refactor: Modularize shamap and nodestore (#5668)

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

include/xrpl/nodestore/Backend.h

@@ -0,0 +1,167 @@
+//------------------------------------------------------------------------------
+/*
+    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_BACKEND_H_INCLUDED
+#define RIPPLE_NODESTORE_BACKEND_H_INCLUDED
+
+#include <xrpl/nodestore/Types.h>
+
+#include <cstdint>
+
+namespace ripple {
+namespace NodeStore {
+
+/** A backend used for the NodeStore.
+
+    The NodeStore uses a swappable backend so that other database systems
+    can be tried. Different databases may offer various features such
+    as improved performance, fault tolerant or distributed storage, or
+    all in-memory operation.
+
+    A given instance of a backend is fixed to a particular key size.
+*/
+class Backend
+{
+public:
+    /** Destroy the backend.
+
+        All open files are closed and flushed. If there are batched writes
+        or other tasks scheduled, they will be completed before this call
+        returns.
+    */
+    virtual ~Backend() = default;
+
+    /** Get the human-readable name of this backend.
+        This is used for diagnostic output.
+    */
+    virtual std::string
+    getName() = 0;
+
+    /** Get the block size for backends that support it
+     */
+    virtual std::optional<std::size_t>
+    getBlockSize() const
+    {
+        return std::nullopt;
+    }
+
+    /** Open the backend.
+        @param createIfMissing Create the database files if necessary.
+        This allows the caller to catch exceptions.
+    */
+    virtual void
+    open(bool createIfMissing = true) = 0;
+
+    /** Returns true is the database is open.
+     */
+    virtual bool
+    isOpen() = 0;
+
+    /** Open the backend.
+        @param createIfMissing Create the database files if necessary.
+        @param appType Deterministic appType used to create a backend.
+        @param uid Deterministic uid used to create a backend.
+        @param salt Deterministic salt used to create a backend.
+        @throws std::runtime_error is function is called not for NuDB backend.
+    */
+    virtual void
+    open(bool createIfMissing, uint64_t appType, uint64_t uid, uint64_t salt)
+    {
+        Throw<std::runtime_error>(
+            "Deterministic appType/uid/salt not supported by backend " +
+            getName());
+    }
+
+    /** Close the backend.
+        This allows the caller to catch exceptions.
+    */
+    virtual void
+    close() = 0;
+
+    /** Fetch a single object.
+        If the object is not found or an error is encountered, the
+        result will indicate the condition.
+        @note This will be called concurrently.
+        @param key A pointer to the key data.
+        @param pObject [out] The created object if successful.
+        @return The result of the operation.
+    */
+    virtual Status
+    fetch(void const* key, std::shared_ptr<NodeObject>* pObject) = 0;
+
+    /** Fetch a batch synchronously. */
+    virtual std::pair<std::vector<std::shared_ptr<NodeObject>>, Status>
+    fetchBatch(std::vector<uint256 const*> const& hashes) = 0;
+
+    /** Store a single object.
+        Depending on the implementation this may happen immediately
+        or deferred using a scheduled task.
+        @note This will be called concurrently.
+        @param object The object to store.
+    */
+    virtual void
+    store(std::shared_ptr<NodeObject> const& object) = 0;
+
+    /** Store a group of objects.
+        @note This function will not be called concurrently with
+              itself or @ref store.
+    */
+    virtual void
+    storeBatch(Batch const& batch) = 0;
+
+    virtual void
+    sync() = 0;
+
+    /** Visit every object in the database
+        This is usually called during import.
+        @note This routine will not be called concurrently with itself
+              or other methods.
+        @see import
+    */
+    virtual void
+    for_each(std::function<void(std::shared_ptr<NodeObject>)> f) = 0;
+
+    /** Estimate the number of write operations pending. */
+    virtual int
+    getWriteLoad() = 0;
+
+    /** Remove contents on disk upon destruction. */
+    virtual void
+    setDeletePath() = 0;
+
+    /** Perform consistency checks on database.
+     *
+     * This method is implemented only by NuDBBackend. It is not yet called
+     * anywhere, but it might be a good idea to one day call it at startup to
+     * avert a crash.
+     */
+    virtual void
+    verify()
+    {
+    }
+
+    /** Returns the number of file descriptors the backend expects to need. */
+    virtual int
+    fdRequired() const = 0;
+};
+
+}  // namespace NodeStore
+}  // namespace ripple
+
+#endif