gccrs: utils: Add bidirectional hashmap class

gcc/rust/ChangeLog:

	* expand/rust-macro-builtins.cc: Include bidirectional map.
	* util/bi-map.h: New file.

2 files changed, 49 insertions, 0 deletions

diff --git a/gcc/rust/expand/rust-macro-builtins.cc b/gcc/rust/expand/rust-macro-builtins.cc
index 9bee712..29a8b8b 100644
--- a/gcc/rust/expand/rust-macro-builtins.cc
+++ b/gcc/rust/expand/rust-macro-builtins.cc
@@ -29,6 +29,7 @@
 #include "rust-macro.h"
 #include "rust-parse.h"
 #include "rust-session-manager.h"
+#include "bi-map.h"
 
 namespace Rust {
 namespace {
diff --git a/gcc/rust/util/bi-map.h b/gcc/rust/util/bi-map.h
new file mode 100644
index 0000000..ab5878d
--- /dev/null
+++ b/gcc/rust/util/bi-map.h
@@ -0,0 +1,48 @@
+// Copyright (C) 2020-2023 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include "rust-system.h"
+
+#ifndef BIMAP_H
+#define BIMAP_H
+
+// very simple bi-directional hashmap
+template <typename K, typename V> class BiMap
+{
+  using v_iter = typename std::unordered_map<K, V>::const_iterator;
+  using k_iter = typename std::unordered_map<V, K>::const_iterator;
+
+public:
+  BiMap (std::unordered_map<K, V> &&original) : map (std::move (original))
+  {
+    for (auto &kv : map)
+      rmap.insert ({kv.second, kv.first});
+  }
+
+  const v_iter lookup (const K &key) const { return map.find (key); }
+  const k_iter lookup (const V &key) const { return rmap.find (key); }
+
+  bool is_iter_ok (const v_iter &iter) const { return iter != map.end (); }
+  bool is_iter_ok (const k_iter &iter) const { return iter != rmap.end (); }
+
+private:
+  std::unordered_map<K, V> map;
+  std::unordered_map<V, K> rmap;
+};
+
+#endif // !BIMAP_H