add 'result'

include/libipc/mmap.h

@@ -0,0 +1,16 @@
+/**
+ * @file mmap.h
+ * @author mutouyun (orz@orzz.org)
+ * @brief Define the methods of memory-mapped file I/O
+ * @date 2022-04-17
+ */
+#pragma once
+
+#include "libipc/def.h"
+#include "libipc/result.h"
+
+LIBIPC_NAMESPACE_BEG_
+
+
+
+LIBIPC_NAMESPACE_END_

include/libipc/result.h

@@ -0,0 +1,37 @@
+/**
+ * @file result.h
+ * @author mutouyun (orz@orzz.org)
+ * @brief Define the return value type with a status code
+ * @date 2022-04-17
+ */
+#pragma once
+
+#include <ostream>  // std::ostream
+#include <cstdint>
+
+#include "libipc/def.h"
+#include "libipc/export.h"
+
+LIBIPC_NAMESPACE_BEG_
+
+class LIBIPC_EXPORT result {
+  std::uint64_t status_;
+
+public:
+  result() noexcept;
+  result(bool ok, std::uint64_t code = 0) noexcept;
+
+  std::uint64_t code() const noexcept;
+  bool ok() const noexcept;
+
+  explicit operator bool() const noexcept {
+    return ok();
+  }
+
+  friend bool operator==(result const &lhs, result const &rhs) noexcept;
+  friend bool operator!=(result const &lhs, result const &rhs) noexcept;
+
+  friend std::ostream &operator<<(std::ostream &o, result const &r) noexcept;
+};
+
+LIBIPC_NAMESPACE_END_

include/libipc/shm.h

@@ -2,6 +2,14 @@
  * @file shm.h
  * @author mutouyun (orz@orzz.org)
  * @brief Define the shared memory access interface
- * @date 2022-04-03
+ * @date 2022-04-17
  */
 #pragma once
+
+#include "libipc/def.h"
+
+LIBIPC_NAMESPACE_BEG_
+
+
+
+LIBIPC_NAMESPACE_END_

src/libipc/result.cpp

@@ -0,0 +1,50 @@
+
+#include "libipc/result.h"
+#include "libipc/utility/horrible_cast.h"
+
+LIBIPC_NAMESPACE_BEG_
+namespace {
+
+struct result_code_info {
+  std::uint64_t ok  : 1;
+  std::uint64_t code: 63;
+};
+
+std::uint64_t make_status(bool ok, std::uint64_t code) noexcept {
+  return horrible_cast<std::uint64_t>(result_code_info{ok ? 1ull : 0ull, code});
+}
+
+result_code_info info_cast(std::uint64_t status) noexcept {
+  return horrible_cast<result_code_info>(status);
+}
+
+} // namespace
+
+result::result() noexcept
+  : result(false, 0) {}
+
+result::result(bool ok, std::uint64_t code) noexcept
+  : status_(make_status(ok, code)) {}
+
+std::uint64_t result::code() const noexcept {
+  return info_cast(status_).code;
+}
+
+bool result::ok() const noexcept {
+  return info_cast(status_).ok != 0;
+}
+
+bool operator==(result const &lhs, result const &rhs) noexcept {
+  return lhs.status_ == rhs.status_;
+}
+
+bool operator!=(result const &lhs, result const &rhs) noexcept {
+  return lhs.status_ != rhs.status_;
+}
+
+std::ostream &operator<<(std::ostream &o, result const &r) noexcept {
+  o << "[" << (r.ok() ? "succ" : "fail") << ", code = " << r.code() << "]";
+  return o;
+}
+
+LIBIPC_NAMESPACE_END_

src/libipc/utility/horrible_cast.h

@@ -0,0 +1,25 @@
+/**
+ * @file src/horrible_cast.h
+ * @author mutouyun (orz@orzz.org)
+ * @date 2022-04-17
+ */
+#pragma once
+
+#include <type_traits>  // std::decay_t
+#include <utility>
+
+#include "libipc/def.h"
+
+LIBIPC_NAMESPACE_BEG_
+
+template <typename T, typename U>
+constexpr auto horrible_cast(U &&in) noexcept
+  -> std::enable_if_t<(sizeof(T) == sizeof(std::decay_t<U>)), T> {
+  union {
+    std::decay_t<U> in;
+    T out;
+  } u {std::forward<U>(in)};
+  return u.out;
+}
+
+LIBIPC_NAMESPACE_END_

src/libipc/utility/pimpl.h

@@ -58,7 +58,7 @@ auto clear(T *p) noexcept -> std::enable_if_t<!is_comfortable<T>::value> {
 
 template <typename T>
 class Obj {
- public:
+public:
   template <typename... A>
   static T *make(A &&... args) {
     return pimpl::make<T>(std::forward<A>(args)...);