ncp是否需要锁

1. terminal 不需要加锁

2. Buffer 可以采用加锁的方式实现， 但也可以采用下面代码的方式实现，即：

    a.  将要读或写的共享变量先读出来，

    b.  然后判断读出来的本地变量的范围是否有效，

    c.  采用本地变量参与后续运算

    d.  最终将本地变量赋值给共享变量

3. 需要思考的地方

    a.  数据加锁和过程加锁方式

    b.  当一个过程需要处理多个共享变量时，是否给整个过程加一个粗粒度的锁，即如何思考过程（操作多个共享变量）的多线程安全性

 

#include <iostream>#if 1AsyncQueue q_readable;AsyncQueue q_term2host;AsyncQueue q_host2term;Terminal terminals[10000];Terminal * find_empty_slot();Terminal * find_terminal(int cid);Terminal * find_terminal(char* mac);struct Protocol{ static bool chk_host_msg(void * msg); static bool chk_term_msg(void * msg); static int get_cid(void * msg); static bool is_host_busi_rsp(void * msg); static bool is_host_auth_rsp(void * msg); static bool is_host_heartbeat(void * msg); static bool is_host_kick_term(void * msg);};struct Buffer{public: Buffer() : st(0), ed(0) {} void reset() { st = ed = 0; } int recv_buf(int sock) { unsigned int ed = ed_; if(ed > 4096) return 0; int cnt = socket_receive(sock, buffer_ + ed, 4096 - ed); if(cnt > 0) {ed += cnt;ed_ = ed; } return cnt; } void * pop_msg() { unsigned int st = st_; unsigned int ed = ed_; if(st > ed || st > 4096 || ed > 4096 || (ed - st) < 3) return NULL; unsigned short len = *(unsigned short *)(buffer_ + st); if(ed-st >= len) {void * p = malloc(len);memcpy(p, buffer_+st, len);st += len;if(st == ed) { st_ = ed_ = 0; }else { st_ = st; }return p; } return NULL; }private: char buffer_[4096]; unsigned int st_; unsigned int ed_;};struct Terminal{ int sock_; State state_; int enckey_; Buffer buf_; void * dec_term_msg(void * msg); void * enc_host_msg(void * msg); bool chk_term_msg(void * msg); bool chk_host_msg(void * msg); void chk_enc_snd_host_msg(void * msg) { if(t->chk_host_msg(msg)) socket_send(sock_, enc_host_msg(msg)); } bool is_empty() {} void shutdown() { buf_.reset(); state = STATE_SHUTDOWN; } void recv_buf() { } void * pop_msg() { }};struct Host_Message_Handler : Thread{ virtual void run() { while(true) {void * msg = NULL;if(msg = g_async_queue_pop(q_host2term)) { if(!Potocol::chk_host_msg(msg)) continue; if(Potocol::is_host_busi_rsp(msg)) {if(Terminal * t = find_terminal(Potocol::get_cid(msg))) t->chk_enc_snd_host_msg(msg); } else if(Potocol::is_host_auth_rsp(msg)) {if(Terminal * t = find_terminal(Potocol::get_mac(msg))) t->chk_enc_snd_host_msg(msg); } else if(Potocol::is_host_heartbeat(msg)) {update_host_heartbeat(); } else if(Potocol::is_host_unicast(msg)) {if(Terminal * t = find_terminal(Potocol::get_cid(msg))) t->chk_enc_snd_host_msg(msg); } else if(Potocol::is_host_multicast(msg)) {for(int i=0; i<10000; ++i) { (&terminals[i])->chk_enc_snd_host_msg(msg); } } else if(Potocol::is_host_kick_term(msg)) {shutdown_term(find_terminal(Potocol::get_cid(msg))); } } } }};struct Terminal_Message_Handler : Thead{ virtual void run() { while(true) {Terminal * t = NULL;if(t = g_async_queue_pop(q_readable)) { t->recv_buf(); void * msg = NULL; while(msg = t->pop_msg()) {void * readable_msg = NULL;if(t->chk_term_msg(readable_msg = t->dec_term_msg(msg))) { g_async_queue_push(q_term2host, readable_msg); } } }else { g_usleep(1000); } } }};struct Epoll : Thread{ virtual void run() { while(true) {int cnt = epoll_wait(events);for(int i=0; i<cnt; ++i) { if(events[i].data.ptr) {Terminal * t = events[i].data.ptr;q_readable.push_back(t); }else {int client = accept_client(events[i].sock);Terminal * t = NULL;if(client > 0 && (t = find_empty_slot())) { epoll_add(client, t); } } }while(g_async_queue_length(q_readable) > 0) g_usleep(1000); } }};int main(){ }#endif