add lib EspSoftwareSerial for ESP32

lib/EspSoftwareSerial/src/circular_queue/MultiDelegate.h

@@ -0,0 +1,567 @@
+/*
+MultiDelegate.h - A queue or event multiplexer based on the efficient Delegate
+class
+Copyright (c) 2019-2020 Dirk O. Kaar. All rights reserved.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#ifndef __MULTIDELEGATE_H
+#define __MULTIDELEGATE_H
+
+#include <iterator>
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+#include <atomic>
+#else
+#include "circular_queue/ghostl.h"
+#endif
+
+#if defined(ESP8266)
+#include <interrupts.h>
+using esp8266::InterruptLock;
+#elif defined(ARDUINO)
+class InterruptLock {
+public:
+    InterruptLock() {
+        noInterrupts();
+    }
+    ~InterruptLock() {
+        interrupts();
+    }
+};
+#else
+#include <mutex>
+#endif
+
+namespace
+{
+
+    template< typename Delegate, typename R, bool ISQUEUE = false, typename... P>
+    struct CallP
+    {
+        static R execute(Delegate& del, P... args)
+        {
+            return del(std::forward<P...>(args...));
+        }
+    };
+
+    template< typename Delegate, bool ISQUEUE, typename... P>
+    struct CallP<Delegate, void, ISQUEUE, P...>
+    {
+        static bool execute(Delegate& del, P... args)
+        {
+            del(std::forward<P...>(args...));
+            return true;
+        }
+    };
+
+    template< typename Delegate, typename R, bool ISQUEUE = false>
+    struct Call
+    {
+        static R execute(Delegate& del)
+        {
+            return del();
+        }
+    };
+
+    template< typename Delegate, bool ISQUEUE>
+    struct Call<Delegate, void, ISQUEUE>
+    {
+        static bool execute(Delegate& del)
+        {
+            del();
+            return true;
+        }
+    };
+
+}
+
+namespace delegate
+{
+    namespace detail
+    {
+
+        template< typename Delegate, typename R, bool ISQUEUE = false, size_t QUEUE_CAPACITY = 32, typename... P>
+        class MultiDelegatePImpl
+        {
+        public:
+            MultiDelegatePImpl() = default;
+            ~MultiDelegatePImpl()
+            {
+                *this = nullptr;
+            }
+
+            MultiDelegatePImpl(const MultiDelegatePImpl&) = delete;
+            MultiDelegatePImpl& operator=(const MultiDelegatePImpl&) = delete;
+
+            MultiDelegatePImpl(MultiDelegatePImpl&& md)
+            {
+                first = md.first;
+                last = md.last;
+                unused = md.unused;
+                nodeCount = md.nodeCount;
+                md.first = nullptr;
+                md.last = nullptr;
+                md.unused = nullptr;
+                md.nodeCount = 0;
+            }
+
+            MultiDelegatePImpl(const Delegate& del)
+            {
+                add(del);
+            }
+
+            MultiDelegatePImpl(Delegate&& del)
+            {
+                add(std::move(del));
+            }
+
+            MultiDelegatePImpl& operator=(MultiDelegatePImpl&& md)
+            {
+                first = md.first;
+                last = md.last;
+                unused = md.unused;
+                nodeCount = md.nodeCount;
+                md.first = nullptr;
+                md.last = nullptr;
+                md.unused = nullptr;
+                md.nodeCount = 0;
+                return *this;
+            }
+
+            MultiDelegatePImpl& operator=(std::nullptr_t)
+            {
+                if (last)
+                    last->mNext = unused;
+                if (first)
+                    unused = first;
+                while (unused)
+                {
+                    auto to_delete = unused;
+                    unused = unused->mNext;
+                    delete(to_delete);
+                }
+                return *this;
+            }
+
+            MultiDelegatePImpl& operator+=(const Delegate& del)
+            {
+                add(del);
+                return *this;
+            }
+
+            MultiDelegatePImpl& operator+=(Delegate&& del)
+            {
+                add(std::move(del));
+                return *this;
+            }
+
+        protected:
+            struct Node_t
+            {
+                ~Node_t()
+                {
+                    mDelegate = nullptr; // special overload in Delegate
+                }
+                Node_t* mNext = nullptr;
+                Delegate mDelegate;
+            };
+
+            Node_t* first = nullptr;
+            Node_t* last = nullptr;
+            Node_t* unused = nullptr;
+            size_t nodeCount = 0;
+
+            // Returns a pointer to an unused Node_t,
+            // or if none are available allocates a new one,
+            // or nullptr if limit is reached
+            Node_t* IRAM_ATTR get_node_unsafe()
+            {
+                Node_t* result = nullptr;
+                // try to get an item from unused items list
+                if (unused)
+                {
+                    result = unused;
+                    unused = unused->mNext;
+                }
+                // if no unused items, and count not too high, allocate a new one
+                else if (nodeCount < QUEUE_CAPACITY)
+                {
+#if defined(ESP8266) || defined(ESP32)            	
+                    result = new (std::nothrow) Node_t;
+#else
+                    result = new Node_t;
+#endif
+                    if (result)
+                        ++nodeCount;
+                }
+                return result;
+            }
+
+            void recycle_node_unsafe(Node_t* node)
+            {
+                node->mDelegate = nullptr; // special overload in Delegate
+                node->mNext = unused;
+                unused = node;
+            }
+
+#ifndef ARDUINO
+            std::mutex mutex_unused;
+#endif
+        public:
+            class iterator : public std::iterator<std::forward_iterator_tag, Delegate>
+            {
+            public:
+                Node_t* current = nullptr;
+                Node_t* prev = nullptr;
+                const Node_t* stop = nullptr;
+
+                iterator(MultiDelegatePImpl& md) : current(md.first), stop(md.last) {}
+                iterator() = default;
+                iterator(const iterator&) = default;
