moveonly: add mp/type-pair.h

Author: ryanofsky

CMakeLists.txt

@@ -48,6 +48,7 @@ set(MP_PUBLIC_HEADERS
   include/mp/type-context.h
   include/mp/type-map.h
   include/mp/type-optional.h
+  include/mp/type-pair.h
   include/mp/type-pointer.h
   include/mp/type-set.h
   include/mp/type-vector.h

include/mp/proxy-types.h

@@ -143,29 +143,6 @@ struct ReadDestUpdate
 
 
 
-template <typename KeyLocalType, typename ValueLocalType, typename Input, typename ReadDest>
-decltype(auto) CustomReadField(TypeList<std::pair<KeyLocalType, ValueLocalType>>,
-    Priority<1>,
-    InvokeContext& invoke_context,
-    Input&& input,
-    ReadDest&& read_dest)
-{
-    const auto& pair = input.get();
-    using Accessors = typename ProxyStruct<typename Decay<decltype(pair)>::Reads>::Accessors;
-
-    ReadField(TypeList<KeyLocalType>(), invoke_context, Make<StructField, std::tuple_element_t<0, Accessors>>(pair),
-        ReadDestEmplace(TypeList<KeyLocalType>(), [&](auto&&... key_args) -> auto& {
-            KeyLocalType* key = nullptr;
-            ReadField(TypeList<ValueLocalType>(), invoke_context, Make<StructField, std::tuple_element_t<1, Accessors>>(pair),
-                ReadDestEmplace(TypeList<ValueLocalType>(), [&](auto&&... value_args) -> auto& {
-                    auto& ret = read_dest.construct(std::piecewise_construct, std::forward_as_tuple(key_args...),
-                        std::forward_as_tuple(value_args...));
-                    key = &ret.first;
-                    return ret.second;
-                }));
-            return *key;
-        }));
-}
 
 // TODO: Should generalize this to work with arbitrary length tuples, not just length 2-tuples.
 template <typename KeyLocalType, typename ValueLocalType, typename Input, typename ReadDest>
@@ -607,21 +584,6 @@ void CustomBuildField(TypeList<std::exception>,
 {
     BuildField(TypeList<std::string>(), invoke_context, output, std::string(value.what()));
 }
-
-// FIXME: Overload on output type instead of value type and switch to std::get and merge with next overload
-template <typename KeyLocalType, typename ValueLocalType, typename Value, typename Output>
-void CustomBuildField(TypeList<std::pair<KeyLocalType, ValueLocalType>>,
-    Priority<1>,
-    InvokeContext& invoke_context,
-    Value&& value,
-    Output&& output)
-{
-    auto pair = output.init();
-    using Accessors = typename ProxyStruct<typename decltype(pair)::Builds>::Accessors;
-    BuildField(TypeList<KeyLocalType>(), invoke_context, Make<StructField, std::tuple_element_t<0, Accessors>>(pair), value.first);
-    BuildField(TypeList<ValueLocalType>(), invoke_context, Make<StructField, std::tuple_element_t<1, Accessors>>(pair), value.second);
-}
-
 // TODO: Should generalize this to work with arbitrary length tuples, not just length 2-tuples.
 template <typename KeyLocalType, typename ValueLocalType, typename Value, typename Output>
 void CustomBuildField(TypeList<std::tuple<KeyLocalType, ValueLocalType>>,

include/mp/type-map.h

@@ -6,6 +6,7 @@
 #define MP_PROXY_TYPE_MAP_H
 
 #include <mp/proxy-types.h>
+#include <mp/type-pair.h>
 #include <mp/util.h>
 
 namespace mp {

include/mp/type-pair.h

@@ -0,0 +1,50 @@
+// Copyright (c) 2025 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 MP_PROXY_TYPE_PAIR_H
+#define MP_PROXY_TYPE_PAIR_H
+
+#include <mp/util.h>
+
+namespace mp {
+// FIXME: Overload on output type instead of value type and switch to std::get and merge with next overload
+template <typename KeyLocalType, typename ValueLocalType, typename Value, typename Output>
+void CustomBuildField(TypeList<std::pair<KeyLocalType, ValueLocalType>>,
+    Priority<1>,
+    InvokeContext& invoke_context,
+    Value&& value,
+    Output&& output)
+{
+    auto pair = output.init();
+    using Accessors = typename ProxyStruct<typename decltype(pair)::Builds>::Accessors;
+    BuildField(TypeList<KeyLocalType>(), invoke_context, Make<StructField, std::tuple_element_t<0, Accessors>>(pair), value.first);
+    BuildField(TypeList<ValueLocalType>(), invoke_context, Make<StructField, std::tuple_element_t<1, Accessors>>(pair), value.second);
+}
+
+template <typename KeyLocalType, typename ValueLocalType, typename Input, typename ReadDest>
+decltype(auto) CustomReadField(TypeList<std::pair<KeyLocalType, ValueLocalType>>,
+    Priority<1>,
+    InvokeContext& invoke_context,
+    Input&& input,
+    ReadDest&& read_dest)
+{
+    const auto& pair = input.get();
+    using Accessors = typename ProxyStruct<typename Decay<decltype(pair)>::Reads>::Accessors;
+
+    ReadField(TypeList<KeyLocalType>(), invoke_context, Make<StructField, std::tuple_element_t<0, Accessors>>(pair),
+        ReadDestEmplace(TypeList<KeyLocalType>(), [&](auto&&... key_args) -> auto& {
+            KeyLocalType* key = nullptr;
+            ReadField(TypeList<ValueLocalType>(), invoke_context, Make<StructField, std::tuple_element_t<1, Accessors>>(pair),
+                ReadDestEmplace(TypeList<ValueLocalType>(), [&](auto&&... value_args) -> auto& {
+                    auto& ret = read_dest.construct(std::piecewise_construct, std::forward_as_tuple(key_args...),
+                        std::forward_as_tuple(value_args...));
+                    key = &ret.first;
+                    return ret.second;
+                }));
+            return *key;
+        }));
+}
+} // namespace mp
+
+#endif // MP_PROXY_TYPE_PAIR_H