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HookDaedalus

Info

Dependencies:
- None
Implementation:
HookDaedalus.d on GitHub

This package allows hooking daedalus functions. The principle is similar HookEngine. We have a function (hooked function) into which we would like to hook another function (hook function).

Tip

Having to hook a Daedalus function should be pretty rare, because you can simply adjust the corresponding function. However, it may become necessary in some contexts.

Initialization

N/A

Functions

HookDaedalusFunc

HookDaedalusFunc

Hooks the function. 

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func void HookDaedalusFunc(var func hooked, var func hook)
Parameters
  • var func hooked
    Hooked function
  • var func hook
    Hook function

HookDaedalusFuncF

HookDaedalusFuncF

Alias to the HookDaedalusFunc function. 

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func void HookDaedalusFuncF(var func hooked, var func hook)
Parameters
  • var func hooked
    Hooked function
  • var func hook
    Hook function

HookDaedalusFuncI

HookDaedalusFuncI

HookDaedalusFunc but with function ID. 

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func void HookDaedalusFuncI(var int hookedID, var int hookID)
Parameters
  • var int hookedID
    ID of hooked function
  • var int hookID
    ID of hook function

HookDaedalusFuncS

HookDaedalusFuncS

HookDaedalusFunc but with function name. 

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func void HookDaedalusFuncS(var string hookedName, var string hookName)
Parameters
  • var string hookedName
    Name of hooked function
  • var string hookName
    Name of hook function

IsHookD

IsHookD

Checks whether a function is already hooking another. Each function can be hooked any number of times, but each function can only hook one other. 

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func int IsHookD(var int funcID)
Parameters
  • var int funcID Symbol index of a hook function

Return value

The function returns TRUE if the function is already hooking another, FALSE is returned otherwise.

ContinueCall

ContinueCall

Continues the program run with the original function. 

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func void ContinueCall()

PassArgumentI

PassArgumentI

Passes an integer as an argument to the original function. Must be called before ContinueCall. 

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func void PassArgumentI(var int i)
Parameters
  • var int i
    Integer argument to forward

PassArgumentS

PassArgumentS

Passes a string as an argument to the original function. Must be called before ContinueCall. 

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func void PassArgumentS(var string s)
Parameters
  • var string s
    String argument to forward

PassArgumentN

PassArgumentN

Passes an instance as an argument to the original function. Must be called before ContinueCall. 

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func void PassArgumentN(var instance n)
Parameters
  • var instance n
    Instance argument to forward

Examples

Hook before function

We have a hook: 

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HookDaedalusFunc(hooked, hook);
The functions can look like that: 
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func void hooked() 
{
    Print("Original function");
};

func void hook() 
{
    Print("Our hook");
    ContinueCall();
};
The results should look like that 
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2
Our hook
Original function

Hook after function

We have the same hook: 

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HookDaedalusFunc(hooked, hook);
The functions are also similar, but the ContinueCall(); is called first: 
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func void hooked() 
{
    Print("Original function");
};

func void hook() 
{
    ContinueCall();
    Print("Our hook");
};
The results should look like that: 
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Original function
Our hook

Arguments and return values

If a function to be hooked expects parameters or returns a value, our hooking function should conform to that. 

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func int hooked(var int i) 
{
     Print("Original function");
     return i+1;
};

func int hook(var int i) 
{
     Print("Our hook");
     PassArgumentI(i);
     ContinueCall();
};
In this case, we may not return the value at the end of the hook because the returned value will just stay on the stack. However, we shouldn't give up on calling PassArgumentI(i) to ensure that it is still on top of the stack when the program continues with hooked.

Manipulation of arguments and return values

We can also manipulate arguments and return values with our hook. 

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func int hook(var int i) 
{
    Print("Our hook");
    PassArgumentI(i+1);     // add 1
    ContinueCall();
    i = MEM_PopIntResult();
    i *= 2;                 // Multiply by 2
    return i;
};

Multiple hooks

A function can be hooked any number of times, but each function can only hook one. New hooks are always inserted after the previous one. The following example illustrates this quite well. 

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HookDaedalusFunc(a, b); // B hooks A
HookDaedalusFunc(a, c); // C hooks A to B
HookDaedalusFunc(a, d); // D hooks A to C

HookDaedalusFunc(c, b); // Ignored because B is already hooking a function

var int i; i = a(1);


// Hooked function
func int a(var int i) 
{
    MEM_Info(ConcatStrings("---  A: ", IntToString(i)));
    return i+1;
};

// First hook function:
// Replaces `a` because the program run is not continued with ContinueCall
func int b(var int i) 
{
    MEM_Info(ConcatStrings("  -- B: ", IntToString(i)));
    return i;
};

// Second hook function:
// Increments the argument before ContinueCall and then decrements the return value
func int c(var int i) 
{
    MEM_Info(ConcatStrings(" -> C: ", IntToString(i)));
    passArgumentI(i+1);
    ContinueCall();

    i = MEM_PopIntResult();
    i -= 1;
    MEM_Info(ConcatStrings(" <- C: ", IntToString(i)));
    return i;
};

// Third hook function:
// Increments the argument before ContinueCall and then decrements the return value
func int d(var int i) 
{
    MEM_Info(ConcatStrings("-> D: ", IntToString(i)));
    passArgumentI(i+1);
    ContinueCall();

    i = MEM_PopIntResult();
    i -= 1;
    MEM_Info(ConcatStrings("<- D: ", IntToString(i)));
    return i;
};

// Output:
// -> D: 1
//  -> C: 2
//   -- B: 3
//  <- C: 2
// <- D: 1