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Simplify the way jobs work and drop the persist type, so all jobs are
fire-and-forget.

Status jobs now managed with two trees of output (new and old), rather
than storing the output in the jobs themselves. When the status line is
processed any jobs which don't appear in the new tree are started and
the output from the old tree displayed. When a job finishes it updates
the new tree with its output and that is used for any subsequent
redraws. When the status interval expires, the new tree is moved to the
old so that all jobs are run again.

This fixes the "#(echo %H:%M:%S)" problem which would lead to thousands
of identical persistent jobs and high memory use (this can still be
achieved by adding "sleep 30" but that is much less likely to happen by
accident).

/* $OpenBSD: job.c,v 1.25 2011/01/26 01:54:56 nicm Exp $ */

/*
 * Copyright (c) 2009 Nicholas Marriott <nicm@users.sourceforge.net>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <sys/socket.h>

#include <fcntl.h>
#include <paths.h>
#include <string.h>
#include <unistd.h>

#include "tmux.h"

/*
 * Job scheduling. Run queued commands in the background and record their
 * output.
 */

void	job_callback(struct bufferevent *, short, void *);

/* All jobs list. */
struct joblist	all_jobs = LIST_HEAD_INITIALIZER(all_jobs);

/* Start a job running, if it isn't already. */
struct job *
job_run(const char *cmd,
    void (*callbackfn)(struct job *), void (*freefn)(void *), void *data)
{
	struct job	*job;
	struct environ	 env;
	pid_t		 pid;
	int		 nullfd, out[2];

	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, out) != 0)
		return (NULL);

	environ_init(&env);
	environ_copy(&global_environ, &env);
	server_fill_environ(NULL, &env);

	switch (pid = fork()) {
	case -1:
		environ_free(&env);
		return (NULL);
	case 0:		/* child */
		clear_signals(1);

		environ_push(&env);
		environ_free(&env);

		if (dup2(out[1], STDOUT_FILENO) == -1)
			fatal("dup2 failed");
		if (out[1] != STDOUT_FILENO)
			close(out[1]);
		close(out[0]);

		nullfd = open(_PATH_DEVNULL, O_RDWR, 0);
		if (nullfd < 0)
			fatal("open failed");
		if (dup2(nullfd, STDIN_FILENO) == -1)
			fatal("dup2 failed");
		if (dup2(nullfd, STDERR_FILENO) == -1)
			fatal("dup2 failed");
		if (nullfd != STDIN_FILENO && nullfd != STDERR_FILENO)
			close(nullfd);

		closefrom(STDERR_FILENO + 1);

		execl(_PATH_BSHELL, "sh", "-c", cmd, (char *) NULL);
		fatal("execl failed");
	}

	/* parent */
	environ_free(&env);
	close(out[1]);

	job = xmalloc(sizeof *job);
	job->cmd = xstrdup(cmd);
	job->pid = pid;
	job->status = 0;

	LIST_INSERT_HEAD(&all_jobs, job, lentry);

	job->callbackfn = callbackfn;
	job->freefn = freefn;
	job->data = data;

	job->fd = out[0];
	setblocking(job->fd, 0);

	job->event = bufferevent_new(job->fd, NULL, NULL, job_callback, job);
	bufferevent_enable(job->event, EV_READ);

	log_debug("run job %p: %s, pid %ld", job, job->cmd, (long) job->pid);
	return (job);
}

/* Kill and free an individual job. */
void
job_free(struct job *job)
{
	log_debug("free job %p: %s", job, job->cmd);

	LIST_REMOVE(job, lentry);
	xfree(job->cmd);

	if (job->freefn != NULL && job->data != NULL)
		job->freefn(job->data);

	if (job->pid != -1)
		kill(job->pid, SIGTERM);
	if (job->fd != -1)
		close(job->fd);
	if (job->event != NULL)
		bufferevent_free(job->event);

	xfree(job);
}

/* Job buffer error callback. */
/* ARGSUSED */
void
job_callback(unused struct bufferevent *bufev, unused short events, void *data)
{
	struct job	*job = data;

	log_debug("job error %p: %s, pid %ld", job, job->cmd, (long) job->pid);

	if (job->pid == -1) {
		if (job->callbackfn != NULL)
			job->callbackfn(job);
		job_free(job);
	} else {
		bufferevent_disable(job->event, EV_READ);
		close(job->fd);
		job->fd = -1;
	}
}

/* Job died (waitpid() returned its pid). */
void
job_died(struct job *job, int status)
{
	log_debug("job died %p: %s, pid %ld", job, job->cmd, (long) job->pid);

	job->status = status;

	if (job->fd == -1) {
		if (job->callbackfn != NULL)
			job->callbackfn(job);
		job_free(job);
	} else
		job->pid = -1;
}