server/select.c

   1 /*
   2  * Server main select() loop
   3  *
   4  * Copyright (C) 1998 Alexandre Julliard
   5  */
   6
   7 #include <assert.h>
   8 #include <errno.h>
   9 #include <signal.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include <sys/time.h>
  14 #include <sys/types.h>
  15 #include <unistd.h>
  16
  17 #include "object.h"
  18
  19 struct timeout_user
  20 {
  21     struct timeout_user  *next;       /* next in sorted timeout list */
  22     struct timeout_user  *prev;       /* prev in sorted timeout list */
  23     struct timeval        when;       /* timeout expiry (absolute time) */
  24     timeout_callback      callback;   /* callback function */
  25     void                 *private;    /* callback private data */
  26 };
  27
  28 static struct select_user *users[FD_SETSIZE]; /* users array */
  29 static fd_set read_set, write_set;          /* current select sets */
  30 static int nb_users;                        /* current number of users */
  31 static int max_fd;                          /* max fd in use */
  32 static struct timeout_user *timeout_head;   /* sorted timeouts list head */
  33 static struct timeout_user *timeout_tail;   /* sorted timeouts list tail */
  34
  35
  36 /* register a user */
  37 void register_select_user( struct select_user *user )
  38 {
  39     assert( !users[user->fd] );
  40
  41     users[user->fd] = user;
  42     if (user->fd > max_fd) max_fd = user->fd;
  43     nb_users++;
  44 }
  45
  46 /* remove a user */
  47 void unregister_select_user( struct select_user *user )
  48 {
  49     assert( users[user->fd] == user );
  50
  51     FD_CLR( user->fd, &read_set );
  52     FD_CLR( user->fd, &write_set );
  53     users[user->fd] = NULL;
  54     if (max_fd == user->fd) while (max_fd && !users[max_fd]) max_fd--;
  55     nb_users--;
  56 }
  57
  58 /* set the events that select waits for on this fd */
  59 void set_select_events( struct select_user *user, int events )
  60 {
  61     assert( users[user->fd] == user );
  62     if (events & READ_EVENT) FD_SET( user->fd, &read_set );
  63     else FD_CLR( user->fd, &read_set );
  64     if (events & WRITE_EVENT) FD_SET( user->fd, &write_set );
  65     else FD_CLR( user->fd, &write_set );
  66 }
  67
  68 /* check if events are pending */
  69 int check_select_events( struct select_user *user, int events )
  70 {
  71     fd_set read_fds, write_fds;
  72     struct timeval tv = { 0, 0 };
  73
  74     FD_ZERO( &read_fds );
  75     FD_ZERO( &write_fds );
  76     if (events & READ_EVENT) FD_SET( user->fd, &read_fds );
  77     if (events & WRITE_EVENT) FD_SET( user->fd, &write_fds );
  78     return select( user->fd + 1, &read_fds, &write_fds, NULL, &tv ) > 0;
  79 }
  80
  81 /* add a timeout user */
  82 struct timeout_user *add_timeout_user( struct timeval *when, timeout_callback func, void *private )
  83 {
  84     struct timeout_user *user;
  85     struct timeout_user *pos;
  86
  87     if (!(user = mem_alloc( sizeof(*user) ))) return NULL;
  88     user->when     = *when;
  89     user->callback = func;
  90     user->private  = private;
  91
  92     /* Now insert it in the linked list */
  93
  94     for (pos = timeout_head; pos; pos = pos->next)
  95     {
  96         if (pos->when.tv_sec > user->when.tv_sec) break;
  97         if ((pos->when.tv_sec == user->when.tv_sec) &&
  98             (pos->when.tv_usec > user->when.tv_usec)) break;
  99     }
 100
 101     if (pos)  /* insert it before 'pos' */
 102     {
 103         if ((user->prev = pos->prev)) user->prev->next = user;
 104         else timeout_head = user;
 105         user->next = pos;
 106         pos->prev = user;
 107     }
 108     else  /* insert it at the tail */
 109     {
 110         user->next = NULL;
 111         if (timeout_tail) timeout_tail->next = user;
