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 #include <time.h>
  41
  42 #include "ae.h"
  43 #include "zmalloc.h"
  44 #include "config.h"
  45
  46 /* Include the best multiplexing layer supported by this system.
  47  * The following should be ordered by performances, descending. */
  48 #ifdef HAVE_EVPORT
  49 #include "ae_evport.c"
  50 #else
  51     #ifdef HAVE_EPOLL
  52     #include "ae_epoll.c"
  53     #else
  54         #ifdef HAVE_KQUEUE
  55         #include "ae_kqueue.c"
  56         #else
  57         #include "ae_select.c"
  58         #endif
  59     #endif
  60 #endif
  61
  62 aeEventLoop *aeCreateEventLoop(int setsize) {
  63     aeEventLoop *eventLoop;
  64     int i;
  65
  66     if ((eventLoop = zmalloc(sizeof(*eventLoop))) == NULL) goto err;
  67     eventLoop->events = zmalloc(sizeof(aeFileEvent)*setsize);
  68     eventLoop->fired = zmalloc(sizeof(aeFiredEvent)*setsize);
  69     if (eventLoop->events == NULL || eventLoop->fired == NULL) goto err;
  70     eventLoop->setsize = setsize;
  71     eventLoop->lastTime = time(NULL);
  72     eventLoop->timeEventHead = NULL;
  73     eventLoop->timeEventNextId = 0;
  74     eventLoop->stop = 0;
  75     eventLoop->maxfd = -1;
  76     eventLoop->beforesleep = NULL;
  77     if (aeApiCreate(eventLoop) == -1) goto err;
  78     /* Events with mask == AE_NONE are not set. So let's initialize the
  79      * vector with it. */
  80     for (i = 0; i < setsize; i++)
  81         eventLoop->events[i].mask = AE_NONE;
  82     return eventLoop;
  83
  84 err:
  85     if (eventLoop) {
  86         zfree(eventLoop->events);
  87         zfree(eventLoop->fired);
  88         zfree(eventLoop);
  89     }
  90     return NULL;
  91 }
  92
  93 void aeDeleteEventLoop(aeEventLoop *eventLoop) {
  94     aeApiFree(eventLoop);
  95     zfree(eventLoop->events);
  96     zfree(eventLoop->fired);
  97     zfree(eventLoop);
  98 }
  99
 100 void aeStop(aeEventLoop *eventLoop) {
 101     eventLoop->stop = 1;
 102 }
 103
 104 int aeCreateFileEvent(aeEventLoop *eventLoop, int fd, int mask,
 105         aeFileProc *proc, void *clientData)
 106 {
 107     if (fd >= eventLoop->setsize) return AE_ERR;
 108     aeFileEvent *fe = &eventLoop->events[fd];
 109
 110     if (aeApiAddEvent(eventLoop, fd, mask) == -1)
 111         return AE_ERR;
 112     fe->mask |= mask;
 113     if (mask & AE_READABLE) fe->rfileProc = proc;
 114     if (mask & AE_WRITABLE) fe->wfileProc = proc;
 115     fe->clientData = clientData;
 116     if (fd > eventLoop->maxfd)
 117         eventLoop->maxfd = fd;
 118     return AE_OK;
 119 }
 120
 121 void aeDeleteFileEvent(aeEventLoop *eventLoop, int fd, int mask)
 122 {
 123     if (fd >= eventLoop->setsize) return;
 124     aeFileEvent *fe = &eventLoop->events[fd];
 125
 126     if (fe->mask == AE_NONE) return;
 127     fe->mask = fe->mask & (~mask);
 128     if (fd == eventLoop->maxfd && fe->mask == AE_NONE) {
 129         /* Update the max fd */
 130         int j;
 131
 132         for (j = eventLoop->maxfd-1; j >= 0; j--)
 133             if (eventLoop->events[j].mask != AE_NONE) break;
 134         eventLoop->maxfd = j;
 135     }
 136     aeApiDelEvent(eventLoop, fd, mask);
 137 }
 138
 139 int aeGetFileEvents(aeEventLoop *eventLoop, int fd) {
 140     if (fd >= eventLoop->setsize) return 0;
 141     aeFileEvent *fe = &eventLoop->events[fd];
 142
 143     return fe->mask;
 144 }
 145
 146 static void aeGetTime(long *seconds, long *milliseconds)
