src/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) 2006-2010, 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 #include <poll.h>
  39 #include <string.h>
  40
  41 #include "ae.h"
  42 #include "zmalloc.h"
  43 #include "config.h"
  44
  45 /* Include the best multiplexing layer supported by this system.
  46  * The following should be ordered by performances, descending. */
  47 #ifdef HAVE_EVPORT
  48 #include "ae_evport.c"
  49 #else
  50     #ifdef HAVE_EPOLL
  51     #include "ae_epoll.c"
  52     #else
  53         #ifdef HAVE_KQUEUE
  54         #include "ae_kqueue.c"
  55         #else
  56         #include "ae_select.c"
  57         #endif
  58     #endif
  59 #endif
  60
  61 aeEventLoop *aeCreateEventLoop(int setsize) {
  62     aeEventLoop *eventLoop;
  63     int i;
  64
  65     if ((eventLoop = zmalloc(sizeof(*eventLoop))) == NULL) goto err;
  66     eventLoop->events = zmalloc(sizeof(aeFileEvent)*setsize);
  67     eventLoop->fired = zmalloc(sizeof(aeFiredEvent)*setsize);
  68     if (eventLoop->events == NULL || eventLoop->fired == NULL) goto err;
  69     eventLoop->setsize = setsize;
  70     eventLoop->lastTime = time(NULL);
  71     eventLoop->timeEventHead = NULL;
  72     eventLoop->timeEventNextId = 0;
  73     eventLoop->stop = 0;
  74     eventLoop->maxfd = -1;
  75     eventLoop->beforesleep = NULL;
  76     if (aeApiCreate(eventLoop) == -1) goto err;
  77     /* Events with mask == AE_NONE are not set. So let's initialize the
  78      * vector with it. */
  79     for (i = 0; i < setsize; i++)
  80         eventLoop->events[i].mask = AE_NONE;
  81     return eventLoop;
  82
  83 err:
  84     if (eventLoop) {
  85         zfree(eventLoop->events);
  86         zfree(eventLoop->fired);
  87         zfree(eventLoop);
  88     }
  89     return NULL;
  90 }
  91
  92 void aeDeleteEventLoop(aeEventLoop *eventLoop) {
  93     aeApiFree(eventLoop);
  94     zfree(eventLoop->events);
  95     zfree(eventLoop->fired);
  96     zfree(eventLoop);
  97 }
  98
  99 void aeStop(aeEventLoop *eventLoop) {
 100     eventLoop->stop = 1;
 101 }
 102
 103 int aeCreateFileEvent(aeEventLoop *eventLoop, int fd, int mask,
 104         aeFileProc *proc, void *clientData)
 105 {
 106     if (fd >= eventLoop->setsize) return AE_ERR;
 107     aeFileEvent *fe = &eventLoop->events[fd];
 108
 109     if (aeApiAddEvent(eventLoop, fd, mask) == -1)
 110         return AE_ERR;
 111     fe->mask |= mask;
 112     if (mask & AE_READABLE) fe->rfileProc = proc;
 113     if (mask & AE_WRITABLE) fe->wfileProc = proc;
 114     fe->clientData = clientData;
 115     if (fd > eventLoop->maxfd)
 116         eventLoop->maxfd = fd;
 117     return AE_OK;
 118 }
 119
 120 void aeDeleteFileEvent(aeEventLoop *eventLoop, int fd, int mask)
 121 {
 122     if (fd >= eventLoop->setsize) return;
 123     aeFileEvent *fe = &eventLoop->events[fd];
 124
 125     if (fe->mask == AE_NONE) return;
 126     fe->mask = fe->mask & (~mask);
 127     if (fd == eventLoop->maxfd && fe->mask == AE_NONE) {
 128         /* Update the max fd */
 129         int j;
 130
 131         for (j = eventLoop->maxfd-1; j >= 0; j--)
 132             if (eventLoop->events[j].mask != AE_NONE) break;
 133         eventLoop->maxfd = j;
 134     }
 135     aeApiDelEvent(eventLoop, fd, mask);
 136 }
 137
 138 int aeGetFileEvents(aeEventLoop *eventLoop, int fd) {
 139     if (fd >= eventLoop->setsize) return 0;
 140     aeFileEvent *fe = &eventLoop->events[fd];
 141
 142     return fe->mask;
 143 }
 144
