windows 直接调用dll

参考：

https://www.cnblogs.com/echojson/p/10743641.html

https://www.cnblogs.com/mafeng/p/8567261.html： GO语言 -- 调用DLL函数，填平所有的坑，最详尽攻略

https://blog.csdn.net/u011896834/article/details/95376558

https://studygolang.com/articles/12273?fr=sidebar ：

Golang通过syscall调用win32的Api

来自：

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下的第二种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下的第二种DLL方法调用", "HELLO !")
    time.Sleep(3 * time.Second)
}
 
func init() {
    fmt.Print("Starting Up\n")
}