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
  42 aeEventLoop *aeCreateEventLoop(void) {
  43     aeEventLoop *eventLoop;
  44
  45     eventLoop = zmalloc(sizeof(*eventLoop));
  46     if (!eventLoop) return NULL;
  47     eventLoop->fileEventHead = NULL;
  48     eventLoop->timeEventHead = NULL;
  49     eventLoop->timeEventNextId = 0;
  50     eventLoop->stop = 0;
  51     return eventLoop;
  52 }
  53
  54 void aeDeleteEventLoop(aeEventLoop *eventLoop) {
  55     zfree(eventLoop);
  56 }
  57
  58 void aeStop(aeEventLoop *eventLoop) {
  59     eventLoop->stop = 1;
  60 }
  61
  62 int aeCreateFileEvent(aeEventLoop *eventLoop, int fd, int mask,
  63         aeFileProc *proc, void *clientData,
  64         aeEventFinalizerProc *finalizerProc)
  65 {
  66     aeFileEvent *fe;
  67
  68     fe = zmalloc(sizeof(*fe));
  69     if (fe == NULL) return AE_ERR;
  70     fe->fd = fd;
  71     fe->mask = mask;
  72     fe->fileProc = proc;
  73     fe->finalizerProc = finalizerProc;
  74     fe->clientData = clientData;
  75     fe->next = eventLoop->fileEventHead;
  76     eventLoop->fileEventHead = fe;
  77     return AE_OK;
  78 }
  79
  80 void aeDeleteFileEvent(aeEventLoop *eventLoop, int fd, int mask)
  81 {
  82     aeFileEvent *fe, *prev = NULL;
  83
  84     fe = eventLoop->fileEventHead;
  85     while(fe) {
  86         if (fe->fd == fd && fe->mask == mask) {
  87             if (prev == NULL)
  88                 eventLoop->fileEventHead = fe->next;
  89             else
  90                 prev->next = fe->next;
  91             if (fe->finalizerProc)
  92                 fe->finalizerProc(eventLoop, fe->clientData);
  93             zfree(fe);
  94             return;
  95         }
  96         prev = fe;
  97         fe = fe->next;
  98     }
  99 }
 100
 101 static void aeGetTime(long *seconds, long *milliseconds)
 102 {
 103     struct timeval tv;
 104
 105     gettimeofday(&tv, NULL);
 106     *seconds = tv.tv_sec;
 107     *milliseconds = tv.tv_usec/1000;
 108 }
 109
 110 static void aeAddMillisecondsToNow(long long milliseconds, long *sec, long *ms) {
 111     long cur_sec, cur_ms, when_sec, when_ms;
 112
 113     aeGetTime(&cur_sec, &cur_ms);
 114     when_sec = cur_sec + milliseconds/1000;
 115     when_ms = cur_ms + milliseconds%1000;
 116     if (when_ms >= 1000) {
 117         when_sec ++;
 118         when_ms -= 1000;
 119     }
 120     *sec = when_sec;
 121     *ms = when_ms;
 122 }
 123
 124 long long aeCreateTimeEvent(aeEventLoop *eventLoop, long long milliseconds,
 125         aeTimeProc *proc, void *clientData,
 126         aeEventFinalizerProc *finalizerProc)
 127 {
 128     long long id = eventLoop->timeEventNextId++;
 129     aeTimeEvent *te;
 130
 131     te = zmalloc(sizeof(*te));
 132     if (te == NULL) return AE_ERR;
 133     te->id = id;
 134     aeAddMillisecondsToNow(milliseconds,&te->when_sec,&te->when_ms);
 135     te->timeProc = proc;
 136     te->finalizerProc = finalizerProc;
 137     te->clientData = clientData;
 138     te->next = eventLoop->timeEventHead;
 139     eventLoop->timeEventHead = te;
 140     return id;
 141 }
 142
 143 int aeDeleteTimeEvent(aeEventLoop *eventLoop, long long id)
 144 {
 145     aeTimeEvent *te, *prev = NULL;
 146
 147     te = eventLoop->timeEventHead;
 148     while(te) {
 149         if (te->id == id) {
 150             if (prev == NULL)
 151                 eventLoop->timeEventHead = te->next;
 152             else
 153                 prev->next = te->next;
 154             if (te->finalizerProc)
 155                 te->finalizerProc(eventLoop, te->clientData);
 156             zfree(te);
 157             return AE_OK;
 158         }
 159         prev = te;
 160         te = te->next;
 161     }
 162     return AE_ERR; /* NO event with the specified ID found */
 163 }
 164
 165 /* Search the first timer to fire.