+                iterator& operator=(const iterator&) = default;
+                iterator& operator=(iterator&&) = default;
+                operator bool() const
+                {
+                    return current && stop;
+                }
+                bool operator==(const iterator& rhs) const
+                {
+                    return current == rhs.current;
+                }
+                bool operator!=(const iterator& rhs) const
+                {
+                    return !operator==(rhs);
+                }
+                Delegate& operator*() const
+                {
+                    return current->mDelegate;
+                }
+                Delegate* operator->() const
+                {
+                    return &current->mDelegate;
+                }
+                iterator& operator++() // prefix
+                {
+                    if (current && stop != current)
+                    {
+                        prev = current;
+                        current = current->mNext;
+                    }
+                    else
+                        current = nullptr; // end
+                    return *this;
+                }
+                iterator& operator++(int) // postfix
+                {
+                    iterator tmp(*this);
+                    operator++();
+                    return tmp;
+                }
+            };
+
+            iterator begin()
+            {
+                return iterator(*this);
+            }
+            iterator end() const
+            {
+                return iterator();
+            }
+
+            const Delegate* add(const Delegate& del)
+            {
+                return add(Delegate(del));
+            }
+
+            const Delegate* add(Delegate&& del)
+            {
+                if (!del)
+                    return nullptr;
+
+#ifdef ARDUINO
+                InterruptLock lockAllInterruptsInThisScope;
+#else
+                std::lock_guard<std::mutex> lock(mutex_unused);
+#endif
+
+                Node_t* item = ISQUEUE ? get_node_unsafe() :
+#if defined(ESP8266) || defined(ESP32)            	
+                    new (std::nothrow) Node_t;
+#else
+                    new Node_t;
+#endif
+                if (!item)
+                    return nullptr;
+
+                item->mDelegate = std::move(del);
+                item->mNext = nullptr;
+
+                if (last)
+                    last->mNext = item;
+                else
+                    first = item;
+                last = item;
+
+                return &item->mDelegate;
+            }
+
+            iterator erase(iterator it)
+            {
+                if (!it)
+                    return end();
+#ifdef ARDUINO
+                InterruptLock lockAllInterruptsInThisScope;
+#else
+                std::lock_guard<std::mutex> lock(mutex_unused);
+#endif
+                auto to_recycle = it.current;
+
+                if (last == it.current)
+                    last = it.prev;
+                it.current = it.current->mNext;
+                if (it.prev)
+                {
+                    it.prev->mNext = it.current;
+                }
+                else
+                {
+                    first = it.current;
+                }
+                if (ISQUEUE)
+                    recycle_node_unsafe(to_recycle);
+                else
+                    delete to_recycle;
+                return it;
+            }
+
+            bool erase(const Delegate* const del)
+            {
+                auto it = begin();
+                while (it)
+                {
+                    if (del == &(*it))
+                    {
+                        erase(it);
+                        return true;
+                    }
+                    ++it;
+                }
+                return false;
+            }
+
+            operator bool() const
+            {
+                return first;
+            }
+
+            R operator()(P... args)
+            {
+                auto it = begin();
+                if (!it)
+                    return {};
+
+                static std::atomic<bool> fence(false);
+                // prevent recursive calls
+#if defined(ARDUINO) && !defined(ESP32)
+                if (fence.load()) return {};
+                fence.store(true);
+#else
+                if (fence.exchange(true)) return {};
+#endif
+
+                R result;
+                do
+                {
+                    result = CallP<Delegate, R, ISQUEUE, P...>::execute(*it, args...);
+                    if (result && ISQUEUE)
+                        it = erase(it);
+                    else
+                        ++it;
+#if defined(ESP8266) || defined(ESP32)
+                    // running callbacks might last too long for watchdog etc.
+                    optimistic_yield(10000);
+#endif
+                } while (it);
+
+                fence.store(false);
+                return result;
+            }
+        };
+
+        template< typename Delegate, typename R = void, bool ISQUEUE = false, size_t QUEUE_CAPACITY = 32>
+        class MultiDelegateImpl : public MultiDelegatePImpl<Delegate, R, ISQUEUE, QUEUE_CAPACITY>
+        {
+        public:
+            using MultiDelegatePImpl<Delegate, R, ISQUEUE, QUEUE_CAPACITY>::MultiDelegatePImpl;
+
+            R operator()()
+            {
+                auto it = this->begin();
+                if (!it)
+                    return {};
+
+                static std::atomic<bool> fence(false);
+                // prevent recursive calls
+#if defined(ARDUINO) && !defined(ESP32)
+                if (fence.load()) return {};
+                fence.store(true);
+#else
+                if (fence.exchange(true)) return {};
+#endif
+
+                R result;
+                do
+                {
+                    result = Call<Delegate, R, ISQUEUE>::execute(*it);
+                    if (result && ISQUEUE)
+                        it = this->erase(it);
+                    else
+                        ++it;
+#if defined(ESP8266) || defined(ESP32)
+                    // running callbacks might last too long for watchdog etc.
