[struct_pack][feat] support user-define global config (#741)

include/ylt/struct_pack/reflection.hpp

@@ -590,6 +590,33 @@ template <typename T, typename = void>
   constexpr bool user_defined_config_by_ADL = user_defined_config_by_ADL_impl<T>::value;
 #endif
 
+template<typename T>
+constexpr decltype(auto) delay_sp_config_eval() {
+  if constexpr (sizeof(T)==0) {
+    return (T*){};
+  }
+  else {
+    return (sp_config*){};
+  }
+}
+
+#if __cpp_concepts >= 201907L
+  template<typename T>
+  concept has_default_config = std::is_same_v<decltype(set_default(decltype(delay_sp_config_eval<T>()){})),struct_pack::sp_config>;
+#else
+  template <typename T, typename = void>
+  struct has_default_config_impl : std::false_type {};
+
+  template <typename T>
+  struct has_default_config_impl<T, std::void_t<
+    std::enable_if_t<std::is_same_v<decltype(set_default(decltype(delay_sp_config_eval<T>()){})),struct_pack::sp_config>>>>
+      : std::true_type {};
+
+  template <typename T>
+  constexpr bool has_default_config = has_default_config_impl<T>::value;
+#endif
+
+
 #if __cpp_concepts >= 201907L
   template <typename Type>
   concept user_defined_config = requires {

include/ylt/struct_pack/type_calculate.hpp

@@ -153,18 +153,25 @@ constexpr decltype(auto) get_type_end_flag() {
   }
 }
 
-template <typename Arg, typename...>
-constexpr uint64_t get_parent_tag_impl() {
-  if constexpr (user_defined_config_by_ADL<Arg>) {
-    return static_cast<uint64_t>(set_sp_config((Arg *)nullptr));
+template <typename T>
+constexpr sp_config get_type_config() {
+  if constexpr (struct_pack::detail::user_defined_config_by_ADL<T>) {
+    return set_sp_config((T *)nullptr);
   }
-  else if constexpr (user_defined_config<Arg>) {
-    return static_cast<uint64_t>(Arg::struct_pack_config);
+  else if constexpr (struct_pack::detail::user_defined_config<T>) {
+    return static_cast<sp_config>(T::struct_pack_config);
+  }
+  else if constexpr (struct_pack::detail::has_default_config<T>) {
+    return set_default(decltype(delay_sp_config_eval<T>()){});
   }
   else {
-    return 0;
+    return sp_config::DEFAULT;
   }
 }
+template <typename T, typename... Args>
+constexpr uint64_t get_parent_tag_impl() {
+  return static_cast<uint64_t>(get_type_config<T>());
+}
 
 template <typename... Args>
 constexpr uint64_t get_parent_tag() {
@@ -715,26 +722,12 @@ template <uint64_t conf, typename T>
 constexpr bool check_if_add_type_literal() {
   constexpr auto config = conf & 0b11;
   if constexpr (config == sp_config::DEFAULT) {
-    if constexpr (struct_pack::detail::user_defined_config_by_ADL<T>) {
-      constexpr auto config = set_sp_config((T *)nullptr) & 0b11;
-      if constexpr (config == sp_config::DEFAULT) {
-        return serialize_static_config<T>::has_type_literal;
-      }
-      else {
-        return config == sp_config::ENABLE_TYPE_INFO;
-      }
-    }
-    else if constexpr (struct_pack::detail::user_defined_config<T>) {
-      constexpr auto config = T::struct_pack_config & 0b11;
-      if constexpr (config == sp_config::DEFAULT) {
-        return serialize_static_config<T>::has_type_literal;
-      }
-      else {
-        return config == sp_config::ENABLE_TYPE_INFO;
-      }
+    constexpr auto config = get_type_config<T>() & 0b11;
+    if constexpr (config == sp_config::DEFAULT) {
+      return serialize_static_config<T>::has_type_literal;
     }
     else {
-      return serialize_static_config<T>::has_type_literal;
+      return config == sp_config::ENABLE_TYPE_INFO;
     }
   }
   else {
@@ -830,22 +823,13 @@ constexpr bool check_if_has_container() {
 template <uint64_t conf, typename T>
 constexpr bool check_if_disable_hash_head_impl() {
   constexpr auto config = conf & 0b11;
-  if constexpr (config != sp_config::DISABLE_ALL_META_INFO) {
-    if constexpr (struct_pack::detail::user_defined_config_by_ADL<T>) {
-      constexpr auto config = set_sp_config((T *)nullptr) & 0b11;
-      if constexpr (config == sp_config::DISABLE_ALL_META_INFO) {
-        return true;
-      }
-    }
-    else if constexpr (struct_pack::detail::user_defined_config<T>) {
-      constexpr auto config = T::struct_pack_config & 0b11;
-      if constexpr (config == sp_config::DISABLE_ALL_META_INFO) {
-        return true;
-      }
-    }
-    return false;
+  if constexpr (config == sp_config::DEFAULT) {
+    constexpr auto config = get_type_config<T>() & 0b11;
+    return config == sp_config::DISABLE_ALL_META_INFO;
+  }
+  else {
+    return config == sp_config::DISABLE_ALL_META_INFO;
   }
-  return true;
 }
 
