Go语言中CGO的使用实践

package main
 
//
// 引用的C头文件需要在注释中声明，紧接着注释需要有import "C"，且这一行和注释之间不能有空格
//
 
/*
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
void myprint(char* s) {
	printf("%s\n", s);
}
*/
import "C"
 
 
import (
	"fmt"
	"unsafe"
)
 
func main() {
	//使用C.CString创建的字符串需要手动释放。
	cs := C.CString("Hello World\n")
	C.myprint(cs)
	C.free(unsafe.Pointer(cs))
	fmt.Println("call C.sleep for 3s")
	C.sleep(3)
	return
}

#include <stdio.h>
void hello()
{
    printf("hello world\n"); 
}

#ifndef HELLO_H
#define HELLO_H
 
void hello(void);
#endif

gcc -c hello.c
ar -cru libhello.a hello.o

package main
 
//使用#cgo定义库路径
 
 
/*
#cgo CFLAGS: -I .
#cgo LDFLAGS: -L . -lhello
#include "hello.h"
*/
import "C"
 
func main() {
	C.hello()
}

package main
 
//
//#include <stdio.h>
//int add(int a, int b);
//
import "C"
 
import (
	"fmt"
)
 
//当使用export的时候，在同一个文件中就不能再定义其它的c函数了，不然会报错。
//使用export导出函数给c语言调用。
 
//export GoAdd
func GoAdd(a, b int) int {
	return a + b
}
 
func main() {
	a := C.add(1, 2)
	fmt.Printf("C.add(1,2) return %d\n", a)
}

package main
 
//
//int GoAdd(int a, int b); 
//
//int add(int a, int b)
//{
//	  return GoAdd(a,b);
//}
//
import "C"

#include <stdio.h>
 
#include "clibrary.h"
 
//参数是函数指针
void some_c_func(callback_fcn callback)
{
	int arg = 2;
	printf("C.some_c_func(): calling callback with arg = %d\n", arg);
	int response = callback(2);
	printf("C.some_c_func(): callback responded with %d\n", response);
}

#ifndef CLIBRARY_H
#define CLIBRARY_H
//定义函数指针
typedef int (*callback_fcn)(int);
void some_c_func(callback_fcn);
#endif

package main
 
/*
#cgo CFLAGS: -I .
#cgo LDFLAGS: -L . -lclibrary
#include "clibrary.h"
int callOnMeGo_cgo(int in); // 声明
*/
import "C"
 
import (
	"fmt"
	"unsafe"
)
 
//export callOnMeGo
func callOnMeGo(in int) int {
	return in + 1
}
 
func main() {
	fmt.Printf("Go.main(): calling C function with callback to us\n")
 
    //使用unsafe.Pointer转换
	C.some_c_func((C.callback_fcn)(unsafe.Pointer(C.callOnMeGo_cgo)))
}

package main
 
/*
 
#include <stdio.h>
int callOnMeGo(int);
 
// The gateway function
int callOnMeGo_cgo(int in)
{
	printf("C.callOnMeGo_cgo(): called with arg = %d\n", in);
    //调用GO函数
	return callOnMeGo(in);
}
*/
import "C"

package gocallback
 
import (
	"fmt"
	"sync"
)
 
/*
extern void go_callback_int(int foo, int p1);
// normally you will have to define function or variables
// in another separate C file to avoid the multiple definition
// errors, however, using "static inline" is a nice workaround
// for simple functions like this one.
static inline void CallMyFunction(int foo) {
	go_callback_int(foo, 5);
}
*/
import "C"