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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License"). See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership. 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.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#ifndef CEPH_CIRCULAR_BUFFER_HH_
+#define CEPH_CIRCULAR_BUFFER_HH_
+
+// A growable double-ended queue container that can be efficiently
+// extended (and shrunk) from both ends. Implementation is a single
+// storage vector.
+//
+// Similar to libstdc++'s std::deque, except that it uses a single level
+// store, and so is more efficient for simple stored items.
+// Similar to boost::circular_buffer_space_optimized, except it uses
+// uninitialized storage for unoccupied elements (and thus move/copy
+// constructors instead of move/copy assignments, which are less efficient).
+
+#include <memory>
+#include <algorithm>
+
+#include "transfer.h"
+
+template <typename T, typename Alloc = std::allocator<T>>
+class circular_buffer {
+ struct impl : Alloc {
+ T* storage = nullptr;
+ // begin, end interpreted (mod capacity)
+ size_t begin = 0;
+ size_t end = 0;
+ size_t capacity = 0;
+ };
+ impl _impl;
+ public:
+ using value_type = T;
+ using size_type = size_t;
+ using reference = T&;
+ using pointer = T*;
+ using const_reference = const T&;
+ using const_pointer = const T*;
+ public:
+ circular_buffer() = default;
+ circular_buffer(circular_buffer&& X);
+ circular_buffer(const circular_buffer& X) = delete;
+ ~circular_buffer();
+ circular_buffer& operator=(const circular_buffer&) = delete;
+ circular_buffer& operator=(circular_buffer&&) = delete;
+ void push_front(const T& data);
+ void push_front(T&& data);
+ template <typename... A>
+ void emplace_front(A&&... args);
+ void push_back(const T& data);
+ void push_back(T&& data);
+ template <typename... A>
+ void emplace_back(A&&... args);
+ T& front();
+ T& back();
+ void pop_front();
+ void pop_back();
+ bool empty() const;
+ size_t size() const;
+ size_t capacity() const;
+ T& operator[](size_t idx);
+ template <typename Func>
+ void for_each(Func func);
+ // access an element, may return wrong or destroyed element
+ // only useful if you do not rely on data accuracy (e.g. prefetch)
+ T& access_element_unsafe(size_t idx);
+ private:
+ void expand();
+ void maybe_expand(size_t nr = 1);
+ size_t mask(size_t idx) const;
+
+ template<typename CB, typename ValueType>
+ struct cbiterator : std::iterator<std::random_access_iterator_tag, ValueType> {
+ typedef std::iterator<std::random_access_iterator_tag, ValueType> super_t;
+
+ ValueType& operator*() const { return cb->_impl.storage[cb->mask(idx)]; }
+ ValueType* operator->() const { return &cb->_impl.storage[cb->mask(idx)]; }
+ // prefix
+ cbiterator<CB, ValueType>& operator++() {
+ idx++;
+ return *this;
+ }
+ // postfix
+ cbiterator<CB, ValueType> operator++(int unused) {
+ auto v = *this;
+ idx++;
+ return v;
+ }
+ // prefix
+ cbiterator<CB, ValueType>& operator--() {
+ idx--;
+ return *this;
+ }
+ // postfix
+ cbiterator<CB, ValueType> operator--(int unused) {
+ auto v = *this;
+ idx--;
+ return v;
+ }
+ cbiterator<CB, ValueType> operator+(typename super_t::difference_type n) const {
+ return cbiterator<CB, ValueType>(cb, idx + n);
+ }
+ cbiterator<CB, ValueType> operator-(typename super_t::difference_type n) const {
+ return cbiterator<CB, ValueType>(cb, idx - n);
+ }
+ cbiterator<CB, ValueType>& operator+=(typename super_t::difference_type n) {
+ idx += n;
+ return *this;
+ }
+ cbiterator<CB, ValueType>& operator-=(typename super_t::difference_type n) {
+ idx -= n;
+ return *this;
+ }
+ bool operator==(const cbiterator<CB, ValueType>& rhs) const {
+ return idx == rhs.idx;
+ }
+ bool operator!=(const cbiterator<CB, ValueType>& rhs) const {
+ return idx != rhs.idx;
+ }
+ bool operator<(const cbiterator<CB, ValueType>& rhs) const {
+ return idx < rhs.idx;
+ }
+ bool operator>(const cbiterator<CB, ValueType>& rhs) const {
+ return idx > rhs.idx;
+ }
+ bool operator>=(const cbiterator<CB, ValueType>& rhs) const {
+ return idx >= rhs.idx;
+ }
+ bool operator<=(const cbiterator<CB, ValueType>& rhs) const {
+ return idx <= rhs.idx;
+ }
+ typename super_t::difference_type operator-(const cbiterator<CB, ValueType>& rhs) const {
+ return idx - rhs.idx;
+ }
+ private:
+ CB* cb;
+ size_t idx;
+ cbiterator<CB, ValueType>(CB* b, size_t i) : cb(b), idx(i) {}
+ friend class circular_buffer;
+ };
+ friend class iterator;
+
+ public:
+ typedef cbiterator<circular_buffer, T> iterator;
+ typedef cbiterator<const circular_buffer, const T> const_iterator;
+
+ iterator begin() {
+ return iterator(this, _impl.begin);
+ }
+ const_iterator begin() const {
+ return const_iterator(this, _impl.begin);
+ }
+ iterator end() {