+                    optimistic_yield(10000);
+#endif
+                } while (it);
+
+                fence.store(false);
+                return result;
+            }
+        };
+
+        template< typename Delegate, typename R, bool ISQUEUE, size_t QUEUE_CAPACITY, typename... P> class MultiDelegate;
+
+        template< typename Delegate, typename R, bool ISQUEUE, size_t QUEUE_CAPACITY, typename... P>
+        class MultiDelegate<Delegate, R(P...), ISQUEUE, QUEUE_CAPACITY> : public MultiDelegatePImpl<Delegate, R, ISQUEUE, QUEUE_CAPACITY, P...>
+        {
+        public:
+            using MultiDelegatePImpl<Delegate, R, ISQUEUE, QUEUE_CAPACITY, P...>::MultiDelegatePImpl;
+        };
+
+        template< typename Delegate, typename R, bool ISQUEUE, size_t QUEUE_CAPACITY>
+        class MultiDelegate<Delegate, R(), ISQUEUE, QUEUE_CAPACITY> : public MultiDelegateImpl<Delegate, R, ISQUEUE, QUEUE_CAPACITY>
+        {
+        public:
+            using MultiDelegateImpl<Delegate, R, ISQUEUE, QUEUE_CAPACITY>::MultiDelegateImpl;
+        };
+
+        template< typename Delegate, bool ISQUEUE, size_t QUEUE_CAPACITY, typename... P>
+        class MultiDelegate<Delegate, void(P...), ISQUEUE, QUEUE_CAPACITY> : public MultiDelegatePImpl<Delegate, void, ISQUEUE, QUEUE_CAPACITY, P...>
+        {
+        public:
+            using MultiDelegatePImpl<Delegate, void, ISQUEUE, QUEUE_CAPACITY, P...>::MultiDelegatePImpl;
+
+            void operator()(P... args)
+            {
+                auto it = this->begin();
+                if (!it)
+                    return;
+
+                static std::atomic<bool> fence(false);
+                // prevent recursive calls
+#if defined(ARDUINO) && !defined(ESP32)
+                if (fence.load()) return;
+                fence.store(true);
+#else
+                if (fence.exchange(true)) return;
+#endif
+
+                do
+                {
+                    CallP<Delegate, void, ISQUEUE, P...>::execute(*it, args...);
+                    if (ISQUEUE)
+                        it = this->erase(it);
+                    else
+                        ++it;
+#if defined(ESP8266) || defined(ESP32)
+                    // running callbacks might last too long for watchdog etc.
+                    optimistic_yield(10000);
+#endif
+                } while (it);
+
+                fence.store(false);
+            }
+        };
+
+        template< typename Delegate, bool ISQUEUE, size_t QUEUE_CAPACITY>
+        class MultiDelegate<Delegate, void(), ISQUEUE, QUEUE_CAPACITY> : public MultiDelegateImpl<Delegate, void, ISQUEUE, QUEUE_CAPACITY>
+        {
+        public:
+            using MultiDelegateImpl<Delegate, void, ISQUEUE, QUEUE_CAPACITY>::MultiDelegateImpl;
+
+            void operator()()
+            {
+                auto it = this->begin();
+                if (!it)
+                    return;
+
+                static std::atomic<bool> fence(false);
+                // prevent recursive calls
+#if defined(ARDUINO) && !defined(ESP32)
+                if (fence.load()) return;
+                fence.store(true);
+#else
+                if (fence.exchange(true)) return;
+#endif
+
+                do
+                {
+                    Call<Delegate, void, ISQUEUE>::execute(*it);
+                    if (ISQUEUE)
+                        it = this->erase(it);
+                    else
+                        ++it;
+#if defined(ESP8266) || defined(ESP32)
+                    // running callbacks might last too long for watchdog etc.
+                    optimistic_yield(10000);
+#endif
+                } while (it);
+
+                fence.store(false);
+            }
+        };
+
+    }
+
+}
+
+/**
+The MultiDelegate class template can be specialized to either a queue or an event multiplexer.
+It is designed to be used with Delegate, the efficient runtime wrapper for C function ptr and C++ std::function.
+@tparam Delegate specifies the concrete type that MultiDelegate bases the queue or event multiplexer on.
+@tparam ISQUEUE modifies the generated MultiDelegate class in subtle ways. In queue mode (ISQUEUE == true),
+               the value of QUEUE_CAPACITY enforces the maximum number of simultaneous items the queue can contain.
+               This is exploited to minimize the use of new and delete by reusing already allocated items, thus
+               reducing heap fragmentation. In event multiplexer mode (ISQUEUE = false), new and delete are
+               used for allocation of the event handler items.
+               If the result type of the function call operator of Delegate is void, calling a MultiDelegate queue
+               removes each item after calling it; a Multidelegate event multiplexer keeps event handlers until
+               explicitly removed.
+               If the result type of the function call operator of Delegate is non-void, in a MultiDelegate queue
+               the type-conversion to bool of that result determines if the item is immediately removed or kept
+               after each call: if true is returned, the item is removed. A Multidelegate event multiplexer keeps event
+               handlers until they are explicitly removed.
+@tparam QUEUE_CAPACITY is only used if ISQUEUE == true. Then, it sets the maximum capacity that the queue dynamically
+               allocates from the heap. Unused items are not returned to the heap, but are managed by the MultiDelegate
+               instance during its own lifetime for efficiency.
+*/
+template< typename Delegate, bool ISQUEUE = false, size_t QUEUE_CAPACITY = 32>
+class MultiDelegate : public delegate::detail::MultiDelegate<Delegate, typename Delegate::target_type, ISQUEUE, QUEUE_CAPACITY>
+{
+public:
+    using delegate::detail::MultiDelegate<Delegate, typename Delegate::target_type, ISQUEUE, QUEUE_CAPACITY>::MultiDelegate;
+};
+
+#endif // __MULTIDELEGATE_H

lib/EspSoftwareSerial/src/circular_queue/circular_queue.h

@@ -0,0 +1,384 @@
+/*
+circular_queue.h - Implementation of a lock-free circular queue for EspSoftwareSerial.
