/*
 * Copyright (C) 2003-2009 Andre Noll <maan@systemlinux.org>
 *
 * Licensed under the GPL v2. For licencing details see COPYING.
 */

/** \file exec.c Helper functions for spawning new processes. */
#include <dirent.h>
#include "para.h"
#include "close_on_fork.h"
#include "error.h"
#include "string.h"
#include "fd.h"

/**
 * Spawn a new process and redirect fd 0, 1, and 2.
 *
 * \param pid Will hold the pid of the created process upon return.
 * \param file Path of the executable to execute.
 * \param args The argument array for the command.
 * \param fds a Pointer to a value-result array.
 *
 * \return Standard.
 *
 * \sa null(4), pipe(2), dup2(2), fork(2), exec(3).
 */
static int para_exec(pid_t *pid, const char *file, char *const *const args, int *fds)
{
	int ret, in[2] = {-1, -1}, out[2] = {-1, -1}, err[2] = {-1, -1},
		null = -1; /* ;) */

	ret = -E_DUP_PIPE;
	if (fds[0] > 0 && pipe(in) < 0)
		goto err_out;
	if (fds[1] > 0 && pipe(out) < 0)
		goto err_out;
	if (fds[2] > 0 && pipe(err) < 0)
		goto err_out;
	if (!fds[0] || !fds[1] || !fds[2]) {
		ret = para_open("/dev/null", O_RDWR, 42);
		if (ret < 0)
			goto err_out;
		null = ret;
	}
	ret = fork();
	if (ret < 0) {
		ret = -ERRNO_TO_PARA_ERROR(errno);
		goto err_out;
	}
	*pid = ret;
	if (!(*pid)) { /* child */
		if (fds[0] >= 0) {
			if (fds[0]) {
				close(in[1]);
				if (in[0] != STDIN_FILENO)
					dup2(in[0], STDIN_FILENO);
			} else
				dup2(null, STDIN_FILENO);
		}
		if (fds[1] >= 0) {
			if (fds[1]) {
				close(out[0]);
				if (out[1] != STDOUT_FILENO)
					dup2(out[1], STDOUT_FILENO);
			} else
				dup2(null, STDOUT_FILENO);
		}
		if (fds[2] >= 0) {
			if (fds[2]) {
				close(err[0]);
				if (err[1] != STDERR_FILENO)
					dup2(err[1], STDERR_FILENO);
			} else
				dup2(null, STDERR_FILENO);
		}
		if (null >= 0)
			close(null);
		execvp(file, args);
		_exit(EXIT_FAILURE);
	}
	if (fds[0] > 0) {
		close(in[0]);
		*fds = in[1];
	}
	if (fds[1] > 0) {
		close(out[1]);
		*(fds + 1) = out[0];
	}
	if (fds[2] > 0) {
		close(err[1]);
		*(fds + 2) = err[0];
	}
	if (null >= 0)
		close(null);
	return 1;
err_out:
	if (err[0] >= 0)
		close(err[0]);
	if (err[1] >= 0)
		close(err[1]);
	if (out[0] >= 0)
		close(out[0]);
	if (out[1] >= 0)
		close(out[1]);
	if (in[0] >= 0)
		close(in[0]);
	if (in[1] >= 0)
		close(in[1]);
	if (null >= 0)
		close(null);
	PARA_ERROR_LOG("%s\n", para_strerror(-ret));
	return ret;
}

/**
 * Exec the given command.
 *
 * \param pid Will hold the pid of the created process upon return.
 * \param cmdline Holds the command and its arguments, seperated by spaces.
 * \param fds A pointer to a value-result array.
 *
 * This function uses fork/exec to create a new process. \a fds must be a
 * pointer to three integers, corresponding to stdin, stdout and stderr
 * respectively. It specifies how to deal with fd 0, 1, 2 in the child. The
 * contents of \a fds are interpreted as follows:
 *
 *	- fd[i] < 0: leave fd \a i alone.
 *	- fd[i] = 0: dup fd \a i to \p /dev/null.
 *	- fd[i] > 0: create a pipe and dup i to one end of that pipe.
 *	Upon return, fd[i] contains the file descriptor of the pipe.
 *
 * 	In any case, all unneeded filedescriptors are closed.
 *
 * \return Standard.
 */
int para_exec_cmdline_pid(pid_t *pid, const char *cmdline, int *fds)
{
	int ret;
	char **argv;
	char *tmp = para_strdup(cmdline);

	split_args(tmp, &argv, " \t");
	ret = para_exec(pid, argv[0], argv, fds);
	free(argv);
	free(tmp);
	return ret;
}