Interface change to @conn_init@ -- return error rather than calling the

[mLib] / sel.c

/* -*-c-*-
 *
 * $Id: sel.c,v 1.9 2001/02/03 19:07:08 mdw Exp $
 *
 * I/O multiplexing support
 *
 * (c) 1999 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of the mLib utilities library.
 *
 * mLib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * mLib is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with mLib; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: sel.c,v $
 * Revision 1.9  2001/02/03 19:07:08  mdw
 * Ensure that timers set to go off in the past don't case a problem.
 *
 * Revision 1.8  2000/03/23 20:42:08  mdw
 * Rearrange timeout handling to avoid list corruptions.
 *
 * Revision 1.7  1999/12/11 11:12:17  mdw
 * Fix comment formatting error.
 *
 * Revision 1.6  1999/09/26 14:28:11  mdw
 * (sel_select): Almost pointless efficiency tweak.
 *
 * Revision 1.5  1999/08/31 17:42:22  mdw
 * New function `sel_force' to force a descriptor to be `selected'.
 *
 * Revision 1.4  1999/08/19 18:30:26  mdw
 * Implement hooks for foreign select-using systems (currently not well
 * tested).
 *
 * Revision 1.3  1999/05/21 22:13:59  mdw
 * Use new `tv' macros.  Fix ordering bug for timeout selectors.
 *
 * Revision 1.2  1999/05/15 10:33:32  mdw
 * Fix copyright notices.
 *
 * Revision 1.1  1999/05/14 21:01:14  mdw
 * Integrated `select' handling bits from the background resolver project.
 *
 */

/*----- Header files ------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>

#include "sel.h"
#include "tv.h"

/*----- Main code ---------------------------------------------------------*/

/* --- @sel_init@ --- *
 *
 * Arguments:	@sel_state *s@ = pointer to a state block to initialize
 *
 * Returns:	---
 *
 * Use:		Initializes a select state block.
 */

void sel_init(sel_state *s)
{
  int i;

  for (i = 0; i < SEL_MODES; i++) {
    s->files[i] = 0;
    FD_ZERO(&s->fd[i]);
  }
  s->timers = 0;
  s->hooks = 0;
  s->args = 0;
}

/* --- @sel_initfile@ --- *
 *
 * Arguments:	@sel_state *s@ = select state to attach to
 *		@sel_file *f@ = pointer to a file block to initialize
 *		@int fd@ = the file descriptor to listen to
 *		@unsigned mode@ = what to listen for
 *		@void (*func)(int fd, unsigned mode, void *p)@ = handler
 *		@void *p@ = argument to pass to handler
 *
 * Returns:	---
 *
 * Use:		Initializes a file block ready for use.  The file block
 *		isn't added to the list of things to do until a call to
 *		@sel_addfile@.
 */

void sel_initfile(sel_state *s, sel_file *f,
		  int fd, unsigned mode,
		  void (*func)(int /*fd*/, unsigned /*mode*/, void */*p*/),
		  void *p)
{
  f->s = s;
  f->fd = fd;
  f->mode = mode;
  f->func = func;
  f->p = p;
}

/* --- @sel_addfile@ --- *
 *
 * Arguments:	@sel_file *f@ = pointer to a file block
 *
 * Returns:	---
 *
 * Use:		Adds a file block into the list of things to listen to.
 */

void sel_addfile(sel_file *f)
{
  sel_file **ff = &f->s->files[f->mode];

  /* --- This little dance looks like line-noise, but it does the job --- */

  while (*ff && (*ff)->fd > f->fd)
    ff = &(*ff)->next;
  f->next = *ff;
  f->prev = (sel_file *)ff;
  if (*ff)
    (*ff)->prev = f;
  *ff = f;
  FD_SET(f->fd, f->s->fd + f->mode);
}

/* --- @sel_force@ --- *
 *
 * Arguments:	@sel_file *f@ = pointer to file selector
 *
 * Returns:	---
 *
 * Use:		Forces a file selector to be considered ready.  This is only
 *		useful during a call to @sel_select@.  Of particular use is
 *		forcing a write selector when there's something interesting
 *		ready for it.
 */

void sel_force(sel_file *f)
{
  if (f->s->args)
    FD_SET(f->fd, &f->s->args->fd[f->mode]);
}

/* --- @sel_rmfile@ --- *
 *
 * Arguments:	@sel_file *f@ = pointer to a file block
 *
 * Returns:	---
 *
 * Use:		Removes a file block from the list of things to listen to.
 */

void sel_rmfile(sel_file *f)
{
  f->prev->next = f->next;
  if (f->next)
    f->next->prev = f->prev;
  FD_CLR(f->fd, f->s->fd + f->mode);
}

/* --- @sel_addtimer@ --- *
 *
 * Arguments:	@sel_state *s@ = pointer to a state block
 *		@sel_timer *t@ = pointer to a timer block
 *		@struct timeval *tv@ = pointer to time to activate
 *		@void (*func)(struct timeval *tv, void *p)@ = handler
 *		@void *p@ = argument for handler function
 *
 * Returns:	---
 *
 * Use:		Registers and sets up a timer.
 */

void sel_addtimer(sel_state *s, sel_timer *t,
		  struct timeval *tv,
		  void (*func)(struct timeval */*tv*/, void */*p*/),
		  void *p)
{
  sel_timer **tt = &s->timers;

  /* --- Set up the timer block --- */

  t->tv = *tv;
  t->func = func;
  t->p = p;

