feat: Read and write LedgerCache to file (#2761)

Fixes #2413.

src/data/impl/LedgerCacheFile.hpp

@@ -0,0 +1,70 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2025, the clio developers.
+
+    Permission to use, copy, modify, and 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.
+*/
+//==============================================================================
+
+#pragma once
+
+#include "data/LedgerCache.hpp"
+#include "data/impl/InputFile.hpp"
+#include "data/impl/OutputFile.hpp"
+
+#include <fmt/format.h>
+#include <xrpl/basics/base_uint.h>
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <string>
+
+namespace data::impl {
+
+class LedgerCacheFile {
+public:
+    struct Header {
+        uint32_t version = kVERSION;
+        uint32_t latestSeq{};
+        uint64_t mapSize{};
+        uint64_t deletedSize{};
+    };
+
+private:
+    static constexpr uint32_t kVERSION = 1;
+
+    std::string path_;
+
+public:
+    template <typename T>
+    struct DataBase {
+        uint32_t latestSeq{0};
+        T map;
+        T deleted;
+    };
+
+    using DataView = DataBase<LedgerCache::CacheMap const&>;
+    using Data = DataBase<LedgerCache::CacheMap>;
+
+    LedgerCacheFile(std::string path);
+
+    std::expected<void, std::string>
+    write(DataView dataView);
+
+    std::expected<Data, std::string>
+    read(uint32_t minLatestSequence);
+};
+
+}  // namespace data::impl