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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ANDROID_SERVICE_UTILS_RING_BUFFER_H
#define ANDROID_SERVICE_UTILS_RING_BUFFER_H
#include <utils/Log.h>
#include <cutils/compiler.h>
#include <iterator>
#include <utility>
#include <vector>
namespace android {
/**
* A RingBuffer class that maintains an array of objects that can grow up to a certain size.
* Elements added to the RingBuffer are inserted in the logical front of the buffer, and
* invalidate all current iterators for that RingBuffer object.
*/
template <class T>
class RingBuffer final {
public:
/**
* Construct a RingBuffer that can grow up to the given length.
*/
RingBuffer(size_t length);
/**
* Forward iterator to this class. Implements an std:forward_iterator.
*/
class iterator : public std::iterator<std::forward_iterator_tag, T> {
public:
iterator(T* ptr, size_t size, size_t pos, size_t ctr);
iterator& operator++();
iterator operator++(int);
bool operator==(const iterator& rhs);
bool operator!=(const iterator& rhs);
T& operator*();
T* operator->();
private:
T* mPtr;
size_t mSize;
size_t mPos;
size_t mCtr;
};
/**
* Constant forward iterator to this class. Implements an std:forward_iterator.
*/
class const_iterator : public std::iterator<std::forward_iterator_tag, T> {
public:
const_iterator(const T* ptr, size_t size, size_t pos, size_t ctr);
const_iterator& operator++();
const_iterator operator++(int);
bool operator==(const const_iterator& rhs);
bool operator!=(const const_iterator& rhs);
const T& operator*();
const T* operator->();
private:
const T* mPtr;
size_t mSize;
size_t mPos;
size_t mCtr;
};
/**
* Adds item to the front of this RingBuffer. If the RingBuffer is at its maximum length,
* this will result in the last element being replaced (this is done using the element's
* assignment operator).
*
* All current iterators are invalidated.
*/
void add(const T& item);
/**
* Moves item to the front of this RingBuffer. Following a call to this, item should no
* longer be used. If the RingBuffer is at its maximum length, this will result in the
* last element being replaced (this is done using the element's assignment operator).
*
* All current iterators are invalidated.
*/
void add(T&& item);
/**
* Construct item in-place in the front of this RingBuffer using the given arguments. If
* the RingBuffer is at its maximum length, this will result in the last element being
* replaced (this is done using the element's assignment operator).
*
* All current iterators are invalidated.
*/
template <class... Args>
void emplace(Args&&... args);
/**
* Get an iterator to the front of this RingBuffer.
*/
iterator begin();
/**
* Get an iterator to the end of this RingBuffer.
*/
iterator end();
/**
* Get a const_iterator to the front of this RingBuffer.
*/
const_iterator begin() const;
/**
* Get a const_iterator to the end of this RingBuffer.
*/
const_iterator end() const;
/**
* Return a reference to the element at a given index. If the index is out of range for
* this ringbuffer, [0, size), the behavior for this is undefined.
*/
T& operator[](size_t index);
/**
* Return a const reference to the element at a given index. If the index is out of range
* for this ringbuffer, [0, size), the behavior for this is undefined.
*/
const T& operator[](size_t index) const;
/**
* Return the current size of this RingBuffer.
*/
size_t size() const;
/**
* Remove all elements from this RingBuffer and set the size to 0.
*/
void clear();
private:
size_t mFrontIdx;
size_t mMaxBufferSize;
std::vector<T> mBuffer;
}; // class RingBuffer
template <class T>
RingBuffer<T>::RingBuffer(size_t length) : mFrontIdx{0}, mMaxBufferSize{length} {}
template <class T>
RingBuffer<T>::iterator::iterator(T* ptr, size_t size, size_t pos, size_t ctr) :
mPtr{ptr}, mSize{size}, mPos{pos}, mCtr{ctr} {}
template <class T>
typename RingBuffer<T>::iterator& RingBuffer<T>::iterator::operator++() {
++mCtr;
if (CC_UNLIKELY(mCtr == mSize)) {
mPos = mSize;
return *this;
}
mPos = ((CC_UNLIKELY(mPos == 0)) ? mSize - 1 : mPos - 1);
return *this;
}
template <class T>
typename RingBuffer<T>::iterator RingBuffer<T>::iterator::operator++(int) {
iterator tmp{mPtr, mSize, mPos, mCtr};
