如何在js-ctypes中使用指针调用一个函数 [英] How to call a function using pointer in js-ctypes

问题描述

$ b

谢谢。

解决方案

如果你有一个C函数的函数指针，那么你需要确保它被正确地解释为指向 FunctionType 。然后，您可以简单地调用它，就像您将使用JavaScript函数一样。例如， GetProcAddress（）返回一个函数指针 - 在下面的代码中，我用void指针声明 GetProcAddress作为返回类型，然后我将该指针转换为匹配 MessageBox（）函数签名的函数类型：



  Components.utils.import（resource：//gre/modules/ctypes.jsm）; 
 
 var BOOL = ctypes.int32_t; 
 var HANDLE = ctypes.voidptr_t; 
 var HMODULE = HANDLE; 
 var HWND = HANDLE; 
 var FARPROC = ctypes.voidptr_t; 
 var LPCTSTR = ctypes.jschar.ptr; 
 var LPCSTR = ctypes.char.ptr; 
 
 var kernel = ctypes.open（kernel32.dll）; 
 var LoadLibrary = kernel.declare（
LoadLibraryW，
 ctypes.winapi_abi，
 HMODULE，//返回类型
 LPCTSTR //参数
） ; 
 var FreeLibrary = kernel.declare（
FreeLibrary，
 ctypes.winapi_abi，
 BOOL，//返回类型
 HMODULE //参数
） ; 
 var GetProcAddress = kernel.declare（
GetProcAddress，
 ctypes.winapi_abi，
 FARPROC，//返回类型
 HMODULE，LPCSTR //参数
）; 
 
 //加载我们感兴趣的库
 var hUser = LoadLibrary（user32）; 
 
 //获取指向函数的指针。 
 var MessageBox = GetProcAddress（hUser，MessageBoxW）; 
 
 //现在我们有一个指向函数的指针，让我们把它转换成正确的类型。 
 var MessageBoxType = ctypes.FunctionType（
 ctypes.winapi_abi，
 ctypes.int32_t，//返回类型
 [HWND，LPCTSTR，LPCTSTR，ctypes.uint32_t] //参数
）; 
 MessageBox = ctypes.cast（MessageBox，MessageBoxType.ptr）; 
 
 //实际上调用函数。 
 MessageBox（null，Test1，Test2，0）; 
 
 //如果不再需要，再次释放库。任何导入的函数
 //指针在这里都应该被认为是无效的。 
 FreeLibrary（hUser）; 
  




I only have a pointer to a function, how to call it in js-ctypes?

Thanks.

解决方案

If you got a function pointer from a C function then you need to make sure it's correctly interpreted as a pointer to FunctionType. Then you can simply call it as you would a JavaScript function. For example, GetProcAddress() returns a function pointer - in the following code I declare GetProcAddress() with a void pointer as return type, then I cast that pointer to a function type matching the signature of the MessageBox() function:

Components.utils.import("resource://gre/modules/ctypes.jsm");

var BOOL = ctypes.int32_t;
var HANDLE = ctypes.voidptr_t;
var HMODULE = HANDLE;
var HWND = HANDLE;
var FARPROC = ctypes.voidptr_t;
var LPCTSTR = ctypes.jschar.ptr;
var LPCSTR = ctypes.char.ptr;

var kernel = ctypes.open("kernel32.dll");
var LoadLibrary = kernel.declare(
    "LoadLibraryW",
    ctypes.winapi_abi,
    HMODULE, // return type
    LPCTSTR // parameters
);
var FreeLibrary = kernel.declare(
    "FreeLibrary",
    ctypes.winapi_abi,
    BOOL, // return type
    HMODULE // parameters
);
var GetProcAddress = kernel.declare(
    "GetProcAddress",
    ctypes.winapi_abi,
    FARPROC, // return type
    HMODULE, LPCSTR // parameters
);

// Load the library we're interested in.
var hUser = LoadLibrary("user32");

// Get the pointer to the function.
var MessageBox = GetProcAddress(hUser, "MessageBoxW");

// Now we have a pointer to a function, let's cast it to the right type.
var MessageBoxType = ctypes.FunctionType(
    ctypes.winapi_abi,
    ctypes.int32_t, // return type
    [HWND, LPCTSTR, LPCTSTR, ctypes.uint32_t] // parameters
);
MessageBox = ctypes.cast(MessageBox, MessageBoxType.ptr);

// Actually call the function.
MessageBox(null, "Test1", "Test2", 0);

// Free the library again if no longer needed. Any imported function
// pointers should be considered invalid at this point.
FreeLibrary(hUser);

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