 template <uint64_t conf, typename T>

src/struct_pack/examples/serialize_config.cpp

@@ -16,6 +16,9 @@
 
 #include <cassert>
 
+#include "ylt/struct_pack/reflection.hpp"
+#include "ylt/struct_pack/type_calculate.hpp"
+
 #define STRUCT_PACK_OPTIMIZE  // add this macro to speed up
                               // serialize/deserialize but it will cost more
                               // time to compile
@@ -26,6 +29,12 @@
 // add this macro to enable support of int128/uint128
 
 #include <ylt/struct_pack.hpp>
+// set global default struct pack config
+namespace struct_pack {
+constexpr sp_config set_default(sp_config*) {
+  return sp_config::DISABLE_TYPE_INFO;
+}
+}  // namespace struct_pack
 
 struct rect {
   int a, b, c, d;

src/struct_pack/tests/test_type_info_config.cpp

@@ -0,0 +1,19 @@
+#include "ylt/struct_pack.hpp"
+#include "ylt/struct_pack/reflection.hpp"
+// set global default struct pack config
+namespace struct_pack {
+constexpr sp_config set_default(sp_config*) {
+  return sp_config::DISABLE_ALL_META_INFO;
+}
+}  // namespace struct_pack
+struct rect {
+  int a, b, c, d;
+};
+struct rect2 {
+  int a, b, c, d;
+};
+constexpr struct_pack::sp_config set_sp_config(rect2*) {
+  return struct_pack::sp_config::DISABLE_TYPE_INFO;
+}
+static_assert(struct_pack::get_needed_size(rect{}).size() == 16);
+static_assert(struct_pack::get_needed_size(rect2{}).size() == 20);

website/docs/en/struct_pack/struct_pack_tips.md

@@ -50,12 +50,28 @@ Also, note that if structure A nests structure B, the configuration for A will n
 For example：
 ```cpp
 struct rect {
-  var_int a, b, c, d;
+  int a, b, c, d;
 };
 ```
 
+## global config
+
+`sp_config::default` is default global config, you can also use other config value by following codes:
+
+```cpp
+namespace struct_pack {
+  //default global config
+  constexpr sp_config set_default(sp_config*){ return sp_config::DISABLE_ALL_META_INFO; }
+}
+static_assert(struct_pack::get_needed_size(rect{}).size()==16);
+```
+
+You can have different config value in different code unit(*.cpp file).
+
 ### config by class static member
 
+This config takes precedence over global config.
+
 Just add a constexpr static member named `struct_pack_config` to the class
 
 ```cpp

website/docs/zh/struct_pack/struct_pack_tips.md

@@ -56,9 +56,26 @@ struct rect {
 };
 ```
 
+### 全局配置
+
+`sp_config::default`是默认情况下的全局配置,你也可以自定义默认的全局配置。
+
+```cpp
+
+namespace struct_pack {
+  //设置全局默认配置
+  constexpr sp_config set_default(sp_config*){ return sp_config::DISABLE_ALL_META_INFO; }
+}
+static_assert(struct_pack::get_needed_size(rect{}).size()==16);
+```
+
+你可以在不同的代码单元（*.cpp文件）中声明不同的默认配置值。
+
 ### 通过类静态成员配置
 
-在类中添加一个constexpr static的成员struct_pack_config即可
+在类中添加一个constexpr static的成员struct_pack_config即可。
+
+该配置的优先级高于全局配置。
 
 ```cpp
 struct rect {