refactor: Modularize shamap and nodestore (#5668)

This change moves the shamap and nodestore from `xrpld` to `libxrpl`.

include/xrpl/nodestore/Factory.h

@@ -0,0 +1,85 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2012, 2013 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or 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.
+*/
+//==============================================================================
+
+#ifndef RIPPLE_NODESTORE_FACTORY_H_INCLUDED
+#define RIPPLE_NODESTORE_FACTORY_H_INCLUDED
+
+#include <xrpl/basics/BasicConfig.h>
+#include <xrpl/beast/utility/Journal.h>
+#include <xrpl/nodestore/Backend.h>
+#include <xrpl/nodestore/Scheduler.h>
+
+#include <nudb/store.hpp>
+
+namespace ripple {
+
+namespace NodeStore {
+
+/** Base class for backend factories. */
+class Factory
+{
+public:
+    virtual ~Factory() = default;
+
+    /** Retrieve the name of this factory. */
+    virtual std::string
+    getName() const = 0;
+
+    /** Create an instance of this factory's backend.
+
+        @param keyBytes The fixed number of bytes per key.
+        @param parameters A set of key/value configuration pairs.
+        @param burstSize Backend burst size in bytes.
+        @param scheduler The scheduler to use for running tasks.
+        @return A pointer to the Backend object.
+    */
+    virtual std::unique_ptr<Backend>
+    createInstance(
+        size_t keyBytes,
+        Section const& parameters,
+        std::size_t burstSize,
+        Scheduler& scheduler,
+        beast::Journal journal) = 0;
+
+    /** Create an instance of this factory's backend.
+
+        @param keyBytes The fixed number of bytes per key.
+        @param parameters A set of key/value configuration pairs.
+        @param burstSize Backend burst size in bytes.
+        @param scheduler The scheduler to use for running tasks.
+        @param context The context used by database.
+        @return A pointer to the Backend object.
+    */
+    virtual std::unique_ptr<Backend>
+    createInstance(
+        size_t keyBytes,
+        Section const& parameters,
+        std::size_t burstSize,
+        Scheduler& scheduler,
+        nudb::context& context,
+        beast::Journal journal)
+    {
+        return {};
+    }
+};
+
+}  // namespace NodeStore
+}  // namespace ripple
+
+#endif