forked from OSchip/llvm-project
97 lines
2.6 KiB
C++
97 lines
2.6 KiB
C++
//===-- esan_circular_buffer.h ----------------------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of EfficiencySanitizer, a family of performance tuners.
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//
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// Circular buffer data structure.
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//===----------------------------------------------------------------------===//
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#include "sanitizer_common/sanitizer_common.h"
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namespace __esan {
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// A circular buffer for POD data whose memory is allocated using mmap.
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// There are two usage models: one is to use initialize/free (for global
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// instances) and the other is to use placement new with the
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// constructor and to call the destructor or free (they are equivalent).
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template<typename T>
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class CircularBuffer {
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public:
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// To support global instances we cannot initialize any field in the
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// default constructor.
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explicit CircularBuffer() {}
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CircularBuffer(uptr BufferCapacity) {
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initialize(BufferCapacity);
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WasConstructed = true;
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}
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~CircularBuffer() {
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if (WasConstructed) // Else caller will call free() explicitly.
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free();
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}
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void initialize(uptr BufferCapacity) {
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Capacity = BufferCapacity;
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// MmapOrDie rounds up to the page size for us.
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Data = (T *)MmapOrDie(Capacity * sizeof(T), "CircularBuffer");
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StartIdx = 0;
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Count = 0;
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WasConstructed = false;
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}
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void free() {
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UnmapOrDie(Data, Capacity * sizeof(T));
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}
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T &operator[](uptr Idx) {
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CHECK_LT(Idx, Count);
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uptr ArrayIdx = (StartIdx + Idx) % Capacity;
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return Data[ArrayIdx];
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}
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const T &operator[](uptr Idx) const {
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CHECK_LT(Idx, Count);
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uptr ArrayIdx = (StartIdx + Idx) % Capacity;
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return Data[ArrayIdx];
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}
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void push_back(const T &Item) {
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CHECK_GT(Capacity, 0);
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uptr ArrayIdx = (StartIdx + Count) % Capacity;
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Data[ArrayIdx] = Item;
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if (Count < Capacity)
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++Count;
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else
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StartIdx = (StartIdx + 1) % Capacity;
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}
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T &back() {
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CHECK_GT(Count, 0);
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uptr ArrayIdx = (StartIdx + Count - 1) % Capacity;
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return Data[ArrayIdx];
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}
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void pop_back() {
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CHECK_GT(Count, 0);
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--Count;
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}
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uptr size() const {
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return Count;
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}
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void clear() {
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StartIdx = 0;
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Count = 0;
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}
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bool empty() const { return size() == 0; }
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private:
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CircularBuffer(const CircularBuffer&);
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void operator=(const CircularBuffer&);
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bool WasConstructed;
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T *Data;
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uptr Capacity;
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uptr StartIdx;
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uptr Count;
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};
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} // namespace __esan
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