I know it stands for Component Object Model.
I just don't know really what the fuck it is.
I have checked the Micro$oft docs, like this page (https://learn.microsoft.com/en-us/windows/win32/com/the-component-object-model).
I find that to be a bunch of mealy-mouthed gobbledygook.
Can someone point me to an explanation of what COM is, how it's used, etc.? In plain English? Understandable and to the point?
It's just a complicated way of interacting with an object.
You get an interface (e.g. IShellLink), which is just a structure full of pointers to "methods".
For example, calling IShellLink.SetShowCmd will set Run in the shortcut (Maximised etc.).
That's my limited understanding when I've had to use it.
Some basic info:
COM in plain C by Jeff Glatt (https://www.codeproject.com/Articles/13601/COM-in-plain-C)
Articles by Jeff Glatt (https://www.codeproject.com/script/Articles/MemberArticles.aspx?amid=88625)
Hey, thanks, Timo! I'm reading that article now, and it is very well written. We'll see if it explains it all.
(I like that the author starts by explaining COM at a low level, not from the point of view of C++ "wrappers", which is nice for us assembly-language programmers.)
With COM you get access to many non-API functions, such as "open a browser":
include \masm32\MasmBasic\MasmBasic.inc ; ## COM demo: open Internet Explorer ##
.code
CLSID_IExplorer GuidFromString("0002DF01-0000-0000-C000-000000000046") ; either use quoted text syntax or...
IID_IWebBrowser2 GuidFromString({D30C1661-CDAF-11D0-8A3E-00C04FC9E26E}) ; ... paste copied registry key name
MyBrowser proc uses edi url
LOCAL vEmpty:VARIANT, hWin, WebInterface
ClearLocals
lea edi, WebInterface
pInterface equ dword ptr [edi]
.if rv(CoCreateInstance, addr CLSID_IExplorer, NULL, CLSCTX_LOCAL_SERVER, addr IID_IWebBrowser2, edi)==S_OK
CoInvoke pInterface, IWebBrowserVtbl.put_StatusBar, VARIANT_FALSE ; OK, now configure the browser
CoInvoke pInterface, IWebBrowserVtbl.put_MenuBar, VARIANT_FALSE ; false = no menu
CoInvoke pInterface, IWebBrowserVtbl.put_Visible, VARIANT_TRUE
CoInvoke pInterface, IWebBrowserVtbl.get_HWND, addr hWin
lea ecx, vEmpty ; Navigate needs pointers to four empty VARIANTS
CoInvoke pInterface, IWebBrowserVtbl.Navigate, Ole$(url), ecx, ecx, ecx, ecx
.endif
ret
MyBrowser endp
Init
.if rv(OleInitialize, NULL)==S_OK
invoke MyBrowser, Chr$("http://masm32.com/board/index.php?action=unread")
invoke OleUninitialize
.endif
EndOfCode
Further reading of the article Timo posted a link to starts to reveal what it's all about:
QuoteA C++ class is really nothing more than a struct whose first member is always a pointer to an array -- an array that contains pointers to all the functions inside of that class. And the first argument passed to each function is always a pointer to the class (i.e., struct) itself. (This is referred to as the hidden "this" pointer.)
I was pretty sure that's what the "vtable" was for. It's starting to come together now. That guy (the author of that article) is good!
Now, what about "CoInvoke" and "CoInitialize"? Are they just ways of getting at all those vtable functions? And what about "apartments"? is that part of COM too?
Quote from: TimoVJL on June 28, 2024, 03:26:09 PMSome basic info:
COM in plain C by Jeff Glatt (https://www.codeproject.com/Articles/13601/COM-in-plain-C)
Articles by Jeff Glatt (https://www.codeproject.com/script/Articles/MemberArticles.aspx?amid=88625)
Thank you Timo for this article, I have been in pain with COM and how to use it with MASM32/64.
