node/caches: Extract cache calculation logic

I strongly recommend reviewing with the following git-diff flags:
  --color-moved=dimmed_zebra --color-moved-ws=allow-indentation-change

[META] In a future commit, this function will be re-used in TestingSetup
       so that the behaviour matches across test and non-test init
       codepaths.

1 files changed, 22 insertions, 0 deletions

diff --git a/src/node/caches.h b/src/node/caches.h
new file mode 100644
index 0000000000..437e7d10e5
--- /dev/null
+++ b/src/node/caches.h
@@ -0,0 +1,22 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_NODE_CACHES_H
+#define BITCOIN_NODE_CACHES_H
+
+#include <cstddef> // for size_t
+#include <cstdint> // for int64_t
+
+class ArgsManager;
+
+struct CacheSizes {
+    int64_t block_tree_db;
+    int64_t coins_db;
+    int64_t coins;
+    int64_t tx_index;
+    int64_t filter_index;
+};
+CacheSizes CalculateCacheSizes(const ArgsManager& args, size_t n_indexes = 0);
+
+#endif // BITCOIN_NODE_CACHES_H