Application Programming Interface Calls and Resources in Assembly Modules

In this section, I demonstrate that the called procedure written in Assembly language can contain not only auxiliary procedures but also calls to application programming interface (API) functions. Furthermore, it can work with resources. Note that these resources are common for all modules of the project. It is possible to have several resource files. The only thing that you'll have to do is ensuring that the names and the identifiers match.

Listing 20.5: The console application written in C++ calls the graphic user interface-mode procedure (Listing 20.6) defined in an Assembly module

 #include <windows. h> #include <stdio.h> // Declare the external function extern "C"__stdcall DIAL1(); void main() {  DIAL1();  ExitProcess(0); } 

 

Listing 20.6: Using resources and application program interface calls in the Assembly module

 // The DIALFORC.RC file // Definitions of constants #define WS_SYSMENU     0x00080000L // Window elements must be initially visible #define WS_VISIBLE     0x10000000L // Border around the elements #define WS_BORDER      0x00800000L // Elements can be sequentially activated //by pressing the <Tab> key #define WS_TABSTOP     0x00010000L // Text in the edit field is // aligned to the left side #define ES_LEFT        0x0000L // Style of all window elements #define WS_CHILD       0x40000000L // Keyboard input is disabled #define ES_READONLY    0x0800L #define DS_3DLOOK      0x0004L // Dialog box definition DIAL1 DIALOG 0, 0, 240, 100 STYLE WS_SYSMENU  DS_3DLOOK CAPTION "An example dialog box with date and time" FONT 8, "Arial" {  CONTROL "", 1, "edit", ES_LEFT  WS_CHILD   WS_VISIBLE  WS_BORDER   WS_TABSTOP  ES_READONLY, 100, 5, 130, 12 } ; The DIALFORC.INC file ; Constants ; This message arrives when the window is closed WM_CLOSE        equ 10h ; This message arrives when the window is created WM_INITDIALOG   equ 110h ; This message arrives when some event occurs to the window element WM_COMMAND      equ 111h ; Message from the timer WM_TIMER        equ 113h ; The message for sending some text to the window element WM_SETTEXT      equ 0Ch ; Prototypes of external procedures EXTERN      SendDlgItemMessageA:NEAR EXTERN      _wsprintfA:NEAR EXTERN      GetLocalTime:NEAR EXTERN      ExitProcess:NEAR EXTERN      GetModuleHandleA:NEAR EXTERN      DialogBoxParamA:NEAR EXTERN      EndDialog:NEAR EXTERN      SetTimer:NEAR EXTERN      KillTimer:NEAR ; Structures ; Message structure MSGSTRUCT STRUC         MSHWND      DD ?         MSMESSAGE   DD ?         MSWPARAM    DD ?         MSLPARAM    DD ?         MSTIME      DD ?         MSPT        DD ? MSGSTRUCT ENDS ; Date-time data structure DAT STRUC         year    DW ?         month   DW ?         dayweek DW ?         day     DW ?         hour    DW ?         min     DW ?         sec     DW ?         msec    DW ? DAT ENDS ; The DIALFORC.ASM file .586P ; Flat memory model .MODEL FLAT, stdcall include dialforc.inc PUBLIC DIAL1 ;-------------------------------------- ; Data segment _DATA SEGMENT         MSG      MSGSTRUCT <?>         HINST    DD 0 ; Application descriptor         PA       DB "DIAL1", 0         TIM      DB "Date %u/%u/%u Time %u:%u:%u", 0         STRCOPY  DB 50 DUP (?)         DATA     DAT <0> _DATA ENDS ; Code segment _TEXT SEGMENT DIAL1 PROC         PUSH  EBP         MOV   EBP, ESP ; Get the application descriptor         PUSH  0         CALL  GetModuleHandleA         MOV   [HINST], EAX ; Create a dialog         PUSH  0         PUSH  OFFSET WNDPROC         PUSH  0         PUSH  OFFSET PA         PUSH  [HINST]         CALL  DialogBoxParamA         CMP   EAX, -1 ;---------------------------------         POP   EBP         RET DIAL1 ENDP ;--------------------------------- ; Window procedure ; Position of parameters in the stack ; [BP+014H]  ; LPARAM ; [BP+10H]   ; WAPARAM ; [BP+0CH]   ; MES ; [BP+8]     ; HWND WNDPROC       PROC         PUSH  EBP         MOV   EBP, ESP         PUSH  EBX         PUSH  ESI         PUSH  EDI ;----------------         CMP   DWORD PTR [EBP+0CH], WM_CLOSE         JNE   L1 ; Reaction to closing a window ; Delete timer 1         PUSH  1 ; Timer identifier         PUSH  DWORD PTR [EBP+08H]         CALL  KillTimer ; Delete timer 2         PUSH  2 ; Timer identifier         PUSH  DWORD PTR [EBP+08H]         CALL  KillTimer ; Close the dialog         PUSH  0         PUSH  DWORD PTR [EBP+08H]         CALL  EndDialog         JMP   FINISH L1:         CMP   DWORD PTR [EBP+0CH], WM_INITDIALOG         JNE   L2 ; Startup initialization ; Set timer 1         PUSH  0    ; Parameter = NULL         PUSH  1000 ; 1-second interval         PUSH  1    ; Timer identifier         PUSH  DWORD PTR [EBP+08H]         CALL  SetTimer ; Set timer 2         PUSH  OFFSET TIMPROC ; Parameter = NULL         PUSH  500            ; 0.5-second interval         PUSH  2              ; Timer identifier         PUSH  DWORD PTR [EBP+08H]         CALL  SetTimer         JMP   FINISH L2:         CMP   DWORD PTR [EBP+0CH], WM_TIMER         JNE   FINISH ; Send the string to the window         PUSH  OFFSET STRCOPY         PUSH  0         PUSH  WM_SETTEXT         PUSH  1 ; Element identifier         PUSH  DWORD PTR [EBP+08H]         CALL  SendDlgItemMessageA FINISH:         POP   EDI         POP   ESI         POP   EBX         POP   EBP         MOV   EAX, 0         RET   16 WNDPROC    ENDP ;------------------------------------------- ; Timer procedure ; Position of parameters in the stack ; [BP+014H]  ; LPARAM --- Time elapsed since Windows startup ; [BP+10H]   ; WAPARAM - Timer identifier ; [BP+0CH]   ; WM_TIMER ; [BP+8]     ; HWND TIMPROC     PROC         PUSH  EBP         MOV   EBP, ESP ; Get the local time         PUSH  OFFSET DATA         CALL  GetLocalTime ; Get the string for date and time output         MOVZX EAX, DATA.sec         PUSH  EAX         MOVZX EAX, DATA.min         PUSH  EAX         MOVZX EAX, DATA.hour         PUSH  EAX         MOVZX EAX, DATA.year         PUSH  EAX         MOVZX EAX, DATA.month         PUSH  EAX         MOVZX EAX, DATA.day         PUSH  EAX         PUSH  OFFSET TIM         PUSH  OFFSET STRCOPY         CALL  _wsprintfA ; Restore the stack         ADD   ESP, 32         POP   EBP         RET   16 TIMPROC ENDP _TEXT ENDS END 

 

To translate this program, proceed as follows :

• First methodIssue the following commands:

   tasm32 /ml dialforc.asm     brcc32 dialforc.rc 

  Then, include the DIALFORC.OBJ and DIALFORC.RES files in the project.

• Second methodThis method differs from the previous one in that the DIALFORC.RC file is included in the project instead of the DIALFORC.RES file. Naturally, it is necessary to remove definitions of constants from that file because all required definitions are in the C header files.