https://zhuanlan.zhihu.com/p/21374980
===============================================
https://zhuanlan.zhihu.com/p/21619218?utm_medium=social&utm_source=wechat_session&from=timeline&isappinstalled=0&s_s_i=akD%2BEQGuE2ymUvWOlk%2BEkZpTXXDTr7pm24gvEBEAW%2Fg%3D&s_r=1
EPOLL事件的两种模型：
Level Triggered (LT) 水平触发.socket接收缓冲区不为空 有数据可读 读事件一直触发.socket发送缓冲区不满 可以继续写入数据 写事件一直触发符合思维习惯，epoll_wait返回的事件就是socket的状态
关键是ET模型这里写的很好了 仔细体会 以后不会再复习了
Edge Triggered (ET) 边沿触发 .socket的接收缓冲区状态变化时触发读事件，即空的接收缓冲区 刚接收到数据时触发读事件.socket的发送缓冲区状态变化时触发写事件，即满的缓冲区 刚空出空间时触发读事件仅在状态变化时触发事件
https://blog.csdn.net/linuxheik/article/details/73294658
这个文章写的也可以但是 没有上面的到位
由上面的情况可以看出 LE模式来数据时候 缓冲区不完全读取结束没有事情 下次该事件他还会继续触发 但是ET （默认就是非阻塞情况哦 ）则不行 必须 将缓冲区读取结束，读到EAGAIN | EWOULDBLOCK且 n < 0 这样该socket连接的缓冲区 下次发生事件（即有数据）时候才会再次触发。
ET 模型 LT 模型的处理方式代码
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define MAX_EVENT_NUMBER 1024
#define BUFFER_SIZE 10
int setnonblocking( int fd )
{
int old_option = fcntl( fd, F_GETFL );
int new_option = old_option | O_NONBLOCK;
fcntl( fd, F_SETFL, new_option );
return old_option;
}
void addfd( int epollfd, int fd, bool enable_et )
{
epoll_event event;
event.data.fd = fd;
event.events = EPOLLIN;
if( enable_et )
{
event.events |= EPOLLET;
}
epoll_ctl( epollfd, EPOLL_CTL_ADD, fd, &event );
setnonblocking( fd );
}
void lt( epoll_event* events, int number, int epollfd, int listenfd )
{
char buf[ BUFFER_SIZE ];
for ( int i = 0; i < number; i++ )
{
int sockfd = events[i].data.fd;
if ( sockfd == listenfd )
{
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof( client_address );
int connfd = accept( listenfd, ( struct sockaddr* )&client_address, &client_addrlength );
addfd( epollfd, connfd, false );
}
else if ( events[i].events & EPOLLIN )
{//只要socket读缓存区中还有未读出的数据 这段代码就会不停的被触发 即使关闭了sock
printf( "event trigger once\n" );
memset( buf, '\0', BUFFER_SIZE );
int ret = recv( sockfd, buf, BUFFER_SIZE-1, 0 );
if( ret <= 0 )
{
close( sockfd );
continue;
}
printf( "get %d bytes of content: %s\n", ret, buf );
}
else
{
printf( "something else happened \n" );
}
}
}
void et( epoll_event* events, int number, int epollfd, int listenfd )
{
char buf[ BUFFER_SIZE ];
for ( int i = 0; i < number; i++ )
{
int sockfd = events[i].data.fd;
if ( sockfd == listenfd )
{
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof( client_address );
int connfd = accept( listenfd, ( struct sockaddr* )&client_address, &client_addrlength );
addfd( epollfd, connfd, true );
}
else if ( events[i].events & EPOLLIN )
{ //for 循环到某个sock连接的缓存区有数据 可读那么就要 while读取读到缓存区没有数据 ET模式
//确保把socket缓冲区存储的数据读取结束 才break 退出while
printf( "event trigger once\n" );
while( 1 )
{
memset( buf, '\0', BUFFER_SIZE );
int ret = recv( sockfd, buf, BUFFER_SIZE-1, 0 );
if( ret < 0 )
{//非阻塞ET模式 下面成立表示sock缓冲区数据读取结束了 此后epoll_wait就能再次触发,就能再一次触发fd 上的EPOLLIN事件
if( ( errno == EAGAIN ) || ( errno == EWOULDBLOCK ) )
{ //无需关闭socket 只说明现在缓冲区没有数据可以读取了 等待下一次触发处理
printf( "read later\n" );
break;//这里 缓冲区数据读取over了 所以break掉当前读取sock的while循环
}
//返回-1 那么说明发生其他错误不是上面的两种错误直接关闭sock
close( sockfd );
break;
}
else if( ret == 0 )
{
close( sockfd );// ==0 ET模式返回0 表示对端已经关闭了
}
else
{ //接收ok
printf( "get %d bytes of content: %s\n", ret, buf );
}
}
}
else
{
printf( "something else happened \n" );
}
}
}
int main( int argc, char* argv[] )
{
if( argc <= 2 )
{
printf( "usage: %s ip_address port_number\n", basename( argv[0] ) );
return 1;
}
const char* ip = argv[1];
int port = atoi( argv[2] );
int ret = 0;
struct sockaddr_in address;
bzero( &address, sizeof( address ) );
address.sin_family = AF_INET;
inet_pton( AF_INET, ip, &address.sin_addr );
address.sin_port = htons( port );
int listenfd = socket( PF_INET, SOCK_STREAM, 0 );
assert( listenfd >= 0 );
ret = bind( listenfd, ( struct sockaddr* )&address, sizeof( address ) );
assert( ret != -1 );
ret = listen( listenfd, 5 );
assert( ret != -1 );
epoll_event events[ MAX_EVENT_NUMBER ];
int epollfd = epoll_create( 5 );
assert( epollfd != -1 );
addfd( epollfd, listenfd, true );
while( 1 )
{
int ret = epoll_wait( epollfd, events, MAX_EVENT_NUMBER, -1 );
if ( ret < 0 )
{
printf( "epoll failure\n" );
break;
}
//lt( events, ret, epollfd, listenfd );
et( events, ret, epollfd, listenfd );
}
close( listenfd );
return 0;
}
和上面不相关
void handleRead(int efd, int fd) {
char buf[4096];
int n = 0;
while ((n=::read(fd, buf, sizeof buf)) > 0) {
if(output_log) printf("read %d bytes\n", n);
string& readed = cons[fd].readed;
readed.append(buf, n);
if (readed.length()>4) {
if (readed.substr(readed.length()-2, 2) == "\n\n" || readed.substr(readed.length()-4, 4) == "\r\n\r\n") {
//当读取到一个完整的http请求，测试发送响应
sendRes(fd);
}
}
}
//这里当socket缓冲区的数据被读取完毕了，return掉 但不能close fd 因为下次该sock缓冲区有数据还会再次触发
//ET 非阻塞就是要读到 EAGAIN 且 n < 0 就是将来sock缓冲区读彻底下次才触发
if (n<0 && (errno == EAGAIN || errno == EWOULDBLOCK))
return;
//实际应用中，n<0应当检查各类错误，如EINTR
if (n < 0) {
printf("read %d error: %d %s\n", fd, errno, strerror(errno));
}
close(fd);
cons.erase(fd);
}