ae.c

   1 /* A simple event-driven programming library. Originally I wrote this code
   2  * for the Jim's event-loop (Jim is a Tcl interpreter) but later translated
   3  * it in form of a library for easy reuse.
   4  *
   5  * Copyright (c) 2006-2009, Salvatore Sanfilippo <antirez at gmail dot com>
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions are met:
  10  *
  11  *   * Redistributions of source code must retain the above copyright notice,
  12  *     this list of conditions and the following disclaimer.
  13  *   * Redistributions in binary form must reproduce the above copyright
  14  *     notice, this list of conditions and the following disclaimer in the
  15  *     documentation and/or other materials provided with the distribution.
  16  *   * Neither the name of Redis nor the names of its contributors may be used
  17  *     to endorse or promote products derived from this software without
  18  *     specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  21  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  24  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  26  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  30  * POSSIBILITY OF SUCH DAMAGE.
  31  */
  32
  33 #include <stdio.h>
  34 #include <sys/time.h>
  35 #include <sys/types.h>
  36 #include <unistd.h>
  37 #include <stdlib.h>
  38
  39 #include "ae.h"
  40 #include "zmalloc.h"
  41 #include "config.h"
  42
  43 /* Include the best multiplexing layer supported by this system.
  44  * The following should be ordered by performances, descending. */
  45 #ifdef HAVE_EPOLL
  46 #include "ae_epoll.c"
  47 #else
  48 #include "ae_select.c"
  49 #endif
  50
  51 aeEventLoop *aeCreateEventLoop(void) {
  52     aeEventLoop *eventLoop;
  53     int i;
  54
  55     eventLoop = zmalloc(sizeof(*eventLoop));
  56     if (!eventLoop) return NULL;
  57     eventLoop->timeEventHead = NULL;
  58     eventLoop->timeEventNextId = 0;
  59     eventLoop->stop = 0;
  60     eventLoop->maxfd = -1;
  61     if (aeApiCreate(eventLoop) == -1) {
  62         zfree(eventLoop);
  63         return NULL;
  64     }
  65     /* Events with mask == AE_NONE are not set. So let's initialize the
  66      * vector with it. */
  67     for (i = 0; i < AE_SETSIZE; i++)
  68         eventLoop->events[i].mask = AE_NONE;
  69     return eventLoop;
  70 }
  71
  72 void aeDeleteEventLoop(aeEventLoop *eventLoop) {
  73     aeApiFree(eventLoop);
  74     zfree(eventLoop);
  75 }
  76
  77 void aeStop(aeEventLoop *eventLoop) {
  78     eventLoop->stop = 1;
  79 }
  80
  81 int aeCreateFileEvent(aeEventLoop *eventLoop, int fd, int mask,
  82         aeFileProc *proc, void *clientData)
  83 {
  84     if (fd >= AE_SETSIZE) return AE_ERR;
  85     aeFileEvent *fe = &eventLoop->events[fd];
  86
  87     if (aeApiAddEvent(eventLoop, fd, mask) == -1)
  88         return AE_ERR;
  89     fe->mask |= mask;
  90     if (mask & AE_READABLE) fe->rfileProc = proc;
  91     if (mask & AE_WRITABLE) fe->wfileProc = proc;
  92     if (mask & AE_EXCEPTION) fe->efileProc = proc;
  93     fe->clientData = clientData;
  94     if (fd > eventLoop->maxfd)
  95         eventLoop->maxfd = fd;
  96     return AE_OK;
  97 }
  98
  99 void aeDeleteFileEvent(aeEventLoop *eventLoop, int fd, int mask)
 100 {
 101     if (fd >= AE_SETSIZE) return;
 102     aeFileEvent *fe = &eventLoop->events[fd];
 103
 104     if (fe->mask == AE_NONE) return;
 105     fe->mask = fe->mask & (~mask);
 106     if (fd == eventLoop->maxfd && fe->mask == AE_NONE) {
 107         /* Update the max fd */
 108         int j;
 109
 110         for (j = eventLoop->maxfd-1; j >= 0; j--)
 111             if (eventLoop->events[j].mask != AE_NONE) break;
 112         eventLoop->maxfd = j;
 113     }
 114     aeApiDelEvent(eventLoop, fd, mask);
 115 }
 116
 117 static void aeGetTime(long *seconds, long *milliseconds)
 118 {
 119     struct timeval tv;
 120
 121     gettimeofday(&tv, NULL);
 122     *seconds = tv.tv_sec;
 123     *milliseconds = tv.tv_usec/1000;
 124 }
 125
 126 static void aeAddMillisecondsToNow(long long milliseconds, long *sec, long *ms) {
 127     long cur_sec, cur_ms, when_sec, when_ms;
 128
 129     aeGetTime(&cur_sec, &cur_ms);
 130     when_sec = cur_sec + milliseconds/1000;
 131     when_ms = cur_ms + milliseconds%1000;
 132     if (when_ms >= 1000) {
 133         when_sec ++;
 134         when_ms -= 1000;
 135     }
 136     *sec = when_sec;
 137     *ms = when_ms;
 138 }
 139
 140 long long aeCreateTimeEvent(aeEventLoop *eventLoop, long long milliseconds,
 141         aeTimeProc *proc, void *clientData,
 142         aeEventFinalizerProc *finalizerProc)
 143 {
 144     long long id = eventLoop->timeEventNextId++;
 145     aeTimeEvent *te;
 146
