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1 | //===-- esan_circular_buffer.h ----------------------------------*- C++ -*-===// |
2 | // | |
3 | // The LLVM Compiler Infrastructure | |
4 | // | |
5 | // This file is distributed under the University of Illinois Open Source | |
6 | // License. See LICENSE.TXT for details. | |
7 | // | |
8 | //===----------------------------------------------------------------------===// | |
9 | // | |
10 | // This file is a part of EfficiencySanitizer, a family of performance tuners. | |
11 | // | |
12 | // Circular buffer data structure. | |
13 | //===----------------------------------------------------------------------===// | |
14 | ||
15 | #include "sanitizer_common/sanitizer_common.h" | |
16 | ||
17 | namespace __esan { | |
18 | ||
19 | // A circular buffer for POD data whose memory is allocated using mmap. | |
20 | // There are two usage models: one is to use initialize/free (for global | |
21 | // instances) and the other is to use placement new with the | |
22 | // constructor and to call the destructor or free (they are equivalent). | |
23 | template<typename T> | |
24 | class CircularBuffer { | |
25 | public: | |
26 | // To support global instances we cannot initialize any field in the | |
27 | // default constructor. | |
28 | explicit CircularBuffer() {} | |
29 | CircularBuffer(uptr BufferCapacity) { | |
30 | initialize(BufferCapacity); | |
31 | WasConstructed = true; | |
32 | } | |
33 | ~CircularBuffer() { | |
34 | if (WasConstructed) // Else caller will call free() explicitly. | |
35 | free(); | |
36 | } | |
37 | void initialize(uptr BufferCapacity) { | |
38 | Capacity = BufferCapacity; | |
39 | // MmapOrDie rounds up to the page size for us. | |
40 | Data = (T *)MmapOrDie(Capacity * sizeof(T), "CircularBuffer"); | |
41 | StartIdx = 0; | |
42 | Count = 0; | |
43 | WasConstructed = false; | |
44 | } | |
45 | void free() { | |
46 | UnmapOrDie(Data, Capacity * sizeof(T)); | |
47 | } | |
48 | T &operator[](uptr Idx) { | |
49 | CHECK_LT(Idx, Count); | |
50 | uptr ArrayIdx = (StartIdx + Idx) % Capacity; | |
51 | return Data[ArrayIdx]; | |
52 | } | |
53 | const T &operator[](uptr Idx) const { | |
54 | CHECK_LT(Idx, Count); | |
55 | uptr ArrayIdx = (StartIdx + Idx) % Capacity; | |
56 | return Data[ArrayIdx]; | |
57 | } | |
58 | void push_back(const T &Item) { | |
59 | CHECK_GT(Capacity, 0); | |
60 | uptr ArrayIdx = (StartIdx + Count) % Capacity; | |
61 | Data[ArrayIdx] = Item; | |
62 | if (Count < Capacity) | |
63 | ++Count; | |
64 | else | |
65 | StartIdx = (StartIdx + 1) % Capacity; | |
66 | } | |
67 | T &back() { | |
68 | CHECK_GT(Count, 0); | |
69 | uptr ArrayIdx = (StartIdx + Count - 1) % Capacity; | |
70 | return Data[ArrayIdx]; | |
71 | } | |
72 | void pop_back() { | |
73 | CHECK_GT(Count, 0); | |
74 | --Count; | |
75 | } | |
76 | uptr size() const { | |
77 | return Count; | |
78 | } | |
79 | void clear() { | |
80 | StartIdx = 0; | |
81 | Count = 0; | |
82 | } | |
83 | bool empty() const { return size() == 0; } | |
84 | ||
85 | private: | |
86 | CircularBuffer(const CircularBuffer&); | |
87 | void operator=(const CircularBuffer&); | |
88 | ||
89 | bool WasConstructed; | |
90 | T *Data; | |
91 | uptr Capacity; | |
92 | uptr StartIdx; | |
93 | uptr Count; | |
94 | }; | |
95 | ||
96 | } // namespace __esan |