summaryrefslogtreecommitdiffstats
path: root/client/shared_cache.hpp
blob: 450116c59ff74c67a6a6cf68fcdc81132e5d4979 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
/*
   Copyright (C) 2009 Red Hat, Inc.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#ifndef _H_SHARED_CACHE
#define _H_SHARED_CACHE

#include "utils.h"
#include "threads.h"

/*class SharedCache::Treat {
    T* get(T*);
    void release(T*);
    const char* name();
};*/

template <class T, class Treat, int HASH_SIZE, class Base = EmptyBase>
class SharedCache : public Base {
public:
    SharedCache()
        : _aborting (false)
    {
        memset(_hash, 0, sizeof(_hash));
    }

    ~SharedCache()
    {
        clear();
    }

    void add(uint64_t id, T* data, bool is_lossy = FALSE)
    {
        Lock lock(_lock);
        Item** item = &_hash[key(id)];

        while (*item) {
            if ((*item)->id == id) {
                (*item)->refs++;
                return;
            }
            item = &(*item)->next;
        }
        *item = new Item(id, data, is_lossy);
        _new_item_cond.notify_all();
    }

    T* get(uint64_t id)
    {
        Lock lock(_lock);
        Item* item = _hash[key(id)];

        for (;;) {
            if (!item) {
                if (_aborting) {
                    THROW("%s aborting", Treat::name());
                }
                _new_item_cond.wait(lock);
                item = _hash[key(id)];
                continue;
            }

            if (item->id != id) {
                item = item->next;
                continue;
            }

            return Treat::get(item->data);
        }
    }

    T* get_lossless(uint64_t id)
    {
        Lock lock(_lock);
        Item* item = _hash[key(id)];

        for (;;) {
            if (!item) {
                if (_aborting) {
                    THROW("%s aborting", Treat::name());
                }
                _new_item_cond.wait(lock);
                item = _hash[key(id)];
                continue;
            }

            if (item->id != id) {
                item = item->next;
                continue;
            }
            break;
        }

        // item has been retreived. Now checking if lossless
        for (;;) {
            if (item->lossy) {
                if (_aborting) {
                    THROW("%s aborting", Treat::name());
                }
                _replace_data_cond.wait(lock);
                continue;
            }

            return Treat::get(item->data);
        }
    }

    void replace(uint64_t id, T* data, bool is_lossy = FALSE)
    {
        Lock lock(_lock);
        Item* item = _hash[key(id)];

        for (;;) {
            if (!item) {
                if (_aborting) {
                    THROW("%s aborting", Treat::name());
                }
                _new_item_cond.wait(lock);
                item = _hash[key(id)];
                continue;
            }

            if (item->id != id) {
                item = item->next;
                continue;
            }

            item->replace(data, is_lossy);
            break;
        }
        _replace_data_cond.notify_all();
    }

    void remove(uint64_t id)
    {
        Lock lock(_lock);
        Item** item = &_hash[key(id)];

        while (*item) {
            if ((*item)->id == id) {
                if (!--(*item)->refs) {
                    Item *rm_item = *item;
                    *item = rm_item->next;
                    delete rm_item;
                }
                return;
            }
            item = &(*item)->next;
        }
        THROW("%s id %" PRIu64 ", not found", Treat::name(), id);
    }

    void clear()
    {
        Lock lock(_lock);
        for (int i = 0; i < HASH_SIZE; i++) {
            while (_hash[i]) {
                Item *item = _hash[i];
                _hash[i] = item->next;
                delete item;
            }
        }
    }

    void abort()
    {
        Lock lock(_lock);
        _aborting = true;
        _new_item_cond.notify_all();
    }

private:
    inline uint32_t key(uint64_t id) {return uint32_t(id) % HASH_SIZE;}

private:
    class Item {
    public:
        Item(uint64_t in_id, T* data, bool is_lossy = FALSE)
            : id (in_id)
            , refs (1)
            , next (NULL)
            , data (Treat::get(data))
            , lossy (is_lossy) {}

        ~Item()
        {
            Treat::release(data);
        }

        void replace(T* new_data, bool is_lossy = FALSE)
        {
            Treat::release(data);
            data = Treat::get(new_data);
            lossy = is_lossy;
        }

        uint64_t id;
        int refs;
        Item* next;
        T* data;
        bool lossy;
    };

    Item* _hash[HASH_SIZE];
    Mutex _lock;
    Condition _new_item_cond;
    Condition _replace_data_cond;
    bool _aborting;
};

#endif