1 /*
2  * Copyright (C) 2017 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef SRC_TRACING_CORE_ID_ALLOCATOR_H_
18 #define SRC_TRACING_CORE_ID_ALLOCATOR_H_
19 
20 #include <stdint.h>
21 
22 #include <type_traits>
23 #include <vector>
24 
25 namespace perfetto {
26 
27 // Handles assigment of IDs (int types) from a fixed-size pool.
28 // Zero is not considered a valid ID.
29 // The base class takes always a uint32_t and the derived class casts and checks
30 // bounds at compile time. This is to avoid bloating code with different
31 // instances of the main class for each size.
32 class IdAllocatorGeneric {
33  public:
34   // |max_id| is inclusive.
35   explicit IdAllocatorGeneric(uint32_t max_id);
36   ~IdAllocatorGeneric();
37 
38   // Returns an ID in the range [1, max_id] or 0 if no more ids are available.
39   uint32_t AllocateGeneric();
40   void FreeGeneric(uint32_t);
41 
42   bool IsEmpty() const;
43 
44  private:
45   IdAllocatorGeneric(const IdAllocatorGeneric&) = delete;
46   IdAllocatorGeneric& operator=(const IdAllocatorGeneric&) = delete;
47 
48   const uint32_t max_id_;
49   uint32_t last_id_ = 0;
50   std::vector<bool> ids_;
51 };
52 
53 template <typename T = uint32_t>
54 class IdAllocator : public IdAllocatorGeneric {
55  public:
IdAllocator(T end)56   explicit IdAllocator(T end) : IdAllocatorGeneric(end) {
57     static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value,
58                   "T must be an unsigned integer");
59     static_assert(sizeof(T) <= sizeof(uint32_t), "T is too big");
60   }
61 
Allocate()62   T Allocate() { return static_cast<T>(AllocateGeneric()); }
Free(T id)63   void Free(T id) { FreeGeneric(id); }
64 };
65 
66 }  // namespace perfetto
67 
68 #endif  // SRC_TRACING_CORE_ID_ALLOCATOR_H_
69