| //===-- sanitizer_ring_buffer.h ---------------------------------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // Simple ring buffer. |
| // |
| //===----------------------------------------------------------------------===// |
| #ifndef SANITIZER_RING_BUFFER_H |
| #define SANITIZER_RING_BUFFER_H |
| |
| #include "sanitizer_common.h" |
| |
| namespace __sanitizer { |
| // RingBuffer<T>: fixed-size ring buffer optimized for speed of push(). |
| // T should be a POD type and sizeof(T) should be divisible by sizeof(void*). |
| // At creation, all elements are zero. |
| template<class T> |
| class RingBuffer { |
| public: |
| COMPILER_CHECK(sizeof(T) % sizeof(void *) == 0); |
| static RingBuffer *New(uptr Size) { |
| void *Ptr = MmapOrDie(SizeInBytes(Size), "RingBuffer"); |
| RingBuffer *RB = reinterpret_cast<RingBuffer*>(Ptr); |
| uptr End = reinterpret_cast<uptr>(Ptr) + SizeInBytes(Size); |
| RB->last_ = RB->next_ = reinterpret_cast<T*>(End - sizeof(T)); |
| return RB; |
| } |
| void Delete() { |
| UnmapOrDie(this, SizeInBytes(size())); |
| } |
| uptr size() const { |
| return last_ + 1 - |
| reinterpret_cast<T *>(reinterpret_cast<uptr>(this) + |
| 2 * sizeof(T *)); |
| } |
| |
| static uptr SizeInBytes(uptr Size) { |
| return Size * sizeof(T) + 2 * sizeof(T*); |
| } |
| |
| uptr SizeInBytes() { return SizeInBytes(size()); } |
| |
| void push(T t) { |
| *next_ = t; |
| next_--; |
| // The condition below works only if sizeof(T) is divisible by sizeof(T*). |
| if (next_ <= reinterpret_cast<T*>(&next_)) |
| next_ = last_; |
| } |
| |
| T operator[](uptr Idx) const { |
| CHECK_LT(Idx, size()); |
| sptr IdxNext = Idx + 1; |
| if (IdxNext > last_ - next_) |
| IdxNext -= size(); |
| return next_[IdxNext]; |
| } |
| |
| private: |
| RingBuffer() {} |
| ~RingBuffer() {} |
| RingBuffer(const RingBuffer&) = delete; |
| |
| // Data layout: |
| // LNDDDDDDDD |
| // D: data elements. |
| // L: last_, always points to the last data element. |
| // N: next_, initially equals to last_, is decremented on every push, |
| // wraps around if it's less or equal than its own address. |
| |
| T *last_; |
| T *next_; |
| T data_[1]; // flexible array. |
| }; |
| |
| } // namespace __sanitizer |
| |
| #endif // SANITIZER_RING_BUFFER_H |