从C ++ / Java / C＃代码调用C方法？

Question

Many of today's programming languages are based on C; like C++, C#, Java, Objective-C. So could I call a C method from C++ code? Or call C from Java or C#? Or is this goal out of reach and unreasonable? Please include a quick code sample for my and everyone else's understanding.

Answer 1

C++,C#, Objective-C, and Java can all call C routines. Here are a few links that will give you an overview of the process needed to call C from each language you asked about.

• Calling C from Java
• Calling C from C++
• Calling C from C#
• Calling C from Objective-C

Answer 2

An example of calling C from C++. Save this C function in a file called ac:

int f() {
   return 42;
}

and compile it:

gcc -c a.c

which will produce a file called ao Now write a C++ program in a file called main.cpp:

#include <iostream>
extern "C" int f();

int main() {
   std::cout << f() << std::endl;
}

and compile and link with:

g++ main.cpp a.o -o myprog

which will produce an execuatable called myprog which prints 42 when run.

Answer 3

To Call C Methods In Java...

there a Keyword "native" in Which You can write machine-dependent C code and invoke it from Java....

Basically it creates a DLL file..then u have to load it in ur program...

a nice example here ....

Answer 4

To call C methods from Java, there are multiple options, including:

• JNA - Java Native Access. Free. Easy to use. Hand-declaration of Java classes and interfaces paralleling existing C structs and functions. Slower than JNI - by a few hundred nanoseconds per call.
• JNI - Java Native Interface. Free. Fastest option. Requires a layer of native glue code between your Java code and the native functions you want to call.
• JNIWrapper - Commercial product, similar to JNA.

Answer 5

要从Java调用C / C ++，还要看看BridJ （它就像JNA与C ++和更好的性能）。