Add wstring_owner, replacing std::wstring.

std::basic_string is nice, but it is not very ergonomic if everything
you really need is to automatically free C strings at end of scope.

I suppose I could have used std::unique_ptr for this, but I suspect
the ergonomics would be worse.

1 files changed, 53 insertions, 11 deletions

diff --git a/c/common.cpp b/c/common.cpp
index bc2d4af..614bfeb 100644
--- a/c/common.cpp
+++ b/c/common.cpp
@@ -2,6 +2,59 @@
 
 #include "common.h"
 
+/* wstring_owner: Simple wrapper for wide C strings. */
+
+wstring_owner::wstring_owner() {}
+
+wstring_owner::wstring_owner(wchar_t* const wsz) : p(wsz) {}
+
+wstring_owner& wstring_owner::operator=(wchar_t* const wsz)
+{
+	if (p != wsz) {
+		delete p;
+		p = wsz;
+	}
+	return *this;
+}
+
+wstring_owner::wstring_owner(wstring_owner&& wso) noexcept : p(std::exchange(wso.p, nullptr)) {}
+
+wstring_owner& wstring_owner::operator=(wstring_owner&& wso) noexcept
+{
+	std::swap(p, wso.p);
+	return *this;
+}
+
+/* Return pointer, releasing ownership. */
+wchar_t* wstring_owner::release()
+{
+	wchar_t* p2 = p;
+	p = nullptr;
+	return p2;
+}
+
+wstring_owner::operator bool() const
+{
+	return p;
+}
+
+wstring_owner::~wstring_owner()
+{
+	delete p;
+}
+
+wstring_owner WsoFromSz(const char* const sz, const int iCp)
+{
+	int cbMultiByte = strlen(sz)+1;
+	int cchWideChar = MultiByteToWideChar(iCp, 0, sz, cbMultiByte, NULL, 0);
+	wchar_t* wsz = new wchar_t[cchWideChar];
+	if (!MultiByteToWideChar(iCp, 0, sz, cbMultiByte, wsz, cchWideChar)) {
+		delete wsz;
+		throw Win32Error(GetLastError());
+	}
+	return wsz;
+}
+
 /* Win32Error: Exception for Windows API errors. */
 
 Win32Error::Win32Error() : dwErr(GetLastError()) {}
@@ -55,17 +108,6 @@ Library::~Library()
 	FreeLibrary(m_hModule);
 }
 
-/* Convert narrow unmanaged string to wide managed string. */
-std::wstring WsFromSz(const char* sz, int iCp)
-{
-	int cbMultiByte = strlen(sz)+1;
-	int cchWideChar = MultiByteToWideChar(iCp, 0, sz, cbMultiByte, NULL, 0);
-	std::wstring ws(cchWideChar, 0);
-	if (!MultiByteToWideChar(iCp, 0, sz, cbMultiByte, ws.data(), cchWideChar))
-		throw Win32Error(GetLastError());
-	return ws;
-}
-
 /* Move message box to center of main window. */
 static LRESULT CALLBACK CBTProc(const int nCode, const WPARAM wParam, const LPARAM lParam) noexcept
 {