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LimitedHandleResource.h
1 /*----------------------------------------------------------------------------*/
2 /* Copyright (c) FIRST 2016-2017. All Rights Reserved. */
3 /* Open Source Software - may be modified and shared by FRC teams. The code */
4 /* must be accompanied by the FIRST BSD license file in the root directory of */
5 /* the project. */
6 /*----------------------------------------------------------------------------*/
7 
8 #pragma once
9 
10 #include <stdint.h>
11 
12 #include <array>
13 #include <memory>
14 
15 #include "HAL/Types.h"
16 #include "HAL/cpp/make_unique.h"
17 #include "HAL/cpp/priority_mutex.h"
18 #include "HandlesInternal.h"
19 
20 namespace hal {
21 
32 template <typename THandle, typename TStruct, int16_t size,
33  HAL_HandleEnum enumValue>
35  friend class LimitedHandleResourceTest;
36 
37  public:
38  LimitedHandleResource() = default;
40  LimitedHandleResource& operator=(const LimitedHandleResource&) = delete;
41 
42  THandle Allocate();
43  std::shared_ptr<TStruct> Get(THandle handle);
44  void Free(THandle handle);
45 
46  private:
47  std::array<std::shared_ptr<TStruct>, size> m_structures;
48  std::array<priority_mutex, size> m_handleMutexes;
49  priority_mutex m_allocateMutex;
50 };
51 
52 template <typename THandle, typename TStruct, int16_t size,
53  HAL_HandleEnum enumValue>
55  // globally lock to loop through indices
56  std::lock_guard<priority_mutex> sync(m_allocateMutex);
57  int16_t i;
58  for (i = 0; i < size; i++) {
59  if (m_structures[i] == nullptr) {
60  // if a false index is found, grab its specific mutex
61  // and allocate it.
62  std::lock_guard<priority_mutex> sync(m_handleMutexes[i]);
63  m_structures[i] = std::make_shared<TStruct>();
64  return static_cast<THandle>(createHandle(i, enumValue));
65  }
66  }
67  return HAL_kInvalidHandle;
68 }
69 
70 template <typename THandle, typename TStruct, int16_t size,
71  HAL_HandleEnum enumValue>
72 std::shared_ptr<TStruct>
73 LimitedHandleResource<THandle, TStruct, size, enumValue>::Get(THandle handle) {
74  // get handle index, and fail early if index out of range or wrong handle
75  int16_t index = getHandleTypedIndex(handle, enumValue);
76  if (index < 0 || index >= size) {
77  return nullptr;
78  }
79  std::lock_guard<priority_mutex> sync(m_handleMutexes[index]);
80  // return structure. Null will propogate correctly, so no need to manually
81  // check.
82  return m_structures[index];
83 }
84 
85 template <typename THandle, typename TStruct, int16_t size,
86  HAL_HandleEnum enumValue>
87 void LimitedHandleResource<THandle, TStruct, size, enumValue>::Free(
88  THandle handle) {
89  // get handle index, and fail early if index out of range or wrong handle
90  int16_t index = getHandleTypedIndex(handle, enumValue);
91  if (index < 0 || index >= size) return;
92  // lock and deallocated handle
93  std::lock_guard<priority_mutex> sync(m_allocateMutex);
94  std::lock_guard<priority_mutex> lock(m_handleMutexes[index]);
95  m_structures[index].reset();
96 }
97 } // namespace hal
The LimitedHandleResource class is a way to track handles.
Definition: LimitedHandleResource.h:34
Definition: priority_mutex.h:53