Re: Convert C-Builder program to Delphi?
From: W. D. (NewsGroups_at_US-Webmasters.com)
Date: 01/28/05
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Date: Fri, 28 Jan 2005 00:42:01 -0600
Maarten Wiltink wrote:
>
> "W. D." <NewsGroups@US-Webmasters.com> wrote in message
> news:41F8884A.539E@US-Webmasters.com...
>
> > [...] Right now this C++ code that I am working on is getting
> > bizzare. As far as I can tell, the following code is for
> > compatibilty with DLLs.
> >
> > I Googled just about everyplace I can think of and still
> > haven't come up with the proper way to translate these
> > to Delphi:
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > #if !defined (DLLFUNC)
> > #define DLLFUNC(ret) extern __declspec(dllexport) ret __stdcall
> > #endif
> >
> > DLLFUNC(int) SomeDLL_Open();
>
> DLLFUNC(T) more or less wraps type T so that declaring a function
> to return it is also usefully exported from a DLL this source is
> linked into.
>
> It is a macro and depends on C preprocessor macros being textual;
> also on the syntactical closeness of the relevant C keywords.
> Delphi does not have them all next to each other and doesn't have
> macros anyway.
>
> Marking functions as exported is done in the project file in Delphi,
> quite separate from the function declaration itself. The calling
> convention is given by a directive added after the declaration but
> it marks up the declaration as a whole, not just the type. (That's
> true also for C, but macros don't care.)
>
> Look for "exports" and "stdcall" in the help.
>
> Groetjes,
> Maarten Wiltink
At 11:53 1/27/2005, Stephen Posey wrote:
>> Oh boy. This C++ code that I am working on is getting
>> bizzare. As far as I can tell, this code is for compatibilty with DLLs.
>>
>> I Googled just about everyplace I can think of and still haven't come up
>with
>> the proper way to translate these to Delphi:
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> #if !defined (DLLFUNC)
>> #define DLLFUNC(ret) extern __declspec(dllexport) ret __stdcall #endif
>>
>>
>> DLLFUNC(int) SomeDLL_Open();
>>
>> DLLFUNC(void) SomeDLL_Close();
>>
>> DLLFUNC(int) SomeDLL_GetData(BYTE* pDataType, const PBYTE* pTheData,
>DWORD* pDataSize);
>>
>> DLLFUNC(int) SomeDLL_Request(BYTE byRequestType, DWORD dwRequestData);
>>
>> // The result returned is based upon the last function attempted within
>this DLL
>> DLLFUNC(int) SomeDLL_GetErrorCondition();
>>
>> typedef int (__stdcall *FUNC_OPEN)();
>> typedef void (__stdcall *FUNC_CLOSE)();
>> typedef int (__stdcall *FUNC_GET)(BYTE*,PBYTE*,DWORD*);
>> typedef void (__stdcall *FUNC_SHOWICON)(BOOL);
>>
>>
>> #endif
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Can anybody spare a hint?
>
>This appears to me to be an overly cute approach of defining a
>consistent interface onto some exported DLL functions. I guess it might
>have some benefit if the calling signature is expected to change, this
>way the only place anything needs to be changed is in the #define macro.
>
>The thing to remember about C/C++ preprocessor #defines is that it's
>really just a TEXT substitution mechanism. Since Delphi doesn't have
>anything quite like this, the usual approach is to expand the #define
>into actual Delphi code; sometimes this comes out as a CONST
>declaration, sometimes it converts to a function, in this case it
>decorates some function declarations elsewhere in your code.
>
>So, what is this actually saying?:
>
> > #define DLLFUNC(ret) extern __declspec(dllexport) ret __stdcall
>
>It says whenever the preprocessor encounters the text string "DLLFUNC",
>replace it with the defined text. the "(ret)" acts as a parameter,
>saying whatever text appears in parentheses after "DLLFUNC" should be
>inserted whereever "ret" appears in the macro string.
>
>So lets get down to cases, first a step-by-step substitution so you can
>see how that works.
