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1 william 10 // Copyright (c) 2005, Google Inc.
2     // All rights reserved.
3     //
4     // Redistribution and use in source and binary forms, with or without
5     // modification, are permitted provided that the following conditions are
6     // met:
7     //
8     // * Redistributions of source code must retain the above copyright
9     // notice, this list of conditions and the following disclaimer.
10     // * Redistributions in binary form must reproduce the above
11     // copyright notice, this list of conditions and the following disclaimer
12     // in the documentation and/or other materials provided with the
13     // distribution.
14     // * Neither the name of Google Inc. nor the names of its
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16     // this software without specific prior written permission.
17     //
18     // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19     // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20     // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21     // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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23     // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24     // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25     // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26     // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27     // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28     // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29    
30     // ---
31     // Author: Craig Silverstein
32     //
33     // This is just a very thin wrapper over densehashtable.h, just
34     // like sgi stl's stl_hash_set is a very thin wrapper over
35     // stl_hashtable. The major thing we define is operator[], because
36     // we have a concept of a data_type which stl_hashtable doesn't
37     // (it only has a key and a value).
38     //
39     // This is more different from dense_hash_map than you might think,
40     // because all iterators for sets are const (you obviously can't
41     // change the key, and for sets there is no value).
42     //
43     // NOTE: this is exactly like sparse_hash_set.h, with the word
44     // "sparse" replaced by "dense", except for the addition of
45     // set_empty_key().
46     //
47     // YOU MUST CALL SET_EMPTY_KEY() IMMEDIATELY AFTER CONSTRUCTION.
48     //
49     // Otherwise your program will die in mysterious ways.
50     //
51     // In other respects, we adhere mostly to the STL semantics for
52     // hash-set. One important exception is that insert() invalidates
53     // iterators entirely. On the plus side, though, erase() doesn't
54     // invalidate iterators at all, or even change the ordering of elements.
55     //
56     // Here are a few "power user" tips:
57     //
58     // 1) set_deleted_key():
59     // If you want to use erase() you must call set_deleted_key(),
60     // in addition to set_empty_key(), after construction.
61     // The deleted and empty keys must differ.
62     //
63     // 2) resize(0):
64     // When an item is deleted, its memory isn't freed right
65     // away. This allows you to iterate over a hashtable,
66     // and call erase(), without invalidating the iterator.
67     // To force the memory to be freed, call resize(0).
68     //
69     // 3) set_resizing_parameters(0.0, 0.8):
70     // Setting the shrink_resize_percent to 0.0 guarantees
71     // that the hash table will never shrink.
72     //
73     // Guide to what kind of hash_set to use:
74     // (1) dense_hash_set: fastest, uses the most memory
75     // (2) sparse_hash_set: slowest, uses the least memory
76     // (3) hash_set (STL): in the middle
77     // Typically I use sparse_hash_set when I care about space and/or when
78     // I need to save the hashtable on disk. I use hash_set otherwise. I
79     // don't personally use dense_hash_set ever; the only use of
80     // dense_hash_set I know of is to work around malloc() bugs in some
81     // systems (dense_hash_set has a particularly simple allocation scheme).
82     //
83     // - dense_hash_set has, typically, a factor of 2 memory overhead (if your
84     // data takes up X bytes, the hash_set uses X more bytes in overhead).
85     // - sparse_hash_set has about 2 bits overhead per entry.
86     // - sparse_hash_map can be 3-7 times slower than the others for lookup and,
87     // especially, inserts. See time_hash_map.cc for details.
88     //
89     // See /usr/(local/)?doc/sparsehash-0.1/dense_hash_set.html
90     // for information about how to use this class.