More questions about COM:
1. Since one would need a valid GUID if one were to write one's own COM utility, is that tool from Micro$oft (GUIDGEN.EXE) available? do you have to have VC or some other package to get that?
2. So what are some of the top examples of COM things we might want to use in an assembly-language program? Jochen gave us one; what are some others?
3. Who here has successfully wrestled with COM and gotten it to work with assembly language? (32-bit preference here)
Quote from: NoCforMe on June 29, 2024, 08:07:12 AMWho here has successfully wrestled with COM and gotten it to work with assembly language?
OpenAdo (https://www.jj2007.eu/MasmBasicQuickReference.htm#Mb1396) is pure COM under the hood.
Quote from: NoCforMe on June 29, 2024, 08:07:12 AM3. Who here has successfully wrestled with COM and gotten it to work with assembly language? (32-bit preference here)
Saving/restoring desktop icon positions using Shell interfaces.
One module:
.const
EXTERNDEF CLSID_ShellWindows:GUID
EXTERNDEF IID_IShellWindows:GUID
EXTERNDEF IID_IDispatch:GUID
EXTERNDEF IID_IServiceProvider:GUID
EXTERNDEF IID_IShellBrowser:GUID
EXTERNDEF IID_IFolderView:GUID
EXTERNDEF SID_STopLevelBrowser:GUID
.code
GetDesktopFolderView proc ppv:PTR IFolderView
local psw:PTR IShellWindows
local pds:PTR IDispatch
local psp:PTR IServiceProvider
local psb:PTR IShellBrowser
local psv:PTR IShellView
local lhwnd:HANDLE
local vtLoc:VARIANT,vtEmpty:VARIANT
sub eax,eax
mov psw,eax
mov pds,eax
mov psp,eax
mov psb,eax
mov psv,eax
mov vtEmpty.dw2,eax
mov vtEmpty.dw1,eax
mov dword ptr vtEmpty.wReserved2,eax
mov dword ptr vtEmpty.vt,eax
mov vtLoc.dw2,eax
mov vtLoc.dw1,eax
mov dword ptr vtLoc.wReserved2,eax
mov dword ptr vtLoc.vt,3
invoke CoCreateInstance,offset CLSID_ShellWindows,0,CLSCTX_ALL,offset IID_IShellWindows,addr psw
test eax,eax
jnz done
covoke psw,IShellWindows,FindWindowSW,addr vtLoc,addr vtEmpty,SWC_DESKTOP,addr lhwnd,SWFO_NEEDDISPATCH,addr pds
test eax,eax
jnz cleanup
covoke pds,IDispatch,QueryInterface,offset IID_IServiceProvider,addr psp
test eax,eax
jnz cleanup
covoke psp,IServiceProvider,QueryService,offset SID_STopLevelBrowser,offset IID_IShellBrowser,addr psb
test eax,eax
jnz cleanup
covoke psb,IShellBrowser,QueryActiveShellView,addr psv
test eax,eax
jnz cleanup
covoke psv,IShellView,QueryInterface,OFFSET IID_IFolderView,ppv
cleanup:
push eax
invoke SafeRelease,psv
invoke SafeRelease,psb
invoke SafeRelease,psp
invoke SafeRelease,pds
invoke SafeRelease,psw
pop eax
done: ret
GetDesktopFolderView endp
See? Easy.
I got game programming book many years ago,using directx
The explanation was DX used com so it could support many different video card drivers ,and com kept pointers to your brand video card and might be updated with new version driver that fix bugs can have different address of a proc because other proc's above it became longer or shorter
Quote from: NoCforMe on June 29, 2024, 08:07:12 AMMore questions about COM:
3. Who here has successfully wrestled with COM and gotten it to work with assembly language? (32-bit preference here)
See
https://masm32.com/board/index.php?topic=10807.0 (https://masm32.com/board/index.php?topic=10807.0)
https://masm32.com/board/index.php?topic=8773.0 (https://masm32.com/board/index.php?topic=8773.0)
The latter one may be especially interesting, since it allows to generate include libs from type libs.