 147 {
 148     struct timeval tv;
 149
 150     gettimeofday(&tv, NULL);
 151     *seconds = tv.tv_sec;
 152     *milliseconds = tv.tv_usec/1000;
 153 }
 154
 155 static void aeAddMillisecondsToNow(long long milliseconds, long *sec, long *ms) {
 156     long cur_sec, cur_ms, when_sec, when_ms;
 157
 158     aeGetTime(&cur_sec, &cur_ms);
 159     when_sec = cur_sec + milliseconds/1000;
 160     when_ms = cur_ms + milliseconds%1000;
 161     if (when_ms >= 1000) {
 162         when_sec ++;
 163         when_ms -= 1000;
 164     }
 165     *sec = when_sec;
 166     *ms = when_ms;
 167 }
 168
 169 long long aeCreateTimeEvent(aeEventLoop *eventLoop, long long milliseconds,
 170         aeTimeProc *proc, void *clientData,
 171         aeEventFinalizerProc *finalizerProc)
 172 {
 173     long long id = eventLoop->timeEventNextId++;
 174     aeTimeEvent *te;
 175
 176     te = zmalloc(sizeof(*te));
 177     if (te == NULL) return AE_ERR;
 178     te->id = id;
 179     aeAddMillisecondsToNow(milliseconds,&te->when_sec,&te->when_ms);
 180     te->timeProc = proc;
 181     te->finalizerProc = finalizerProc;
 182     te->clientData = clientData;
 183     te->next = eventLoop->timeEventHead;
 184     eventLoop->timeEventHead = te;
 185     return id;
 186 }
 187
 188 int aeDeleteTimeEvent(aeEventLoop *eventLoop, long long id)
 189 {
 190     aeTimeEvent *te, *prev = NULL;
 191
 192     te = eventLoop->timeEventHead;
 193     while(te) {
 194         if (te->id == id) {
 195             if (prev == NULL)
 196                 eventLoop->timeEventHead = te->next;
 197             else
 198                 prev->next = te->next;
 199             if (te->finalizerProc)
 200                 te->finalizerProc(eventLoop, te->clientData);
 201             zfree(te);
 202             return AE_OK;
 203         }
 204         prev = te;
 205         te = te->next;
 206     }
 207     return AE_ERR; /* NO event with the specified ID found */
 208 }
 209
 210 /* Search the first timer to fire.
 211  * This operation is useful to know how many time the select can be
 212  * put in sleep without to delay any event.
 213  * If there are no timers NULL is returned.
 214  *
 215  * Note that's O(N) since time events are unsorted.
 216  * Possible optimizations (not needed by Redis so far, but...):
 217  * 1) Insert the event in order, so that the nearest is just the head.
 218  *    Much better but still insertion or deletion of timers is O(N).
 219  * 2) Use a skiplist to have this operation as O(1) and insertion as O(log(N)).
 220  */
 221 static aeTimeEvent *aeSearchNearestTimer(aeEventLoop *eventLoop)
 222 {
 223     aeTimeEvent *te = eventLoop->timeEventHead;
 224     aeTimeEvent *nearest = NULL;
 225
 226     while(te) {
 227         if (!nearest || te->when_sec < nearest->when_sec ||
 228                 (te->when_sec == nearest->when_sec &&
 229                  te->when_ms < nearest->when_ms))
 230             nearest = te;
 231         te = te->next;
 232     }
 233     return nearest;
 234 }
 235
 236 /* Process time events */
 237 static int processTimeEvents(aeEventLoop *eventLoop) {
 238     int processed = 0;
 239     aeTimeEvent *te;
 240     long long maxId;
 241     time_t now = time(NULL);
 242
 243     /* If the system clock is moved to the future, and then set back to the
 244      * right value, time events may be delayed in a random way. Often this
 245      * means that scheduled operations will not be performed soon enough.