 145 static void aeGetTime(long *seconds, long *milliseconds)
 146 {
 147     struct timeval tv;
 148
 149     gettimeofday(&tv, NULL);
 150     *seconds = tv.tv_sec;
 151     *milliseconds = tv.tv_usec/1000;
 152 }
 153
 154 static void aeAddMillisecondsToNow(long long milliseconds, long *sec, long *ms) {
 155     long cur_sec, cur_ms, when_sec, when_ms;
 156
 157     aeGetTime(&cur_sec, &cur_ms);
 158     when_sec = cur_sec + milliseconds/1000;
 159     when_ms = cur_ms + milliseconds%1000;
 160     if (when_ms >= 1000) {
 161         when_sec ++;
 162         when_ms -= 1000;
 163     }
 164     *sec = when_sec;
 165     *ms = when_ms;
 166 }
 167
 168 long long aeCreateTimeEvent(aeEventLoop *eventLoop, long long milliseconds,
 169         aeTimeProc *proc, void *clientData,
 170         aeEventFinalizerProc *finalizerProc)
 171 {
 172     long long id = eventLoop->timeEventNextId++;
 173     aeTimeEvent *te;
 174
 175     te = zmalloc(sizeof(*te));
 176     if (te == NULL) return AE_ERR;
 177     te->id = id;
 178     aeAddMillisecondsToNow(milliseconds,&te->when_sec,&te->when_ms);
 179     te->timeProc = proc;
 180     te->finalizerProc = finalizerProc;
 181     te->clientData = clientData;
 182     te->next = eventLoop->timeEventHead;
 183     eventLoop->timeEventHead = te;
 184     return id;
 185 }
 186
 187 int aeDeleteTimeEvent(aeEventLoop *eventLoop, long long id)
 188 {
 189     aeTimeEvent *te, *prev = NULL;
 190
 191     te = eventLoop->timeEventHead;
 192     while(te) {
 193         if (te->id == id) {
 194             if (prev == NULL)
 195                 eventLoop->timeEventHead = te->next;
 196             else
 197                 prev->next = te->next;
 198             if (te->finalizerProc)
 199                 te->finalizerProc(eventLoop, te->clientData);
 200             zfree(te);
 201             return AE_OK;
 202         }
 203         prev = te;
 204         te = te->next;
 205     }
 206     return AE_ERR; /* NO event with the specified ID found */
 207 }
 208
 209 /* Search the first timer to fire.
 210  * This operation is useful to know how many time the select can be
 211  * put in sleep without to delay any event.
 212  * If there are no timers NULL is returned.
 213  *
 214  * Note that's O(N) since time events are unsorted.
 215  * Possible optimizations (not needed by Redis so far, but...):
 216  * 1) Insert the event in order, so that the nearest is just the head.
 217  *    Much better but still insertion or deletion of timers is O(N).
 218  * 2) Use a skiplist to have this operation as O(1) and insertion as O(log(N)).
 219  */
 220 static aeTimeEvent *aeSearchNearestTimer(aeEventLoop *eventLoop)
 221 {
 222     aeTimeEvent *te = eventLoop->timeEventHead;
 223     aeTimeEvent *nearest = NULL;
 224
 225     while(te) {
 226         if (!nearest || te->when_sec < nearest->when_sec ||
 227                 (te->when_sec == nearest->when_sec &&
 228                  te->when_ms < nearest->when_ms))
 229             nearest = te;
 230         te = te->next;
 231     }
 232     return nearest;
 233 }
 234
 235 /* Process time events */
 236 static int processTimeEvents(aeEventLoop *eventLoop) {
 237     int processed = 0;
 238     aeTimeEvent *te;
 239     long long maxId;
 240     time_t now = time(NULL);
 241
 242     /* If the system clock is moved to the future, and then set back to the
 243      * right value, time events may be delayed in a random way. Often this
 244      * means that scheduled operations will not be performed soon enough.