+Copyright (c) 2019 Dirk O. Kaar. All rights reserved.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#ifndef __circular_queue_h
+#define __circular_queue_h
+
+#ifdef ARDUINO
+#include <Arduino.h>
+#endif
+
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+#include <atomic>
+#include <memory>
+#include <algorithm>
+#include "Delegate.h"
+using std::min;
+#else
+#include "ghostl.h"
+#endif
+
+#if !defined(ESP32) && !defined(ESP8266)
+#define IRAM_ATTR
+#endif
+
+#if defined(__GNUC__)
+#undef ALWAYS_INLINE_ATTR
+#define ALWAYS_INLINE_ATTR __attribute__((always_inline))
+#else
+#define ALWAYS_INLINE_ATTR
+#endif
+
+/*!
+    @brief	Instance class for a single-producer, single-consumer circular queue / ring buffer (FIFO).
+            This implementation is lock-free between producer and consumer for the available(), peek(),
+            pop(), and push() type functions.
+*/
+template< typename T, typename ForEachArg = void >
+class circular_queue
+{
+public:
+    /*!
+        @brief	Constructs a valid, but zero-capacity dummy queue.
+    */
+    circular_queue() : m_bufSize(1)
+    {
+        m_inPos.store(0);
+        m_outPos.store(0);
+    }
+    /*!
+        @brief  Constructs a queue of the given maximum capacity.
+    */
+    circular_queue(const size_t capacity) : m_bufSize(capacity + 1), m_buffer(new T[m_bufSize])
+    {
+        m_inPos.store(0);
+        m_outPos.store(0);
+    }
+    circular_queue(circular_queue&& cq) :
+        m_bufSize(cq.m_bufSize), m_buffer(cq.m_buffer), m_inPos(cq.m_inPos.load()), m_outPos(cq.m_outPos.load())
+    {}
+    ~circular_queue()
+    {
+        m_buffer.reset();
+    }
+    circular_queue(const circular_queue&) = delete;
+    circular_queue& operator=(circular_queue&& cq)
+    {
+        m_bufSize = cq.m_bufSize;
+        m_buffer = cq.m_buffer;
+        m_inPos.store(cq.m_inPos.load());
+        m_outPos.store(cq.m_outPos.load());
+    }
+    circular_queue& operator=(const circular_queue&) = delete;
+
+    /*!
+        @brief	Get the numer of elements the queue can hold at most.
+    */
+    size_t capacity() const
+    {
+        return m_bufSize - 1;
+    }
+
+    /*!
+        @brief	Resize the queue. The available elements in the queue are preserved.
+                This is not lock-free and concurrent producer or consumer access
+                will lead to corruption.
+        @return True if the new capacity could accommodate the present elements in
+                the queue, otherwise nothing is done and false is returned.
+    */
+    bool capacity(const size_t cap);
+
+    /*!
+        @brief	Discard all data in the queue.
+    */
+    void flush()
+    {
+        m_outPos.store(m_inPos.load());
+    }
+
+    /*!
+        @brief	Get a snapshot number of elements that can be retrieved by pop.
+    */
+    size_t IRAM_ATTR available() const
+    {
+        int avail = static_cast<int>(m_inPos.load() - m_outPos.load());
+        if (avail < 0) avail += m_bufSize;
+        return avail;
+    }
+
+    /*!
+        @brief	Get the remaining free elementes for pushing.
+    */
+    size_t IRAM_ATTR available_for_push() const
+    {
+        int avail = static_cast<int>(m_outPos.load() - m_inPos.load()) - 1;
+        if (avail < 0) avail += m_bufSize;
+        return avail;
+    }
+
+    /*!
+        @brief	Peek at the next element pop will return without removing it from the queue.
+        @return An rvalue copy of the next element that can be popped. If the queue is empty,
+                return an rvalue copy of the element that is pending the next push.
+    */
+    T peek() const
+    {
+        const auto outPos = m_outPos.load(std::memory_order_relaxed);
+        std::atomic_thread_fence(std::memory_order_acquire);
+        return m_buffer[outPos];
+    }
+
+    /*!
+        @brief	Peek at the next pending input value.
+        @return A reference to the next element that can be pushed.
+    */
+    T& IRAM_ATTR pushpeek()
+    {
+        const auto inPos = m_inPos.load(std::memory_order_relaxed);
+        std::atomic_thread_fence(std::memory_order_acquire);
+        return m_buffer[inPos];
+    }
+
+    /*!
+        @brief	Release the next pending input value, accessible by pushpeek(), into the queue.
+        @return true if the queue accepted the value, false if the queue
+                was full.
+    */
+    bool IRAM_ATTR push()
+    {
+        const auto inPos = m_inPos.load(std::memory_order_acquire);
+        const size_t next = (inPos + 1) % m_bufSize;
+        if (next == m_outPos.load(std::memory_order_relaxed)) {
+            return false;
+        }
+        std::atomic_thread_fence(std::memory_order_release);
+        m_inPos.store(next, std::memory_order_release);
+        return true;
+    }
+
+    /*!
+        @brief	Move the rvalue parameter into the queue.
+        @return true if the queue accepted the value, false if the queue
+                was full.
+    */
+    bool IRAM_ATTR push(T&& val)
+    {
+        const auto inPos = m_inPos.load(std::memory_order_acquire);
+        const size_t next = (inPos + 1) % m_bufSize;
+        if (next == m_outPos.load(std::memory_order_relaxed)) {
+            return false;
+        }
+        m_buffer[inPos] = std::move(val);
+        std::atomic_thread_fence(std::memory_order_release);
+        m_inPos.store(next, std::memory_order_release);
+        return true;
+    }
+
+    /*!