++(*this);
return tmp;
}
template <class T>
bool RingBuffer<T>::iterator::operator==(const iterator& rhs) {
return (mPtr + mPos) == (rhs.mPtr + rhs.mPos);
}
template <class T>
bool RingBuffer<T>::iterator::operator!=(const iterator& rhs) {
return (mPtr + mPos) != (rhs.mPtr + rhs.mPos);
}
template <class T>
T& RingBuffer<T>::iterator::operator*() {
return *(mPtr + mPos);
}
template <class T>
T* RingBuffer<T>::iterator::operator->() {
return mPtr + mPos;
}
template <class T>
RingBuffer<T>::const_iterator::const_iterator(const T* ptr, size_t size, size_t pos, size_t ctr) :
mPtr{ptr}, mSize{size}, mPos{pos}, mCtr{ctr} {}
template <class T>
typename RingBuffer<T>::const_iterator& RingBuffer<T>::const_iterator::operator++() {
++mCtr;
if (CC_UNLIKELY(mCtr == mSize)) {
mPos = mSize;
return *this;
}
mPos = ((CC_UNLIKELY(mPos == 0)) ? mSize - 1 : mPos - 1);
return *this;
}
template <class T>
typename RingBuffer<T>::const_iterator RingBuffer<T>::const_iterator::operator++(int) {
const_iterator tmp{mPtr, mSize, mPos, mCtr};
++(*this);
return tmp;
}
template <class T>
bool RingBuffer<T>::const_iterator::operator==(const const_iterator& rhs) {
return (mPtr + mPos) == (rhs.mPtr + rhs.mPos);
}
template <class T>
bool RingBuffer<T>::const_iterator::operator!=(const const_iterator& rhs) {
return (mPtr + mPos) != (rhs.mPtr + rhs.mPos);
}
template <class T>
const T& RingBuffer<T>::const_iterator::operator*() {
return *(mPtr + mPos);
}
template <class T>
const T* RingBuffer<T>::const_iterator::operator->() {
return mPtr + mPos;
}
template <class T>
void RingBuffer<T>::add(const T& item) {
if (mBuffer.size() < mMaxBufferSize) {
mBuffer.push_back(item);
mFrontIdx = ((mFrontIdx + 1) % mMaxBufferSize);
return;
}
mBuffer[mFrontIdx] = item;
mFrontIdx = ((mFrontIdx + 1) % mMaxBufferSize);
}
template <class T>
void RingBuffer<T>::add(T&& item) {
if (mBuffer.size() != mMaxBufferSize) {
mBuffer.push_back(std::forward<T>(item));
mFrontIdx = ((mFrontIdx + 1) % mMaxBufferSize);
return;
}
// Only works for types with move assignment operator
mBuffer[mFrontIdx] = std::forward<T>(item);
mFrontIdx = ((mFrontIdx + 1) % mMaxBufferSize);
}
template <class T>
template <class... Args>
void RingBuffer<T>::emplace(Args&&... args) {
if (mBuffer.size() != mMaxBufferSize) {
mBuffer.emplace_back(std::forward<Args>(args)...);
mFrontIdx = ((mFrontIdx + 1) % mMaxBufferSize);
return;
}
// Only works for types with move assignment operator
mBuffer[mFrontIdx] = T(std::forward<Args>(args)...);
mFrontIdx = ((mFrontIdx + 1) % mMaxBufferSize);
}
template <class T>
typename RingBuffer<T>::iterator RingBuffer<T>::begin() {
size_t tmp = (mBuffer.size() == 0) ? 0 : mBuffer.size() - 1;
return iterator(mBuffer.data(), mBuffer.size(), (mFrontIdx == 0) ? tmp : mFrontIdx - 1, 0);
}
template <class T>
typename RingBuffer<T>::iterator RingBuffer<T>::end() {
size_t s = mBuffer.size();
return iterator(mBuffer.data(), s, s, s);
}
template <class T>
typename RingBuffer<T>::const_iterator RingBuffer<T>::begin() const {
size_t tmp = (mBuffer.size() == 0) ? 0 : mBuffer.size() - 1;
return const_iterator(mBuffer.data(), mBuffer.size(),
(mFrontIdx == 0) ? tmp : mFrontIdx - 1, 0);
}
template <class T>
typename RingBuffer<T>::const_iterator RingBuffer<T>::end() const {
size_t s = mBuffer.size();
return const_iterator(mBuffer.data(), s, s, s);
}
template <class T>
T& RingBuffer<T>::operator[](size_t index) {
LOG_ALWAYS_FATAL_IF(index >= mBuffer.size(), "Index %zu out of bounds, size is %zu.",
index, mBuffer.size());
size_t pos = (index >= mFrontIdx) ?
mBuffer.size() - 1 - (index - mFrontIdx) : mFrontIdx - 1 - index;
return mBuffer[pos];
}
template <class T>
const T& RingBuffer<T>::operator[](size_t index) const {
LOG_ALWAYS_FATAL_IF(index >= mBuffer.size(), "Index %zu out of bounds, size is %zu.",
index, mBuffer.size());
size_t pos = (index >= mFrontIdx) ?
mBuffer.size() - 1 - (index - mFrontIdx) : mFrontIdx - 1 - index;
return mBuffer[pos];
}
template <class T>
size_t RingBuffer<T>::size() const {
return mBuffer.size();
}
template <class T>
void RingBuffer<T>::clear() {
mBuffer.clear();
mFrontIdx = 0;
}
}; // namespace android
#endif // ANDROID_SERVICE_UTILS_RING_BUFFER_H