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

Fixes #2413.

src/data/LedgerCache.cpp

@@ -20,6 +20,7 @@
 #include "data/LedgerCache.hpp"
 
 #include "data/Types.hpp"
+#include "data/impl/LedgerCacheFile.hpp"
 #include "etl/Models.hpp"
 #include "util/Assert.hpp"
 
@@ -27,9 +28,14 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <map>
 #include <mutex>
 #include <optional>
 #include <shared_mutex>
+#include <string>
+#include <utility>
 #include <vector>
 
 namespace data {
@@ -251,4 +257,34 @@ LedgerCache::getSuccessorHitRate() const
     return static_cast<float>(successorHitCounter_.get().value()) / successorReqCounter_.get().value();
 }
 
+std::expected<void, std::string>
+LedgerCache::saveToFile(std::string const& path) const
+{
+    if (not isFull()) {
+        return std::unexpected{"Ledger cache is not full"};
+    }
+
+    impl::LedgerCacheFile file{path};
+    std::unique_lock lock{mtx_};
+    impl::LedgerCacheFile::DataView data{.latestSeq = latestSeq_, .map = map_, .deleted = deleted_};
+    return file.write(data);
+}
+
+std::expected<void, std::string>
+LedgerCache::loadFromFile(std::string const& path, uint32_t minLatestSequence)
+{
+    impl::LedgerCacheFile file{path};
+    auto data = file.read(minLatestSequence);
+    if (not data.has_value()) {
+        return std::unexpected(std::move(data).error());
+    }
+    auto [latestSeq, map, deleted] = std::move(data).value();
+    std::unique_lock lock{mtx_};
+    latestSeq_ = latestSeq;
+    map_ = std::move(map);
+    deleted_ = std::move(deleted);
+    full_ = true;
+    return {};
+}
+
 }  // namespace data