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diff_pointer_convert.cpp
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diff_pointer_convert.cpp
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#include <iostream>
#include <sstream>
#include <cstring>
using namespace std;
/// 测试不同类型指针转化,涉及计算不同成员变量在类型对象不同的偏移地址。
struct overlapped_data
{
overlapped_data()
: data(0), data_len(0)
{}
~overlapped_data()
{
if (data)
delete[] data;
}
unsigned char* data;
size_t data_len;
// ... more ...
std::string to_str() const
{
ostringstream oss;
oss << " [&data]" << &data << " [data_len]" << data_len;
return oss.str();
}
};
class asyn_io_operation
{
public:
asyn_io_operation()
: lparam(0), rparam(0) {}
/// member data
overlapped_data data;
int lparam;
int rparam;
// overlapped_data data; // define it here also ok. as the following OVERLAPPED_DATA2ASYN_IO_OPERATION.
std::string to_str() const
{
ostringstream oss;
oss << data.to_str() << " [lparam]" << lparam << " [rparam]" << rparam;
return oss.str();
}
const overlapped_data* data_ptr() const
{
return &data;
}
overlapped_data* data_ptr()
{
return &data;
}
// ... more ...
};
#define OVERLAPPED_DATA2ASYN_IO_OPERATION(ptr) (asyn_io_operation*) ((char*)(ptr) - (char*)(&((static_cast<asyn_io_operation*>(0))->data)))
void do_handle_io_operation(asyn_io_operation* io_operation)
{
std::cout << io_operation->to_str() << "\n";
// ... more ...
}
overlapped_data* do_handle_overlapped_data(overlapped_data* data)//overlapped_data&
{
// ... more ...
if (data->data)
delete[] data;
const size_t SET_DATA_LEN = 100;
data->data = new unsigned char [SET_DATA_LEN];
data->data_len = SET_DATA_LEN;
memset(data->data, '1', data->data_len );
asyn_io_operation* io_opration = OVERLAPPED_DATA2ASYN_IO_OPERATION(data);
io_opration->lparam = SET_DATA_LEN;
io_opration->rparam = SET_DATA_LEN;
return data;
}
int main()
{
/// 测试不同类型指针转化,涉及计算不同成员变量在类型对象不同的偏移地址。
{
std::cout << " " << &((static_cast<asyn_io_operation*>(0))->data) << "\n";
std::cout << " " << &((static_cast<asyn_io_operation*>(0))->lparam) << "\n";
std::cout << " " << &((static_cast<asyn_io_operation*>(0))->rparam) << "\n";
asyn_io_operation io_op;
do_handle_io_operation((&io_op));
do_handle_overlapped_data(io_op.data_ptr());
do_handle_io_operation((&io_op));
}
/*********/
//assert (!" assert false here.");
cout << " Hello world!" << endl;
return 0;
}