go 调用dll char*传输

参考：http://www.voidcn.com/article/p-ofnbgvoa-bpv.html

https://stackoverflow.com/questions/53721215/syscall-mustloaddll-mustfindproc-throws-the-specified-procedure-could-not-be-fo

c++:

MYLIBDLL char* testchar(int plus1);
MYLIBDLL void greet(char *name);

void greet(char *name)
{
	printf("Hello, %s!\n", name);
}
char* testchar(int plus1) {

	char* str = "hello world111111";
	return str;
}

main.go代码：

package main

import (
    "syscall"
    "unsafe"
    "fmt"
)
import "C"

func callDll() {


    dll := syscall.MustLoadDLL("hik_client.dll")

    procGreet := dll.MustFindProc("greet")
    procGreet.Call(uintptr(unsafe.Pointer(syscall.StringBytePtr("Cynhard11"))))

    procName := dll.MustFindProc("testchar")
    r, _, _ := procName.Call(1)
    // 获取C返回的指针。
    // 注意C返回的r为char*，对应的Go类型为*byte
    p := (*byte)(unsafe.Pointer(r))
    // 定义一个[]byte切片，用来存储C返回的字符串
    data := make([]byte, 0)
    // 遍历C返回的char指针，直到 '\0' 为止
    for *p != 0 {
        data = append(data, *p)  // 将得到的byte追加到末尾
        r += unsafe.Sizeof(byte(0))  // 移动指针，指向下一个char
        p = (*byte)(unsafe.Pointer(r))  // 获取指针的值，此时指针已经指向下一个char
    }
    name := string(data)  // 将data转换为字符串

    fmt.Printf("Hello, %s!\n", name)

    //var a = make([]byte, 256)
    //
    //
    //dll32 := syscall.NewLazyDLL("hik_client.dll")
    //fmt.Println("call dll:", dll32.Name)
    //GetPeopleName := dll32.NewProc("testchar")
    //
    //ret,_,err := GetPeopleName.Call(uintptr(unsafe.Pointer(&a)),2)
    //if err != nil {
    //    fmt.Println(ret,a)
    //    aaa := C.GoString(ret)
    //    //C.free(unsafe.Pointer(cs))
    //    //C.free(unsafe.Pointer(result))
    //    //fmt.Println(aaa,a)
    //}
    //result, a, _ := g.Call(4)


    //fmt.Println("result is :", ret)
}

func main() {
    fmt.Println("start111111111!")
    callDll()
    //fmt.Println(C.add(2, 1))
}