 112         else timeout_head = user;
 113         user->prev = timeout_tail;
 114         timeout_tail = user;
 115     }
 116     return user;
 117 }
 118
 119 /* remove a timeout user */
 120 void remove_timeout_user( struct timeout_user *user )
 121 {
 122     if (user->next) user->next->prev = user->prev;
 123     else timeout_tail = user->prev;
 124     if (user->prev) user->prev->next = user->next;
 125     else timeout_head = user->next;
 126     free( user );
 127 }
 128
 129 /* make an absolute timeout value from a relative timeout in milliseconds */
 130 void make_timeout( struct timeval *when, int timeout )
 131 {
 132     gettimeofday( when, 0 );
 133     if (!timeout) return;
 134     if ((when->tv_usec += (timeout % 1000) * 1000) >= 1000000)
 135     {
 136         when->tv_usec -= 1000000;
 137         when->tv_sec++;
 138     }
 139     when->tv_sec += timeout / 1000;
 140 }
 141
 142 /* handle an expired timeout */
 143 static void handle_timeout( struct timeout_user *user )
 144 {
 145     if (user->next) user->next->prev = user->prev;
 146     else timeout_tail = user->prev;
 147     if (user->prev) user->prev->next = user->next;
 148     else timeout_head = user->next;
 149     user->callback( user->private );
 150     free( user );
 151 }
 152
 153 /* server main loop */
 154 void select_loop(void)
 155 {
 156     int i, ret;
 157
 158     setsid();
 159     signal( SIGPIPE, SIG_IGN );
 160
 161     while (nb_users)
 162     {
 163         fd_set read = read_set, write = write_set;
 164         if (timeout_head)
 165         {
 166             struct timeval tv, now;
 167             gettimeofday( &now, NULL );
 168             if ((timeout_head->when.tv_sec < now.tv_sec) ||
 169                 ((timeout_head->when.tv_sec == now.tv_sec) &&
 170                  (timeout_head->when.tv_usec < now.tv_usec)))
 171             {
 172                 handle_timeout( timeout_head );
 173                 continue;
 174             }
 175             tv.tv_sec = timeout_head->when.tv_sec - now.tv_sec;
 176             if ((tv.tv_usec = timeout_head->when.tv_usec - now.tv_usec) < 0)
 177             {
 178                 tv.tv_usec += 1000000;
 179                 tv.tv_sec--;
 180             }
 181 #if 0
 182             printf( "select: " );
 183             for (i = 0; i <= max_fd; i++) printf( "%c", FD_ISSET( i, &read_set ) ? 'r' :
 184                                                   (FD_ISSET( i, &write_set ) ? 'w' : '-') );
 185             printf( " timeout %d.%06d\n", tv.tv_sec, tv.tv_usec );
 186 #endif
 187             ret = select( max_fd + 1, &read, &write, NULL, &tv );
 188         }
 189         else  /* no timeout */
 190         {
 191 #if 0
 192             printf( "select: " );
 193             for (i = 0; i <= max_fd; i++) printf( "%c", FD_ISSET( i, &read_set ) ? 'r' :
 194                                                   (FD_ISSET( i, &write_set ) ? 'w' : '-') );
 195             printf( " no timeout\n" );
 196 #endif
 197             ret = select( max_fd + 1, &read, &write, NULL, NULL );
 198         }
 199
 200         if (!ret) continue;
 201         if (ret == -1) {
 202             if (errno == EINTR) continue;
 203             perror("select");
 204         }
 205
 206         for (i = 0; i <= max_fd; i++)
 207         {
 208             int event = 0;
 209             if (FD_ISSET( i, &write )) event |= WRITE_EVENT;
 210             if (FD_ISSET( i, &read ))  event |= READ_EVENT;
 211
 212             /* Note: users[i] might be NULL here, because an event routine
 213                called in an earlier pass of this loop might have removed
 214                the current user ... */
 215             if (event && users[i])
 216                 users[i]->func( event, users[i]->private );
 217         }
 218     }
 219 }