| int CALLBACK LibMain(hinst, wDataSeg, cbHeapSize, lpszCmdLine) | |||||
| HINSTANCE hinst; | /* handle of library instance | */ | |||
| WORD wDataSeg; | /* library data segment | */ | |||
| WORD cbHeapSize; | /* default heap size | */ | |||
| LPSTR lpszCmdLine; | /* command-line arguments | */ | |||
The LibMain function is called by the system to initialize a dynamic-link library (DLL). A DLL must contain the LibMain function if the library is linked with the file LIBENTRY.OBJ.
hinst
Identifies the instance of the DLL.
wDataSeg
Specifies the value of the data segment (DS) register.
cbHeapSize
Specifies the size of the heap defined in the module-definition file. (The LibEntry routine in LIBENTRY.OBJ uses this value to initialize the local heap.)
lpszCmdLine
Points to a null-terminated string specifying command-line information. This parameter is rarely used by DLLs.
The function should return 1 if it is successful. Otherwise, it should return 0.
The LibMain function is called by LibEntry, which is called by Windows when the DLL is loaded. The LibEntry routine is provided in the LIBENTRY.OBJ module. LibEntry initializes the DLL's heap (if a HEAPSIZE value is specified in the DLL's module-definition file) before calling the LibMain function.
The following example shows a typical LibMain function:
int CALLBACK LibMain(HINSTANCE hinst, WORD wDataSeg, WORD cbHeap,
LPSTR lpszCmdLine )
{
HGLOBAL hgblClassStruct;
LPWNDCLASS lpClassStruct;
static HINSTANCE hinstLib;
/* Has the library been initialized yet? */
if (hinstLib == NULL) {
hgblClassStruct = GlobalAlloc(GHND, sizeof(WNDCLASS));
if (hgblClassStruct != NULL) {
lpClassStruct = (LPWNDCLASS) GlobalLock(hgblClassStruct);
if (lpClassStruct != NULL) {
/* Define the class attributes. */
lpClassStruct->style = CS_HREDRAW | CS_VREDRAW |
CS_DBLCLKS | CS_GLOBALCLASS;
lpClassStruct->lpfnWndProc = DllWndProc;
lpClassStruct->cbWndExtra = 0;
lpClassStruct->hInstance = hinst;
lpClassStruct->hIcon = NULL;
lpClassStruct->hCursor = LoadCursor(NULL, IDC_ARROW);
lpClassStruct->hbrBackground =
(HBRUSH) (COLOR_WINDOW + 1);
lpClassStruct->lpszMenuName = NULL;
lpClassStruct->lpszClassName = "MyClassName";
hinstLib = (RegisterClass(lpClassStruct)) ?
hinst : NULL;
GlobalUnlock(hgblClassStruct);
}
GlobalFree(hgblClassStruct);
}
}
return (hinstLib ? 1 : 0); /* return 1 = success; 0 = fail */
}