add: [imp] sys::error object

include/libimp/system.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <string>
+#include <ostream>  // std::ostream
 #include <cstdint>
 
 #include "libimp/def.h"
@@ -32,6 +33,28 @@ LIBIMP_EXPORT std::string error_str(result_code) noexcept;
  */
 LIBIMP_EXPORT std::string error_msg(result_code) noexcept;
 
+/**
+ * @brief The system error object.
+ */
+class LIBIMP_EXPORT error {
+  result_code r_code_;
+
+public:
+  explicit error() noexcept;
+  explicit error(result_code rc) noexcept;
+
+  result_code code() const noexcept;
+  std::uint64_t value() const noexcept;
+  explicit operator bool() const noexcept;
+
+  std::string str() const noexcept;
+
+  friend bool operator==(error const &lhs, error const &rhs) noexcept;
+  friend bool operator!=(error const &lhs, error const &rhs) noexcept;
+
+  friend std::ostream &operator<<(std::ostream &o, error const &e);
+};
+
 /**
  * @brief Get system configuration information at run time
  */
@@ -42,3 +65,12 @@ LIBIMP_EXPORT std::int64_t conf(info) noexcept;
 
 } // namespace sys
 LIBIMP_NAMESPACE_END_
+
+template <>
+struct fmt::formatter<::LIBIMP_::sys::error>
+          : formatter<std::string> {
+  template <typename FormatContext>
+  auto format(::LIBIMP_::sys::error r, FormatContext &ctx) {
+    return format_to(ctx.out(), "{}", ::LIBIMP_::sys::error_msg(r.code()));
+  }
+};

src/libimp/system.cpp

@@ -18,5 +18,42 @@ std::string error_msg(result_code code) noexcept {
   }
 }
 
+/// @brief The system error object.
+
+error::error() noexcept
+  : error(error_code()) {}
+
+error::error(result_code rc) noexcept
+  : r_code_(rc) {}
+
+result_code error::code() const noexcept {
+  return r_code_;
+}
+
+std::uint64_t error::value() const noexcept {
+  return r_code_.value();
+}
+
+error::operator bool() const noexcept {
+  return !!r_code_;
+}
+
+std::string error::str() const noexcept {
+  return error_str(r_code_);
+}
+
+bool operator==(error const &lhs, error const &rhs) noexcept {
+  return lhs.code() == rhs.code();
+}
+
+bool operator!=(error const &lhs, error const &rhs) noexcept {
+  return lhs.code() != rhs.code();
+}
+
+std::ostream &operator<<(std::ostream &o, error const &e) {
+  o << error_msg(e.code());
+  return o;
+}
+
 } // namespace sys
 LIBIMP_NAMESPACE_END_

test/test_imp_system.cpp

@@ -1,5 +1,6 @@
 
 #include <iostream>
+#include <string>
 
 #include "gtest/gtest.h"
 #include "fmt/format.h"
@@ -14,8 +15,6 @@
 #endif
 
 TEST(system, error_code) {
-  std::cout << fmt::format("{}\n", imp::sys::error_msg(imp::sys::error_code()));
-
   imp::sys::error_code({false, 111});
   auto err = imp::sys::error_code();
   EXPECT_FALSE(err);
@@ -23,20 +22,28 @@ TEST(system, error_code) {
 
   imp::sys::error_code({});
   EXPECT_TRUE(imp::sys::error_code());
+
+  imp::sys::error e_obj {err};
+  EXPECT_EQ(err.value(), e_obj.value());
+  auto e_msg = fmt::format("{}", imp::sys::error_msg(imp::sys::error_code()));
+  std::stringstream ss;
+  ss << imp::sys::error{};
+  EXPECT_EQ(e_msg, ss.str());
+  std::cout << e_msg << "\n";
 }
 
 TEST(system, error_str) {
 #if defined(LIBIMP_OS_WIN)
-  std::u16string u16_ok, u16_err;
+  std::wstring u16_ok, u16_err;
   LANGID lId = ::GetSystemDefaultLangID();
   switch (lId) {
   case 0x0804:
-    u16_ok  = u"操作成功完成。\r\n";
-    u16_err = u"句柄无效。\r\n";
+    u16_ok  = L"操作成功完成。\r\n";
+    u16_err = L"句柄无效。\r\n";
     break;
   case 0x0409:
-    u16_ok  = u"The operation completed successfully.\r\n";
-    u16_err = u"The handle is invalid.\r\n";
+    u16_ok  = L"The operation completed successfully.\r\n";
+    u16_err = L"The handle is invalid.\r\n";
     break;
   default:
     return;