91    
92     #ifndef _DENSE_HASH_SET_H_
93     #define _DENSE_HASH_SET_H_
94    
95     #include <google/sparsehash/sparseconfig.h>
96     #include <stdio.h> // for FILE * in read()/write()
97     #include <algorithm> // for the default template args
98     #include <functional> // for equal_to
99     #include <memory> // for alloc<>
100     #include <utility> // for pair<>
101     #include HASH_FUN_H // defined in config.h
102     #include <google/sparsehash/densehashtable.h>
103    
104    
105     _START_GOOGLE_NAMESPACE_
106    
107     using STL_NAMESPACE::pair;
108    
109     template <class Value,
110     class HashFcn = SPARSEHASH_HASH<Value>, // defined in sparseconfig.h
111     class EqualKey = STL_NAMESPACE::equal_to<Value>,
112     class Alloc = STL_NAMESPACE::allocator<Value> >
113     class dense_hash_set {
114     private:
115     // Apparently identity is not stl-standard, so we define our own
116     struct Identity {
117     Value& operator()(Value& v) const { return v; }
118     const Value& operator()(const Value& v) const { return v; }
119     };
120    
121     // The actual data
122     typedef dense_hashtable<Value, Value, HashFcn, Identity, EqualKey, Alloc> ht;
123     ht rep;
124    
125     public:
126     typedef typename ht::key_type key_type;
127     typedef typename ht::value_type value_type;
128     typedef typename ht::hasher hasher;
129     typedef typename ht::key_equal key_equal;
130    
131     typedef typename ht::size_type size_type;
132     typedef typename ht::difference_type difference_type;
133     typedef typename ht::const_pointer pointer;
134     typedef typename ht::const_pointer const_pointer;
135     typedef typename ht::const_reference reference;
136     typedef typename ht::const_reference const_reference;
137    
138     typedef typename ht::const_iterator iterator;
139     typedef typename ht::const_iterator const_iterator;
140    
141    
142     // Iterator functions -- recall all iterators are const
143     iterator begin() const { return rep.begin(); }
144     iterator end() const { return rep.end(); }
145    
146    
147     // Accessor functions
148     hasher hash_funct() const { return rep.hash_funct(); }
149     key_equal key_eq() const { return rep.key_eq(); }
150    
151    
152     // Constructors
153     explicit dense_hash_set(size_type expected_max_items_in_table = 0,
154     const hasher& hf = hasher(),
155     const key_equal& eql = key_equal())
156     : rep(expected_max_items_in_table, hf, eql) { }
157    
158     template <class InputIterator>
159     dense_hash_set(InputIterator f, InputIterator l,
160     size_type expected_max_items_in_table = 0,
161     const hasher& hf = hasher(),
162     const key_equal& eql = key_equal())
163     : rep(expected_max_items_in_table, hf, eql) {
164     rep.insert(f, l);
165     }
166     // We use the default copy constructor
167     // We use the default operator=()
168     // We use the default destructor
169    
170     void clear() { rep.clear(); }
171     // This clears the hash set without resizing it down to the minimum
172     // bucket count, but rather keeps the number of buckets constant
173     void clear_no_resize() { rep.clear_no_resize(); }
174     void swap(dense_hash_set& hs) { rep.swap(hs.rep); }
175    
176    
177     // Functions concerning size
178     size_type size() const { return rep.size(); }
179     size_type max_size() const { return rep.max_size(); }
180     bool empty() const { return rep.empty(); }
181     size_type bucket_count() const { return rep.bucket_count(); }
182     size_type max_bucket_count() const { return rep.max_bucket_count(); }
183    
184     void resize(size_type hint) { rep.resize(hint); }
185    
186     void set_resizing_parameters(float shrink, float grow) {
187     return rep.set_resizing_parameters(shrink, grow);
188     }
189    
190     // Lookup routines
191     iterator find(const key_type& key) const { return rep.find(key); }
192    
193     size_type count(const key_type& key) const { return rep.count(key); }
194    
195     pair<iterator, iterator> equal_range(const key_type& key) const {
196     return rep.equal_range(key);
197     }
198    
199     // Insertion routines
200     pair<iterator, bool> insert(const value_type& obj) {
201     pair<typename ht::iterator, bool> p = rep.insert(obj);
202     return pair<iterator, bool>(p.first, p.second); // const to non-const
203     }
204     template <class InputIterator>
205     void insert(InputIterator f, InputIterator l) { rep.insert(f, l); }
206     void insert(const_iterator f, const_iterator l) { rep.insert(f, l); }
207     // required for std::insert_iterator; the passed-in iterator is ignored
208     iterator insert(iterator, const value_type& obj) { return insert(obj).first; }
209    
210    
211     // Deletion and empty routines
212     // THESE ARE NON-STANDARD! I make you specify an "impossible" key
213     // value to identify deleted and empty buckets. You can change the
214     // deleted key as time goes on, or get rid of it entirely to be insert-only.
215     void set_empty_key(const key_type& key) { rep.set_empty_key(key); }
216     void set_deleted_key(const key_type& key) { rep.set_deleted_key(key); }
217     void clear_deleted_key() { rep.clear_deleted_key(); }
218    
219     // These are standard
220     size_type erase(const key_type& key) { return rep.erase(key); }
221     void erase(iterator it) { rep.erase(it); }
222     void erase(iterator f, iterator l) { rep.erase(f, l); }
223    
224    
225     // Comparison
226     bool operator==(const dense_hash_set& hs) const { return rep == hs.rep; }
227     bool operator!=(const dense_hash_set& hs) const { return rep != hs.rep; }
228    
229    
230     // I/O -- this is an add-on for writing metainformation to disk
231     bool write_metadata(FILE *fp) { return rep.write_metadata(fp); }
232     bool read_metadata(FILE *fp) { return rep.read_metadata(fp); }
233     bool write_nopointer_data(FILE *fp) { return rep.write_nopointer_data(fp); }
234     bool read_nopointer_data(FILE *fp) { return rep.read_nopointer_data(fp); }
235     };
236    
237     template <class Val, class HashFcn, class EqualKey, class Alloc>
238     inline void swap(dense_hash_set<Val, HashFcn, EqualKey, Alloc>& hs1,
239     dense_hash_set<Val, HashFcn, EqualKey, Alloc>& hs2) {
240     hs1.swap(hs2);
241     }
242    
243     _END_GOOGLE_NAMESPACE_
244    
245     #endif /* _DENSE_HASH_SET_H_ */

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