Move shard map handling into a separate file

Moved the handling of shard maps into another file.

server/modules/routing/schemarouter/shard_map.hh

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#pragma once
+
+#include <maxscale/cppdefs.hh>
+
+#include <maxscale/service.h>
+#include <maxscale/hashtable.h>
+#include <maxscale/spinlock.hh>
+
+enum shard_map_state
+{
+    SHMAP_UNINIT, /*< No databases have been added to this shard map */
+    SHMAP_READY, /*< All available databases have been added */
+    SHMAP_STALE /*< The shard map has old data or has not been updated recently */
+};
+
+/**
+ * A map of the shards tied to a single user.
+ */
+typedef struct shard_map
+{
+    HASHTABLE *hash; /*< A hashtable of database names and the servers which
+                       * have these databases. */
+    SPINLOCK lock;
+    time_t last_updated;
+    enum shard_map_state state; /*< State of the shard map */
+} shard_map_t;
+
+/** TODO: Replace these */
+int hashkeyfun(const void* key);
+int hashcmpfun(const void *, const void *);
+void keyfreefun(void* data);
+
+/** TODO: Don't use this everywhere */
+/** Size of the hashtable used to store ignored databases */
+#define SCHEMAROUTER_HASHSIZE 100
+
+/**
+ * Allocate a shard map and initialize it.
+ * @return Pointer to new shard_map_t or NULL if memory allocation failed
+ */
+shard_map_t* shard_map_alloc();
+
+/**
+ * Check if the shard map is out of date and update its state if necessary.
+ * @param router Router instance
+ * @param map Shard map to update
+ * @return Current state of the shard map
+ */
+enum shard_map_state shard_map_update_state(shard_map_t *self, double refresh_min_interval);
+
+/**
+ * Replace a shard map with another one. This function copies the contents of
+ * the source shard map to the target and frees the source memory.
+ * @param target Target shard map to replace
+ * @param source Source shard map to use
+ */
+void replace_shard_map(shard_map_t **target, shard_map_t **source);
+
+/**
+ * Return the newer of two shard maps
+ *
+ * @param stored The currently stored shard map
+ * @param current The replacement map the current client is using
+ * @return The newer of the two shard maps
+ */
+shard_map_t* get_latest_shard_map(shard_map_t *stored, shard_map_t *current);