指向 scala-native 中的指针的指针

Posted 2023-03-10

【中文标题】指向 scala-native 中的指针的指针

【英文标题】：pointer to pointer in scala-native

【发布时间】：2017-05-02 04:25:55

【问题描述】：

我正在尝试将 czmq 与 scala-native 一起使用，但我还没有找到在 scala-native 中创建指针的方法。

这里是外部：

@native.link("czmq")
@native.extern
object czmq 

//struct _zsock_t 
//    uint32_t tag;               //  Object tag for runtime detection
//    void *handle;               //  The libzmq socket handle
//    char *endpoint;             //  Last bound endpoint, if any
//    char *cache;                //  Holds last zsock_brecv strings
//    int type;                   //  Socket type
//    size_t cache_size;          //  Current size of cache
//    uint32_t routing_id;        //  Routing ID for server sockets
//;

  type zsock_t = native.CStruct7[
                                native.CUnsignedLongLong,
                                native.Ptr[Byte],
                                native.CString,
                                native.CString,
                                native.CInt,
                                native.CSize,
                                native.CUnsignedLongLong]

  def zsock_new_push(endpoint: native.CString): native.Ptr[zsock_t] = native.extern
  def zsock_new_pull(endpoint: native.CString): native.Ptr[zsock_t] = native.extern
  def zstr_send(dest: native.Ptr[Unit], str: native.CString): native.CInt = native.extern
  def zstr_recv(src: native.Ptr[Unit]): native.CString = native.extern
  //void zsock_destroy (zsock_t **self_p)
  def zsock_destroy(self_p: native.Ptr[native.Ptr[zsock_t]]):Unit = native.extern

这是我的简单主要方法：

object Main 
  def main(args: Array[String]): Unit =
    val push = czmq.zsock_new_push(c"inproc://example")
    val pull = czmq.zsock_new_pull(c"inproc://example")
    czmq.zstr_send(push.cast[Ptr[Unit]], c"Hello World")  
    val s = fromCString(czmq.zstr_recv(pull.cast[Ptr[Unit]]))
    println("msg: "+s)
    czmq.zsock_destroy(push) // doesn't compile
    czmq.zsock_destroy(pull) // doesn't compile
  

所以问题是如何使push 和pull 变量指针像c 中的& 一样？

【参考方案1】：

我已经联系了 gitter 上的 scala-native 团队，答案是使用 stackalloc

val ppush = stackalloc[Ptr[czmq.zsock_t]]
val ppull = stackalloc[Ptr[czmq.zsock_t]]
!ppush = push
!ppull = pull
czmq.zsock_destroy(ppush)
czmq.zsock_destroy(ppull)