[and btw. it also shows how extraordinary good friends Hutch and I were :bgrin: ]
Quote from: NoCforMe on June 29, 2024, 08:07:12 AMMore questions about COM:
1. Since one would need a valid GUID if one were to write one's own COM utility, is that tool from Micro$oft (GUIDGEN.EXE) available? do you have to have VC or some other package to get that?
I'm using Visual Studio and you can get GUID from IDE as the article show screenshot, and there is guidgen.exe in Developers CMD Path.
The FreeBASIC Editor for Windows ( WinFBE ) is providing GUID generators :
https://github.com/PaulSquires/WinFBE/releases (https://github.com/PaulSquires/WinFBE/releases)
WinFBE_Suite\Tools\GUIDgen\GUIDgen.exe
WinFBE_Suite\Tools\GUIDgen\GUIDgen32.exe
WinFBE_Suite\Tools\GUIDgen\GUIDgen64.exe
UuidCreate function (https://learn.microsoft.com/en-us/windows/win32/api/rpcdce/nf-rpcdce-uuidcreate)
Quote from: _japheth on June 29, 2024, 04:40:47 PMQuote from: NoCforMe on June 29, 2024, 08:07:12 AMMore questions about COM:
3. Who here has successfully wrestled with COM and gotten it to work with assembly language? (32-bit preference here)
See
https://masm32.com/board/index.php?topic=10807.0 (https://masm32.com/board/index.php?topic=10807.0)
https://masm32.com/board/index.php?topic=8773.0 (https://masm32.com/board/index.php?topic=8773.0)
The latter one may be especially interesting, since it allows to generate include libs from type libs.
[and btw. it also shows how extraordinary good friends Hutch and I were :bgrin: ]
All asm DX demos/ games are using com interface independent of my old ddraw code, dx8,dx9,dx10,dx11,dx12 asm code uses custom invoke like siekmanski coinvoke first get address in table and call
Quote from: sinsi on June 29, 2024, 09:28:30 PMUuidCreate function (https://learn.microsoft.com/en-us/windows/win32/api/rpcdce/nf-rpcdce-uuidcreate)
So can that be used as a stand-alone function? No need to do any kind of network initialization? it just reaches out over the Intertubes and grabs a GUID?
If so, kewl! I could easily write my own GUIDGEN.EXE.
Hi NoCforMe,
QuoteSo can that be used as a stand-alone function?
Exactly. Here is an example :
#include "stdafx.h"
#pragma comment(lib, "rpcrt4.lib") // UuidCreate - Minimum supported OS Win 2000
#include <windows.h>
#include <iostream>
using namespace std;
int main()
{
UUID uuid;
UuidCreate(&uuid);
char *str;
UuidToStringA(&uuid, (RPC_CSTR*)&str);
cout << str << endl;
RpcStringFreeA((RPC_CSTR*)&str);
return 0;
}https://github.com/tillo/UuidCreate/blob/master/ucwrap/ucwrap/ucwrap.cpp (https://github.com/tillo/UuidCreate/blob/master/ucwrap/ucwrap/ucwrap.cpp)
Quote from: sinsi on June 29, 2024, 09:28:30 PMUuidCreate function (https://learn.microsoft.com/en-us/windows/win32/api/rpcdce/nf-rpcdce-uuidcreate)
OK, I tried that.
Problems!1. There's no mention of
UuidCreate() in any of the Masm32 stuff (include files). There is, however, reference to
ExUuidCreate(), which seems to do the exact same thing.
2. OK, fine. Except that I couldn't link the program because apparently there's no includelib for that function anywhere.
3. OK, fine. I used
LoadLibrary() and
GetProcAddress() to get a pointer to that function in its DLL (
ntoskrnl.exe).
4. OK, fine, I was able to get the proc address. But when I called it, I got an access violation
inside the DLL.
(32-bit program here; is the DLL also 32-bit?)