 246      *
 247      * Here we try to detect system clock skews, and force all the time
 248      * events to be processed ASAP when this happens: the idea is that
 249      * processing events earlier is less dangerous than delaying them
 250      * indefinitely, and practice suggests it is. */
 251     if (now < eventLoop->lastTime) {
 252         te = eventLoop->timeEventHead;
 253         while(te) {
 254             te->when_sec = 0;
 255             te = te->next;
 256         }
 257     }
 258     eventLoop->lastTime = now;
 259
 260     te = eventLoop->timeEventHead;
 261     maxId = eventLoop->timeEventNextId-1;
 262     while(te) {
 263         long now_sec, now_ms;
 264         long long id;
 265
 266         if (te->id > maxId) {
 267             te = te->next;
 268             continue;
 269         }
 270         aeGetTime(&now_sec, &now_ms);
 271         if (now_sec > te->when_sec ||
 272             (now_sec == te->when_sec && now_ms >= te->when_ms))
 273         {
 274             int retval;
 275
 276             id = te->id;
 277             retval = te->timeProc(eventLoop, id, te->clientData);
 278             processed++;
 279             /* After an event is processed our time event list may
 280              * no longer be the same, so we restart from head.
 281              * Still we make sure to don't process events registered
 282              * by event handlers itself in order to don't loop forever.
 283              * To do so we saved the max ID we want to handle.
 284              *
 285              * FUTURE OPTIMIZATIONS:
 286              * Note that this is NOT great algorithmically. Redis uses
 287              * a single time event so it's not a problem but the right
 288              * way to do this is to add the new elements on head, and
 289              * to flag deleted elements in a special way for later
 290              * deletion (putting references to the nodes to delete into
 291              * another linked list). */
 292             if (retval != AE_NOMORE) {
 293                 aeAddMillisecondsToNow(retval,&te->when_sec,&te->when_ms);
 294             } else {
 295                 aeDeleteTimeEvent(eventLoop, id);
 296             }
 297             te = eventLoop->timeEventHead;
 298         } else {
 299             te = te->next;
 300         }
 301     }
 302     return processed;
 303 }
 304
 305 /* Process every pending time event, then every pending file event
 306  * (that may be registered by time event callbacks just processed).
 307  * Without special flags the function sleeps until some file event
 308  * fires, or when the next time event occurrs (if any).
 309  *
 310  * If flags is 0, the function does nothing and returns.
 311  * if flags has AE_ALL_EVENTS set, all the kind of events are processed.
 312  * if flags has AE_FILE_EVENTS set, file events are processed.
 313  * if flags has AE_TIME_EVENTS set, time events are processed.
 314  * if flags has AE_DONT_WAIT set the function returns ASAP until all
 315  * the events that's possible to process without to wait are processed.
