Create a skeleton SAPI TtsEngine COM object.

src/windows/com/comentrypoints.c

  */
 
 #include "config.h"
+#define INITGUID
 
 #include <windows.h>
 
-HRESULT __stdcall DllGetClassObject(REFCLSID classId, REFIID iface, void **pObject)
+// {61D23633-CE59-4101-8158-569FC6B51B49}
+DEFINE_GUID(CLSID_TtsEngine, 0x61d23633, 0xce59, 0x4101, 0x81, 0x58, 0x56, 0x9f, 0xc6, 0xb5, 0x1b, 0x49);
+
+extern HRESULT __stdcall TtsEngine_CreateInstance(IClassFactory *iface, IUnknown *outer, REFIID iid, void **object);
+
+ULONG ObjectCount = 0;
+static ULONG LockCount = 0;
+
+static ULONG __stdcall ClassFactory_AddRef(IClassFactory *iface)
+{
+	return 1;
+}
+
+static ULONG __stdcall ClassFactory_Release(IClassFactory *iface)
 {
-	if (!pObject)
-		return E_POINTER;
+	return 1;
+}
 
-	*pObject = NULL;
+static HRESULT __stdcall ClassFactory_QueryInterface(IClassFactory *iface, REFIID iid, void **object)
+{
+	if (IsEqualGUID(iid, &IID_IUnknown) || IsEqualGUID(iid, &IID_IClassFactory)) {
+		*object = iface;
+		iface->lpVtbl->AddRef(iface);
+		return S_OK;
+	}
+
+	*object = NULL;
+	return E_NOINTERFACE;
+}
+
+static HRESULT __stdcall ClassFactory_LockServer(IClassFactory *iface, BOOL lock)
+{
+	if (lock)
+		InterlockedIncrement(&LockCount);
+	else
+		InterlockedDecrement(&LockCount);
+	return S_OK;
+}
+
+static const IClassFactoryVtbl TtsEngine_ClassFactoryVtbl = {
+	ClassFactory_QueryInterface,
+	ClassFactory_AddRef,
+	ClassFactory_Release,
+	TtsEngine_CreateInstance,
+	ClassFactory_LockServer
+};
+static IClassFactory TtsEngine_ClassFactory = { &TtsEngine_ClassFactoryVtbl };
+
+HRESULT __stdcall DllGetClassObject(REFCLSID classId, REFIID iid, void **object)
+{
+	if (IsEqualCLSID(classId, &CLSID_TtsEngine))
+		return ClassFactory_QueryInterface(&TtsEngine_ClassFactory, iid, object);
+
+	*object = NULL;
 	return CLASS_E_CLASSNOTAVAILABLE;
 }
 
 HRESULT __stdcall DllCanUnloadNow(void)
 {
-	return S_OK;
+	return (ObjectCount == 0 && LockCount == 0) ? S_OK : S_FALSE;
 }

src/windows/com/ttsengine.cpp

+/*
+ * Copyright (C) 2016 Reece H. Dunn
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see: <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <windows.h>
+#include <sapiddk.h>
+
+#include <new>
+
+extern "C" ULONG ObjectCount;
+
+struct TtsEngine
+	: public ISpObjectWithToken
+	, public ISpTTSEngine
+{
+	TtsEngine();
+	~TtsEngine();
+
+	// IUnknown
+
+	ULONG __stdcall AddRef();
+	ULONG __stdcall Release();
+
+	HRESULT __stdcall QueryInterface(REFIID iid, void **object);
+
+	// ISpObjectWithToken
+
+	HRESULT __stdcall GetObjectToken(ISpObjectToken **token);
+	HRESULT __stdcall SetObjectToken(ISpObjectToken *token);
+
+	// ISpTTSEngine
+
+	HRESULT __stdcall
+	Speak(DWORD flags,
+	      REFGUID formatId,
+	      const WAVEFORMATEX *format,
+	      const SPVTEXTFRAG *textFragList,
+	      ISpTTSEngineSite *site);
+
+	HRESULT __stdcall
+	GetOutputFormat(const GUID *targetFormatId,
+	                const WAVEFORMATEX *targetFormat,
+	                GUID *formatId,
+	                WAVEFORMATEX **format);
+private:
+	ULONG refCount;
+};
+
+TtsEngine::TtsEngine()
+	: refCount(1)
+{
+	InterlockedIncrement(&ObjectCount);
+}
+
+TtsEngine::~TtsEngine()
+{
+	InterlockedDecrement(&ObjectCount);
+}
+
+ULONG __stdcall TtsEngine::AddRef()
+{
+	return InterlockedIncrement(&refCount);
+}
+
+ULONG __stdcall TtsEngine::Release()
+{
+	ULONG ret = InterlockedDecrement(&refCount);
+	if (ret == 0)
+		delete this;
+	return ret;
+}
+
+HRESULT __stdcall TtsEngine::QueryInterface(REFIID iid, void **object)
+{
+	*object = NULL;
+	if (IsEqualIID(iid, IID_IUnknown) || IsEqualIID(iid, IID_ISpTTSEngine))
+		*object = (ISpTTSEngine *)this;
+	else if (IsEqualIID(iid, IID_ISpObjectWithToken))
+		*object = (ISpObjectWithToken *)this;
+	else
+		return E_NOINTERFACE;
+
+	this->AddRef();
+	return S_OK;
+}
+
+HRESULT __stdcall TtsEngine::GetObjectToken(ISpObjectToken **token)
+{
+	return E_NOTIMPL;
+}
+
+HRESULT __stdcall TtsEngine::SetObjectToken(ISpObjectToken *token)
+{
+	return E_NOTIMPL;
+}
+
+HRESULT __stdcall
+TtsEngine::Speak(DWORD flags,
+                 REFGUID formatId,
+                 const WAVEFORMATEX *format,
+                 const SPVTEXTFRAG *textFragList,
+                 ISpTTSEngineSite *site)
+{
+	return E_NOTIMPL;
+}
+
+HRESULT __stdcall
+TtsEngine::GetOutputFormat(const GUID *targetFormatId,
+                           const WAVEFORMATEX *targetFormat,
+                           GUID *formatId,
+                           WAVEFORMATEX **format)
+{
+	return E_NOTIMPL;
+}
+
+extern "C" HRESULT __stdcall TtsEngine_CreateInstance(IClassFactory *iface, IUnknown *outer, REFIID iid, void **object)
+{
+	if (outer != NULL)
+		return CLASS_E_NOAGGREGATION;
+
+	TtsEngine *engine = new (std::nothrow) TtsEngine();
+	if (!engine)
+		return E_OUTOFMEMORY;
+
+	HRESULT ret = engine->QueryInterface(iid, object);
+	engine->Release();
+	return ret;
+}

src/windows/libespeak-ng.vcxproj

     <ClCompile Include="..\libespeak-ng\voices.c" />
     <ClCompile Include="..\libespeak-ng\wavegen.c" />
     <ClCompile Include="com\comentrypoints.c" />
+    <ClCompile Include="com\ttsengine.cpp" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="..\include\espeak-ng\espeak_ng.h" />

src/windows/libespeak-ng.vcxproj.filters

     <ClCompile Include="com\comentrypoints.c">
       <Filter>Source Files\com</Filter>
     </ClCompile>
+    <ClCompile Include="com\ttsengine.cpp">
+      <Filter>Source Files\com</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="config.h">