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Revision 15 - (show annotations) (download)
Mon Sep 6 13:44:19 2010 UTC (10 years, 2 months ago) by william
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initial checkout of r3113 from upstream repository
1 // 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
15 // contributors may be used to endorse or promote products derived from
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
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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_map 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 // NOTE: this is exactly like sparse_hash_map.h, with the word
40 // "sparse" replaced by "dense", except for the addition of
41 // set_empty_key().
42 //
43 // YOU MUST CALL SET_EMPTY_KEY() IMMEDIATELY AFTER CONSTRUCTION.
44 //
45 // Otherwise your program will die in mysterious ways.
46 //
47 // In other respects, we adhere mostly to the STL semantics for
48 // hash-map. One important exception is that insert() invalidates
49 // iterators entirely. On the plus side, though, erase() doesn't
50 // invalidate iterators at all, or even change the ordering of elements.
51 //
52 // Here are a few "power user" tips:
53 //
54 // 1) set_deleted_key():
55 // If you want to use erase() you must call set_deleted_key(),
56 // in addition to set_empty_key(), after construction.
57 // The deleted and empty keys must differ.
58 //
59 // 2) resize(0):
60 // When an item is deleted, its memory isn't freed right
61 // away. This allows you to iterate over a hashtable,
62 // and call erase(), without invalidating the iterator.
63 // To force the memory to be freed, call resize(0).
64 //
65 // 3) set_resizing_parameters(0.0, 0.8):
66 // Setting the shrink_resize_percent to 0.0 guarantees
67 // that the hash table will never shrink.
68 //
69 // Guide to what kind of hash_map to use:
70 // (1) dense_hash_map: fastest, uses the most memory
71 // (2) sparse_hash_map: slowest, uses the least memory
72 // (3) hash_map (STL): in the middle
73 // Typically I use sparse_hash_map when I care about space and/or when
74 // I need to save the hashtable on disk. I use hash_map otherwise. I
75 // don't personally use dense_hash_map ever; the only use of
76 // dense_hash_map I know of is to work around malloc() bugs in some
77 // systems (dense_hash_map has a particularly simple allocation scheme).
78 //
79 // - dense_hash_map has, typically, a factor of 2 memory overhead (if your
80 // data takes up X bytes, the hash_map uses X more bytes in overhead).
81 // - sparse_hash_map has about 2 bits overhead per entry.
82 // - sparse_hash_map can be 3-7 times slower than the others for lookup and,
83 // especially, inserts. See time_hash_map.cc for details.
84 //
85 // See /usr/(local/)?doc/sparsehash-0.1/dense_hash_map.html
86 // for information about how to use this class.
87
88 #ifndef _DENSE_HASH_MAP_H_
89 #define _DENSE_HASH_MAP_H_
90
91 #include <google/sparsehash/sparseconfig.h>
92 #include <stdio.h> // for FILE * in read()/write()
93 #include <algorithm> // for the default template args
94 #include <functional> // for equal_to
95 #include <memory> // for alloc<>
96 #include <utility> // for pair<>
97 #include HASH_FUN_H // defined in config.h
98 #include <google/sparsehash/densehashtable.h>
99
100
101 _START_GOOGLE_NAMESPACE_
102
103 using STL_NAMESPACE::pair;
104
105 template <class Key, class T,
106 class HashFcn = SPARSEHASH_HASH<Key>, // defined in sparseconfig.h
107 class EqualKey = STL_NAMESPACE::equal_to<Key>,
108 class Alloc = STL_NAMESPACE::allocator<T> >
109 class dense_hash_map {
110 private:
111 // Apparently select1st is not stl-standard, so we define our own
112 struct SelectKey {
113 const Key& operator()(const pair<const Key, T>& p) const {
114 return p.first;
115 }
116 };
117
118 // The actual data
119 typedef dense_hashtable<pair<const Key, T>, Key, HashFcn,
120 SelectKey, EqualKey, Alloc> ht;
121 ht rep;
122
123 public:
124 typedef typename ht::key_type key_type;
125 typedef T data_type;
126 typedef T mapped_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::pointer pointer;
134 typedef typename ht::const_pointer const_pointer;
135 typedef typename ht::reference reference;
136 typedef typename ht::const_reference const_reference;
137
138 typedef typename ht::iterator iterator;
139 typedef typename ht::const_iterator const_iterator;
140
141 // Iterator functions
142 iterator begin() { return rep.begin(); }
143 iterator end() { return rep.end(); }
144 const_iterator begin() const { return rep.begin(); }