 166  * This operation is useful to know how many time the select can be
 167  * put in sleep without to delay any event.
 168  * If there are no timers NULL is returned.
 169  *
 170  * Note that's O(N) since time events are unsorted.
 171  * Possible optimizations (not needed by Redis so far, but...):
 172  * 1) Insert the event in order, so that the nearest is just the head.
 173  *    Much better but still insertion or deletion of timers is O(N).
 174  * 2) Use a skiplist to have this operation as O(1) and insertion as O(log(N)).
 175  */
 176 static aeTimeEvent *aeSearchNearestTimer(aeEventLoop *eventLoop)
 177 {
 178     aeTimeEvent *te = eventLoop->timeEventHead;
 179     aeTimeEvent *nearest = NULL;
 180
 181     while(te) {
 182         if (!nearest || te->when_sec < nearest->when_sec ||
 183                 (te->when_sec == nearest->when_sec &&
 184                  te->when_ms < nearest->when_ms))
 185             nearest = te;
 186         te = te->next;
 187     }
 188     return nearest;
 189 }
 190
 191 /* Process time events */
 192 static int processTimeEvents(aeEventLoop *eventLoop) {
 193     int processed = 0;
 194     aeTimeEvent *te;
 195     long long maxId;
 196
 197     te = eventLoop->timeEventHead;
 198     maxId = eventLoop->timeEventNextId-1;
 199     while(te) {
 200         long now_sec, now_ms;
 201         long long id;
 202
 203         if (te->id > maxId) {
 204             te = te->next;
 205             continue;
 206         }
 207         aeGetTime(&now_sec, &now_ms);
 208         if (now_sec > te->when_sec ||
 209             (now_sec == te->when_sec && now_ms >= te->when_ms))
 210         {
 211             int retval;
 212
 213             id = te->id;
 214             retval = te->timeProc(eventLoop, id, te->clientData);
 215             processed++;
 216             /* After an event is processed our time event list may
 217              * no longer be the same, so we restart from head.
 218              * Still we make sure to don't process events registered
 219              * by event handlers itself in order to don't loop forever.
 220              * To do so we saved the max ID we want to handle.
 221              *
 222              * FUTURE OPTIMIZATIONS:
 223              * Note that this is NOT great algorithmically. Redis uses
 224              * a single time event so it's not a problem but the right
 225              * way to do this is to add the new elements on head, and
 226              * to flag deleted elements in a special way for later
 227              * deletion (putting references to the nodes to delete into
 228              * another linked list). */
 229             if (retval != AE_NOMORE) {
 230                 aeAddMillisecondsToNow(retval,&te->when_sec,&te->when_ms);
 231             } else {
 232                 aeDeleteTimeEvent(eventLoop, id);
 233             }
 234             te = eventLoop->timeEventHead;
 235         } else {
 236             te = te->next;
 237         }
 238     }
 239     return processed;
 240 }
 241
 242 /* Process every pending time event, then every pending file event
 243  * (that may be registered by time event callbacks just processed).
 244  * Without special flags the function sleeps until some file event
 245  * fires, or when the next time event occurrs (if any).
 246  *
 247  * If flags is 0, the function does nothing and returns.
 248  * if flags has AE_ALL_EVENTS set, all the kind of events are processed.
 249  * if flags has AE_FILE_EVENTS set, file events are processed.
 250  * if flags has AE_TIME_EVENTS set, time events are processed.
 251  * if flags has AE_DONT_WAIT set the function returns ASAP until all
 252  * the events that's possible to process without to wait are processed.
