Question

考虑这些C函数：

#define INDICATE_SPECIAL_CASE -1
void prepare (long *length_or_indicator);
void execute ();

prepare函数用于存储指向延迟long *输出变量的指针。

它可以在C中使用：

int main (void) {
    long length_or_indicator;
    prepare (&length_or_indicator);
    execute ();
    if (length_or_indicator == INDICATE_SPECIAL_CASE) {
        // do something to handle special case
    }
    else {
        long length = lengh_or_indicator;
        // do something to handle the normal case which has a length
    }
}

我想在Vala中实现这样的目标：

int main (void) {
    long length;
    long indicator;
    prepare (out length, out indicator);
    execute ();
    if (indicator == INDICATE_SPECIAL_CASE) {
        // do something to handle special case
    }
    else {
        // do something to handle the normal case which has a length
    }
}

如何在Vala中编写prepare ()和INDICATE_SPECIAL_CASE的绑定？

是否可以将变量拆分为两个？

即使在调用out之后写入prepare ()变量（在execute ()中），是否可以避免使用指针？

Answer 1

使用out的问题是Vala会在此过程中生成大量临时变量，这会导致引用错误。你可能想要做的是在你的VAPI中创建一个隐藏所有这些的方法：

[CCode(cname = "prepare")]
private void _prepare (long *length_or_indicator);
[CCode(cname = "execute")]
private void _execute ();
[CCode(cname = "prepare_and_exec")]
public bool execute(out long length) {
  long length_or_indicator = 0;
  prepare (&length_or_indicator);
  execute ();
  if (length_or_indicator == INDICATE_SPECIAL_CASE) {
     length = 0;
     return false;
  } else {
     length = lengh_or_indicator;
     return true;
 }
}

如何用双重函数绑定参数？

1 个答案: