rippled/include/xrpl/ledger/CachedView.h

#ifndef XRPL_LEDGER_CACHEDVIEW_H_INCLUDED
#define XRPL_LEDGER_CACHEDVIEW_H_INCLUDED

#include <xrpl/basics/hardened_hash.h>
#include <xrpl/ledger/CachedSLEs.h>
#include <xrpl/ledger/ReadView.h>

#include <mutex>
#include <type_traits>

namespace xrpl {

namespace detail {

class CachedViewImpl : public DigestAwareReadView
{
private:
    DigestAwareReadView const& base_;
    CachedSLEs& cache_;
    std::mutex mutable mutex_;
    std::unordered_map<key_type, uint256, hardened_hash<>> mutable map_;

public:
    CachedViewImpl() = delete;
    CachedViewImpl(CachedViewImpl const&) = delete;
    CachedViewImpl&
    operator=(CachedViewImpl const&) = delete;

    CachedViewImpl(DigestAwareReadView const* base, CachedSLEs& cache)
        : base_(*base), cache_(cache)
    {
    }

    //
    // ReadView
    //

    bool
    exists(Keylet const& k) const override;

    std::shared_ptr<SLE const>
    read(Keylet const& k) const override;

    bool
    open() const override
    {
        return base_.open();
    }

    LedgerInfo const&
    info() const override
    {
        return base_.info();
    }

    Fees const&
    fees() const override
    {
        return base_.fees();
    }

    Rules const&
    rules() const override
    {
        return base_.rules();
    }

    std::optional<key_type>
    succ(
        key_type const& key,
        std::optional<key_type> const& last = std::nullopt) const override
    {
        return base_.succ(key, last);
    }

    std::unique_ptr<sles_type::iter_base>
    slesBegin() const override
    {
        return base_.slesBegin();
    }

    std::unique_ptr<sles_type::iter_base>
    slesEnd() const override
    {
        return base_.slesEnd();
    }

    std::unique_ptr<sles_type::iter_base>
    slesUpperBound(uint256 const& key) const override
    {
        return base_.slesUpperBound(key);
    }

    std::unique_ptr<txs_type::iter_base>
    txsBegin() const override
    {
        return base_.txsBegin();
    }

    std::unique_ptr<txs_type::iter_base>
    txsEnd() const override
    {
        return base_.txsEnd();
    }

    bool
    txExists(key_type const& key) const override
    {
        return base_.txExists(key);
    }

    tx_type
    txRead(key_type const& key) const override
    {
        return base_.txRead(key);
    }

    //
    // DigestAwareReadView
    //

    std::optional<digest_type>
    digest(key_type const& key) const override
    {
        return base_.digest(key);
    }
};

}  // namespace detail

/** Wraps a DigestAwareReadView to provide caching.

    @tparam Base A subclass of DigestAwareReadView
*/
template <class Base>
class CachedView : public detail::CachedViewImpl
{
private:
    static_assert(std::is_base_of<DigestAwareReadView, Base>::value, "");

    std::shared_ptr<Base const> sp_;

public:
    using base_type = Base;

    CachedView() = delete;
    CachedView(CachedView const&) = delete;
    CachedView&
    operator=(CachedView const&) = delete;

    CachedView(std::shared_ptr<Base const> const& base, CachedSLEs& cache)
        : CachedViewImpl(base.get(), cache), sp_(base)
    {
    }

    /** Returns the base type.

        @note This breaks encapsulation and bypasses the cache.
    */
    std::shared_ptr<Base const> const&
    base() const
    {
        return sp_;
    }
};

}  // namespace xrpl

#endif