LedgerHashesEntry.h

#pragma once
 
#include <xrpl/basics/base_uint.h>
#include <xrpl/beast/utility/Journal.h>
#include <xrpl/ledger/ApplyView.h>
#include <xrpl/ledger/ReadView.h>
#include <xrpl/ledger/entries/SLEBase.h>
#include <xrpl/protocol/Indexes.h>
#include <xrpl/protocol/LedgerFormats.h>
#include <xrpl/protocol/SField.h>
#include <xrpl/protocol/STVector256.h>
 
#include <cstddef>
#include <optional>
 
namespace xrpl {
 
template <typename ViewT>
class LedgerHashesEntry : public SLEBase<ViewT, ltLEDGER_HASHES>
{
public:
    using Base = SLEBase<ViewT, ltLEDGER_HASHES>;
 
    // Inherit base constructors: adopt an existing SLE, or resolve one from a
    // Keylet against the view.
    using Base::Base;
 
    explicit LedgerHashesEntry(
        Base::ViewRefType view,
        beast::Journal j = beast::Journal{beast::Journal::getNullSink()})
        : Base(keylet::skip(), view, j)
    {
    }

    [[nodiscard]] std::optional<UInt256>
    hashAt(std::size_t diff) const
    {
        if (!this->exists())
            return std::nullopt;
        STVector256 const vec = (*this)->getFieldV256(sfHashes);
        if (vec.size() > diff)
            return vec[vec.size() - diff - 1];
        return std::nullopt;
    }
};
 
using LedgerHashesEntryR = LedgerHashesEntry<ReadView>;
using LedgerHashesEntryW = LedgerHashesEntry<ApplyView>;
 
}  // namespace xrpl