>
> > DLLFUNC(int) SomeDLL_Open();
>
>1. We found DLLFUNC so insert its definition at that location in the source:
>
> extern __declspec(dllexport) ret __stdcall
>
>2. Append the original call
>
> extern __declspec(dllexport) ret __stdcall SomeDLL_Open();
>
>3. Now we passed in "int" as the parameter, so replace any instances of
>"ret" with "int":
>
> extern __declspec(dllexport) int __stdcall SomeDLL_Open();
>
>So, that's what the code looks like at after the first macro pass. Now,
>"__declspec" is a standard C++ macro, read about __declspec here:
>
>http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore/html
>/_core_export_from_a_dll_using___declspec.28.dllexport.29.asp
>
>But given what it does, I don't think you need to worry too much about
>its exact expansion. My first guess at a Delphi translation:
>
> function SomeDLL_Open(): Integer; stdcall; name 'SomeDLL_Open';
>
>This declaration would go in a "Exports" section of your DLL.
>
>Similarly:
>
> > DLLFUNC(void) SomeDLL_Close();
>
> extern __declspec(dllexport) void __stdcall SomeDLL_Close();
>
> > DLLFUNC(int) SomeDLL_GetData(BYTE* pDataType, const PBYTE* pTheData,
> > DWORD* pDataSize);
>
> extern __declspec(dllexport) int __stdcall SomeDLL_GetData(
> BYTE* pDataType, const PBYTE* pTheData, DWORD* pDataSize);
>
> > DLLFUNC(int) SomeDLL_Request(BYTE byRequestType, DWORD dwRequestData);
>
> extern __declspec(dllexport) int __stdcall SomeDLL_Request(
> BYTE byRequestType, DWORD dwRequestData);
>
> > DLLFUNC(int) SomeDLL_GetErrorCondition();
>
> extern __declspec(dllexport) int __stdcall SomeDLL_GetErrorCondition()
>
>HTH
Yes, it sure did--Thanks Stephen. (thanks Maarten, and Eugenijus too!)
What I came up with that compiled is:
// Trashed the macro, and manually constructed the statements...
// C++: DLLFUNC(int) SomeDLL_Open();
Function SomeDLL_Open(): Integer; StdCall;
Exports SomeDLL_Open Name 'SomeDLL_Open';
// Apparently, the 'Exports' keyword can be placed anywhere, so
// why not just after the Function is declared?
// C++: DLLFUNC(void) SomeDLL_Close();
Procedure SomeDLL_Close(); StdCall;
Exports SomeDLL_Close Name 'SomeDLL_Close';
// C++: DLLFUNC(int) SomeDLL_GetData(BYTE* pDataType,
// const PBYTE* pTheData, DWORD* pDataSize);
Function SomeDLL_GetData(pDataType: Byte; const pTheData: PBYTE;
pDataSize: LongInt): Integer; StdCall;
Exports SomeDLL_GetData NAME 'SomeDLL_GetData';
// C++: DLLFUNC(int) SomeDLL_Request(BYTE byRequestType, DWORD
dwRequestData);
Function SomeDLL_Request(byRequestType: Byte; dwRequestData: LongInt):
Integer; StdCall;
Exports SomeDLL_Request NAME 'SomeDLL_Request';
Now I have a few more questions: Even though this format
compiles, will I have any problems with the pointers that
I pretty much ignored in these translations? If so, how
should I alter this code?
Also, Type definitions 1, & 2, below seem to make sense,
but #3 has multiple data types as arguments. And #4 has
that extra parameter, 'BOOL'. What should I do in this
case?
// (1) C++: typedef int (__stdcall *FUNC_OPEN)();
Type FUNC_OPEN = Function(): Integer; StdCall;
// (2) C++: typedef void (__stdcall *FUNC_CLOSE)();
Type FUNC_CLOSE = Function(): Integer; StdCall;
// (3) C++: typedef int (__stdcall *FUNC_GET)(BYTE*,PBYTE*,DWORD*);
Type FUNC_GET = Function({ ???? }): Integer; StdCall;
// (4) C++: typedef void (__stdcall *FUNC_SHOWICON)(BOOL);
Type FUNC_SHOWICON = Procedure(); StdCall;
Thanks for all the light you guys are shining my way!
- Next message: Jigar Mehta: "how to start with templates ??"
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