 245      *
 246      * Here we try to detect system clock skews, and force all the time
 247      * events to be processed ASAP when this happens: the idea is that
 248      * processing events earlier is less dangerous than delaying them
 249      * indefinitely, and practice suggests it is. */
 250     if (now < eventLoop->lastTime) {
 251         te = eventLoop->timeEventHead;
 252         while(te) {
 253             te->when_sec = 0;
 254             te = te->next;
 255         }
 256     }
 257     eventLoop->lastTime = now;
 258
 259     te = eventLoop->timeEventHead;
 260     maxId = eventLoop->timeEventNextId-1;
 261     while(te) {
 262         long now_sec, now_ms;
 263         long long id;
 264
 265         if (te->id > maxId) {
 266             te = te->next;
 267             continue;
 268         }
 269         aeGetTime(&now_sec, &now_ms);
 270         if (now_sec > te->when_sec ||
 271             (now_sec == te->when_sec && now_ms >= te->when_ms))
 272         {
 273             int retval;
 274
 275             id = te->id;
 276             retval = te->timeProc(eventLoop, id, te->clientData);
 277             processed++;
 278             /* After an event is processed our time event list may
 279              * no longer be the same, so we restart from head.
 280              * Still we make sure to don't process events registered
 281              * by event handlers itself in order to don't loop forever.
 282              * To do so we saved the max ID we want to handle.
 283              *
 284              * FUTURE OPTIMIZATIONS:
 285              * Note that this is NOT great algorithmically. Redis uses
 286              * a single time event so it's not a problem but the right
 287              * way to do this is to add the new elements on head, and
 288              * to flag deleted elements in a special way for later
 289              * deletion (putting references to the nodes to delete into
 290              * another linked list). */
 291             if (retval != AE_NOMORE) {
 292                 aeAddMillisecondsToNow(retval,&te->when_sec,&te->when_ms);
 293             } else {
 294                 aeDeleteTimeEvent(eventLoop, id);
 295             }
 296             te = eventLoop->timeEventHead;
 297         } else {
 298             te = te->next;
 299         }
 300     }
 301     return processed;
 302 }
 303
 304 /* Process every pending time event, then every pending file event
 305  * (that may be registered by time event callbacks just processed).
 306  * Without special flags the function sleeps until some file event
 307  * fires, or when the next time event occurrs (if any).
 308  *
 309  * If flags is 0, the function does nothing and returns.
 310  * if flags has AE_ALL_EVENTS set, all the kind of events are processed.
 311  * if flags has AE_FILE_EVENTS set, file events are processed.
 312  * if flags has AE_TIME_EVENTS set, time events are processed.
 313  * if flags has AE_DONT_WAIT set the function returns ASAP until all
 314  * the events that's possible to process without to wait are processed.
