From 89f1c684d73ce275671f2cf5c312dd75af1f18d8 Mon Sep 17 00:00:00 2001
From: Egor Tensin <Egor.Tensin@gmail.com>
Date: Wed, 21 Oct 2020 03:39:05 +0300
Subject: add Shared{Memory,Object} classes

---
 include/winapi/shmem.hpp | 125 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 include/winapi/shmem.hpp

(limited to 'include/winapi')

diff --git a/include/winapi/shmem.hpp b/include/winapi/shmem.hpp
new file mode 100644
index 0000000..0fb2b76
--- /dev/null
+++ b/include/winapi/shmem.hpp
@@ -0,0 +1,125 @@
+// Copyright (c) 2020 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "winapi-common" project.
+// For details, see https://github.com/egor-tensin/winapi-common.
+// Distributed under the MIT License.
+
+#pragma once
+
+#include "handle.hpp"
+
+#include <boost/config.hpp>
+
+#include <cstddef>
+#include <memory>
+#include <string>
+#include <type_traits>
+#include <utility>
+
+namespace winapi {
+
+class SharedMemory {
+public:
+    static SharedMemory create(const std::string& name, std::size_t nb);
+    static SharedMemory open(const std::string& name);
+
+    // VS 2013 won't generate these automatically:
+    SharedMemory(SharedMemory&&) BOOST_NOEXCEPT_OR_NOTHROW;
+    SharedMemory& operator=(SharedMemory) BOOST_NOEXCEPT_OR_NOTHROW;
+    void swap(SharedMemory&) BOOST_NOEXCEPT_OR_NOTHROW;
+    SharedMemory(const SharedMemory&) = delete;
+
+    void* get() const { return m_addr.get(); }
+    void* ptr() const { return get(); }
+
+private:
+    struct Unmap {
+        void operator()(void*) const;
+    };
+
+    SharedMemory() = default;
+
+    SharedMemory(Handle&& handle, void* addr) : m_handle{std::move(handle)}, m_addr{addr} {}
+
+    Handle m_handle;
+    std::unique_ptr<void, Unmap> m_addr;
+};
+
+inline void swap(SharedMemory& a, SharedMemory& b) BOOST_NOEXCEPT_OR_NOTHROW {
+    a.swap(b);
+}
+
+template <typename T>
+class SharedObject {
+public:
+    typedef typename std::aligned_storage<sizeof(T), __alignof(T)>::type AlignedType;
+
+    template <typename... Args>
+    static SharedObject create(const std::string& name, Args&&... args) {
+        SharedObject obj{SharedMemory::create(name, sizeof(AlignedType))};
+        new (obj.ptr()) T(std::forward<Args>(args)...);
+        obj.m_destruct = true;
+        return obj;
+    }
+
+    static SharedObject open(const std::string& name) {
+        SharedObject obj{SharedMemory::open(name)};
+        return obj;
+    }
+
+    SharedObject(SharedObject&& other) BOOST_NOEXCEPT_OR_NOTHROW
+        : m_shmem{std::move(other.m_shmem)},
+          m_destruct{other.m_destruct} {}
+
+    SharedObject& operator=(SharedObject other) BOOST_NOEXCEPT_OR_NOTHROW {
+        swap(other);
+        return *this;
+    }
+
+    ~SharedObject() {
+        if (m_destruct && ptr()) {
+            ptr()->~T();
+        }
+    }
+
+    void swap(SharedObject& other) BOOST_NOEXCEPT_OR_NOTHROW {
+        using std::swap;
+        swap(m_shmem, other.m_shmem);
+        swap(m_destruct, other.m_destruct);
+    }
+
+    T* ptr() const { return reinterpret_cast<T*>(m_shmem.ptr()); }
+    T& get() const { return *ptr(); }
+
+    T* operator->() const { return ptr(); }
+    T& operator*() const { return get(); }
+
+private:
+    explicit SharedObject(SharedMemory&& shmem) : m_shmem{std::move(shmem)} {}
+
+    SharedMemory m_shmem;
+    // Destruct only once, no matter the number of mappings.
+    bool m_destruct = false;
+
+    SharedObject(const SharedObject&) = delete;
+};
+
+template <typename T>
+inline void swap(SharedObject<T>& a, SharedObject<T>& b) BOOST_NOEXCEPT_OR_NOTHROW {
+    a.swap(b);
+}
+
+} // namespace winapi
+
+namespace std {
+
+template <>
+inline void swap(winapi::SharedMemory& a, winapi::SharedMemory& b) BOOST_NOEXCEPT_OR_NOTHROW {
+    a.swap(b);
+}
+
+template <typename T>
+inline void swap(winapi::SharedObject<T>& a, winapi::SharedObject<T>& b) BOOST_NOEXCEPT_OR_NOTHROW {
+    a.swap(b);
+}
+
+} // namespace std
-- 
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