如何在Go语言中调用DLL？

go语言通过syscall实现对操作系统的调用，从网上找了几个例子，汇集如下：

例子一

关键代码共四行：

 h := syscall.LoadLibrary("kernel32.dll")
 proc := syscall.GetProcAddress(h, "GetVersion") 
 r := syscall.Syscall(uintptr(proc), 0, 0, 0, 0) 
 syscall.FreeLibrary(h) 

完成整代码如下：

package main   

import (  
  "syscall"  
)  

func main(){  
    h, err := syscall.LoadLibrary("kernel32.dll")  
    if err != nil {  
      abort("LoadLibrary", err)  
    }  
  defer syscall.FreeLibrary(h)  
  proc, err := syscall.GetProcAddress(h, "GetVersion")  
  if err != nil {  
    abort("GetProcAddress", err)  
  }  
  r, _, _ := syscall.Syscall(uintptr(proc), 0, 0, 0, 0)  
  print_version(uint32(r))  
}  

func abort(funcname string, err error) {  
  panic(funcname + " failed: " + err.Error())  
}  

func print_version(v uint32) {  
    major := byte(v)  
    minor := uint8(v >> 8)  
    build := uint16(v >> 16)  
    print("windows version ", major, ".", minor, " (Build ", build, ")\n")  
}  

例子二

package main
import (
    "fmt"
    "syscall"
    "time"
    "unsafe"
)

const (
    MB_OK                = 0x00000000
    MB_OKCANCEL          = 0x00000001
    MB_ABORTRETRYIGNORE  = 0x00000002
    MB_YESNOCANCEL       = 0x00000003
    MB_YESNO             = 0x00000004
    MB_RETRYCANCEL       = 0x00000005
    MB_CANCELTRYCONTINUE = 0x00000006
    MB_ICONHAND          = 0x00000010
    MB_ICONQUESTION      = 0x00000020
    MB_ICONEXCLAMATION   = 0x00000030
    MB_ICONASTERISK      = 0x00000040
    MB_USERICON          = 0x00000080
    MB_ICONWARNING       = MB_ICONEXCLAMATION
    MB_ICONERROR         = MB_ICONHAND
    MB_ICONINFORMATION   = MB_ICONASTERISK
    MB_ICONSTOP          = MB_ICONHAND

    MB_DEFBUTTON1 = 0x00000000
    MB_DEFBUTTON2 = 0x00000100
    MB_DEFBUTTON3 = 0x00000200
    MB_DEFBUTTON4 = 0x00000300
)

func abort(funcname string, err syscall.Errno) {
    panic(funcname + " failed: " + err.Error())
}

var (
    //    kernel32, _        = syscall.LoadLibrary("kernel32.dll")
    //    getModuleHandle, _ = syscall.GetProcAddress(kernel32, "GetModuleHandleW")

    user32, _     = syscall.LoadLibrary("user32.dll")
    messageBox, _ = syscall.GetProcAddress(user32, "MessageBoxW")
)

func IntPtr(n int) uintptr {
    return uintptr(n)
}

func StrPtr(s string) uintptr {
    return uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(s)))
}

func MessageBox(caption, text string, style uintptr) (result int) {
    ret, _, callErr := syscall.Syscall9(messageBox,
        4,
        0,
        StrPtr(text),
        StrPtr(caption),
        style,
        0, 0, 0, 0, 0)
    if callErr != 0 {
        abort("Call MessageBox", callErr)
    }
    result = int(ret)
    return
}

//func GetModuleHandle() (handle uintptr) {
//    if ret, _, callErr := syscall.Syscall(getModuleHandle, 0, 0, 0, 0); callErr != 0 {
//        abort("Call GetModuleHandle", callErr)
//    } else {
//        handle = ret
//    }
//    return
//}

// windows下的另一种DLL方法调用
func ShowMessage2(title, text string) {
    user32 := syscall.NewLazyDLL("user32.dll")
    MessageBoxW := user32.NewProc("MessageBoxW")
    MessageBoxW.Call(IntPtr(0), StrPtr(text), StrPtr(title), IntPtr(0))
}

func main() {
    //    defer syscall.FreeLibrary(kernel32)
    defer syscall.FreeLibrary(user32)

    //fmt.Printf("Retern: %d\n", MessageBox("Done Title", "This test is Done.", MB_YESNOCANCEL))
    num := MessageBox("Done Title", "This test is Done.", MB_YESNOCANCEL)
    fmt.Printf("Get Retrun Value Before MessageBox Invoked: %d\n", num)
    ShowMessage2("windows下的另一种DLL方法调用", "HELLO !")
    time.Sleep(3 * time.Second)
}

func init() {
    fmt.Print("Starting Up\n")
}

例子三，获取Windows默认路径

作者：kuuyee 链接：https://hacpai.com/article/1446417162636

获取 Windows 的系统默认目录

Windows 系统目录函数请参考 MSDN：https://msdn.microsoft.com/en-us/library/windows/desktop/bb762181%28v=vs.85%29.aspx

package main

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

var (
    shell         = syscall.MustLoadDLL("Shell32.dll")
    getFolderPath = shell.MustFindProc("SHGetFolderPathW")
)

const (
    CSIDL_DESKTOP = 0    //用户桌面默认目录
    CSIDL_APPDATA = 26    //用户AppData目录
)

func main() {
    b := make([]uint16, syscall.MAX_PATH)

    // https://msdn.microsoft.com/en-us/library/windows/desktop/bb762181%28v=vs.85%29.aspx
    // 这里第二个参数CSIDL_A必须定义为const，否则编译报错
    r, _, err := getFolderPath.Call(0, CSIDL_DESKTOP, 0, 0, uintptr(unsafe.Pointer(&b[0])))
    if uint32(r) != 0 {
        fmt.Sprintf("获取DIR错误：", err)
    }
    a_dir := syscall.UTF16ToString(b)

    r, _, err = getFolderPath.Call(0, CSIDL_APPDATA, 0, 0, uintptr(unsafe.Pointer(&b[0])))
    if uint32(r) != 0 {
        fmt.Sprintf("获取DIR错误：", err)
    }
    b_dir := syscall.UTF16ToString(b)

    fmt.Printf("目录ID：%d  目录地址：%s\n", CSIDL_DESKTOP, a_dir)
    fmt.Printf("目录ID：%d  目录地址：%s\n", CSIDL_APPDATA, b_dir)
}

SHGetFolderPathW 的第二个参数必须定义为 const，否则编译不过

输出

目录ID：0 目录地址：C:\Users\kuuyee\Desktop
目录ID：26 目录地址：C:\Users\kuuyee\AppData\Roaming