upd: [imp] modify interface of the system header file

include/libimp/system.h

@@ -12,17 +12,16 @@
 
 #include "libimp/def.h"
 #include "libimp/export.h"
-#include "libimp/result.h"
+#include "libimp/error.h"
-#include "libimp/fmt_cpo.h"
 
 LIBIMP_NAMESPACE_BEG_
 namespace sys {
 
 /**
- * @brief Get/Set the system error code
+ * @brief Get/Set the system error number
  */
-LIBIMP_EXPORT result_code error_code() noexcept;
+LIBIMP_EXPORT result_code error_no() noexcept;
-LIBIMP_EXPORT void error_code(result_code) noexcept;
+LIBIMP_EXPORT void error_no(result_code) noexcept;
 
 /**
  * @brief Gets a text description of the system error
@@ -30,29 +29,16 @@ LIBIMP_EXPORT void error_code(result_code) noexcept;
 LIBIMP_EXPORT std::string error_str(result_code) noexcept;
 
 /**
- * @brief A text description string with an error number attached
+ * @brief Identifies the operating system error category.
+ * @see https://en.cppreference.com/w/cpp/error/system_category
  */
-LIBIMP_EXPORT std::string error_msg(result_code) noexcept;
+LIBIMP_EXPORT error_category const &category() noexcept;
 
 /**
- * @brief The system error object.
+ * @brief A platform-dependent error code.
+ * @see https://en.cppreference.com/w/cpp/error/error_code
  */
-class LIBIMP_EXPORT error {
+LIBIMP_EXPORT error_code error() noexcept;
-  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 LIBIMP_EXPORT bool operator==(error const &lhs, error const &rhs) noexcept;
-  friend LIBIMP_EXPORT bool operator!=(error const &lhs, error const &rhs) noexcept;
-};
 
 /**
  * @brief Get system configuration information at run time
@@ -62,12 +48,5 @@ enum class info : std::int32_t {
 };
 LIBIMP_EXPORT result<std::int64_t> conf(info) noexcept;
 
-/**
- * @brief @brief Custom defined fmt_to method for imp::fmt
- */
-inline bool tag_invoke(decltype(::LIBIMP::fmt_to), fmt_context &ctx, error r) noexcept {
-  return fmt_to(ctx, error_msg(r.code()));
-}
-
 } // namespace sys
 LIBIMP_NAMESPACE_END_

src/libimp/platform/posix/system.h

@@ -19,20 +19,20 @@ namespace sys {
 #endif
 
 /**
- * @brief Get the system error code
+ * @brief Get the system error number
  * https://man7.org/linux/man-pages/man3/errno.3.html
  */
-result_code error_code() noexcept {
+result_code error_no() noexcept {
   auto err = errno;
   if (err == ENOERR) return {ENOERR};
   return {false, std::uint64_t(err)};
 }
 
 /**
- * @brief Set the system error code
+ * @brief Set the system error number
  * https://man7.org/linux/man-pages/man3/errno.3.html
  */
-void error_code(result_code code) noexcept {
+void error_no(result_code code) noexcept {
   errno = code ? ENOERR : (int)code.value();
 }
 

src/libimp/platform/win/codecvt.h

@@ -36,7 +36,7 @@ std::size_t cvt_cstr(char const *src, std::size_t slen, wchar_t *des, std::size_
   int cch_wc = (des == nullptr) ? 0 : (int)dlen;
   int size_needed = ::MultiByteToWideChar(CP_ACP, 0, src, (int)slen, des, cch_wc);
   if (size_needed <= 0) {
-    log.error("failed: MultiByteToWideChar(CP_ACP). error = ", sys::error_code());
+    log.error("failed: MultiByteToWideChar(CP_ACP). error = ", sys::error_no());
   }
   return size_needed;
 }
@@ -51,7 +51,7 @@ std::size_t cvt_cstr(wchar_t const *src, std::size_t slen, char *des, std::size_
   int cb_mb = (des == nullptr) ? 0 : (int)dlen;
   int size_needed = ::WideCharToMultiByte(CP_ACP, 0, src, (int)slen, des, cb_mb, NULL, NULL);
   if (size_needed <= 0) {
-    log.error("failed: WideCharToMultiByte(CP_ACP). error = ", sys::error_code());
+    log.error("failed: WideCharToMultiByte(CP_ACP). error = ", sys::error_no());
   }
   return size_needed;
 }

