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