检查函数是否与C中的typedef函数类型相同？

Question

我有以下代码：

typedef int state_requester(void* request_paramaters); 

int doSomething(state_requester* requester) { 

    // This if statement is what I'm trying to 
    // figure out how to do. 

    if (requester isoftype state_requester) { 
     requester(NULL); 
     return 1; 
    } 

    return 0; 
} 

我试图找到一种方法来验证 参数传递实际上是尝试执行之前，一个有效的state_requester 功能格式。

上面的代码只是一个例子，显然不是事情真正起作用。我只需要知道如何做if (x isoftype y)关于函数typedefs。

Answer 1

尽管没有真正的方法可以直接验证数据是否属于特定类型，但我已经设定了一种方法来'推测'该类型匹配。

这并不是100％保证它是指定的类型。但是，它会假定它基于类型代码。

我也添加了一些测试。我在几分钟内写了这篇文章，所以我确信它有改进的空间，而且我绝不是本地开发人员。我只是有需要而已。如果它帮助某人，真棒！

#include <stdio.h> 
#include <stdlib.h> 


// Type Definitions 

// These are the type definitions that can be used to check for type 
// They need to be unique so that only types starting with these 
// prefixes will be presumed to be of the type specified. 
typedef enum type { 
    TYPE_StateRequester = 0x10f3ccd3, 
    TYPE_OtherThing = 0x09331c8c 
} type; 


// State Requester Definitions & Functions 

typedef int state_requester_f(void* request_parameters); 

// Since we want to check the "type" of a function reference, 
// we need to wrap it in a struct along with it's type code. 
struct state_requester_t { 
    int type; 
    state_requester_f* call; 
} typedef state_requester_t; 

state_requester_t new_state_requester(state_requester_f* call) { 
    state_requester_t sr; 
    sr.type = TYPE_StateRequester; 
    sr.call = call; 
    return sr; 
} 

// This function will check if data is of type StateRequester 
// 
// If the data sent to this function is not of the length 
// nessecary for the state_requester type, - OR - 
// it's type property is not equal to the StateRequester type 
// then we will presume that this data is NOT of type StateRequester 
uint8_t is_state_requester(void* data, size_t len) { 
    return len == sizeof(state_requester_t) && 
      ((state_requester_t*)data)->type == TYPE_StateRequester; 
} 


// Testing functions 

int test_caller(void* data) { 
    printf("Got to the test_caller function.\n"); 

    return 0; 
} 

int main(int agc, char *argv[]) { 

    // Create an actual state_requester_t definitiion 
    state_requester_t sr = new_state_requester(&test_caller); 

    // Test to see if it's validated as a state_requester_t 
    if (is_state_requester(&sr, sizeof(state_requester_t))) { 
     printf("Yes, variable 'sr' is presumadely of type state_requester_t\n"); 
     sr.call(NULL); 
    } else { 
     printf("No, variable 'sr' is not of type state_requester_t\n"); 
    } 

    // Create a phony state_requester_t definition, 
    // but keep it the same length as a regular 
    // state_requester_t 
    void* a = malloc(sizeof(state_requester_t)); 

    // Test to see if it's validated as a state_requester_t 
    if (is_state_requester(a, sizeof(state_requester_t))) { 
     printf("Yes, variable 'a' is presumadely of type state_requester_t\n"); 
    } else { 
     printf("No, variable 'a' is not of type state_requester_t\n"); 
    } 

    free(a); 

    // Create a phony state_requester_t with an improper length 
    void* b = malloc(5); 

    // Test to see if it's validated as a state_requester_t 
    if (is_state_requester(b, sizeof(state_requester_t))) { 
     printf("Yes, variable 'b' is presumadely of type state_requester_t\n"); 
    } else { 
     printf("No, variable 'b' is not of type state_requester_t\n"); 
    }  

    free(b); 

    return 0; 
} 

Answer 2

你不能这样做，在C.

类型在编译期进行检查，而不是运行时。

注意：requester是类型state_requester*，而不是state_requester。