when we want to access this object we use the following frame of code:
document.write("firstProperty : " + newObject.firstProperty + "
");
document.write("secondProperty is : " + newObject.secondProperty + "
");
II Approach.(using user-defined function)
function newObject (firstProperty , secondProperty){
this.firstProperty = firstProperty ;
this.secondProperty= secondProperty;
}
.....
var myNewObject = new newObject ("firstProperty value", "secondProp value");
document.write("firstProperty is : " + myNewObject.firstProperty + "
");
document.write("secondProperty is : " + myNewObject.secondProperty+ "
");
Assigning methods to object.
Objects are composed of attributes. If an attribute contains a function, it is considered to be a method of the object otherwise, the attribute is considered a property.
function someFunctionOfThirdProperty(parammeter){ this.thirdProperty= parammeter; } function newObject (firstProperty , secondProperty){ this.firstProperty = firstProperty ; this.secondProperty= secondProperty; this.someFunctionOfThirdProperty=someFunctionOfThirdProperty;//!!!! } .... var myNewObject = new newObject ("firstProperty value", "secondProp value"); myNewObject.someFunctionOfThirdProperty("parammeterValue"); document.write("firstProperty is : " + myNewObject.firstProperty + " "); document.write("secondProperty is : " + myNewObject.secondProperty+ " "); document.write("thirdProperty is : " + myNewObject.thirdProperty+ " ");with keyword
with (object){
properties used without the object name and dot }
replace the function above with this function:
function someFunctionOfThirdProperty(parammeter){
with(this){
thirdProperty= parammeter;
}
}
// Somename.cpp
#include "SysInfo.h"
BOOL __stdcall DllMain(HINSTANCE hInst, DWORD dwReason, LPVOID lpReserved) {
return TRUE;
}
//write some functions in C
extern "C" __declspec(dllexport) int __stdcall someFunction() { int retVal; //write some C code// write some code in assembler_asm { mov eax, 1 mov retVal, eax } // return result return (retVal)2)to use dumpbin tool in order to get thwe right name of the Function. Something like that: dumpbin -exports Somename.dll in order to get some output like the following: ordinal hint RVA name//write some other functions in C1 0 00001005 ?someFunction@@YGXPAD@ZThe Compiler in order to prepare functionw for overloading gives to functions new names,This step can be ommited if you use the extern "C" keyward . In this manner the C compiler is informed to don't decorate the function name.Here @ shows the function uses the standard calling convention stdcallmore about calling conventions here 3)to call functions in dll through some C# programstdcall
The stdcall calling convention is a variation on the Pascal calling convention in which the callee is responsible for cleaning up the stack, but the parameters are pushed onto the stack in right-to-left order, as in the _cdecl calling convention. Registers EAX, ECX, and EDX are designated for use within the function. Return values are stored in the EAX register.
stdcall is the standard calling convention for the Microsoft Win32 API and for Open Watcom C++./ Main.cs using System; using System.Runtime.InteropServices; class MainClass { [DllImport("Somename.dll")] static extern int someFunction(); // main program public static void Main() { //get someFunction() result try { int param = someFunction(); Console.WriteLine("Param value = {0}", param .ToString() ); } catch (DllNotFoundException e) { Console.WriteLine(e.ToString()); } catch (EntryPointNotFoundException e) { Console.WriteLine(e.ToString()); } } };
EnumWindows unmanaged DLL function.
CallBack(int hwnd, int lparam) is the managed callback function
hwnd:handle to the window
lparam:application defined parameter
using System; using System.Runtime.InteropServices; public delegate bool CallBack(int hwnd, int lParam); public class EnumReportApp { [DllImport("user32")] public static extern int EnumWindows(CallBack x, int y); public static void Main() { CallBack myCallBack = new CallBack(EnumReportApp.Report); EnumWindows(myCallBack, 0); } public static bool Report(int hwnd, int lParam) { Console.Write("Window handle is "); Console.WriteLine(hwnd);
//Callback functions generally return nonzero values to indicate success //and zero to indicate failure. This example explicitly sets the return v //alue to true to continue the enumeration.
return true;
}
}
Similar enumeration functions are: EnumFontFamilies, EnumPrinters
The usage of a callback is usually in asynchronous logic.