 315  *
 316  * The function returns the number of events processed. */
 317 int aeProcessEvents(aeEventLoop *eventLoop, int flags)
 318 {
 319     int processed = 0, numevents;
 320
 321     /* Nothing to do? return ASAP */
 322     if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS)) return 0;
 323
 324     /* Note that we want call select() even if there are no
 325      * file events to process as long as we want to process time
 326      * events, in order to sleep until the next time event is ready
 327      * to fire. */
 328     if (eventLoop->maxfd != -1 ||
 329         ((flags & AE_TIME_EVENTS) && !(flags & AE_DONT_WAIT))) {
 330         int j;
 331         aeTimeEvent *shortest = NULL;
 332         struct timeval tv, *tvp;
 333
 334         if (flags & AE_TIME_EVENTS && !(flags & AE_DONT_WAIT))
 335             shortest = aeSearchNearestTimer(eventLoop);
 336         if (shortest) {
 337             long now_sec, now_ms;
 338
 339             /* Calculate the time missing for the nearest
 340              * timer to fire. */
 341             aeGetTime(&now_sec, &now_ms);
 342             tvp = &tv;
 343             tvp->tv_sec = shortest->when_sec - now_sec;
 344             if (shortest->when_ms < now_ms) {
 345                 tvp->tv_usec = ((shortest->when_ms+1000) - now_ms)*1000;
 346                 tvp->tv_sec --;
 347             } else {
 348                 tvp->tv_usec = (shortest->when_ms - now_ms)*1000;
 349             }
 350             if (tvp->tv_sec < 0) tvp->tv_sec = 0;
 351             if (tvp->tv_usec < 0) tvp->tv_usec = 0;
 352         } else {
 353             /* If we have to check for events but need to return
 354              * ASAP because of AE_DONT_WAIT we need to se the timeout
 355              * to zero */
 356             if (flags & AE_DONT_WAIT) {
 357                 tv.tv_sec = tv.tv_usec = 0;
 358                 tvp = &tv;
 359             } else {
 360                 /* Otherwise we can block */
 361                 tvp = NULL; /* wait forever */
 362             }
 363         }
 364
 365         numevents = aeApiPoll(eventLoop, tvp);
 366         for (j = 0; j < numevents; j++) {
 367             aeFileEvent *fe = &eventLoop->events[eventLoop->fired[j].fd];
 368             int mask = eventLoop->fired[j].mask;
 369             int fd = eventLoop->fired[j].fd;
 370             int rfired = 0;
 371
 372             /* note the fe->mask & mask & ... code: maybe an already processed
 373              * event removed an element that fired and we still didn't
 374              * processed, so we check if the event is still valid. */
 375             if (fe->mask & mask & AE_READABLE) {
 376                 rfired = 1;
 377                 fe->rfileProc(eventLoop,fd,fe->clientData,mask);
 378             }
 379             if (fe->mask & mask & AE_WRITABLE) {
 380                 if (!rfired || fe->wfileProc != fe->rfileProc)
 381                     fe->wfileProc(eventLoop,fd,fe->clientData,mask);
 382             }
 383             processed++;
 384         }
 385     }
 386     /* Check time events */
 387     if (flags & AE_TIME_EVENTS)
 388         processed += processTimeEvents(eventLoop);
 389
 390     return processed; /* return the number of processed file/time events */
 391 }
 392
 393 /* Wait for millseconds until the given file descriptor becomes
 394  * writable/readable/exception */
 395 int aeWait(int fd, int mask, long long milliseconds) {
 396     struct pollfd pfd;
 397     int retmask = 0, retval;
 398
 399     memset(&pfd, 0, sizeof(pfd));
 400     pfd.fd = fd;
 401     if (mask & AE_READABLE) pfd.events |= POLLIN;
 402     if (mask & AE_WRITABLE) pfd.events |= POLLOUT;
 403
 404     if ((retval = poll(&pfd, 1, milliseconds))== 1) {
 405         if (pfd.revents & POLLIN) retmask |= AE_READABLE;
 406         if (pfd.revents & POLLOUT) retmask |= AE_WRITABLE;
 407         if (pfd.revents & POLLERR) retmask |= AE_WRITABLE;
 408         if (pfd.revents & POLLHUP) retmask |= AE_WRITABLE;
 409         return retmask;
 410     } else {
 411         return retval;
 412     }
 413 }
 414
 415 void aeMain(aeEventLoop *eventLoop) {
 416     eventLoop->stop = 0;
 417     while (!eventLoop->stop) {
 418         if (eventLoop->beforesleep != NULL)
 419             eventLoop->beforesleep(eventLoop);
 420         aeProcessEvents(eventLoop, AE_ALL_EVENTS);
 421     }
 422 }
 423
 424 char *aeGetApiName(void) {
 425     return aeApiName();
 426 }
 427
 428 void aeSetBeforeSleepProc(aeEventLoop *eventLoop, aeBeforeSleepProc *beforesleep) {
 429     eventLoop->beforesleep = beforesleep;
 430 }