Help/Support How to return a value to a function with parameters?

[PixelYT 9 Moto E4 7.1.1]

Let's say I have this function in the dump.cs:

protected void ammo(int value, bool reload); // 0x289235

and I hooked it like this:

void(*old_ammo)(void *instance, int value, bool reload);
void ammo(void *instance, int value, bool reload)
{
if(instance != NULL)
{
// do something
}
return old_ammo(instance, value, reload);
}
MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

How would I set values to the parameters?

Would I do it like this:

void(*old_ammo)(void *instance, int value, bool reload);
void ammo(void *instance, int value, bool reload)
{
if(instance != NULL)
{
  return ammo(instance, 9999, false);
}
return old_ammo(instance, value, reload);
}
MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

or like this?

void(*old_ammo)(void *instance, int value, bool reload);
void ammo(void *instance, int value, bool reload)
{
if(instance != NULL)
{
  return 9999, false;
}
return old_ammo(instance, value, reload);
}
MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

Which one is correct?

 If none are correct, then how would I do it?

Updated May 14, 2021 by PixelYT
Added additional information

[Ted2 38.9k Donor]

  On 5/14/2021 at 9:09 PM, PixelYT said:

Would I do it like this:

void(*old_ammo)(void *instance, int value, bool reload);
void ammo(void *instance, int value, bool reload)
{
if(instance != NULL)
{
  return ammo(instance, 9999, false);
}
return old_ammo(instance, value, reload);
}
MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

Expand  

This one is the one you need for setting the parameters.

[PixelYT 9 Moto E4 7.1.1]

  On 5/16/2021 at 7:55 PM, Ted2 said:

This one is the one you need for setting the parameters.

Expand  

Thanks sir! :))

[Ted2 38.9k Donor]

  On 5/16/2021 at 7:58 PM, PixelYT said:

Thanks sir! :))

Expand  

Sorry, I just spotted a mistake. You should return old_ammo(instance, 9999,false); 

 

Not ammo(instance, 9999, false);

[PixelYT 9 Moto E4 7.1.1]

  On 5/16/2021 at 8:01 PM, Ted2 said:

Sorry, I just spotted a mistake. You should return old_ammo(instance, 9999,false); 

 

Not ammo(instance, 9999, false);

Expand  

so we when we are setting values to parameters, we use the old_ammo but when there is no parameters we just use the ammo and inside of it return 99999 or whatever we want, right?

[Ted2 38.9k Donor]

Hmm, sorry. I was checking the post on phone which sucks. I just checked on my laptop and...

 

The method you're hooking is a void, which means it doesn't return anything. Void methods are called to perform certain things rather than returning something. So this ammo method has two parameters: ammo and reload. You can make them always 9999 and false, but you do not return them.

A valid hook would look like this:

// This holds the original state of the method, some people prefer to call it "orig_ammo" instead because of that.
void(*old_ammo)(void *instance, int value, bool reload);

// This is the hooked method, where you can do whatever you want
void ammo(void *instance, int value, bool reload) {
  	// Just a note; I don't think instance will ever be NULL.
	if(instance != NULL) {
		// set ammo to 9999 and reload to false
		old_ammo(instance, 9999, false);
	}
	// Do what it normally does
	old_ammo(instance, value, reload);
}


MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

 

I've added some comments to the code, so I hope you understand better then.

[PixelYT 9 Moto E4 7.1.1]

  On 5/16/2021 at 8:21 PM, Ted2 said:

Hmm, sorry. I was checking the post on phone which sucks. I just checked on my laptop and...

 

The method you're hooking is a void, which means it doesn't return anything. Void methods are called to perform certain things rather than returning something. So this ammo method has two parameters: ammo and reload. You can make them always 9999 and false, but you do not return them.

A valid hook would look like this:

// This holds the original state of the method, some people prefer to call it "orig_ammo" instead because of that.
void(*old_ammo)(void *instance, int value, bool reload);

// This is the hooked method, where you can do whatever you want
void ammo(void *instance, int value, bool reload) {
  	// Just a note; I don't think instance will ever be NULL.
	if(instance != NULL) {
		// set ammo to 9999 and reload to false
		old_ammo(instance, 9999, false);
	}
	// Do what it normally does
	old_ammo(instance, value, reload);
}


MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

 

I've added some comments to the code, so I hope you understand better then.

Expand  

oh wow, now i understand. It's just like how when we hook an Update method and use function pointers on it, we don't use return because the Update method is a void which means it doesn't return anything. Thank you, now I understand, i just didn't know that when we hook a method that is a void but not the Update method, we just call the function and set it's parameters without return.

Updated May 16, 2021 by PixelYT
Added additional information

[PixelYT 9 Moto E4 7.1.1]

  On 5/16/2021 at 8:21 PM, Ted2 said:

Hmm, sorry. I was checking the post on phone which sucks. I just checked on my laptop and...

 

The method you're hooking is a void, which means it doesn't return anything. Void methods are called to perform certain things rather than returning something. So this ammo method has two parameters: ammo and reload. You can make them always 9999 and false, but you do not return them.

A valid hook would look like this:

// This holds the original state of the method, some people prefer to call it "orig_ammo" instead because of that.
void(*old_ammo)(void *instance, int value, bool reload);

// This is the hooked method, where you can do whatever you want
void ammo(void *instance, int value, bool reload) {
  	// Just a note; I don't think instance will ever be NULL.
	if(instance != NULL) {
		// set ammo to 9999 and reload to false
		old_ammo(instance, 9999, false);
	}
	// Do what it normally does
	old_ammo(instance, value, reload);
}


MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

 

I've added some comments to the code, so I hope you understand better then.

Expand  

One more question: inside of the if(instance != NULL) statement, don't we use ammo to set parameters to whatever we like and then after it, we just put the old_ammo in case instance is NULL? Like this and not like the above one:

void(*old_ammo)(void *instance, int value, bool reload); // this holds the original value of the method
void ammo(void *instance, int value, bool reload) // this is the hooked method where we change the value to whatever we like
{
if(instance != NULL)
{
  ammo(instance, 9999, false); // Use the hooked method to change int value to 9999, and bool reload to false
}
 old_ammo(instance, value, reload); // in case instance is NULL, call the old_ammo which holds the original value
}
MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

 

Updated May 17, 2021 by PixelYT
Added additional information

[Ted2 38.9k Donor]

  On 5/16/2021 at 11:48 PM, PixelYT said:

One more question: inside of the if(instance != NULL) statement, don't we use ammo to set parameters to whatever we like and then after it, we just put the old_ammo in case instance is NULL? Like this and not like the above one:

void(*old_ammo)(void *instance, int value, bool reload); // this holds the original value of the method
void ammo(void *instance, int value, bool reload) // this is the hooked method where we change the value to whatever we like
{
if(instance != NULL)
{
  ammo(instance, 9999, false); // Use the hooked method to change int value to 9999, and bool reload to false
}
 old_ammo(instance, value, reload); // in case instance is NULL, call the old_ammo which holds the original value
}
MsHookFunction((void*)getAbsoluteAddress(0x289235), (void*)ammo, (void**)&old_ammo);

 

Expand  

Nope. As the void ammo(bla, bla, bla) {} is the replacement method of the original method (which you named old_ammo), here you write your own logic of the method. If you only need to change the parameter values, you can just call the original method (old_ammo) with your own values and that will be enough. You could also do: 

void ammo(void *instance, int value, bool reload) {
	value = 9999;
	reload = false;
	old_ammo(instance, value, reload);
}

In this example you alter the parameter values it was originally called with and then call the method itself with your new values.