145 const_iterator end() const { return rep.end(); }
146
147
148 // Accessor functions
149 hasher hash_funct() const { return rep.hash_funct(); }
150 key_equal key_eq() const { return rep.key_eq(); }
151
152
153 // Constructors
154 explicit dense_hash_map(size_type expected_max_items_in_table = 0,
155 const hasher& hf = hasher(),
156 const key_equal& eql = key_equal())
157 : rep(expected_max_items_in_table, hf, eql) { }
158
159 template <class InputIterator>
160 dense_hash_map(InputIterator f, InputIterator l,
161 size_type expected_max_items_in_table = 0,
162 const hasher& hf = hasher(),
163 const key_equal& eql = key_equal())
164 : rep(expected_max_items_in_table, hf, eql) {
165 rep.insert(f, l);
166 }
167 // We use the default copy constructor
168 // We use the default operator=()
169 // We use the default destructor
170
171 void clear() { rep.clear(); }
172 // This clears the hash map without resizing it down to the minimum
173 // bucket count, but rather keeps the number of buckets constant
174 void clear_no_resize() { rep.clear_no_resize(); }
175 void swap(dense_hash_map& hs) { rep.swap(hs.rep); }
176
177
178 // Functions concerning size
179 size_type size() const { return rep.size(); }
180 size_type max_size() const { return rep.max_size(); }
181 bool empty() const { return rep.empty(); }
182 size_type bucket_count() const { return rep.bucket_count(); }
183 size_type max_bucket_count() const { return rep.max_bucket_count(); }
184
185 void resize(size_type hint) { rep.resize(hint); }
186
187 void set_resizing_parameters(float shrink, float grow) {
188 return rep.set_resizing_parameters(shrink, grow);
189 }
190
191 // Lookup routines
192 iterator find(const key_type& key) { return rep.find(key); }
193 const_iterator find(const key_type& key) const { return rep.find(key); }
194
195 data_type& operator[](const key_type& key) { // This is our value-add!
196 iterator it = find(key);
197 if (it != end()) {
198 return it->second;
199 } else {
200 return insert(value_type(key, data_type())).first->second;
201 }
202 }
203
204 size_type count(const key_type& key) const { return rep.count(key); }
205
206 pair<iterator, iterator> equal_range(const key_type& key) {
207 return rep.equal_range(key);
208 }
209 pair<const_iterator, const_iterator> equal_range(const key_type& key) const {
210 return rep.equal_range(key);
211 }
212
213 // Insertion routines
214 pair<iterator, bool> insert(const value_type& obj) { return rep.insert(obj); }
215 template <class InputIterator>
216 void insert(InputIterator f, InputIterator l) { rep.insert(f, l); }
217 void insert(const_iterator f, const_iterator l) { rep.insert(f, l); }
218 // required for std::insert_iterator; the passed-in iterator is ignored
219 iterator insert(iterator, const value_type& obj) { return insert(obj).first; }
220
221
222 // Deletion and empty routines
223 // THESE ARE NON-STANDARD! I make you specify an "impossible" key
224 // value to identify deleted and empty buckets. You can change the
225 // deleted key as time goes on, or get rid of it entirely to be insert-only.
226 void set_empty_key(const key_type& key) { // YOU MUST CALL THIS!
227 rep.set_empty_key(value_type(key, data_type())); // rep wants a value
228 }
229 void set_deleted_key(const key_type& key) {
230 rep.set_deleted_key(value_type(key, data_type())); // rep wants a value
231 }
232 void clear_deleted_key() { rep.clear_deleted_key(); }
233
234 // These are standard
235 size_type erase(const key_type& key) { return rep.erase(key); }
236 void erase(iterator it) { rep.erase(it); }
237 void erase(iterator f, iterator l) { rep.erase(f, l); }
238
239
240 // Comparison
241 bool operator==(const dense_hash_map& hs) const { return rep == hs.rep; }
242 bool operator!=(const dense_hash_map& hs) const { return rep != hs.rep; }
243
244
245 // I/O -- this is an add-on for writing metainformation to disk
246 bool write_metadata(FILE *fp) { return rep.write_metadata(fp); }
247 bool read_metadata(FILE *fp) { return rep.read_metadata(fp); }
248 bool write_nopointer_data(FILE *fp) { return rep.write_nopointer_data(fp); }
249 bool read_nopointer_data(FILE *fp) { return rep.read_nopointer_data(fp); }
250 };
251
252 // We need a global swap as well
253 template <class Key, class T, class HashFcn, class EqualKey, class Alloc>
254 inline void swap(dense_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm1,
255 dense_hash_map<Key, T, HashFcn, EqualKey, Alloc>& hm2) {
256 hm1.swap(hm2);
257 }
258
259 _END_GOOGLE_NAMESPACE_
260
261 #endif /* _DENSE_HASH_MAP_H_ */

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