/*
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* =====================================================================================
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*
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* Filename: robust.h
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*
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* Description:
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*
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* Version: 1.0
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* Created: 2021年04月27日 10时04分29秒
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* Revision: none
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* Compiler: gcc
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*
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* Author: Li Chao (), lichao@aiotlink.com
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* Organization:
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*
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* =====================================================================================
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*/
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#ifndef ROBUST_Q31RCWYU
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#define ROBUST_Q31RCWYU
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#include <atomic>
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#include <chrono>
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#include <memory>
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#include <string.h>
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#include <string>
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#include <sys/types.h>
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#include <unistd.h>
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namespace robust
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{
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using namespace std::chrono;
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using namespace std::chrono_literals;
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void QuickSleep();
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class RobustReqRep
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{
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typedef uint32_t State;
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typedef std::string Msg;
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typedef std::chrono::steady_clock::duration Duration;
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public:
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enum ErrorCode {
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eSuccess = 0,
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eTimeout = EAGAIN,
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eSizeError = EINVAL,
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};
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explicit RobustReqRep(const uint32_t max_len) :
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capacity_(max_len), state_(eStateInit), timestamp_(Duration(0)), size_(0) {}
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void PutReady() { state_.store(eStateReady); }
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bool Ready() const { return state_.load() == eStateReady; }
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uint32_t capacity() const { return capacity_; }
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int ClientRequest(const Msg &request, Msg &reply)
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{
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int r = ClientWriteRequest(request);
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if (r == eSuccess) {
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r = ClientReadReply(reply);
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}
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return r;
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}
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int ClientReadReply(Msg &reply);
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int ClientWriteRequest(const Msg &request);
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int ServerReadRequest(Msg &request);
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int ServerWriteReply(const Msg &reply);
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private:
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RobustReqRep(const RobustReqRep &);
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RobustReqRep(RobustReqRep &&);
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RobustReqRep &operator=(const RobustReqRep &) = delete;
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RobustReqRep &operator=(RobustReqRep &&) = delete;
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enum {
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eStateInit = 0,
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eStateReady = 0x19833891,
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eClientWriteBegin,
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eClientWriteEnd,
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eServerReadBegin,
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eServerReadEnd,
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eServerWriteBegin,
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eServerWriteEnd,
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eClientReadBegin,
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eClientReadEnd = eStateReady,
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};
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bool StateCas(State exp, State val);
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void Write(const Msg &msg)
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{
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size_.store(msg.size());
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memcpy(buf, msg.data(), msg.size());
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}
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void Read(Msg &msg) { msg.assign(buf, size_.load()); }
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const uint32_t capacity_;
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std::atomic<State> state_;
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static_assert(sizeof(State) == sizeof(state_), "atomic should has no extra data.");
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std::atomic<Duration> timestamp_;
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std::atomic<int32_t> size_;
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char buf[4];
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};
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template <bool isRobust = false>
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class CasMutex
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{
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static pid_t pid()
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{
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static pid_t val = getpid();
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return val;
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}
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static bool Killed(pid_t pid)
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{
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char buf[64] = {0};
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snprintf(buf, sizeof(buf) - 1, "/proc/%d/stat", pid);
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return access(buf, F_OK) != 0;
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}
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public:
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CasMutex() :
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meta_(0) {}
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int try_lock()
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{
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const auto t = steady_clock::now().time_since_epoch().count();
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auto old = meta_.load();
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int r = 0;
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if (!Locked(old)) {
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r = MetaCas(old, Meta(1, pid()));
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} else if (isRobust && Killed(Pid(old))) {
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r = static_cast<int>(MetaCas(old, Meta(1, pid()))) << 1;
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if (r) {
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printf("captured pid %d -> %d, r = %d\n", Pid(old), pid(), r);
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}
