source: src/Common/PersistentMap.h@ 4b8b2a4

ADT ast-experimental
Last change on this file since 4b8b2a4 was 1febef62, checked in by Aaron Moss <a3moss@…>, 7 years ago

Fix gcc-7 errors in persistent map
  • Property mode set to 100644
File size: 7.5 KB
Line 
1//
2// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// PersistentMap.h --
8//
9// Author : Aaron B. Moss
10// Created On : Thu Mar 7 15:50:00 2019
11// Last Modified By : Aaron B. Moss
12// Last Modified On : Thu Mar 7 15:50:00 2019
13// Update Count : 1
14//
15
16#pragma once
17
18#include <cassert> // for assertf
19#include <cstddef> // for size_t
20#include <functional> // for hash, equal_to
21#include <memory> // for shared_ptr, enable_shared_from_this, make_shared
22#include <unordered_map> // for unordered_map
23#include <utility> // for forward, move
24
25/// Wraps a hash table in a persistent data structure, using a technique based
26/// on the persistent array in Conchon & Filliatre "A Persistent Union-Find
27/// Data Structure"
28
29template<typename Key, typename Val,
30 typename Hash = std::hash<Key>, typename Eq = std::equal_to<Key>>
31class PersistentMap
32 : public std::enable_shared_from_this<PersistentMap<Key, Val, Hash, Eq>> {
33public:
34 /// Type of this class
35 using Self = PersistentMap<Key, Val, Hash, Eq>;
36 /// Type of pointer to this class
37 using Ptr = std::shared_ptr<Self>;
38
39 /// Types of version nodes
40 enum Mode {
41 BASE, ///< Root node of version tree
42 REM, ///< Key removal node
43 INS, ///< Key update node
44 UPD ///< Key update node
45 };
46
47private:
48 using Base = std::unordered_map<Key, Val, Hash, Eq>;
49
50 /// Insertion/update node
51 struct Ins {
52 Ptr base; ///< Modified map
53 Key key; ///< Key inserted
54 Val val; ///< Value stored
55
56 template<typename P, typename K, typename V>
57 Ins(P&& p, K&& k, V&& v)
58 : base(std::forward<P>(p)), key(std::forward<K>(k)), val(std::forward<V>(v)) {}
59 };
60
61 /// Removal node
62 struct Rem {
63 Ptr base; ///< Modified map
64 Key key; ///< Key removed
65
66 template<typename P, typename K>
67 Rem(P&& p, K&& k) : base(std::forward<P>(p)), key(std::forward<K>(k)) {}
68 };
69
70 /// Underlying storage
71 union Data {
72 char def;
73 Base base;
74 Ins ins;
75 Rem rem;
76
77 Data() : def('\0') {}
78 ~Data() {}
79 } data;
80
81 /// Type of node
82 mutable Mode mode;
83
84 /// get mutable reference as T
85 template<typename T>
86 T& as() { return reinterpret_cast<T&>(data); }
87
88 /// get const reference as T
89 template<typename T>
90 const T& as() const { return reinterpret_cast<const T&>(data); }
91
92 /// get rvalue reference as T
93 template<typename T>
94 T&& take_as() { return std::move(as<T>()); }
95
96 /// initialize as T
97 template<typename T, typename... Args>
98 void init( Args&&... args ) {
99 new( &as<T>() ) T { std::forward<Args>(args)... };
100 }
101
102 /// reset as current mode
103 void reset() {
104 switch( mode ) {
105 case BASE: as<Base>().~Base(); break;
106 case REM: as<Rem>().~Rem(); break;
107 case INS: case UPD: as<Ins>().~Ins(); break;
108 }
109 }
110
111 /// reset as base
112 void reset_as_base() {
113 as<Base>().~Base();
114 }
115
116public:
117 using key_type = typename Base::key_type;
118 using mapped_type = typename Base::mapped_type;
119 using value_type = typename Base::value_type;
120 using size_type = typename Base::size_type;
121 using difference_type = typename Base::difference_type;
122 using iterator = typename Base::const_iterator;
123
124 PersistentMap() : data(), mode(BASE) { init<Base>(); }
125
126 PersistentMap( Base&& b ) : data(), mode(BASE) { init<Base>(std::move(b)); }
127
128 PersistentMap( const Self& o ) = delete;
129
130 Self& operator= ( const Self& o ) = delete;
131
132 ~PersistentMap() { reset(); }
133
134 /// Create a pointer to a new, empty persistent map
135 static Ptr new_ptr() { return std::make_shared<Self>(); }
136
137 /// reroot persistent map at current node
138 void reroot() const {
139 // recursive base case
140 if ( mode == BASE ) return;
141
142 // reroot base
143 Self* mut_this = const_cast<Self*>(this);
144 Ptr base = ( mode == REM ) ? mut_this->as<Rem>().base : mut_this->as<Ins>().base;