 147     te = zmalloc(sizeof(*te));
 148     if (te == NULL) return AE_ERR;
 149     te->id = id;
 150     aeAddMillisecondsToNow(milliseconds,&te->when_sec,&te->when_ms);
 151     te->timeProc = proc;
 152     te->finalizerProc = finalizerProc;
 153     te->clientData = clientData;
 154     te->next = eventLoop->timeEventHead;
 155     eventLoop->timeEventHead = te;
 156     return id;
 157 }
 158
 159 int aeDeleteTimeEvent(aeEventLoop *eventLoop, long long id)
 160 {
 161     aeTimeEvent *te, *prev = NULL;
 162
 163     te = eventLoop->timeEventHead;
 164     while(te) {
 165         if (te->id == id) {
 166             if (prev == NULL)
 167                 eventLoop->timeEventHead = te->next;
 168             else
 169                 prev->next = te->next;
 170             if (te->finalizerProc)
 171                 te->finalizerProc(eventLoop, te->clientData);
 172             zfree(te);
 173             return AE_OK;
 174         }
 175         prev = te;
 176         te = te->next;
 177     }
 178     return AE_ERR; /* NO event with the specified ID found */
 179 }
 180
 181 /* Search the first timer to fire.
 182  * This operation is useful to know how many time the select can be
 183  * put in sleep without to delay any event.
 184  * If there are no timers NULL is returned.
 185  *
 186  * Note that's O(N) since time events are unsorted.
 187  * Possible optimizations (not needed by Redis so far, but...):
 188  * 1) Insert the event in order, so that the nearest is just the head.
 189  *    Much better but still insertion or deletion of timers is O(N).
 190  * 2) Use a skiplist to have this operation as O(1) and insertion as O(log(N)).
 191  */
 192 static aeTimeEvent *aeSearchNearestTimer(aeEventLoop *eventLoop)
 193 {
 194     aeTimeEvent *te = eventLoop->timeEventHead;
 195     aeTimeEvent *nearest = NULL;
 196
 197     while(te) {
 198         if (!nearest || te->when_sec < nearest->when_sec ||
 199                 (te->when_sec == nearest->when_sec &&
 200                  te->when_ms < nearest->when_ms))
 201             nearest = te;
 202         te = te->next;
 203     }
 204     return nearest;
 205 }
 206
 207 /* Process time events */
 208 static int processTimeEvents(aeEventLoop *eventLoop) {
 209     int processed = 0;
 210     aeTimeEvent *te;
 211     long long maxId;
 212
 213     te = eventLoop->timeEventHead;
 214     maxId = eventLoop->timeEventNextId-1;
 215     while(te) {
 216         long now_sec, now_ms;
 217         long long id;
 218
 219         if (te->id > maxId) {
 220             te = te->next;
 221             continue;
 222         }
 223         aeGetTime(&now_sec, &now_ms);
 224         if (now_sec > te->when_sec ||
 225             (now_sec == te->when_sec && now_ms >= te->when_ms))
 226         {
 227             int retval;
 228
 229             id = te->id;
 230             retval = te->timeProc(eventLoop, id, te->clientData);
 231             processed++;
 232             /* After an event is processed our time event list may
 233              * no longer be the same, so we restart from head.
 234              * Still we make sure to don't process events registered
 235              * by event handlers itself in order to don't loop forever.
 236              * To do so we saved the max ID we want to handle.
 237              *
 238              * FUTURE OPTIMIZATIONS:
 239              * Note that this is NOT great algorithmically. Redis uses
 240              * a single time event so it's not a problem but the right
 241              * way to do this is to add the new elements on head, and
 242              * to flag deleted elements in a special way for later
 243              * deletion (putting references to the nodes to delete into
 244              * another linked list). */
 245             if (retval != AE_NOMORE) {
 246                 aeAddMillisecondsToNow(retval,&te->when_sec,&te->when_ms);
 247             } else {
 248                 aeDeleteTimeEvent(eventLoop, id);
 249             }
 250             te = eventLoop->timeEventHead;
 251         } else {
 252             te = te->next;
 253         }
 254     }
 255     return processed;
 256 }
 257
 258 /* Process every pending time event, then every pending file event
 259  * (that may be registered by time event callbacks just processed).
 260  * Without special flags the function sleeps until some file event
 261  * fires, or when the next time event occurrs (if any).
 262  *
 263  * If flags is 0, the function does nothing and returns.
 264  * if flags has AE_ALL_EVENTS set, all the kind of events are processed.
 265  * if flags has AE_FILE_EVENTS set, file events are processed.
 266  * if flags has AE_TIME_EVENTS set, time events are processed.
