Convert String Version CLSID to GUID

[Zen]

What I need to do is write a procedure that converts a string version of a CLSID (of the type that you use to open a registry key under: HKEY_CLASSES_ROOT\CLSID) to a real live CLSID that I can use with CoCreateInstance or a Class Moniker.

These strings have this format:
{22D6F312-B0F6-11D0-94AB-0080C74C7E95}    (This one happens to be Windows Media Player)

...So, I've been searching the macros.asm file for cool macros that I can use for this purpose (...\masm32\macros\macros.asm)
And,...well,...I'm embarrassed to admit that I have NEVER written a macro,...and they mystify me,...as I don't really understand the syntax (like QWORD does),...
Anyway,...I've found a number of macros that look promising. If you scroll down to line 4248 (of macros.asm), you will find a section entitled:
sscanf conversion macros. The MSDN documentation is here: sscanf, _sscanf_l, swscanf, _swscanf_l

...But, I wanted to do it the hard way,...'cause I'm trying to prove that I'm NOT a mediocre assembly programmer,...
...So,...I have a couple of simple questions: Where the heck is, crt_sscanf ??? He invokes it in all those macros,...
...And,...is this REALLY a good idea ??? Is there a better way ??? Is sscanf really a good a good approach ???

Can't I just convert the string byte by byte into DWORDs and WORDs and then assemble it into the CLSID structure ???

Code Select Expand

    GUID STRUCT
        Data1 dd ?
        Data2 dw ?
        Data3 dw ?
        Data4 db 8 dup(?)
    GUID ENDS


...As you all probably know,...A CLSID and a GUID have exactly the same structure, just a different name,...

[jj2007]

GuidFromString

[Zen]

...Yeah, I thought of that,...Even better: CLSIDFromString, MSDN

...There's also this, which I found in Japheth's COM stuff:

Code Select Expand

    DEFINE_GUID macro name,l,w1,w2,b1,b2,b3,b4,b5,b6,b7,b8
exitm <name GUID { l , w1 , w2 , { b1 , b2 , b3 , b4 , b5 , b6 , b7 , b8 } } >
    exitm <externdef name:GUID>
    endm


[jj2007]

...Yeah, I thought of that,...Even better: CLSIDFromString, MSDN

CLSIDFromString is convenient is the string is generated somewhere. If it is in the .data section, the macro is more efficient: 16 bytes vs about 44.

[qWord]

Code Select Expand

UUID macro name,guid
s2uuid_data1 = @CatStr(<0>,@SubStr(<&guid>,2 ,8),<h>)
s2uuid_data2 = @CatStr(<0>,@SubStr(<&guid>,11,4),<h>)
s2uuid_data3 = @CatStr(<0>,@SubStr(<&guid>,16,4),<h>)
s2uuid_bytes TEXTEQU <>
FOR index,<21,23,26,28,30,32,34,36>
s2uuid_bytes TEXTEQU s2uuid_bytes,<,0>,@SubStr(<&guid>,index,2),<h>
ENDM
s2uuid_bytes SUBSTR s2uuid_bytes,2
name GUID <s2uuid_data1,s2uuid_data2,s2uuid_data3,<s2uuid_bytes>>
endm

Code Select Expand

align 16
UUID IID_IFoo,"22D6F312-B0F6-11D0-94AB-0080C74C7E95"
UUID IID_IFoo2,{23D6F312-B0F6-11D0-94AB-0080C74C7E95}

[Zen]

JOCHEN,
Thanks, for the information. I'll have to try both techniques just to see if I actually understand what's happening,...

...And,...QWORD,...Thanks,...it's amazing how little I know about macros. It's embarrassing. But, I studied the UUID macro for quite some time, and, I think I understand it (although I have my doubts). I actually had to look up @CatStr and @SubStr, because I've never used them in code. One question: what is <h> ??? I'm guessing that the h is for hexadecimal,...and, this designates the text string as hex.
From, Programmer's Guide Microsoft MASM: "You can define symbolic integer constants with either of the data assignment directives, EQU or the equal sign (=). These directives assign values to symbols during assembly, not during program execution. Symbolic constants are used to assign names to constant values."
...Heck,...I didn't even know that,...
...I also had to read up on: FOR Loops and Variable-Length Parameters to understand the FOR directive (never used that one, either),...

