Move common Win32 functions for releasing IUnknown* and DLL function access into

new WinType.h header.

1 files changed, 59 insertions, 0 deletions

diff --git a/win32/WinTypes.h b/win32/WinTypes.h
new file mode 100644
index 000000000..44a12f38b
--- /dev/null
+++ b/win32/WinTypes.h
@@ -0,0 +1,59 @@
+// Scintilla source code edit control
+/** @file WinTypes.h
+ ** Implement safe release of COM objects and access to functions in DLLs.
+ ** Header contains all implementation - there is no .cxx file.
+ **/
+// Copyright 2020-2021 by Neil Hodgson <neilh@scintilla.org>
+// The License.txt file describes the conditions under which this software may be distributed.
+
+#ifndef WINTYPES_H
+#define WINTYPES_H
+
+namespace Scintilla::Internal {
+
+// Release an IUnknown* and set to nullptr.
+// While IUnknown::Release must be noexcept, it isn't marked as such so produces
+// warnings which are avoided by the catch.
+template <class T>
+inline void ReleaseUnknown(T *&ppUnknown) noexcept {
+	if (ppUnknown) {
+		try {
+			ppUnknown->Release();
+		} catch (...) {
+			// Never occurs
+		}
+		ppUnknown = nullptr;
+	}
+}
+
+struct UnknownReleaser {
+	// Called by unique_ptr to destroy/free the resource
+	template <class T>
+	void operator()(T *pUnknown) noexcept {
+		// same as ReleaseUnknown() in PlatWin.h
+		try {
+			pUnknown->Release();
+		} catch (...) {
+			// IUnknown::Release must not throw, ignore if it does.
+		}
+	}
+};
+
+
+/// Find a function in a DLL and convert to a function pointer.
+/// This avoids undefined and conditionally defined behaviour.
+template<typename T>
+inline T DLLFunction(HMODULE hModule, LPCSTR lpProcName) noexcept {
+	if (!hModule) {
+		return nullptr;
+	}
+	FARPROC function = ::GetProcAddress(hModule, lpProcName);
+	static_assert(sizeof(T) == sizeof(function));
+	T fp {};
+	memcpy(&fp, &function, sizeof(T));
+	return fp;
+}
+
+}
+
+#endif