rippled/include/xrpl/shamap/FullBelowCache.h

#pragma once

#include <xrpl/basics/KeyCache.h>
#include <xrpl/basics/TaggedCache.h>
#include <xrpl/basics/base_uint.h>
#include <xrpl/beast/insight/Collector.h>
#include <xrpl/beast/insight/NullCollector.h>
#include <xrpl/beast/utility/Journal.h>

#include <atomic>
#include <chrono>
#include <cstddef>
#include <cstdint>
#include <string>

namespace xrpl {

namespace detail {

/**
 * Remembers which tree keys have all descendants resident.
 * This optimizes the process of acquiring a complete tree.
 */
class BasicFullBelowCache
{
private:
    using CacheType = KeyCache;

public:
    static constexpr auto kDefaultCacheTargetSize = 0;

    using key_type = uint256;
    using clock_type = CacheType::clock_type;

    /**
     * Construct the cache.
     *
     * @param name A label for diagnostics and stats reporting.
     * @param collector The collector to use for reporting stats.
     * @param targetSize The cache target size.
     * @param targetExpirationSeconds The expiration time for items.
     */
    BasicFullBelowCache(
        std::string const& name,
        clock_type& clock,
        beast::Journal j,
        beast::insight::Collector::ptr const& collector = beast::insight::NullCollector::make(),
        std::size_t targetSize = kDefaultCacheTargetSize,
        std::chrono::seconds expiration = std::chrono::minutes{2})
        : cache_(name, targetSize, expiration, clock, j, collector), gen_(1)
    {
    }

    /**
     * Return the clock associated with the cache.
     */
    clock_type&
    clock()
    {
        return cache_.clock();
    }

    /**
     * Return the number of elements in the cache.
     * Thread safety:
     *     Safe to call from any thread.
     */
    std::size_t
    size() const
    {
        return cache_.size();
    }

    /**
     * Remove expired cache items.
     * Thread safety:
     *     Safe to call from any thread.
     */
    void
    sweep()
    {
        cache_.sweep();
    }

    /**
     * Refresh the last access time of an item, if it exists.
     * Thread safety:
     *     Safe to call from any thread.
     * @param key The key to refresh.
     * @return `true` If the key exists.
     */
    bool
    touchIfExists(key_type const& key)
    {
        return cache_.touchIfExists(key);
    }

    /**
     * Insert a key into the cache.
     * If the key already exists, the last access time will still
     * be refreshed.
     * Thread safety:
     *     Safe to call from any thread.
     * @param key The key to insert.
     */
    void
    insert(key_type const& key)
    {
        cache_.insert(key);
    }

    /**
     * generation determines whether cached entry is valid
     */
    std::uint32_t
    getGeneration() const
    {
        return gen_;
    }

    void
    clear()
    {
        cache_.clear();
        ++gen_;
    }

    void
    reset()
    {
        cache_.clear();
        gen_ = 1;
    }

private:
    CacheType cache_;
    std::atomic<std::uint32_t> gen_;
};

}  // namespace detail

using FullBelowCache = detail::BasicFullBelowCache;

}  // namespace xrpl