src/libimp/platform/win/system.h

@@ -21,10 +21,10 @@ LIBIMP_NAMESPACE_BEG_
 namespace sys {
 
 /**
- * @brief Get the system error code
+ * @brief Get the system error number
  * https://docs.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-getlasterror
  */
-result_code error_code() noexcept {
+result_code error_no() noexcept {
   auto err = ::GetLastError();
   if (err == ERROR_SUCCESS) {
     return {ERROR_SUCCESS};
@@ -33,10 +33,10 @@ result_code error_code() noexcept {
 }
 
 /**
- * @brief Set the system error code
+ * @brief Set the system error number
  * https://docs.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-setlasterror
  */
-void error_code(result_code code) noexcept {
+void error_no(result_code code) noexcept {
   DWORD err = code ? ERROR_SUCCESS : (DWORD)code.value();
   ::SetLastError(err);
 }

src/libimp/system.cpp

@@ -1,4 +1,6 @@
 
+#include "libimp/system.h"
+#include "libimp/fmt.h"
 #include "libimp/detect_plat.h"
 #if defined(LIBIMP_OS_WIN)
 # include "libimp/platform/win/system.h"
@@ -6,47 +8,30 @@
 # include "libimp/platform/posix/system.h"
 #endif
 
+namespace {
+
+class system_error_category : public ::LIBIMP::error_category {
+public:
+  std::string name() const {
+    return "system";
+  }
+  std::string message(::LIBIMP::result_code r) const {
+    return ::LIBIMP::fmt(r.value(), ::LIBIMP::sys::error_str(r));
+  }
+};
+
+} // namespace
+
 LIBIMP_NAMESPACE_BEG_
 namespace sys {
 
-std::string error_msg(result_code code) noexcept {
+error_category const &category() noexcept {
-  LIBIMP_TRY {
+  static system_error_category ec;
-    return fmt("[", code.value(), ", \"", error_str(code), "\"]");
+  return ec;
-  } LIBIMP_CATCH(...) {
-    return error_str(code);
-  }
 }
 
-/// @brief The system error object.
+error_code error() noexcept {
-
+  return error_code{error_no(), category()};
-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();
 }
 
 } // namespace sys

src/libipc/platform/win/get_sa.h

@@ -30,7 +30,8 @@ inline LPSECURITY_ATTRIBUTES get_sa() {
       using namespace ::LIBIMP;
       log::grip log {"get_sa"};
       if (!::InitializeSecurityDescriptor(&sd_, SECURITY_DESCRIPTOR_REVISION)) {
-        log.error("failed: InitializeSecurityDescriptor(SECURITY_DESCRIPTOR_REVISION). error = ", sys::error());
+        log.error("failed: InitializeSecurityDescriptor(SECURITY_DESCRIPTOR_REVISION). "
+                  "error = ", sys::error());
         return;
       }
       if (!::SetSecurityDescriptorDacl(&sd_, TRUE, NULL, FALSE)) {

test/imp/test_imp_system.cpp

@@ -14,19 +14,16 @@
 #else
 #endif
 
-TEST(system, error_code) {
+TEST(system, error_no) {
-  imp::sys::error_code({false, 111});
+  imp::sys::error_no({false, 111});
-  auto err = imp::sys::error_code();
+  auto err = imp::sys::error_no();
   EXPECT_FALSE(err);
   EXPECT_EQ(err.value(), 111);
 
-  imp::sys::error_code({});
+  imp::sys::error_no({});
-  EXPECT_TRUE(imp::sys::error_code());
+  EXPECT_TRUE(imp::sys::error_no());
 
-  imp::sys::error e_obj {err};
+  auto e_msg = imp::sys::error_str(imp::sys::error_no());
-  EXPECT_EQ(err.value(), e_obj.value());
-  auto e_msg = imp::fmt(imp::sys::error_msg(imp::sys::error_code()));
-  EXPECT_EQ(e_msg, imp::fmt(imp::sys::error()));
   std::cout << e_msg << "\n";
 }