这里是swig typemap，它将c++类型转换为python类型。

# ifdef SWIGPYTHON

  %typemap(in) (char *data, size_t datasize) {
    Py_ssize_t len;
    PyBytes_AsStringAndSize($input, &$1, &len);
    $2 = (size_t)len;
  }

  %typemap(in, numinputs=0) (char**data, size_t *datasize)(char *temp, size_t tempsize) {
    $1 = &temp;
    $2 = &tempsize;
  }

  %typemap(argout) (char**data, size_t *datasize) {
    if(*$1) {
      $result = PyBytes_FromStringAndSize(*$1, *$2);
      free(*$1);
    }
  }

# endif

你能做同样的事吗，但是对于java语言？所以答案是

# ifdef SWIGJAVA

  %typemap(in) (char *data, size_t datasize) {
    convertJavaBytesToC++Bytes();
    ...something else...
  }
...

所以我需要它来生成正确的java Package 器代码
我想翻译成java的c++函数声明：

public void getFrames(char**data, size_t *datasize) {
    std::string s = getFramesAsString();
    size_t size = s.length();
    char *c = new char[size];
    s.copy(c, size, 0);
    *datasize = size;
    *data = c;
};
public void putFrame(char *data, size_t datasize) {
    const std::lock_guard<std::mutex> lock(frames_mtx);
    frames.push_front(std::string(data, datasize));
};