LedgerHolder.h

#pragma once
 
#include <xrpl/basics/CountedObject.h>
#include <xrpl/basics/contract.h>
#include <xrpl/ledger/Ledger.h>
 
#include <memory>
#include <mutex>
#include <utility>
 
namespace xrpl {
 
// Can std::atomic<std::shared_ptr>> make this lock free?
 
// VFALCO NOTE This class can be replaced with atomic<shared_ptr<...>>

class LedgerHolder : public CountedObject<LedgerHolder>
{
public:
    // Update the held ledger
    void
    set(std::shared_ptr<Ledger const> ledger)
    {
        if (!ledger)
            logicError("LedgerHolder::set with nullptr");
        if (!ledger->isImmutable())
            logicError("LedgerHolder::set with mutable Ledger");
        std::scoped_lock const sl(lock_);
        heldLedger_ = std::move(ledger);
    }
 
    // Return the (immutable) held ledger
    std::shared_ptr<Ledger const>
    get()
    {
        std::scoped_lock const sl(lock_);
        return heldLedger_;
    }
 
    bool
    empty()
    {
        std::scoped_lock const sl(lock_);
        return heldLedger_ == nullptr;
    }
 
private:
    std::mutex lock_;
    std::shared_ptr<Ledger const> heldLedger_;
};
 
}  // namespace xrpl