1 /**
2  * @file   unique_rwlock.h
3  *
4  * @section LICENSE
5  *
6  * The MIT License
7  *
8  * @copyright Copyright (c) 2021 TileDB, Inc.
9  *
10  * Permission is hereby granted, free of charge, to any person obtaining a copy
11  * of this software and associated documentation files (the "Software"), to deal
12  * in the Software without restriction, including without limitation the rights
13  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
14  * copies of the Software, and to permit persons to whom the Software is
15  * furnished to do so, subject to the following conditions:
16  *
17  * The above copyright notice and this permission notice shall be included in
18  * all copies or substantial portions of the Software.
19  *
20  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
23  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
24  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
25  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
26  * THE SOFTWARE.
27  *
28  * @section DESCRIPTION
29  *
30  * This file defines and implements the UniqueRWLock<R> class and
31  * type-defintions for UniqueReadLock and UniqueWriteLock.
32  */
33 
34 #ifndef TILEDB_UNIQUE_RWLOCK_H
35 #define TILEDB_UNIQUE_RWLOCK_H
36 
37 #include "tiledb/common/macros.h"
38 #include "tiledb/common/rwlock.h"
39 
40 namespace tiledb {
41 namespace common {
42 
43 template <bool R>
44 class UniqueRWLock final {
45  public:
46   /* ********************************* */
47   /*     CONSTRUCTORS & DESTRUCTORS    */
48   /* ********************************* */
49 
50   /*
51    * Value constructor. Locks `rwlock` and releases
52    * it in the destructor. If template-type `R` is
53    * true, this class performs read-locking. Otherwise,
54    * this performs write-locking.
55    *
56    * @param rwlock the read-write lock.
57    */
UniqueRWLock(RWLock * const rwlock)58   explicit UniqueRWLock(RWLock* const rwlock)
59       : rwlock_(rwlock)
60       , locked_(false) {
61     assert(rwlock_);
62 
63     lock();
64   }
65 
66   /** Destructor. Releases the read-write lock. */
~UniqueRWLock()67   ~UniqueRWLock() {
68     if (locked_)
69       unlock();
70   }
71 
72   DISABLE_COPY_AND_COPY_ASSIGN(UniqueRWLock);
73   DISABLE_MOVE_AND_MOVE_ASSIGN(UniqueRWLock);
74 
75   /* ********************************* */
76   /*                API                */
77   /* ********************************* */
78 
79   /** Acquires the read-write lock. */
lock()80   void lock() {
81     assert(!locked_);
82 
83     if (R)
84       rwlock_->read_lock();
85     else
86       rwlock_->write_lock();
87 
88     locked_ = true;
89   }
90 
91   /** Releases the read-write lock. */
unlock()92   void unlock() {
93     assert(locked_);
94 
95     if (R)
96       rwlock_->read_unlock();
97     else
98       rwlock_->write_unlock();
99 
100     locked_ = false;
101   }
102 
103  private:
104   /* ********************************* */
105   /*         PRIVATE ATTRIBUTES        */
106   /* ********************************* */
107 
108   /** The read-write lock. */
109   RWLock* const rwlock_;
110 
111   /** True if holding a lock on `rwlock_`. */
112   bool locked_;
113 };
114 
115 // Type-define UniqueReadLock and UniqueWriteLock.
116 using UniqueReadLock = UniqueRWLock<true>;
117 using UniqueWriteLock = UniqueRWLock<false>;
118 
119 }  // namespace common
120 }  // namespace tiledb
121 
122 #endif  // TILEDB_UNIQUE_RWLOCK_H
123