本文主要是介绍漫话Redis源码之八十一，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
fd_set是网络编程中很重要的结构体，rfds是读描述集， wfds是写描述集合，这是使用需要非常清晰，看最后的select, 知道怎么样了吧：
#include <sys/select.h>
#include <string.h>typedef struct aeApiState {fd_set rfds, wfds;/* We need to have a copy of the fd sets as it's not safe to reuse* FD sets after select(). */fd_set _rfds, _wfds;
} aeApiState;static int aeApiCreate(aeEventLoop *eventLoop) {aeApiState *state = zmalloc(sizeof(aeApiState));if (!state) return -1;FD_ZERO(&state->rfds);FD_ZERO(&state->wfds);eventLoop->apidata = state;return 0;
}static int aeApiResize(aeEventLoop *eventLoop, int setsize) {/* Just ensure we have enough room in the fd_set type. */if (setsize >= FD_SETSIZE) return -1;return 0;
}static void aeApiFree(aeEventLoop *eventLoop) {zfree(eventLoop->apidata);
}static int aeApiAddEvent(aeEventLoop *eventLoop, int fd, int mask) {aeApiState *state = eventLoop->apidata;if (mask & AE_READABLE) FD_SET(fd,&state->rfds);if (mask & AE_WRITABLE) FD_SET(fd,&state->wfds);return 0;
}static void aeApiDelEvent(aeEventLoop *eventLoop, int fd, int mask) {aeApiState *state = eventLoop->apidata;if (mask & AE_READABLE) FD_CLR(fd,&state->rfds);if (mask & AE_WRITABLE) FD_CLR(fd,&state->wfds);
}static int aeApiPoll(aeEventLoop *eventLoop, struct timeval *tvp) {aeApiState *state = eventLoop->apidata;int retval, j, numevents = 0;memcpy(&state->_rfds,&state->rfds,sizeof(fd_set));memcpy(&state->_wfds,&state->wfds,sizeof(fd_set));retval = select(eventLoop->maxfd+1,&state->_rfds,&state->_wfds,NULL,tvp);if (retval > 0) {for (j = 0; j <= eventLoop->maxfd; j++) {int mask = 0;aeFileEvent *fe = &eventLoop->events[j];if (fe->mask == AE_NONE) continue;if (fe->mask & AE_READABLE && FD_ISSET(j,&state->_rfds))mask |= AE_READABLE;if (fe->mask & AE_WRITABLE && FD_ISSET(j,&state->_wfds))mask |= AE_WRITABLE;eventLoop->fired[numevents].fd = j;eventLoop->fired[numevents].mask = mask;numevents++;}}return numevents;
}static char *aeApiName(void) {return "select";
}
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