dense_hashtable<V,K,HF,ExK,SetK,EqK,A> &x,
|
dense_hashtable<V,K,HF,ExK,SetK,EqK,A> &y) {
|
x.swap(y);
|
}
|
|
#undef JUMP_
|
|
template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
|
const typename dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::size_type
|
dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::ILLEGAL_BUCKET;
|
|
// How full we let the table get before we resize. Knuth says .8 is
|
// good -- higher causes us to probe too much, though saves memory.
|
// However, we go with .5, getting better performance at the cost of
|
// more space (a trade-off densehashtable explicitly chooses to make).
|
// Feel free to play around with different values, though, via
|
// max_load_factor() and/or set_resizing_parameters().
|
template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
|
const int dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_PCT = 50;
|
|
// How empty we let the table get before we resize lower.
|
// It should be less than OCCUPANCY_PCT / 2 or we thrash resizing.
|
template <class V, class K, class HF, class ExK, class SetK, class EqK, class A>
|
const int dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_EMPTY_PCT
|
= static_cast<int>(0.4 *
|
dense_hashtable<V,K,HF,ExK,SetK,EqK,A>::HT_OCCUPANCY_PCT);
|
|
_END_GOOGLE_NAMESPACE_
|
|
#endif /* _DENSEHASHTABLE_H_ */
|