+        @brief	Push a copy of the parameter into the queue.
+        @return true if the queue accepted the value, false if the queue
+                was full.
+    */
+    inline bool IRAM_ATTR push(const T& val) ALWAYS_INLINE_ATTR
+    {
+        T v(val);
+        return push(std::move(v));
+    }
+
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+    /*!
+        @brief	Push copies of multiple elements from a buffer into the queue,
+                in order, beginning at buffer's head.
+        @return The number of elements actually copied into the queue, counted
+                from the buffer head.
+    */
+    size_t push_n(const T* buffer, size_t size);
+#endif
+
+    /*!
+        @brief	Pop the next available element from the queue.
+        @return An rvalue copy of the popped element, or a default
+                value of type T if the queue is empty.
+    */
+    T pop();
+
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+    /*!
+        @brief	Pop multiple elements in ordered sequence from the queue to a buffer.
+                If buffer is nullptr, simply discards up to size elements from the queue.
+        @return The number of elements actually popped from the queue to
+                buffer.
+    */
+    size_t pop_n(T* buffer, size_t size);
+#endif
+
+    /*!
+        @brief	Iterate over and remove each available element from queue,
+                calling back fun with an rvalue reference of every single element.
+    */
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+    void for_each(const Delegate<void(T&&), ForEachArg>& fun);
+#else
+    void for_each(Delegate<void(T&&), ForEachArg> fun);
+#endif
+
+    /*!
+        @brief	In reverse order, iterate over, pop and optionally requeue each available element from the queue,
+                calling back fun with a reference of every single element.
+                Requeuing is dependent on the return boolean of the callback function. If it
+                returns true, the requeue occurs.
+    */
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+    bool for_each_rev_requeue(const Delegate<bool(T&), ForEachArg>& fun);
+#else
+    bool for_each_rev_requeue(Delegate<bool(T&), ForEachArg> fun);
+#endif
+
+protected:
+    size_t m_bufSize;
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+    std::unique_ptr<T[]> m_buffer;
+#else
+    std::unique_ptr<T> m_buffer;
+#endif
+    std::atomic<size_t> m_inPos;
+    std::atomic<size_t> m_outPos;
+};
+
+template< typename T, typename ForEachArg >
+bool circular_queue<T, ForEachArg>::capacity(const size_t cap)
+{
+    if (cap + 1 == m_bufSize) return true;
+    else if (available() > cap) return false;
+    std::unique_ptr<T[] > buffer(new T[cap + 1]);
+    const auto available = pop_n(buffer, cap);
+    m_buffer.reset(buffer);
+    m_bufSize = cap + 1;
+    m_inPos.store(available, std::memory_order_relaxed);
+    m_outPos.store(0, std::memory_order_relaxed);
+    return true;
+}
+
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+template< typename T, typename ForEachArg >
+size_t circular_queue<T, ForEachArg>::push_n(const T* buffer, size_t size)
+{
+    const auto inPos = m_inPos.load(std::memory_order_acquire);
+    const auto outPos = m_outPos.load(std::memory_order_relaxed);
+
+    size_t blockSize = (outPos > inPos) ? outPos - 1 - inPos : (outPos == 0) ? m_bufSize - 1 - inPos : m_bufSize - inPos;
+    blockSize = min(size, blockSize);
+    if (!blockSize) return 0;
+    int next = (inPos + blockSize) % m_bufSize;
+
+    auto dest = m_buffer.get() + inPos;
+    std::copy_n(std::make_move_iterator(buffer), blockSize, dest);
+    size = min(size - blockSize, outPos > 1 ? static_cast<size_t>(outPos - next - 1) : 0);
+    next += size;
+    dest = m_buffer.get();
+    std::copy_n(std::make_move_iterator(buffer + blockSize), size, dest);
+
+    std::atomic_thread_fence(std::memory_order_release);
+    m_inPos.store(next, std::memory_order_release);
+    return blockSize + size;
+}
+#endif
+
+template< typename T, typename ForEachArg >
+T circular_queue<T, ForEachArg>::pop()
+{
+    const auto outPos = m_outPos.load(std::memory_order_acquire);
+    if (m_inPos.load(std::memory_order_relaxed) == outPos) return {};
+
+    std::atomic_thread_fence(std::memory_order_acquire);
+
+    auto val = std::move(m_buffer[outPos]);
+
+    m_outPos.store((outPos + 1) % m_bufSize, std::memory_order_release);
+    return val;
+}
+
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+template< typename T, typename ForEachArg >
+size_t circular_queue<T, ForEachArg>::pop_n(T* buffer, size_t size) {
+    size_t avail = size = min(size, available());
+    if (!avail) return 0;
+    const auto outPos = m_outPos.load(std::memory_order_acquire);
+    size_t n = min(avail, static_cast<size_t>(m_bufSize - outPos));
+
+    std::atomic_thread_fence(std::memory_order_acquire);
+
+    if (buffer) {
+        buffer = std::copy_n(std::make_move_iterator(m_buffer.get() + outPos), n, buffer);
+        avail -= n;
+        std::copy_n(std::make_move_iterator(m_buffer.get()), avail, buffer);
+    }
+
+    m_outPos.store((outPos + size) % m_bufSize, std::memory_order_release);
