Introduce malloc module (part 1) (#900)

* feat: Introduce `malloc.py` for COM memory management.

Introduces `malloc.py` which provides `IMalloc` interface
definition.
Renamed `test_outparam.py` to `test_from_outparam.py`.
Update `pyproject.toml` for renamed test file.

* test: Add blank `test_malloc.py` for `IMalloc` interface.

* fix: Eliminate the testcase.

Author: junkmd

comtypes/malloc.py

@@ -0,0 +1,77 @@
+import logging
+from ctypes import (
+    HRESULT,
+    POINTER,
+    OleDLL,
+    WinDLL,
+    byref,
+    c_int,
+    c_size_t,
+    c_ulong,
+    c_void_p,
+    c_wchar,
+    c_wchar_p,
+    cast,
+    memmove,
+    sizeof,
+    wstring_at,
+)
+from ctypes.wintypes import DWORD, LPVOID
+
+from comtypes import COMMETHOD, GUID, IUnknown
+from comtypes.GUID import _CoTaskMemFree
+
+logger = logging.getLogger(__name__)
+
+
+class IMalloc(IUnknown):
+    _iid_ = GUID("{00000002-0000-0000-C000-000000000046}")
+    _methods_ = [
+        COMMETHOD([], c_void_p, "Alloc", ([], c_ulong, "cb")),
+        COMMETHOD([], c_void_p, "Realloc", ([], c_void_p, "pv"), ([], c_ulong, "cb")),
+        COMMETHOD([], None, "Free", ([], c_void_p, "py")),
+        COMMETHOD([], c_ulong, "GetSize", ([], c_void_p, "pv")),
+        COMMETHOD([], c_int, "DidAlloc", ([], c_void_p, "pv")),
+        COMMETHOD([], None, "HeapMinimize"),  # 25
+    ]
+
+
+_ole32 = OleDLL("ole32")
+
+_CoGetMalloc = _ole32.CoGetMalloc
+_CoGetMalloc.argtypes = [DWORD, POINTER(POINTER(IMalloc))]
+_CoGetMalloc.restype = HRESULT
+
+_ole32_nohresult = WinDLL("ole32")
+
+SIZE_T = c_size_t
+_CoTaskMemAlloc = _ole32_nohresult.CoTaskMemAlloc
+_CoTaskMemAlloc.argtypes = [SIZE_T]
+_CoTaskMemAlloc.restype = LPVOID
+
+malloc = POINTER(IMalloc)()
+_CoGetMalloc(1, byref(malloc))
+assert bool(malloc)
+
+
+def from_outparam(self):
+    if not self:
+        return None
+    result = wstring_at(self)
+    # `DidAlloc` method returns;
+    # *  1 (allocated)
+    # *  0 (not allocated)
+    # * -1 (cannot determine or NULL)
+    # https://learn.microsoft.com/en-us/windows/win32/api/objidl/nf-objidl-imalloc-didalloc
+    assert malloc.DidAlloc(self), "memory was NOT allocated by CoTaskMemAlloc"
+    _CoTaskMemFree(self)
+    return result
+
+
+def comstring(text, typ=c_wchar_p):
+    size = (len(text) + 1) * sizeof(c_wchar)
+    mem = _CoTaskMemAlloc(size)
+    logger.debug("malloc'd 0x%x, %d bytes" % (mem, size))
+    ptr = cast(mem, typ)
+    memmove(mem, text, size)
+    return ptr

comtypes/test/test_outparam.py comtypes/test/test_from_outparam.pycomtypes/test/test_outparam.py renamed to comtypes/test/test_from_outparam.py

@@ -0,0 +1,6 @@
+import unittest as ut
+
+from comtypes.malloc import IMalloc  # noqa
+
+
+class Test(ut.TestCase): ...

comtypes/test/test_malloc.py

@@ -89,7 +89,7 @@ ignore = ["E402"]
 "comtypes/test/test_client.py" = ["F401"]
 "comtypes/test/test_dict.py" = ["F841"]
 "comtypes/test/test_eventinterface.py" = ["F841"]
-"comtypes/test/test_outparam.py" = ["F841"]
+"comtypes/test/test_from_outparam.py" = ["F841"]
 "comtypes/test/test_sapi.py" = ["E401"]
 "comtypes/test/test_server.py" = ["F401", "F841"]
 "comtypes/test/test_subinterface.py" = ["E401", "F401", "F403", "F405"]