Fix NULL pointer access error in SynthDriverAudioStream (#17607)

This is a fix for the NULL pointer access error introduced by #17592 and reported in this comment.

According to Microsoft's documentation, the pcbWritten parameter in ISequentialStream::Write and the plibNewPosition parameter in IStream::Seek can be NULL, in which case the function should ignore the output parameter and succeed.

Description of user facing changes
None

Description of development approach
ISequentialStream_RemoteWrite and IStream_RemoteSeek are changed to use the low level implementation. This makes checking the output parameter easier. Then, check if the output pointer is NULL before assigning the output value.

source/synthDrivers/sapi5.py

@@ -4,14 +4,14 @@
 # This file is covered by the GNU General Public License.
 # See the file COPYING for more details.
 
-from ctypes import POINTER, c_ubyte, c_wchar_p, cast, windll, _Pointer
+from ctypes import POINTER, c_ubyte, c_ulong, c_wchar_p, cast, windll, _Pointer
 from enum import IntEnum
 import locale
 from collections import OrderedDict, deque
 from typing import TYPE_CHECKING
 from comInterfaces.SpeechLib import ISpEventSource, ISpNotifySource, ISpNotifySink
 import comtypes.client
-from comtypes import COMError, COMObject, IUnknown, hresult, ReturnHRESULT
+from comtypes import COMError, COMObject, IUnknown, hresult
 import winreg
 import nvwave
 from objidl import _LARGE_INTEGER, _ULARGE_INTEGER, IStream
@@ -50,8 +50,12 @@ class SpeechVoiceEvents(IntEnum):
 
 if TYPE_CHECKING:
 	LP_c_ubyte = _Pointer[c_ubyte]
+	LP_c_ulong = _Pointer[c_ulong]
+	LP__ULARGE_INTEGER = _Pointer[_ULARGE_INTEGER]
 else:
 	LP_c_ubyte = POINTER(c_ubyte)
+	LP_c_ulong = POINTER(c_ulong)
+	LP__ULARGE_INTEGER = POINTER(_ULARGE_INTEGER)
 
 
 class SynthDriverAudioStream(COMObject):
@@ -68,36 +72,57 @@ def __init__(self, synthRef: weakref.ReferenceType):
 		self.synthRef = synthRef
 		self._writtenBytes = 0
 
-	def ISequentialStream_RemoteWrite(self, pv: LP_c_ubyte, cb: int) -> int:
+	def ISequentialStream_RemoteWrite(
+		self,
+		this: int,
+		pv: LP_c_ubyte,
+		cb: int,
+		pcbWritten: LP_c_ulong,
+	) -> int:
 		"""This is called when SAPI wants to write (output) a wave data chunk.
 		:param pv: A pointer to the first wave data byte.
 		:param cb: The number of bytes to write.
-		:returns: The number of bytes written.
+		:param pcbWritten: A pointer to a variable where the actual number of bytes written will be stored.
+			Can be null.
+		:returns: HRESULT code.
 		"""
 		synth = self.synthRef()
+		if pcbWritten:
+			pcbWritten[0] = 0
 		if synth is None:
 			log.debugWarning("Called Write method on AudioStream while driver is dead")
-			return 0
+			return hresult.E_UNEXPECTED
 		if not synth.isSpeaking:
-			return 0
+			return hresult.E_FAIL
 		synth.player.feed(pv, cb)
+		if pcbWritten:
+			pcbWritten[0] = cb
 		self._writtenBytes += cb
-		return cb
-
-	def IStream_RemoteSeek(self, dlibMove: _LARGE_INTEGER, dwOrigin: int) -> _ULARGE_INTEGER:
+		return hresult.S_OK
+
+	def IStream_RemoteSeek(
+		self,
+		this: int,
+		dlibMove: _LARGE_INTEGER,
+		dwOrigin: int,
+		plibNewPosition: LP__ULARGE_INTEGER,
+	) -> int:
 		"""This is called when SAPI wants to get the current stream position.
 		Seeking to another position is not supported.
 		:param dlibMove: The displacement to be added to the location indicated by the dwOrigin parameter.
 			Only 0 is supported.
 		:param dwOrigin: The origin for the displacement specified in dlibMove.
 			Only 1 (STREAM_SEEK_CUR) is supported.
-		:returns: The current stream position.
+		:param plibNewPosition: A pointer to a ULARGE_INTEGER where the current stream position will be stored.
+			Can be null.
+		:returns: HRESULT code.
 		"""
 		if dwOrigin == 1 and dlibMove.QuadPart == 0:
 			# SAPI is querying the current position.
-			return _ULARGE_INTEGER(self._writtenBytes)
-		# Return E_NOTIMPL without logging an error.
-		raise ReturnHRESULT(hresult.E_NOTIMPL, None)
+			if plibNewPosition:
+				plibNewPosition.QuadPart = self._writtenBytes
+			return hresult.S_OK
+		return hresult.E_NOTIMPL
 
 	def IStream_Commit(self, grfCommitFlags: int):
 		"""This is called when MSSP wants to flush the written data.