 267  * if flags has AE_DONT_WAIT set the function returns ASAP until all
 268  * the events that's possible to process without to wait are processed.
 269  *
 270  * The function returns the number of events processed. */
 271 int aeProcessEvents(aeEventLoop *eventLoop, int flags)
 272 {
 273     int processed = 0, numevents;
 274
 275     /* Nothing to do? return ASAP */
 276     if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS)) return 0;
 277
 278     /* Note that we want call select() even if there are no
 279      * file events to process as long as we want to process time
 280      * events, in order to sleep until the next time event is ready
 281      * to fire. */
 282     if (eventLoop->maxfd != -1 ||
 283         ((flags & AE_TIME_EVENTS) && !(flags & AE_DONT_WAIT))) {
 284         int j;
 285         aeTimeEvent *shortest = NULL;
 286         struct timeval tv, *tvp;
 287
 288         if (flags & AE_TIME_EVENTS && !(flags & AE_DONT_WAIT))
 289             shortest = aeSearchNearestTimer(eventLoop);
 290         if (shortest) {
 291             long now_sec, now_ms;
 292
 293             /* Calculate the time missing for the nearest
 294              * timer to fire. */
 295             aeGetTime(&now_sec, &now_ms);
 296             tvp = &tv;
 297             tvp->tv_sec = shortest->when_sec - now_sec;
 298             if (shortest->when_ms < now_ms) {
 299                 tvp->tv_usec = ((shortest->when_ms+1000) - now_ms)*1000;
 300                 tvp->tv_sec --;
 301             } else {
 302                 tvp->tv_usec = (shortest->when_ms - now_ms)*1000;
 303             }
 304             if (tvp->tv_sec < 0) tvp->tv_sec = 0;
 305             if (tvp->tv_usec < 0) tvp->tv_usec = 0;
 306         } else {
 307             /* If we have to check for events but need to return
 308              * ASAP because of AE_DONT_WAIT we need to se the timeout
 309              * to zero */
 310             if (flags & AE_DONT_WAIT) {
 311                 tv.tv_sec = tv.tv_usec = 0;
 312                 tvp = &tv;
 313             } else {
 314                 /* Otherwise we can block */
 315                 tvp = NULL; /* wait forever */
 316             }
 317         }
 318
 319         numevents = aeApiPoll(eventLoop, tvp);
 320         for (j = 0; j < numevents; j++) {
 321             aeFileEvent *fe = &eventLoop->events[eventLoop->fired[j].fd];
 322             int mask = eventLoop->fired[j].mask;
 323             int fd = eventLoop->fired[j].fd;
 324
 325             /* note the fe->mask & mask & ... code: maybe an already processed
 326              * event removed an element that fired and we still didn't
 327              * processed, so we check if the event is still valid. */
 328             if (fe->mask & mask & AE_READABLE)
 329                 fe->rfileProc(eventLoop,fd,fe->clientData,mask);
 330             if (fe->mask & mask & AE_WRITABLE && fe->wfileProc != fe->rfileProc)
 331                 fe->wfileProc(eventLoop,fd,fe->clientData,mask);
 332             if (fe->mask & mask & AE_EXCEPTION &&
 333                                        fe->efileProc != fe->wfileProc &&
 334                                        fe->efileProc != fe->rfileProc)
 335                 fe->efileProc(eventLoop,fd,fe->clientData,mask);
 336             processed++;
 337         }
 338     }
 339     /* Check time events */
 340     if (flags & AE_TIME_EVENTS)
 341         processed += processTimeEvents(eventLoop);
 342
 343     return processed; /* return the number of processed file/time events */
 344 }
 345
 346 /* Wait for millseconds until the given file descriptor becomes
 347  * writable/readable/exception */
 348 int aeWait(int fd, int mask, long long milliseconds) {
 349     struct timeval tv;
 350     fd_set rfds, wfds, efds;
 351     int retmask = 0, retval;
 352
 353     tv.tv_sec = milliseconds/1000;
 354     tv.tv_usec = (milliseconds%1000)*1000;
 355     FD_ZERO(&rfds);
 356     FD_ZERO(&wfds);
 357     FD_ZERO(&efds);
 358
 359     if (mask & AE_READABLE) FD_SET(fd,&rfds);
 360     if (mask & AE_WRITABLE) FD_SET(fd,&wfds);
 361     if (mask & AE_EXCEPTION) FD_SET(fd,&efds);
 362     if ((retval = select(fd+1, &rfds, &wfds, &efds, &tv)) > 0) {
 363         if (FD_ISSET(fd,&rfds)) retmask |= AE_READABLE;
 364         if (FD_ISSET(fd,&wfds)) retmask |= AE_WRITABLE;
 365         if (FD_ISSET(fd,&efds)) retmask |= AE_EXCEPTION;
 366         return retmask;
 367     } else {
 368         return retval;
 369     }
 370 }
 371
 372 void aeMain(aeEventLoop *eventLoop)
 373 {
 374     eventLoop->stop = 0;
 375     while (!eventLoop->stop)
 376         aeProcessEvents(eventLoop, AE_ALL_EVENTS);
 377 }