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}
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return r;
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}
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int lock()
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{
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int r = 0;
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do {
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r = try_lock();
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} while (r == 0);
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return r;
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}
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void unlock()
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{
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auto old = meta_.load();
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if (Locked(old) && Pid(old) == pid()) {
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MetaCas(old, Meta(0, pid()));
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}
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}
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private:
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std::atomic<uint64_t> meta_;
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bool Locked(uint64_t meta) { return (meta >> 63) != 0; }
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pid_t Pid(uint64_t meta) { return meta & ~(uint64_t(1) << 63); }
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uint64_t Meta(uint64_t lk, pid_t pid) { return (lk << 63) | pid; }
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bool MetaCas(uint64_t exp, uint64_t val) { return meta_.compare_exchange_strong(exp, val); }
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static_assert(sizeof(pid_t) < sizeof(uint64_t));
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};
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template <class Lock>
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class Guard
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{
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public:
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Guard(Lock &l) :
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l_(l) { l_.lock(); }
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~Guard() { l_.unlock(); }
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private:
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Guard(const Guard &);
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Guard(Guard &&);
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Lock &l_;
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};
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template <class D, class Alloc = std::allocator<D>>
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class CircularBuffer
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{
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typedef uint32_t size_type;
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typedef uint32_t count_type;
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typedef uint64_t meta_type;
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static size_type Pos(meta_type meta) { return meta & 0xFFFFFFFF; }
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static count_type Count(meta_type meta) { return meta >> 32; }
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static size_type Meta(meta_type count, size_type pos) { return (count << 32) | pos; }
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public:
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typedef D Data;
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CircularBuffer(const size_type cap) :
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CircularBuffer(cap, Alloc()) {}
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CircularBuffer(const size_type cap, Alloc const &al) :
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state_(0), capacity_(cap), mhead_(0), mtail_(0), al_(al), buf(al_.allocate(cap))
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{
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if (!buf) {
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throw("error allocate buffer: out of mem!");
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}
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}
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~CircularBuffer()
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{
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al_.deallocate(buf, capacity_);
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}
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size_type size() const { return (capacity_ + tail() - head()) % capacity_; }
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bool full() const { return (capacity_ + tail() + 1 - head()) % capacity_ == 0; }
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bool empty() const { return head() == tail(); }
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bool push_back(Data d)
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{
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Guard<MutexT> guard(mutex_);
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if (!full()) {
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auto old = mtail();
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buf[Pos(old)] = d;
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return mtail_.compare_exchange_strong(old, next(old));
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} else {
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return false;
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}
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}
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bool pop_front(Data &d)
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{
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Guard<MutexT> guard(mutex_);
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if (!empty()) {
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auto old = mhead();
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d = buf[Pos(old)];
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return mhead_.compare_exchange_strong(old, next(old));
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} else {
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return false;
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}
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}
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bool Ready() const { return state_.load() == eStateReady; }
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void PutReady() { state_.store(eStateReady); }
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private:
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CircularBuffer(const CircularBuffer &);
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CircularBuffer(CircularBuffer &&);
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CircularBuffer &operator=(const CircularBuffer &) = delete;
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CircularBuffer &operator=(CircularBuffer &&) = delete;
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typedef CasMutex<true> MutexT;
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// static_assert(sizeof(MutexT) == 16);
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meta_type next(meta_type meta) const { return Meta(Count(meta) + 1, (Pos(meta) + 1) % capacity_); }
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size_type head() const { return Pos(mhead()); }
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size_type tail() const { return Pos(mtail()); }
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meta_type mhead() const { return mhead_.load(); }
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meta_type mtail() const { return mtail_.load(); }
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// data
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enum { eStateReady = 0x19833891 };
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std::atomic<uint32_t> state_;
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const size_type capacity_;
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MutexT mutex_;
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std::atomic<meta_type> mhead_;
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std::atomic<meta_type> mtail_;
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Alloc al_;
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typename Alloc::pointer buf = nullptr;
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};
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} // namespace robust
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#endif // end of include guard: ROBUST_Q31RCWYU
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