Integrated `select' handling bits from the background resolver project.

[mLib] / sel.c

/* -*-c-*-
 *
 * $Id: sel.c,v 1.1 1999/05/14 21:01:14 mdw Exp $
 *
 * I/O multiplexing support
 *
 * (c) 1999 Mark Wooding
 */

/*----- 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 1.1  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)
{
  s->files = 0;
  s->timers = 0;
  FD_ZERO(&s->fd[SEL_READ]);
  FD_ZERO(&s->fd[SEL_WRITE]);
  FD_ZERO(&s->fd[SEL_EXC]);
}

/* --- @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;

  /* --- 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_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) > 0)
    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_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)
{
  fd_set fd[SEL_MODES];
  struct timeval tv;
  int err;

  memcpy(fd, s->fd, sizeof(s->fd));
  if (s->timers) {
    struct timeval now;
    gettimeofday(&now, 0);
    tv_sub(&tv, &now, &s->timers->tv);
    err = select(s->files ? s->files->fd + 1 : 0,
                 fd + SEL_READ, fd + SEL_WRITE, fd + SEL_EXC,
                 &tv);
    gettimeofday(&tv, 0);
  } else
    err = select(s->files ? s->files->fd + 1 : 0,
                 fd + SEL_READ, fd + SEL_WRITE, fd + SEL_EXC,
                 0);

  if (err < 0)
    return (err);

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

  {
    sel_file *f, *ff;
    for (f = s->files; f; f = ff) {
      ff = f->next;
      if (FD_ISSET(f->fd, fd + f->mode))
        f->func(f->fd, f->mode, f->p);
    }
  }

  return (0);
}

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