  /* --- More line noise --- */
  
  while (*tt && TV_CMP(&(*tt)->tv, <, tv))
    tt = &(*tt)->next;
  t->next = *tt;
  t->prev = (sel_timer *)tt;
  if (*tt)
    (*tt)->prev = t;
  *tt = t;
}

/* --- @sel_rmtimer@ --- *
 *
 * Arguments:	@sel_timer *t@ = pointer to timer block
 *
 * Returns:	---
 *
 * Use:		Removes a timer from the list of timers.
 */

void sel_rmtimer(sel_timer *t)
{
  t->prev->next = t->next;
  if (t->next)
    t->next->prev = t->prev;
}

/* --- @sel_addhook@ --- *
 *
 * Arguments:	@sel_state *s@ = pointer to state block
 *		@sel_hook *h@ = pointer to hook block
 *		@sel_hookfn before, after@ = hook functions
 *		@void *p@ = pointer argument to pass to hook functions
 *
 * Returns:	---
 *
 * Use:		Registers hook functions to be called on each select call.
 */

void sel_addhook(sel_state *s, sel_hook *h,
		 sel_hookfn before, sel_hookfn after,
		 void *p)
{
  h->before = before;
  h->after = after;
  h->p = p;
  h->next = s->hooks;
  h->prev = (sel_hook *)&s->hooks;
  if (s->hooks)
    s->hooks->prev = h;
  s->hooks = h;
}

/* --- @sel_rmhook@ --- *
 *
 * Arguments:	@sel_hook *h@ = pointer to hook block
 *
 * Returns:	---
 *
 * Use:		Removes hook functions.
 */

void sel_rmhook(sel_hook *h)
{
  if (h->next)
    h->next->prev = h->prev;
  h->prev->next = h->next;
}

/* --- @sel_fdmerge@ --- *
 *
 * Arguments:   @fd_set *dest@ = destination FD set
 *              @fd_set *fd@ = pointer to set to merge
 *              @int maxfd@ = highest numbered descriptor in @fd@ + 1
 *
 * Returns:     Actual highest numbered descriptor.
 *
 * Use:         Merges file descriptor sets, and returns an accurate @maxfd@
 *              value.
 */

int sel_fdmerge(fd_set *dest, fd_set *fd, int maxfd)
{
  int i, m = -1;

  for (i = 0; i < maxfd; i++) {
    if (FD_ISSET(i, fd)) {
      FD_SET(i, dest);
      m = i;
    }
  }

  return (m + 1);
}

/* --- @sel_select@ --- *
 *
 * Arguments:	@sel_state *s@ = pointer to state block
 *
 * Returns:	Zero if all OK, -1 on error.
 *
 * Use:		Does a @select@ call (or equivalent @poll@).
 */

int sel_select(sel_state *s)
{
  sel_args a;
  int err;

  /* --- Initialize the argument block --- */

  {
    int i;
    a.maxfd = 0;
    for (i = 0; i < SEL_MODES; i++) {
      if (s->files[i] && s->files[i]->fd >= a.maxfd)
	a.maxfd = s->files[i]->fd + 1;
    }
  }

  memcpy(a.fd, s->fd, sizeof(a.fd));
  if (s->timers || s->hooks)
    gettimeofday(&a.now, 0);
  if (!s->timers)
    a.tvp = 0;
  else {
    if (TV_CMP(&s->timers->tv, >, &a.now))
      TV_SUB(&a.tv, &s->timers->tv, &a.now);
    else {
      a.tv.tv_sec = 0;
      a.tv.tv_usec = 0;
    }
    a.tvp = &a.tv;
  }
  s->args = &a;

  /* --- Grind through the pre hooks --- */

  {
    sel_hook *h = s->hooks;
    while (h) {
      sel_hook *hh = h;
      h = h->next;
      if (hh->before)
	hh->before(s, &a, hh->p);
    }
  }

  /* --- Run the @select@ call --- */
  
  if ((err = select(a.maxfd,
		    &a.fd[SEL_READ], &a.fd[SEL_WRITE], &a.fd[SEL_EXC],
		    a.tvp)) < 0) {
    s->args = 0;
    return (err);
  }

  if (a.tvp)
    gettimeofday(&a.now, 0);

  /* --- Run through the hooks again --- */

  {
    sel_hook *h = s->hooks;
    while (h) {
      sel_hook *hh = h;
      h = h->next;
      if (hh->after)
	hh->after(s, &a, hh->p);
    }
  }

  /* --- Run through the timers --- */

  if (s->timers && TV_CMP(&s->timers->tv, <=, &a.now)) {
    sel_timer *t, *tt;
    tt = s->timers;
    for (t = tt; t && TV_CMP(&t->tv, <=, &a.now); t = t->next)
      ;
    if (t) {
      t->prev->next = 0;
      t->prev = (sel_timer *)&s->timers;
    }
    s->timers = t;
    for (t = tt; t; t = tt) {
      tt = t->next;
      t->func(&a.now, t->p);
    }
  }

  /* --- And finally run through the files --- *
   *
   * Do reads first.  It's quite possible that a read might prompt a write,
   * but the other way around is less likely.  Fortunately, the modes are
   * in the right order for this.
   */

  {
    int i;

    for (i = 0; i < SEL_MODES; i++) {
      sel_file *f, *ff;
      for (f = s->files[i]; f; f = ff) {
	ff = f->next;
	if (FD_ISSET(f->fd, a.fd + i))
	  f->func(f->fd, i, f->p);
      }
    }
  }

  s->args = 0;
  return (0);
}

/*----- That's all, folks -------------------------------------------------*/