 316  *
 317  * The function returns the number of events processed. */
 318 int aeProcessEvents(aeEventLoop *eventLoop, int flags)
 319 {
 320     int processed = 0, numevents;
 321
 322     /* Nothing to do? return ASAP */
 323     if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS)) return 0;
 324
 325     /* Note that we want call select() even if there are no
 326      * file events to process as long as we want to process time
 327      * events, in order to sleep until the next time event is ready
 328      * to fire. */
 329     if (eventLoop->maxfd != -1 ||
 330         ((flags & AE_TIME_EVENTS) && !(flags & AE_DONT_WAIT))) {
 331         int j;
 332         aeTimeEvent *shortest = NULL;
 333         struct timeval tv, *tvp;
 334
 335         if (flags & AE_TIME_EVENTS && !(flags & AE_DONT_WAIT))
 336             shortest = aeSearchNearestTimer(eventLoop);
 337         if (shortest) {
 338             long now_sec, now_ms;
 339
 340             /* Calculate the time missing for the nearest
 341              * timer to fire. */
 342             aeGetTime(&now_sec, &now_ms);
 343             tvp = &tv;
 344             tvp->tv_sec = shortest->when_sec - now_sec;
 345             if (shortest->when_ms < now_ms) {
 346                 tvp->tv_usec = ((shortest->when_ms+1000) - now_ms)*1000;
 347                 tvp->tv_sec --;
 348             } else {
 349                 tvp->tv_usec = (shortest->when_ms - now_ms)*1000;
 350             }
 351             if (tvp->tv_sec < 0) tvp->tv_sec = 0;
 352             if (tvp->tv_usec < 0) tvp->tv_usec = 0;
 353         } else {
 354             /* If we have to check for events but need to return
 355              * ASAP because of AE_DONT_WAIT we need to se the timeout
 356              * to zero */
 357             if (flags & AE_DONT_WAIT) {
 358                 tv.tv_sec = tv.tv_usec = 0;
 359                 tvp = &tv;
 360             } else {
 361                 /* Otherwise we can block */
 362                 tvp = NULL; /* wait forever */
 363             }
 364         }
 365
 366         numevents = aeApiPoll(eventLoop, tvp);
 367         for (j = 0; j < numevents; j++) {
 368             aeFileEvent *fe = &eventLoop->events[eventLoop->fired[j].fd];
 369             int mask = eventLoop->fired[j].mask;
 370             int fd = eventLoop->fired[j].fd;
 371             int rfired = 0;
 372
 373             /* note the fe->mask & mask & ... code: maybe an already processed
 374              * event removed an element that fired and we still didn't
 375              * processed, so we check if the event is still valid. */
 376             if (fe->mask & mask & AE_READABLE) {
 377                 rfired = 1;
 378                 fe->rfileProc(eventLoop,fd,fe->clientData,mask);
 379             }
 380             if (fe->mask & mask & AE_WRITABLE) {
 381                 if (!rfired || fe->wfileProc != fe->rfileProc)
 382                     fe->wfileProc(eventLoop,fd,fe->clientData,mask);
 383             }
 384             processed++;
 385         }
 386     }
 387     /* Check time events */
 388     if (flags & AE_TIME_EVENTS)
 389         processed += processTimeEvents(eventLoop);
 390
 391     return processed; /* return the number of processed file/time events */
 392 }
 393
 394 /* Wait for millseconds until the given file descriptor becomes
 395  * writable/readable/exception */
 396 int aeWait(int fd, int mask, long long milliseconds) {
 397     struct pollfd pfd;
 398     int retmask = 0, retval;
 399
 400     memset(&pfd, 0, sizeof(pfd));
 401     pfd.fd = fd;
 402     if (mask & AE_READABLE) pfd.events |= POLLIN;
 403     if (mask & AE_WRITABLE) pfd.events |= POLLOUT;
 404
 405     if ((retval = poll(&pfd, 1, milliseconds))== 1) {
 406         if (pfd.revents & POLLIN) retmask |= AE_READABLE;
 407         if (pfd.revents & POLLOUT) retmask |= AE_WRITABLE;
 408         if (pfd.revents & POLLERR) retmask |= AE_WRITABLE;
 409         if (pfd.revents & POLLHUP) retmask |= AE_WRITABLE;
 410         return retmask;
 411     } else {
 412         return retval;
 413     }
 414 }
 415
 416 void aeMain(aeEventLoop *eventLoop) {
 417     eventLoop->stop = 0;
 418     while (!eventLoop->stop) {
 419         if (eventLoop->beforesleep != NULL)
 420             eventLoop->beforesleep(eventLoop);
 421         aeProcessEvents(eventLoop, AE_ALL_EVENTS);
 422     }
 423 }
 424
 425 char *aeGetApiName(void) {
 426     return aeApiName();
 427 }
 428
 429 void aeSetBeforeSleepProc(aeEventLoop *eventLoop, aeBeforeSleepProc *beforesleep) {
 430     eventLoop->beforesleep = beforesleep;
 431 }