+    return size;
+}
+#endif
+
+template< typename T, typename ForEachArg >
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+void circular_queue<T, ForEachArg>::for_each(const Delegate<void(T&&), ForEachArg>& fun)
+#else
+void circular_queue<T, ForEachArg>::for_each(Delegate<void(T&&), ForEachArg> fun)
+#endif
+{
+    auto outPos = m_outPos.load(std::memory_order_acquire);
+    const auto inPos = m_inPos.load(std::memory_order_relaxed);
+    std::atomic_thread_fence(std::memory_order_acquire);
+    while (outPos != inPos)
+    {
+        fun(std::move(m_buffer[outPos]));
+        outPos = (outPos + 1) % m_bufSize;
+        m_outPos.store(outPos, std::memory_order_release);
+    }
+}
+
+template< typename T, typename ForEachArg >
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+bool circular_queue<T, ForEachArg>::for_each_rev_requeue(const Delegate<bool(T&), ForEachArg>& fun)
+#else
+bool circular_queue<T, ForEachArg>::for_each_rev_requeue(Delegate<bool(T&), ForEachArg> fun)
+#endif
+{
+    auto inPos0 = circular_queue<T, ForEachArg>::m_inPos.load(std::memory_order_acquire);
+    auto outPos = circular_queue<T, ForEachArg>::m_outPos.load(std::memory_order_relaxed);
+    if (outPos == inPos0) return false;
+    auto pos = inPos0;
+    auto outPos1 = inPos0;
+    const auto posDecr = circular_queue<T, ForEachArg>::m_bufSize - 1;
+    std::atomic_thread_fence(std::memory_order_acquire);
+    do {
+        pos = (pos + posDecr) % circular_queue<T, ForEachArg>::m_bufSize;
+        T&& val = std::move(circular_queue<T, ForEachArg>::m_buffer[pos]);
+        if (fun(val))
+        {
+            outPos1 = (outPos1 + posDecr) % circular_queue<T, ForEachArg>::m_bufSize;
+            if (outPos1 != pos) circular_queue<T, ForEachArg>::m_buffer[outPos1] = std::move(val);
+        }
+    } while (pos != outPos);
+    std::atomic_thread_fence(std::memory_order_release);
+    circular_queue<T, ForEachArg>::m_outPos.store(outPos1, std::memory_order_release);
+    return true;
+}
+
+#endif // __circular_queue_h

lib/EspSoftwareSerial/src/circular_queue/circular_queue_mp.h

@@ -0,0 +1,310 @@
+/*
+circular_queue_mp.h - Implementation of a lock-free circular queue for EspSoftwareSerial.
+Copyright (c) 2019 Dirk O. Kaar. All rights reserved.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#ifndef __circular_queue_mp_h
+#define __circular_queue_mp_h
+
+#include "circular_queue.h"
+
+#if defined(ESP8266)
+#include <interrupts.h>
+using esp8266::InterruptLock;
+#endif
+
+/*!
+    @brief	Instance class for a multi-producer, single-consumer circular queue / ring buffer (FIFO).
+            This implementation is lock-free between producers and consumer for the available(), peek(),
+            pop(), and push() type functions.
+*/
+template< typename T, typename ForEachArg = void >
+class circular_queue_mp : protected circular_queue<T, ForEachArg>
+{
+public:
+    circular_queue_mp() : circular_queue<T, ForEachArg>()
+    {
+        m_inPos_mp.store(0);
+        m_concurrent_mp.store(0);
+    }
+    circular_queue_mp(const size_t capacity) : circular_queue<T, ForEachArg>(capacity)
+    {
+        m_inPos_mp.store(0);
+        m_concurrent_mp.store(0);
+    }
+    circular_queue_mp(circular_queue_mp<T, ForEachArg>&& cq) : circular_queue<T, ForEachArg>(std::move(cq))
+    {
+        m_inPos_mp.store(cq.m_inPos_mp.load());
+        m_concurrent_mp.store(cq.m_concurrent_mp.load());
+    }
+    circular_queue_mp& operator=(circular_queue_mp&& cq)
+    {
+        circular_queue<T, ForEachArg>::operator=(std::move(cq));
+        m_inPos_mp.store(cq.m_inPos_mp.load());
+        m_concurrent_mp.store(cq.m_concurrent_mp.load());
+    }
+    circular_queue_mp& operator=(const circular_queue_mp&) = delete;
+
+    using circular_queue<T, ForEachArg>::capacity;
+    using circular_queue<T, ForEachArg>::flush;
+    using circular_queue<T, ForEachArg>::peek;
+    using circular_queue<T, ForEachArg>::pop;
+    using circular_queue<T, ForEachArg>::pop_n;
+    using circular_queue<T, ForEachArg>::for_each;
+    using circular_queue<T, ForEachArg>::for_each_rev_requeue;
+
+    T& pushpeek() = delete;
+    bool push() = delete;
+
+    inline size_t IRAM_ATTR available() const ALWAYS_INLINE_ATTR
+    {
+        return circular_queue<T, ForEachArg>::available();
+    }
+    inline size_t IRAM_ATTR available_for_push() const ALWAYS_INLINE_ATTR
+    {
+        return circular_queue<T, ForEachArg>::available_for_push();
+    }
+
+    /*!
+        @brief	Resize the queue. The available elements in the queue are preserved.
+                This is not lock-free and concurrent producer or consumer access
+                will lead to corruption.
+        @return True if the new capacity could accommodate the present elements in
+                the queue, otherwise nothing is done and false is returned.
+    */
+    bool capacity(const size_t cap);
+
+    /*!
+        @brief	Move the rvalue parameter into the queue, guarded
+                for multiple concurrent producers.
+        @return true if the queue accepted the value, false if the queue
+                was full.