Aaargh! Any suggestions? Vortex said it would be easy ...
Hi NoCforMe,
I remember 10 years ago we played with COM here.
See https://masm32.com/board/index.php?topic=3215.msg33806#msg33806 (https://masm32.com/board/index.php?topic=3215.msg33806#msg33806)
We found that METHOD macro by qWord was the best for our purpose.
;METHOD macro by qWord
METHOD MACRO name,args:VARARG
LOCAL _type1,_type2
_type1 TYPEDEF PROTO args
_type2 TYPEDEF PTR _type1
EXITM <name _type2 ?>
ENDMInterface structures must be defined like this
IDispatch STRUCT
METHOD(QueryInterface, _this:LPVOID,riid:LPVOID,ppvObj:LPVOID)
METHOD(AddRef, _this:LPVOID)
METHOD(Release, _this:LPVOID)
METHOD(GetTypeInfoCount, _this:LPVOID,pctinfo:UINT)
METHOD(GetTypeInfo, _this:LPVOID,iTInfo:UINT,lcid:LCID,ppTInfo:LPVOID)
METHOD(GetIDsOfNames, _this:LPVOID,riid:LPVOID,rgszNames:LPOLESTR,cNames:UINT,lcid:LCID,rgDispId:LPVOID)
METHOD(dInvoke, _this:LPVOID,dispIdMember:DWORD,riid:LPVOID,lcid:LCID,wFlags:DWORD,pDispParams:LPVOID,pVarResult:LPVOID,pExcepInfo:LPVOID,puArgErr:UINT)
IDispatch ENDSIf you can find Colib pack by Ernest Murphy ( I don't have a link to it ) it may help you to understand how to work with COM in assembly. It has docs folder:
QuoteHaving no idea what one may come here seeking, I make no statement as to
what order you should review this material.
However, those who would wish a path to follow may find this order acceptable:
Accessing COM Objects from Assembly.doc
Standard for COM in MASM32.doc
Adapting Quick Editor for COM.doc
Creating a COM object in ASM.doc
MyCom2 and the CoLib.doc
Inside CoLib.doc
UsingCoLib to Build a Visual Control.doc
Hi NoCforMe,
Can you try the code below?
include \masm32\include\masm32rt.inc
include \masm32\include\rpcrt4.inc
includelib \masm32\lib\rpcrt4.lib
.data
.data?
u1 _GUID <?>
buffer dd ?
.code
start:
invoke UuidCreate,ADDR u1
invoke UuidToString,ADDR u1,ADDR buffer
invoke StdOut,buffer
invoke RpcStringFree,ADDR buffer
invoke ExitProcess,0
END start
Thanks; I arrived at the same solution but by a roundabout way, finding UuidCreate() in rpcrt4.dll (using LoadLibrary() and GetProcAddress()), and yes, it works. (I didn't know about those other include files.)
I'm just curious about one thing: every time we call UuidCreate(), that means one less GUID in the world, correct? Any chance they could run out of them eventually? I just wasted 8 or 10 myself.
Lessee: 32 hex digits, so that means there are what, 16^32 possible combos? (Are all combinations valid?) Not even sure what number that is. Pretty big, though.
Found an article on Stack Overflow (https://stackoverflow.com/questions/29682209/is-there-any-possibility-that-guid-will-all-be-used-up) on this very subject. Apparently there's no danger of us running out of GUIDs any time soon.
Can CoCreateGuid ever return GUID_NULL? Raymond Chen (https://devblogs.microsoft.com/oldnewthing/20140326-00/?p=1393)
...
// create UNICODE string like "{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}"
wchar_t s[50];
StringFromGUID2(&uuid, s, sizeof(s));
printf("%ls\n", s);
...
I wrote a GUID utility for assembly-language programmers (https://masm32.com/board/index.php?topic=12077.msg132143#new). Please check it out.
Edgar made a Help 2 Viewer over ten years ago and i used it with poide help system.
Was written with GoAsm.
So that used COM?