 253  *
 254  * The function returns the number of events processed. */
 255 int aeProcessEvents(aeEventLoop *eventLoop, int flags)
 256 {
 257     int maxfd = 0, numfd = 0, processed = 0;
 258     fd_set rfds, wfds, efds;
 259     aeFileEvent *fe = eventLoop->fileEventHead;
 260
 261     /* Nothing to do? return ASAP */
 262     if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS)) return 0;
 263
 264     FD_ZERO(&rfds);
 265     FD_ZERO(&wfds);
 266     FD_ZERO(&efds);
 267
 268     /* Check file events */
 269     if (flags & AE_FILE_EVENTS) {
 270         while (fe != NULL) {
 271             if (fe->mask & AE_READABLE) FD_SET(fe->fd, &rfds);
 272             if (fe->mask & AE_WRITABLE) FD_SET(fe->fd, &wfds);
 273             if (fe->mask & AE_EXCEPTION) FD_SET(fe->fd, &efds);
 274             if (maxfd < fe->fd) maxfd = fe->fd;
 275             numfd++;
 276             fe = fe->next;
 277         }
 278     }
 279     /* Note that we want call select() even if there are no
 280      * file events to process as long as we want to process time
 281      * events, in order to sleep until the next time event is ready
 282      * to fire. */
 283     if (numfd || ((flags & AE_TIME_EVENTS) && !(flags & AE_DONT_WAIT))) {
 284         int retval;
 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         } else {
 305             /* If we have to check for events but need to return
 306              * ASAP because of AE_DONT_WAIT we need to se the timeout
 307              * to zero */
 308             if (flags & AE_DONT_WAIT) {
 309                 tv.tv_sec = tv.tv_usec = 0;
 310                 tvp = &tv;
 311             } else {
 312                 /* Otherwise we can block */
 313                 tvp = NULL; /* wait forever */
 314             }
 315         }
 316
 317         retval = select(maxfd+1, &rfds, &wfds, &efds, tvp);
 318         if (retval > 0) {
 319             fe = eventLoop->fileEventHead;
 320             while(fe != NULL) {
 321                 int fd = (int) fe->fd;
 322
 323                 if ((fe->mask & AE_READABLE && FD_ISSET(fd, &rfds)) ||
 324                     (fe->mask & AE_WRITABLE && FD_ISSET(fd, &wfds)) ||
 325                     (fe->mask & AE_EXCEPTION && FD_ISSET(fd, &efds)))
 326                 {
 327                     int mask = 0;
 328
 329                     if (fe->mask & AE_READABLE && FD_ISSET(fd, &rfds))
 330                         mask |= AE_READABLE;
 331                     if (fe->mask & AE_WRITABLE && FD_ISSET(fd, &wfds))
 332                         mask |= AE_WRITABLE;
 333                     if (fe->mask & AE_EXCEPTION && FD_ISSET(fd, &efds))
 334                         mask |= AE_EXCEPTION;
 335                     fe->fileProc(eventLoop, fe->fd, fe->clientData, mask);
 336                     processed++;
 337                     /* After an event is processed our file event list
 338                      * may no longer be the same, so what we do
 339                      * is to clear the bit for this file descriptor and
 340                      * restart again from the head. */
 341                     fe = eventLoop->fileEventHead;
 342                     FD_CLR(fd, &rfds);
 343                     FD_CLR(fd, &wfds);
 344                     FD_CLR(fd, &efds);
 345                 } else {
 346                     fe = fe->next;
 347                 }
 348             }
 349         }
 350     }
 351     /* Check time events */
 352     if (flags & AE_TIME_EVENTS)
 353         processed += processTimeEvents(eventLoop);
 354
 355     return processed; /* return the number of processed file/time events */
 356 }
 357
 358 /* Wait for millseconds until the given file descriptor becomes
 359  * writable/readable/exception */
 360 int aeWait(int fd, int mask, long long milliseconds) {
 361     struct timeval tv;
 362     fd_set rfds, wfds, efds;
 363     int retmask = 0, retval;
 364
 365     tv.tv_sec = milliseconds/1000;
 366     tv.tv_usec = (milliseconds%1000)*1000;
 367     FD_ZERO(&rfds);
 368     FD_ZERO(&wfds);
 369     FD_ZERO(&efds);
 370
 371     if (mask & AE_READABLE) FD_SET(fd,&rfds);
 372     if (mask & AE_WRITABLE) FD_SET(fd,&wfds);
 373     if (mask & AE_EXCEPTION) FD_SET(fd,&efds);
 374     if ((retval = select(fd+1, &rfds, &wfds, &efds, &tv)) > 0) {
 375         if (FD_ISSET(fd,&rfds)) retmask |= AE_READABLE;
 376         if (FD_ISSET(fd,&wfds)) retmask |= AE_WRITABLE;
 377         if (FD_ISSET(fd,&efds)) retmask |= AE_EXCEPTION;
 378         return retmask;
 379     } else {
 380         return retval;
 381     }
 382 }
 383
 384 void aeMain(aeEventLoop *eventLoop)
 385 {
 386     eventLoop->stop = 0;
 387     while (!eventLoop->stop)
 388         aeProcessEvents(eventLoop, AE_ALL_EVENTS);
 389 }