+    */
+    bool push(T&& val);
+
+    /*!
+        @brief	Push a copy of the parameter into the queue, guarded
+                for multiple concurrent producers.
+        @return true if the queue accepted the value, false if the queue
+                was full.
+    */
+    inline bool IRAM_ATTR push(const T& val) ALWAYS_INLINE_ATTR
+    {
+        T v(val);
+        return push(std::move(v));
+    }
+
+    /*!
+        @brief	Push copies of multiple elements from a buffer into the queue,
+                in order, beginning at buffer's head. This is safe for
+                multiple producers.
+        @return The number of elements actually copied into the queue, counted
+                from the buffer head.
+    */
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+    size_t push_n(const T* buffer, size_t size);
+#endif
+
+protected:
+    std::atomic<size_t> m_inPos_mp;
+    std::atomic<int> m_concurrent_mp;
+};
+
+template< typename T, typename ForEachArg >
+bool circular_queue_mp<T, ForEachArg>::capacity(const size_t cap)
+{
+    if (cap + 1 == circular_queue<T, ForEachArg>::m_bufSize) return true;
+    else if (!circular_queue<T, ForEachArg>::capacity(cap)) return false;
+    m_inPos_mp.store(circular_queue<T, ForEachArg>::m_inPos.load(std::memory_order_relaxed),
+        std::memory_order_relaxed);
+    m_concurrent_mp.store(0, std::memory_order_relaxed);
+    return true;
+}
+
+template< typename T, typename ForEachArg >
+bool IRAM_ATTR circular_queue_mp<T, ForEachArg>::push(T&& val)
+{
+    size_t inPos_mp;
+    size_t next;
+#if !defined(ESP32) && defined(ARDUINO)
+    class InterruptLock {
+    public:
+        InterruptLock() {
+            noInterrupts();
+        }
+        ~InterruptLock() {
+            interrupts();
+        }
+    };
+    {
+        InterruptLock lock;
+#else
+    ++m_concurrent_mp;
+    do
+    {
+#endif
+        inPos_mp = m_inPos_mp.load(std::memory_order_relaxed);
+        next = (inPos_mp + 1) % circular_queue<T, ForEachArg>::m_bufSize;
+        if (next == circular_queue<T, ForEachArg>::m_outPos.load(std::memory_order_relaxed)) {
+#if !defined(ESP32) && defined(ARDUINO)
+            return false;
+        }
+        m_inPos_mp.store(next, std::memory_order_relaxed);
+        m_concurrent_mp.store(m_concurrent_mp.load(std::memory_order_relaxed) + 1,
+            std::memory_order_relaxed);
+        std::atomic_thread_fence(std::memory_order_release);
+    }
+#else
+            int concurrent_mp;
+            do
+            {
+                inPos_mp = m_inPos_mp.load();
+                concurrent_mp = m_concurrent_mp.load();
+                if (1 == concurrent_mp)
+                {
+                    circular_queue<T, ForEachArg>::m_inPos.store(inPos_mp, std::memory_order_release);
+                }
+            }
+            while (!m_concurrent_mp.compare_exchange_weak(concurrent_mp, concurrent_mp - 1));
+            return false;
+        }
+    }
+    while (!m_inPos_mp.compare_exchange_weak(inPos_mp, next));
+#endif
+
+    circular_queue<T, ForEachArg>::m_buffer[inPos_mp] = std::move(val);
+
+    std::atomic_thread_fence(std::memory_order_release);
+
+#if !defined(ESP32) && defined(ARDUINO)
+    {
+        InterruptLock lock;
+        if (1 == m_concurrent_mp.load(std::memory_order_relaxed))
+        {
+            inPos_mp = m_inPos_mp.load(std::memory_order_relaxed);
+            circular_queue<T, ForEachArg>::m_inPos.store(inPos_mp, std::memory_order_relaxed);
+        }
+        m_concurrent_mp.store(m_concurrent_mp.load(std::memory_order_relaxed) - 1,
+            std::memory_order_relaxed);
+        std::atomic_thread_fence(std::memory_order_release);
+    }
+#else
+    int concurrent_mp;
+    do
+    {
+        inPos_mp = m_inPos_mp.load();
+        concurrent_mp = m_concurrent_mp.load();
+        if (1 == concurrent_mp)
+        {
+            circular_queue<T, ForEachArg>::m_inPos.store(inPos_mp, std::memory_order_release);
+        }
+    }
+    while (!m_concurrent_mp.compare_exchange_weak(concurrent_mp, concurrent_mp - 1));
+#endif
+
+    return true;
+}
+
+#if defined(ESP8266) || defined(ESP32) || !defined(ARDUINO)
+template< typename T, typename ForEachArg >
+size_t circular_queue_mp<T, ForEachArg>::push_n(const T* buffer, size_t size)
+{
+    const auto outPos = circular_queue<T, ForEachArg>::m_outPos.load(std::memory_order_relaxed);
+    size_t inPos_mp;
+    size_t next;
+    size_t blockSize;
+#if !defined(ESP32) && defined(ARDUINO)
+    {
+        InterruptLock lock;
+#else
+    ++m_concurrent_mp;
+    do
+    {
+#endif
+        inPos_mp = m_inPos_mp.load(std::memory_order_relaxed);
+        blockSize = (outPos > inPos_mp) ? outPos - 1 - inPos_mp : (outPos == 0) ? circular_queue<T, ForEachArg>::m_bufSize - 1 - inPos_mp : circular_queue<T, ForEachArg>::m_bufSize - inPos_mp;
+        blockSize = min(size, blockSize);
+        if (!blockSize)
+        {
