call32v2.zip
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This program is placed in the public domain. Please feel free to redistribute
as you wish. No guarantees are made as to its suitability or usefulness,
and no support can be provided [by Peter Golde].
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However, since I modified the .dll and pretty well understand how it
works I will try to answer questions that arise from
the use of this .dll. Also, due to the price charged for the
.dll, I won't promise anything that takes away from my paying job.
I must thank Peter Golde for coming up with the original.
You are welcome to contact me at:
Rob Lichtefeld
Spalding Software, Inc.
333 Research Ct
Suite 220
Norcross, GA 30092 USA
robl@spaldingsoftware.com
1. Summary
CALL32.DLL is a DLL that can be used for calling routines in 32-bit DLLs on Windows XP, ME, 2000, NT, and 9x. It may or may not work on other 32-bit operating systems.
Using it, a Visual Basic program, running in the Win16 subsystem, can declare and call functions in any 32-bit DLL (including, but not limited to, the system DLLs). CALL32.DLL works on both the x86 and MIPS versions on NT. It has not been tested on Alpha or other versions, but should work.
You should install the CALL32.DLL in the Windows System folder. This will allow all programs that use it to share the one copy and to make sure that all programs use the most recent version. As a general rule, if you didn't write a .dll you are distributing it should go into the Windows System or System32 folder.
2. Usage
To call a function in a 32-bit DLL, follow the following steps:
A) Declare the CALL32 functions as follows (each Declare should be on a single line):
Declare Function Declare32 Lib "call32.dll" (ByVal Func$, ByVal Library$, ByVal Args$) As Long
Declare Sub FreeCall32IDs Lib "call32.dll" ()B) Next, declare the function(s) you wish to call. Declare it in the ordinary fashion, with the following exceptions:
For example, if you are calling the function:
GetWindowText(HWND hwnd, LPSTR lpsz, int cch)declare it as follows (remember that ints and all handles are 32 bits, so use a Long):
Declare Function GetWindowText Lib "call32.dll" Alias "Call32" (ByVal hwnd As Long, ByVal lpsz As String, ByVal cch As Long, ByVal id As Long) As Long
C) In the initialization section of your application,
you declare the actual library and name of the function you want to call
with the Declare32 function. Pass it the name of
the function, the library, and a string describing the argument types.
Each letter in the string declares the type of one argument,
and should be either:
"i" for a 32 bit integer or handle type,
"p" for any pointer type, or
"w" for an HWND parameter you want to pass
a 16 bit HWND to and
have be automatically
converted to a 32 bit HWND.
The return value of Declare32 should be saved away in a global variable to be passed as the last parameter to the function you declared earlier. So, continue the example, you would call:
idGetWindowText = Declare32("GetWindowText", "user32", "wpi")
(As a side note, this would be more properly declared as
D) To call the function, you would just call:
cbCopy = GetWindowText(hwnd, sz, cb, idGetWindowText)
E) In the shutdown section of your application,
you should call the FreeCall32IDs subroutine to free the libraries that
were loaded by the .DLL for your program. If you do not call this
subroutine, the libraries will not be freed. This causes the counter
for the 32-bit DLLs to never be decremented and thus never unloaded from
memory.
3. Data Types and Handles
It is important to use the correct data types when calling DLL functions.
There are two important points to pay attention
to when using CALL32.DLL. First, only 32 bit integers can be
passed to a DLL procedures. Since virtually all 32 bit
functions take int, UINT, LONG, DWORD, or HANDLE parameters, which
are all 32 bits, this is not a major restriction. However, you must
remember to always declare functions arguments are Long, and not Integer.
Secondly, 16 bit handles and 32 bit handles are not interchangable.
For example, a 16 bit bitmap handle that you get from calling
a 16 bit DLL or from the VB environment cannot be passed to a 32 bit
function expecting a bitmap handle. Similarly, a
32 bit handle gotten from a 32 bit function cannot be passed to a 16
bit DLL. The only exception is window handles (HWND). If
you declare a function parameter with the "w" letter in the argument
description string passed to Declare32, the corresponding
parameter will be automatically converted from a 16 bit HWND to a 32
bit HWND when the call is made. You must still declare the argument
as a LONG. This is convenient, for example, when passing the value
returned by the "hWnd" property of a control to a 32 bit DLL function.
Only windows created by your application can be translated.
Summary of data types:
| C data type | Type specified in Declare | Character for Declare32 |
| int, UINT | ByVal Long | i |
| LONG, DWORD | ByVal Long | i |
| HANDLE | ByVal Long | i |
| WORD, short | not supported | |
| HWND | ByVal Long | w (i for no 16->32 translation) |
| LPSTR | ByVal String | p |
| LPLONG, LPDWORD,LPUINT, int FAR * | Long | p |
| LPWORD | Integer | p |
4. Note on Declare32 function names
Declare32 will automatically try three different names for the function
name you pass in. First, it uses the exact
name you pass in. If that function name isn't found, it converts
the name to the stdcall decorated name convention,
by adding an underscore at the beginning, and adding "@nn" at the end,
where "nn" is the number of bytes of arguments. If
that name isn't found, it adds an "A" to the end of the original name
to try the Win32 ANSI function calling convention.
5. Run-time Error Summary
The following run-time errors can be generated by CALL32.DLL
30001 Can't load DLL: "|" (error=|)
The DLL name passed to Declare32 was not the name of a
valid 32 bit DLL. The Win32 error code is specified at
the
end of the error message, this can help determine why
the DLL didn't load.
30002 Can't find specified function
The function name passed to Declare32 could not be found
in the DLL.
30003 Invalid parameter definition string
The parameter definition string passed to Declare32 had
an invalid character in it, or was too long (32 parameters
is the limit).
30004 Not running on Windows NT
The program is not running in the Windows16 subsystem
of
Windows NT.
30005 Invalid window handle
The 16 bit window handle passed as a parameter declared
with the 'w' character was not a valid 16 bit window handle,
or refers to a window from a different process.
6. Change History
2.02 (1/5/99)
Added some small calls to assist in making the apps appear to the OS
as a 32-bit app.
2.00 (9/10/96)
Fixed problem with running more than one VB program calling the
.DLL at one time:
1.01 (9/27/93)
1.00 (8/31/93)