如何在js-ctypes中使用指针调用函数

Question

我只有一个指向函数的指针,如何在js-ctypes中调用它？

谢谢.

Answer 1

如果你有一个来自C函数的函数指针,那么你需要确保它被正确解释为指向FunctionType的指针.然后,您可以像调用JavaScript函数一样调用它.例如,GetProcAddress()返回一个函数指针 - 在下面的代码中我GetProcAddress()用void指针作为返回类型声明,然后我将该指针强制转换为与函数签名匹配的函数类型MessageBox():

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);