+#if !defined(ESP32) && defined(ARDUINO)
+            return 0;
+        }
+        next = (inPos_mp + blockSize) % circular_queue<T, ForEachArg>::m_bufSize;
+        m_inPos_mp.store(next, std::memory_order_relaxed);
+        m_concurrent_mp.store(m_concurrent_mp.load(std::memory_order_relaxed) + 1,
+            std::memory_order_relaxed);
+        std::atomic_thread_fence(std::memory_order_release);
+    }
+#else
+            int concurrent_mp = m_concurrent_mp.load();
+            do
+            {
+                inPos_mp = m_inPos_mp.load();
+                concurrent_mp = m_concurrent_mp.load();
+                if (1 == concurrent_mp)
+                {
+                    circular_queue<T, ForEachArg>::m_inPos.store(inPos_mp, std::memory_order_release);
+                }
+            }
+            while (!m_concurrent_mp.compare_exchange_weak(concurrent_mp, concurrent_mp - 1));
+            return false;
+        }
+    }
+    while (!m_inPos_mp.compare_exchange_weak(inPos_mp, next));
+#endif
+
+    auto dest = circular_queue<T, ForEachArg>::m_buffer.get() + inPos_mp;
+    std::copy_n(std::make_move_iterator(buffer), blockSize, dest);
+    size = min(size - blockSize, outPos > 1 ? static_cast<size_t>(outPos - next - 1) : 0);
+    next += size;
+    dest = circular_queue<T, ForEachArg>::m_buffer.get();
+    std::copy_n(std::make_move_iterator(buffer + blockSize), size, dest);
+
+    std::atomic_thread_fence(std::memory_order_release);
+
+#if !defined(ESP32) && defined(ARDUINO)
+    {
+        InterruptLock lock;
+        if (1 == m_concurrent_mp.load(std::memory_order_relaxed))
+        {
+            inPos_mp = m_inPos_mp.load(std::memory_order_relaxed);
+            circular_queue<T, ForEachArg>::m_inPos.store(inPos_mp, std::memory_order_relaxed);
+        }
+        m_concurrent_mp.store(m_concurrent_mp.load(std::memory_order_relaxed) - 1,
+            std::memory_order_relaxed);
+        std::atomic_thread_fence(std::memory_order_release);
+    }
+#else
+    int concurrent_mp;
+    do
+    {
+        inPos_mp = m_inPos_mp.load();
+        concurrent_mp = m_concurrent_mp.load();
+        if (1 == concurrent_mp)
+        {
+            circular_queue<T, ForEachArg>::m_inPos.store(inPos_mp, std::memory_order_release);
+        }
+    }
+    while (!m_concurrent_mp.compare_exchange_weak(concurrent_mp, concurrent_mp - 1));
+#endif
+
+    return blockSize + size;
+}
+
+#endif
+
+#endif // __circular_queue_mp_h

lib/EspSoftwareSerial/src/circular_queue/ghostl.h

@@ -0,0 +1,94 @@
+/*
+ghostl.h - Implementation of a bare-bones, mostly no-op, C++ STL shell
+           that allows building some Arduino ESP8266/ESP32
+           libraries on Aruduino AVR.
+Copyright (c) 2019 Dirk O. Kaar. All rights reserved.
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+#ifndef __ghostl_h
+#define __ghostl_h
+
+#if defined(ARDUINO_ARCH_SAMD)
+#include <atomic>
+#endif
+
+using size_t = decltype(sizeof(char));
+
+namespace std
+{
+#if !defined(ARDUINO_ARCH_SAMD)
+    typedef enum memory_order {
+        memory_order_relaxed,
+        memory_order_acquire,
+        memory_order_release,
+        memory_order_seq_cst
+    } memory_order;
+    template< typename T > class atomic {
+    private:
+        T value;
+    public:
+        atomic() {}
+        atomic(T desired) { value = desired; }
+        void store(T desired, std::memory_order = std::memory_order_seq_cst) volatile noexcept { value = desired; }
+        T load(std::memory_order = std::memory_order_seq_cst) const volatile noexcept { return value; }
+    };
+    inline void atomic_thread_fence(std::memory_order order) noexcept {}
+    template< typename T > T&& move(T& t) noexcept { return static_cast<T&&>(t); }
+#endif
+
+    template< typename T, size_t long N > struct array
+    {
+        T _M_elems[N];
+        decltype(sizeof(0)) size() const { return N; }
+        T& operator[](decltype(sizeof(0)) i) { return _M_elems[i]; }
+        const T& operator[](decltype(sizeof(0)) i) const { return _M_elems[i]; }
+    };
+
+    template< typename T > class unique_ptr
+    {
+    public:
+        using pointer = T*;
+        unique_ptr() noexcept : ptr(nullptr) {}
+        unique_ptr(pointer p) : ptr(p) {}
+        pointer operator->() const noexcept { return ptr; }
+        T& operator[](decltype(sizeof(0)) i) const { return ptr[i]; }
+        void reset(pointer p = pointer()) noexcept
+        {
+            delete ptr;
+            ptr = p;
+        }
+        T& operator*() const { return *ptr; }
+    private:
+        pointer ptr;
+    };
+
+    template< typename T > using function = T*;
+    using nullptr_t = decltype(nullptr);
+
+    template<typename T>
+    struct identity {
+        typedef T type;
+    };
+
+    template <typename T>
+    inline T&& forward(typename identity<T>::type& t) noexcept
+    {
+        return static_cast<typename identity<T>::type&&>(t);
+    }
+}
+
+#endif // __ghostl_h