+ return iterator(this, _impl.end);
+ }
+ const_iterator end() const {
+ return const_iterator(this, _impl.end);
+ }
+ const_iterator cbegin() const {
+ return const_iterator(this, _impl.begin);
+ }
+ const_iterator cend() const {
+ return const_iterator(this, _impl.end);
+ }
+};
+
+template <typename T, typename Alloc>
+inline size_t circular_buffer<T, Alloc>::mask(size_t idx) const {
+ return idx & (_impl.capacity - 1);
+}
+
+template <typename T, typename Alloc>
+inline bool circular_buffer<T, Alloc>::empty() const {
+ return _impl.begin == _impl.end;
+}
+
+template <typename T, typename Alloc>
+inline size_t circular_buffer<T, Alloc>::size() const {
+ return _impl.end - _impl.begin;
+}
+
+template <typename T, typename Alloc>
+inline size_t circular_buffer<T, Alloc>::capacity() const {
+ return _impl.capacity;
+}
+
+template <typename T, typename Alloc>
+inline circular_buffer<T, Alloc>::circular_buffer(circular_buffer&& x)
+ : _impl(std::move(x._impl)) {
+ x._impl = {};
+}
+
+template <typename T, typename Alloc>
+template <typename Func>
+inline void circular_buffer<T, Alloc>::for_each(Func func) {
+ auto s = _impl.storage;
+ auto m = _impl.capacity - 1;
+ for (auto i = _impl.begin; i != _impl.end; ++i) {
+ func(s[i & m]);
+ }
+}
+
+template <typename T, typename Alloc>
+inline circular_buffer<T, Alloc>::~circular_buffer() {
+ for_each([this] (T& obj) {
+ _impl.destroy(&obj);
+ });
+ _impl.deallocate(_impl.storage, _impl.capacity);
+}
+
+template <typename T, typename Alloc>
+void circular_buffer<T, Alloc>::expand() {
+ auto new_cap = std::max<size_t>(_impl.capacity * 2, 1);
+ auto new_storage = _impl.allocate(new_cap);
+ auto p = new_storage;
+ try {
+ for_each([this, &p] (T& obj) {
+ transfer_pass1(_impl, &obj, p);
+ p++;
+ });
+ } catch (...) {
+ while (p != new_storage) {
+ _impl.destroy(--p);
+ }
+ _impl.deallocate(new_storage, new_cap);
+ throw;
+ }
+ p = new_storage;
+ for_each([this, &p] (T& obj) {
+ transfer_pass2(_impl, &obj, p++);
+ });
+ std::swap(_impl.storage, new_storage);
+ std::swap(_impl.capacity, new_cap);
+ _impl.begin = 0;
+ _impl.end = p - _impl.storage;
+ _impl.deallocate(new_storage, new_cap);
+}
+
+template <typename T, typename Alloc>
+inline void circular_buffer<T, Alloc>::maybe_expand(size_t nr) {
+ if (_impl.end - _impl.begin + nr > _impl.capacity) {
+ expand();
+ }
+}
+
+template <typename T, typename Alloc>
+inline void circular_buffer<T, Alloc>::push_front(const T& data) {
+ maybe_expand();
+ auto p = &_impl.storage[mask(_impl.begin - 1)];
+ _impl.construct(p, data);
+ --_impl.begin;
+}
+
+template <typename T, typename Alloc>
+inline void circular_buffer<T, Alloc>::push_front(T&& data) {
+ maybe_expand();
+ auto p = &_impl.storage[mask(_impl.begin - 1)];
+ _impl.construct(p, std::move(data));
+ --_impl.begin;
+}
+
+template <typename T, typename Alloc>
+template <typename... Args>
+inline void circular_buffer<T, Alloc>::emplace_front(Args&&... args) {
+ maybe_expand();
+ auto p = &_impl.storage[mask(_impl.begin - 1)];
+ _impl.construct(p, std::forward<Args>(args)...);
+ --_impl.begin;
+}
+
+template <typename T, typename Alloc>
+inline void circular_buffer<T, Alloc>::push_back(const T& data) {
+ maybe_expand();
+ auto p = &_impl.storage[mask(_impl.end)];
+ _impl.construct(p, data);
+ ++_impl.end;
+}
+
+template <typename T, typename Alloc>
+inline void circular_buffer<T, Alloc>::push_back(T&& data) {
+ maybe_expand();
+ auto p = &_impl.storage[mask(_impl.end)];
+ _impl.construct(p, std::move(data));
+ ++_impl.end;
+}
+
+template <typename T, typename Alloc>
+template <typename... Args>
+inline void circular_buffer<T, Alloc>::emplace_back(Args&&... args) {
+ maybe_expand();
+ auto p = &_impl.storage[mask(_impl.end)];
+ _impl.construct(p, std::forward<Args>(args)...);
+ ++_impl.end;
+}
+
+template <typename T, typename Alloc>
+inline T& circular_buffer<T, Alloc>::front() {
+ return _impl.storage[mask(_impl.begin)];
+}
+
+template <typename T, typename Alloc>
+inline T& circular_buffer<T, Alloc>::back() {
+ return _impl.storage[mask(_impl.end - 1)];
+}
+
+template <typename T, typename Alloc>
+inline void circular_buffer<T, Alloc>::pop_front() {
+ _impl.destroy(&front());
+ ++_impl.begin;
+}
+
+template <typename T, typename Alloc>
+inline void circular_buffer<T, Alloc>::pop_back() {
+ _impl.destroy(&back());
+ --_impl.end;
+}
+
+template <typename T, typename Alloc>
+inline T& circular_buffer<T, Alloc>::operator[](size_t idx) {
+ return _impl.storage[mask(_impl.begin + idx)];
+}
+
+template <typename T, typename Alloc>
+inline T& circular_buffer<T, Alloc>::access_element_unsafe(size_t idx) {
+ return _impl.storage[mask(_impl.begin + idx)];
+}
+
+#endif /* CEPH_CIRCULAR_BUFFER_HH_ */
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