libev，為什么在evloop中接收事件的編號為3？

Question

void callback(struct ev_loop *loop, ev_io *w, int events)
{
    if (EV_READ == events) {
      ...
    }
    else if (EV_WRITE == events) {
      ...
    }
    else {
      here recv event's number is 3
    }
}

在libev源代碼“ ev.h”中，我沒有找到定義數字0x03的宏

EV_READ     =            0x01, /* ev_io detected read will not block */
EV_WRITE    =            0x02, /* ev_io detected write will not block */

Answer 1

這是一個面具。 3表示可讀條件和可寫條件均可供處理。

嘗試類似

if (events & EV_READ) {  // something is readable
  ...
}
if (events & EV_WRITE) { // something is writable
  ...
}