运行WinNT和Win2000的系统上,这些APIs在Microsoft提供的DLL(mswsock.dll)里实现,可以通过链接mswsock.lib或者通过WSAioctl的SIO_GET_EXTENSION_FUNCTION_POINTER操作动态调用这些扩展APIs.
未获取函数指针就调用函数(如直接连接mswsock.lib并直接调用AcceptEx)的消耗是很大的,因为AcceptEx 实际上是存在于Winsock2结构体系之外的。每次应用程序常试在服务提供层上(mswsock之上)调用AcceptEx时,都要先通过WSAIoctl获取该函数指针。如果要避免这个很影响性能的操作,应用程序最好是直接从服务提供层通过WSAIoctl先获取这些APIs的指针。
需要注意的是,通过WSAIoctl获取AcceptEx函数指针时,只需要传递给WSAIoctl一个有效的SOCKET即可,该Socket的类型不会影响获取的AcceptEx函数指针。
同理可以获取Connectex与GetAcceptExSockaddrs函数指针。
代码如下:
typedef BOOL (WINAPI *AcceptExPtr)(SOCKET, SOCKET, PVOID, DWORD, DWORD, DWORD, LPDWORD, LPOVERLAPPED); typedef BOOL (WINAPI *ConnectExPtr)(SOCKET, const struct sockaddr *, int, PVOID, DWORD, LPDWORD, LPOVERLAPPED); typedef void (WINAPI *GetAcceptExSockaddrsPtr)(PVOID, DWORD, DWORD, DWORD, LPSOCKADDR *, LPINT, LPSOCKADDR *, LPINT); struct win32_extension_fns { AcceptExPtr AcceptEx; ConnectExPtr ConnectEx; GetAcceptExSockaddrsPtr GetAcceptExSockaddrs; }; #ifndef WSAID_ACCEPTEX #define WSAID_ACCEPTEX {0xb5367df1,0xcbac,0x11cf,{0x95,0xca,0x00,0x80,0x5f,0x48,0xa1,0x92}} #endif #ifndef WSAID_CONNECTEX #define WSAID_CONNECTEX {0x25a207b9,0xddf3,0x4660,{0x8e,0xe9,0x76,0xe5,0x8c,0x74,0x06,0x3e}} #endif #ifndef WSAID_GETACCEPTEXSOCKADDRS #define WSAID_GETACCEPTEXSOCKADDRS {0xb5367df2,0xcbac,0x11cf,{0x95,0xca,0x00,0x80,0x5f,0x48,0xa1,0x92}} #endif void * get_extension_function(SOCKET s, const GUID *which_fn) { void *ptr = NULL; DWORD bytes=0; WSAIoctl(s, SIO_GET_EXTENSION_FUNCTION_POINTER, (GUID*)which_fn, sizeof(*which_fn), &ptr, sizeof(ptr), &bytes, NULL, NULL); return ptr; }
调用:
const GUID acceptex = WSAID_ACCEPTEX; const GUID connectex = WSAID_CONNECTEX; const GUID getacceptexsockaddrs = WSAID_GETACCEPTEXSOCKADDRS; SOCKET s = socket(AF_INET, SOCK_STREAM, 0); if (s == INVALID_SOCKET) return; ext->AcceptEx = (AcceptExPtr)get_extension_function(s, &acceptex); ext->ConnectEx = (ConnectExPtr)get_extension_function(s, &connectex); ext->GetAcceptExSockaddrs = (GetAcceptExSockaddrsPtr)get_extension_function(s,&getacceptexsockaddrs); closesocket(s);
时间: 2024-10-01 00:37:39