...So,...I learned alot just from that macro example,...Thanks, again,...I appreciate it,...

[Zen]

Well, I couldn't get CLSIDFromString or QWORD's macro to work.
In the case of CLSIDFromString, I couldn't get the correct string format in the first place.  The documentation states: "Converts a string generated by the StringFromCLSID function back into the original CLSID." I tried various different CLSID string formats, and kept getting a return value of: CO_E_CLASSSTRING (The class string was improperly formatted.)

In the case of QWORD's macro, I'm sure I was calling it incorrectly (the UUID macro compiles without error). My initial impression was to use pointers, but I didn't. And, I had no idea where the converted CLSID was supposed to end up, so I just zeroed a GUID structure. My code was like this:

Code Select Expand

      invoke RtlZeroMemory, ADDR COMClassClsid, SIZEOF CLSID    ;       
[Line 79]      UUID EnteredCLSID, COMClassClsid

Just to make sure, I also called it like this:

Code Select Expand

      invoke RtlZeroMemory, ADDR COMClassClsid, SIZEOF CLSID    ;       
[Line 79]      UUID COMClassClsid, EnteredCLSID


...Where COMClassClsid was a CLSID structure (CLSID EQU <GUID>)

Code Select Expand

    GUID STRUCT
        Data1 dd ?
        Data2 dw ?
        Data3 dw ?
        Data4 db 8 dup(?)
    GUID ENDS

...And,...EnteredCLSID is a character buffer with the string version of the CLSID in it (same format as in the first post).
{22D6F312-B0F6-11D0-94AB-0080C74C7E95}

I kept getting the same error when I tried to compile,...

Code Select Expand

***********
ASCII build
***********

F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2093: count value too l
arge
@SubStr(1): Macro Called From
  @CatStr(1): Macro Called From
   UUID(2): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  @CatStr(1): Macro Called From
   UUID(3): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  MacroLoop(1): iteration 1: Macro Called From
   UUID(7): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  MacroLoop(1): iteration 2: Macro Called From
   UUID(7): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  MacroLoop(1): iteration 3: Macro Called From
   UUID(7): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  MacroLoop(1): iteration 4: Macro Called From
   UUID(7): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  MacroLoop(1): iteration 5: Macro Called From
   UUID(7): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  MacroLoop(1): iteration 6: Macro Called From
   UUID(7): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  MacroLoop(1): iteration 7: Macro Called From
   UUID(7): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
@SubStr(1): Macro Called From
  MacroLoop(1): iteration 8: Macro Called From
   UUID(7): Macro Called From
    F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2091: index value past
end of string
UUID(8): Macro Called From
  F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
F:\Test COM Class Decoder\COMClasRoutns.inc(79) : error A2206: missing operator
in expression
UUID(1): Macro Called From
  F:\Test COM Class Decoder\COMClasRoutns.inc(79): Include File
_
Assembly Error

COMClasRoutns.inc is the include file in which I call QWORD's UUID macro.

[qWord]

Zen, that was a misunderstanding from my side: the macro does only work with constants at assembly time.
The function CLSIDFromString does expect an Unicode string.

[Zen]

...Ooohhh,...
Well, that's helpful,...anyway,...Thanks,...
I'll play around with it. Convert it to a procedure, maybe. I think I got the general idea of how it was supposed to work,...
(I don't know what I was thinking,...a macro expands at assembly time, doesn't it ???...I have SO much to learn)

UPDATE: Using MultiByteToWideChar I converted the string version CLSID to a real UNICODE string CLSID (and then, to an actual CLSID by calling CLSIDFromString).
And, this returned NOERROR. It works,...and, is almost foolproof.
...Cool, thanks, dudes, for the info,...
Now, I can call CreateClassMoniker (I've converted the IMoniker struct from one of Japheth's old files). That also works.
Progress,...:icon_eek:

...Oh,...and thanks, JOCHEN,...I'll study it,...