145 base->reroot();
146
147 // remove map from base
148 Base base_map = base->template take_as<Base>();
149 base->reset_as_base();
150
151 // switch base to inverse of self and mutate base map
152 switch ( mode ) {
153 case REM: {
154 Rem& self = mut_this->as<Rem>();
155 auto it = base_map.find( self.key );
156
157 base->template init<Ins>(
158 mut_this->shared_from_this(), std::move(self.key), std::move(it->second) );
159 base->mode = INS;
160
161 base_map.erase( it );
162 break;
163 }
164 case INS: {
165 Ins& self = mut_this->as<Ins>();
166
167 base->template init<Rem>( mut_this->shared_from_this(), self.key );
168 base->mode = REM;
169
170 base_map.emplace( std::move(self.key), std::move(self.val) );
171 break;
172 }
173 case UPD: {
174 Ins& self = mut_this->as<Ins>();
175 auto it = base_map.find( self.key );
176
177 base->template init<Ins>(
178 mut_this->shared_from_this(), std::move(self.key), std::move(it->second) );
179 base->mode = UPD;
180
181 it->second = std::move(self.val);
182 break;
183 }
184 case BASE: assertf(false, "unreachable"); break;
185 }
186
187 // set base map into self
188 mut_this->reset();
189 mut_this->init<Base>( std::move(base_map) );
190 mode = BASE;
191 }
192
193private:
194 /// the base after rerooting at the current node
195 const Base& rerooted() const {
196 reroot();
197 return as<Base>();
198 }
199
200public:
201 /// true iff the map is empty
202 bool empty() const { return rerooted().empty(); }
203
204 /// number of entries in map
205 size_type size() const { return rerooted().size(); }
206
207 /// begin iterator for map; may be invalidated by calls to non-iteration functions
208 /// or functions on other maps in the same tree
209 iterator begin() const { return rerooted().begin(); }
210
211 /// end iterator for map; may be invalidated by calls to non-iteration functions
212 /// or functions on other maps in the same tree
213 iterator end() const { return rerooted().end(); }
214
215 /// underlying map iterator for value
216 iterator find(const Key& k) const { return rerooted().find( k ); }
217
218 /// check if value is present
219 size_type count(const Key& k) const { return rerooted().count( k ); }
220
221 /// get value; undefined behaviour if not present
222 const Val& get(const Key& k) const {
223 const Base& self = rerooted();
224 auto it = self.find( k );
225 return it->second;
226 }
227
228 /// get value; returns default if not present
229 template<typename V>
230 Val get_or_default(const Key& k, V&& d) const {
231 const Base& self = rerooted();
232 auto it = self.find( k );
233 if ( it == self.end() ) return d;
234 else return it->second;
235 }
236
237 /// set value, storing new map in output variable
238 template<typename K, typename V>
239 Ptr set(K&& k, V&& v) {
240 reroot();
241
242 // transfer map to new node
243 Ptr ret = std::make_shared<Self>( take_as<Base>() );
244 reset_as_base();
245 Base& base_map = ret->template as<Base>();
246
247 // check if this is update or insert
248 auto it = base_map.find( k );
249 if ( it == base_map.end() ) {
250 // set self to REM node and insert into base
251 init<Rem>( ret, k );
252 mode = REM;
253
254 base_map.emplace_hint( it, std::forward<K>(k), std::forward<V>(v) );
255 } else {
256 // set self to UPD node and modify base
257 init<Ins>( ret, std::forward<K>(k), std::move(it->second) );
258 mode = UPD;
259
260 it->second = std::forward<V>(v);
261 }
262
263 return ret;
264 }
265
266 /// remove value, storing new map in output variable; does nothing if key not in map
267 Ptr erase(const Key& k) {
268 reroot();
269
270 // exit early if key does not exist in map
271 if ( ! as<Base>().count( k ) ) return this->shared_from_this();
272
273 // transfer map to new node
274 Ptr ret = std::make_shared<Self>( take_as<Base>() );
275 reset_as_base();
276 Base& base_map = ret->template as<Base>();
277
278 // set self to INS node and remove from base
279 init<Ins>( ret, k, base_map[k] );
280 mode = INS;
281
282 base_map.erase( k );
283
284 return ret;
285 }
286};
287
288// Local Variables: //
289// tab-width: 4 //
290// mode: c++ //
291// compile-command: "make install" //
292// End: //
Note: See TracBrowser for help on using the repository browser.