xahaud/include/xrpl/basics/LocalValue.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012, 2013 Ripple Labs Inc.

    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#ifndef RIPPLE_BASICS_LOCALVALUE_H_INCLUDED
#define RIPPLE_BASICS_LOCALVALUE_H_INCLUDED

#include <boost/thread/tss.hpp>
#include <chrono>
#include <memory>
#include <unordered_map>

namespace ripple {

namespace detail {

struct LocalValues
{
    explicit LocalValues() = default;

    bool onCoro = true;
    void* coroPtr = nullptr;  // Pointer to owning JobQueue::Coro (if any)

    // When true, SHAMap::finishFetch() will poll-wait for missing nodes
    // instead of returning empty. Only set by partial sync code paths.
    bool partialSyncWait = false;

    // Configurable timeout for SHAMap node fetching during partial sync.
    // Zero means use the default (30s). RPC handlers can set this to
    // customize poll-wait behavior.
    std::chrono::milliseconds fetchTimeout{0};

    struct BasicValue
    {
        virtual ~BasicValue() = default;
        virtual void*
        get() = 0;
    };

    template <class T>
    struct Value : BasicValue
    {
        T t_;

        Value() = default;
        explicit Value(T const& t) : t_(t)
        {
        }

        void*
        get() override
        {
            return &t_;
        }
    };

    // Keys are the address of a LocalValue.
    std::unordered_map<void const*, std::unique_ptr<BasicValue>> values;

    static inline void
    cleanup(LocalValues* lvs)
    {
        if (lvs && !lvs->onCoro)
            delete lvs;
    }
};

template <class = void>
boost::thread_specific_ptr<detail::LocalValues>&
getLocalValues()
{
    static boost::thread_specific_ptr<detail::LocalValues> tsp(
        &detail::LocalValues::cleanup);
    return tsp;
}

}  // namespace detail

template <class T>
class LocalValue
{
public:
    template <class... Args>
    LocalValue(Args&&... args) : t_(std::forward<Args>(args)...)
    {
    }

    /** Stores instance of T specific to the calling coroutine or thread. */
    T&
    operator*();

    /** Stores instance of T specific to the calling coroutine or thread. */
    T*
    operator->()
    {
        return &**this;
    }

private:
    T t_;
};

template <class T>
T&
LocalValue<T>::operator*()
{
    auto lvs = detail::getLocalValues().get();
    if (!lvs)
    {
        lvs = new detail::LocalValues();
        lvs->onCoro = false;
        detail::getLocalValues().reset(lvs);
    }
    else
    {
        auto const iter = lvs->values.find(this);
        if (iter != lvs->values.end())
            return *reinterpret_cast<T*>(iter->second->get());
    }

    return *reinterpret_cast<T*>(
        lvs->values
            .emplace(this, std::make_unique<detail::LocalValues::Value<T>>(t_))
            .first->second->get());
}

// Returns pointer to current coroutine if running inside one, nullptr otherwise
inline void*
getCurrentCoroPtr()
{
    auto lvs = detail::getLocalValues().get();
    if (lvs && lvs->onCoro)
        return lvs->coroPtr;
    return nullptr;
}

// Check if partial sync wait is enabled for the current coroutine context.
inline bool
isPartialSyncWaitEnabled()
{
    auto lvs = detail::getLocalValues().get();
    if (lvs && lvs->onCoro)
        return lvs->partialSyncWait;
    return false;
}

// Enable/disable partial sync wait for the current coroutine context.
inline void
setPartialSyncWait(bool enabled)
{
    auto lvs = detail::getLocalValues().get();
    if (lvs && lvs->onCoro)
        lvs->partialSyncWait = enabled;
}

// Get the configured fetch timeout for current coroutine context.
// Returns 0ms if not in a coroutine or no custom timeout set.
inline std::chrono::milliseconds
getCoroFetchTimeout()
{
    auto lvs = detail::getLocalValues().get();
    if (lvs && lvs->onCoro)
        return lvs->fetchTimeout;
    return std::chrono::milliseconds{0};
}

// Set the fetch timeout for the current coroutine context.
// Only works if called from within a coroutine.
inline void
setCoroFetchTimeout(std::chrono::milliseconds timeout)
{
    auto lvs = detail::getLocalValues().get();
    if (lvs && lvs->onCoro)
        lvs->fetchTimeout = timeout;
}

}  // namespace ripple

#endif