添加部分有用的小组件

include/libipc/def.h

@@ -9,7 +9,10 @@
 #include <cstddef>
 #include <cstdint>
 
-#define LIBIPC_NAMESPACE_BEG_ namespace ipc {
+#if !defined(LIBIPC_NAMESPACE)
+# define LIBIPC_NAMESPACE ipc
+#endif
+#define LIBIPC_NAMESPACE_BEG_ namespace LIBIPC_NAMESPACE {
 #define LIBIPC_NAMESPACE_END_ }
 
 LIBIPC_NAMESPACE_BEG_

src/libipc/utility/construct.h

@@ -0,0 +1,35 @@
+/**
+ * @file src/construct.h
+ * @author mutouyun (orz@orzz.org)
+ * @brief Construct an object from a memory buffer
+ * @date 2022-02-27
+ */
+#pragma once
+
+#include <new>          // placement-new
+#include <type_traits>  // std::enable_if_t
+#include <utility>      // std::forward
+
+#include "libipc/def.h"
+
+LIBIPC_NAMESPACE_BEG_
+
+template <typename T, typename... A>
+auto construct(void *p, A &&... args)
+  -> std::enable_if_t<::std::is_constructible<T, A...>::value, T *> {
+  return ::new (p) T(std::forward<A>(args)...);
+}
+
+template <typename T, typename... A>
+auto construct(void *p, A &&... args)
+  -> std::enable_if_t<!::std::is_constructible<T, A...>::value, T *> {
+  return ::new (p) T{std::forward<A>(args)...};
+}
+
+template <typename T>
+void *destroy(T *p) noexcept {
+  p->~T();
+  return p;
+}
+
+LIBIPC_NAMESPACE_END_

src/libipc/utility/pimpl.h

@@ -0,0 +1,73 @@
+/**
+ * @file src/pimpl.h
+ * @author mutouyun (orz@orzz.org)
+ * @brief Pointer To Implementation (pImpl) idiom
+ * @date 2022-02-27
+ */
+#pragma once
+
+#include <utility>
+#include <type_traits>
+#include <cstdint>
+
+#include "libipc/utility/construct.h"
+#include "libipc/def.h"
+
+LIBIPC_NAMESPACE_BEG_
+namespace pimpl {
+
+template <typename T, typename R = T *>
+struct is_comfortable {
+  enum : bool {
+    value = (sizeof(T) <= sizeof(R)) && (alignof(T) <= alignof(R))
+  };
+};
+
+template <typename T, typename... A>
+auto make(A &&... args) -> std::enable_if_t<is_comfortable<T>::value, T *> {
+  T *buf {};
+  // construct an object using memory of a pointer
+  construct<T>(&buf, std::forward<A>(args)...);
+  return buf;
+}
+
+template <typename T>
+auto get(T * const (& p)) noexcept -> std::enable_if_t<is_comfortable<T>::value, T *> {
+  return reinterpret_cast<T*>(&const_cast<char &>(reinterpret_cast<char const &>(p)));
+}
+
+template <typename T>
+auto clear(T *p) noexcept -> std::enable_if_t<is_comfortable<T>::value> {
+  if (p != nullptr) destroy(get(p));
+}
+
+template <typename T, typename... A>
+auto make(A &&... args) -> std::enable_if_t<!is_comfortable<T>::value, T *> {
+  return new T{std::forward<A>(args)...};
+}
+
+template <typename T>
+auto get(T * const (& p)) noexcept -> std::enable_if_t<!is_comfortable<T>::value, T *> {
+  return p;
+}
+
+template <typename T>
+auto clear(T *p) noexcept -> std::enable_if_t<!is_comfortable<T>::value> {
+  if (p != nullptr) delete p;
+}
+
+template <typename T>
+class Obj {
+ public:
+  template <typename... A>
+  static T *make(A &&... args) {
+    return pimpl::make<T>(std::forward<A>(args)...);
+  }
+
+  void clear() noexcept {
+    pimpl::clear(static_cast<T *>(const_cast<Obj *>(this)));
+  }
+};
+
+} // namespace pimpl
+LIBIPC_NAMESPACE_END_

test/test_src_utility.cpp

@@ -0,0 +1,68 @@
+
+#include <type_traits>  // std::aligned_storage_t
+#include <cstdint>
+
+#include "gtest/gtest.h"
+
+#include "libipc/utility/construct.h"
+#include "libipc/utility/pimpl.h"
+
+TEST(utility, construct) {
+  struct Foo {
+    int a_;
+    short b_;
+    char c_;
+  };
+  std::aligned_storage_t<sizeof(Foo)> foo;
+  Foo *pfoo = ipc::construct<Foo>(&foo, 123, short{321}, '1');
+  EXPECT_EQ(pfoo->a_, 123);
+  EXPECT_EQ(pfoo->b_, 321);
+  EXPECT_EQ(pfoo->c_, '1');
+
+  struct Bar : Foo {
+    Bar(int a, short b, char c)
+        : Foo{a, b, c} {}
+  };
+  std::aligned_storage_t<sizeof(Bar)> bar;
+  Bar *pbar = ipc::construct<Bar>(&bar, 123, short(321), '1');
+  EXPECT_EQ(pbar->a_, 123);
+  EXPECT_EQ(pbar->b_, 321);
+  EXPECT_EQ(pbar->c_, '1');
+}
+
+namespace {
+
+struct Foo : ipc::pimpl::Obj<Foo> {
+  int *pi_;
+  Foo(int *pi) : pi_(pi) {}
+};
+
+struct Bar : ipc::pimpl::Obj<Bar> {
+  int *pi_;
+  int *pj_;
+  Bar(int *pi, int *pj) : pi_(pi), pj_(pj) {}
+};
+
+} // namespace
+
+TEST(utility, pimpl_is_comfortable) {
+  EXPECT_TRUE ((ipc::pimpl::is_comfortable<std::int32_t, std::int64_t>::value));
+  EXPECT_TRUE ((ipc::pimpl::is_comfortable<std::int64_t, std::int64_t>::value));
+  EXPECT_FALSE((ipc::pimpl::is_comfortable<std::int64_t, std::int32_t>::value));
+
+  EXPECT_TRUE ((ipc::pimpl::is_comfortable<Foo>::value));
+  EXPECT_FALSE((ipc::pimpl::is_comfortable<Bar>::value));
+}
+
+TEST(utility, pimpl_inherit) {
+  int i = 123;
+  Foo *pfoo = Foo::make(&i);
+  EXPECT_EQ(ipc::pimpl::get(pfoo)->pi_, &i);
+  pfoo->clear();
+
+  int j = 321;
+  Bar *pbar = Bar::make(&i, &j);
+  EXPECT_EQ(ipc::pimpl::get(pbar)->pi_, &i);
+  EXPECT_EQ(ipc::pimpl::get(pbar)->pj_, &j);
+  pbar->clear();
+}