1 /** 2 * @file resource_pool.h 3 * 4 * @section LICENSE 5 * 6 * The MIT License 7 * 8 * @copyright Copyright (c) 2020-2021 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 defines a pool of resources that can be shared for example amongst 31 * threads. 32 */ 33 34 #ifndef RESOURCE_POOL_H 35 #define RESOURCE_POOL_H 36 37 namespace tiledb { 38 namespace sm { 39 40 template <class T, template <class> class P> 41 class ResourceHandle { 42 public: ResourceHandle(P<T> & p,unsigned int n)43 ResourceHandle(P<T>& p, unsigned int n) 44 : p_(p) 45 , n_(n) { 46 } 47 get()48 T& get() { 49 return p_.at(n_); 50 } 51 release()52 void release() { 53 p_.release(n_); 54 } 55 56 private: 57 /** The pool that issued this handle. */ 58 P<T>& p_; 59 60 /** The index of a vector within the pool to the resource. */ 61 unsigned int n_; 62 }; 63 64 /** 65 * @tparam T The resource type 66 * @tparam P Class P<T> provides instances of ResourceGuard<T> 67 */ 68 template <class T, template <class> class P> 69 class ResourceGuard { 70 public: 71 /** Constructor. */ ResourceGuard(P<T> & p)72 ResourceGuard(P<T>& p) 73 : h_(p.take()) { 74 } 75 76 /** Destructor. */ ~ResourceGuard()77 ~ResourceGuard() { 78 h_.release(); 79 } 80 81 /** Get the handle. */ get()82 T& get() { 83 return h_.get(); 84 } 85 86 private: 87 /** A resource handle from the provider. */ 88 typename P<T>::resource_handle h_; 89 }; 90 91 template <class T> 92 class ResourcePool { 93 public: 94 using resource_handle = ResourceHandle<T, tiledb::sm::ResourcePool>; 95 96 /** Constructor. */ ResourcePool(unsigned int n)97 ResourcePool(unsigned int n) 98 : resources_(n) 99 , unused_(n) 100 , unused_idx_(n - 1) { 101 for (unsigned int i = 0; i < n; i++) 102 unused_[i] = i; 103 } 104 105 /** Take a resource from the pool. */ take()106 resource_handle take() { 107 std::lock_guard x(m_); 108 if (unused_idx_ == -1) 109 throw std::runtime_error("Ran out of resources in resource pool"); 110 return ResourceHandle(*this, unused_[unused_idx_--]); 111 } 112 113 private: 114 /** Release a resource from the pool. */ release(unsigned int n)115 void release(unsigned int n) { 116 std::lock_guard x(m_); 117 unused_[++unused_idx_] = n; 118 } 119 120 /** Access a resource from the internal vector. */ at(unsigned int n)121 T& at(unsigned int n) { 122 return resources_.at(n); 123 } 124 125 /** Vector of resources. */ 126 std::vector<T> resources_; 127 128 /** Vector of unused resource indexes. */ 129 std::vector<unsigned int> unused_; 130 131 /** Index of the last valid resource in the unused vector. */ 132 int unused_idx_; 133 134 /** Mutex protecting unused_ and unused_idx_. */ 135 std::mutex m_; 136 137 friend class ResourceHandle<T, tiledb::sm::ResourcePool>; 138 }; 139 140 } // namespace sm 141 } // namespace tiledb 142 143 #endif // TILEDB_MULTI_THREADED_RESOURCE_PROVIDER_H