#include "ruby/config.h"

#ifdef RUBY_EXTCONF_H
# include RUBY_EXTCONF_H
#endif

#include <ctype.h>
#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <fcntl.h>

#ifdef HAVE_PWD_H
# include <pwd.h>
#endif

#ifdef HAVE_SYS_IOCTL_H
# include <sys/ioctl.h>
#endif

#ifdef HAVE_LIBUTIL_H
# include <libutil.h>
#endif

#ifdef HAVE_UTIL_H
# include <util.h>
#endif

#ifdef HAVE_PTY_H
# include <pty.h>
#endif

#if defined(HAVE_SYS_PARAM_H)
 /* for __FreeBSD_version */
# include <sys/param.h>
#endif

#ifdef HAVE_SYS_WAIT_H
# include <sys/wait.h>
#else
# define WIFSTOPPED(status) (((status) & 0xff) == 0x7f)
#endif

#ifdef HAVE_SYS_STROPTS_H
#include <sys/stropts.h>
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "internal.h"
#include "internal/process.h"
#include "internal/signal.h"
#include "ruby/io.h"
#include "ruby/util.h"

#define	DEVICELEN	16

#ifndef HAVE_SETEUID
# ifdef HAVE_SETREUID
#  define seteuid(e)	setreuid(-1, (e))
# else /* NOT HAVE_SETREUID */
#  ifdef HAVE_SETRESUID
#   define seteuid(e)	setresuid(-1, (e), -1)
#  else /* NOT HAVE_SETRESUID */
    /* I can't set euid. (;_;) */
#  endif /* HAVE_SETRESUID */
# endif /* HAVE_SETREUID */
#endif /* NO_SETEUID */

static VALUE eChildExited;

/* Returns the exit status of the child for which PTY#check
 * raised this exception
 */
static VALUE
echild_status(VALUE self)
{
    return rb_ivar_get(self, rb_intern("status"));
}

struct pty_info {
    int fd;
    rb_pid_t child_pid;
};

static void getDevice(int*, int*, char [DEVICELEN], int);

static int start_new_session(char *errbuf, size_t errbuf_len);
static int obtain_ctty(int master, int slave, const char *slavename, char *errbuf, size_t errbuf_len);
static int drop_privilege(char *errbuf, size_t errbuf_len);

struct child_info {
    int master, slave;
    const char *slavename;
    VALUE execarg_obj;
    struct rb_execarg *eargp;
};

static int
chfunc(void *data, char *errbuf, size_t errbuf_len)
{
    const struct child_info *carg = data;
    int master = carg->master;
    int slave = carg->slave;
    const char *slavename = carg->slavename;

    if (start_new_session(errbuf, errbuf_len))
        return -1;

    if (obtain_ctty(master, slave, slavename, errbuf, errbuf_len))
        return -1;

    if (drop_privilege(errbuf, errbuf_len))
        return -1;

    return rb_exec_async_signal_safe(carg->eargp, errbuf, errbuf_len);
}

#define ERROR_EXIT(str) do { \
        strlcpy(errbuf, (str), errbuf_len); \
        return -1; \
    } while (0)

/*
 * Set free from process group and controlling terminal
 */
static int
start_new_session(char *errbuf, size_t errbuf_len)
{
#ifdef HAVE_SETSID
    (void) setsid();
#else /* HAS_SETSID */
# ifdef HAVE_SETPGRP
#  ifdef SETPGRP_VOID
    if (setpgrp() == -1)
        ERROR_EXIT("setpgrp()");
#  else /* SETPGRP_VOID */
    if (setpgrp(0, getpid()) == -1)
        ERROR_EXIT("setpgrp()");
    {
        int i = rb_cloexec_open("/dev/tty", O_RDONLY, 0);
        if (i < 0) ERROR_EXIT("/dev/tty");
        rb_update_max_fd(i);
        if (ioctl(i, TIOCNOTTY, (char *)0))
            ERROR_EXIT("ioctl(TIOCNOTTY)");
        close(i);
    }
#  endif /* SETPGRP_VOID */
# endif /* HAVE_SETPGRP */
#endif /* HAS_SETSID */
    return 0;
}

/*
 * obtain new controlling terminal
 */
static int
obtain_ctty(int master, int slave, const char *slavename, char *errbuf, size_t errbuf_len)
{
#if defined(TIOCSCTTY)
    close(master);
    (void) ioctl(slave, TIOCSCTTY, (char *)0);
    /* errors ignored for sun */
#else
    close(slave);
    slave = rb_cloexec_open(slavename, O_RDWR, 0);
    if (slave < 0) {
        ERROR_EXIT("open: pty slave");
    }
    rb_update_max_fd(slave);
    close(master);
#endif
    dup2(slave,0);
    dup2(slave,1);
    dup2(slave,2);
    if (slave > 2) (void)!close(slave);
    return 0;
}

static int
drop_privilege(char *errbuf, size_t errbuf_len)
{
#if defined(HAVE_SETEUID) || defined(HAVE_SETREUID) || defined(HAVE_SETRESUID)
    if (seteuid(getuid())) ERROR_EXIT("seteuid()");
#endif
    return 0;
}

#undef ERROR_EXIT

static void
establishShell(int argc, VALUE *argv, struct pty_info *info,
               char SlaveName[DEVICELEN])
{
    int 		master, slave, status = 0;
    rb_pid_t		pid;
    char		*p;
    VALUE		v;
    struct child_info   carg;
    char		errbuf[32];

    if (argc == 0) {
        const char *shellname = "/bin/sh";

        if ((p = getenv("SHELL")) != NULL) {
            shellname = p;
        }
        else {
#if defined HAVE_PWD_H
            const char *username = getenv("USER");
            if (username == NULL)
                username = getlogin();
            if (username != NULL) {
                struct passwd *pwent = getpwnam(username);
                if (pwent && pwent->pw_shell)
                    shellname = pwent->pw_shell;
            }
#endif
        }
        v = rb_str_new2(shellname);
        argc = 1;
        argv = &v;
    }

    carg.execarg_obj = rb_execarg_new(argc, argv, 1, 0);
    carg.eargp = rb_execarg_get(carg.execarg_obj);
    rb_execarg_parent_start(carg.execarg_obj);

    getDevice(&master, &slave, SlaveName, 0);

    carg.master = master;
    carg.slave = slave;
    carg.slavename = SlaveName;
    errbuf[0] = '\0';
    pid = rb_fork_async_signal_safe(&status, chfunc, &carg, Qnil, errbuf, sizeof(errbuf));

    if (pid < 0) {
        int e = errno;
        close(master);
        close(slave);
        rb_execarg_parent_end(carg.execarg_obj);
        errno = e;
        if (status) rb_jump_tag(status);
        rb_sys_fail(errbuf[0] ? errbuf : "fork failed");
    }

    close(slave);
    rb_execarg_parent_end(carg.execarg_obj);

    info->child_pid = pid;
    info->fd = master;

    RB_GC_GUARD(carg.execarg_obj);
}

#if (defined(HAVE_POSIX_OPENPT) || defined(HAVE_PTSNAME)) && !defined(HAVE_PTSNAME_R)
/* glibc only, not obsolete interface on Tru64 or HP-UX */
static int
ptsname_r(int fd, char *buf, size_t buflen)
{
    extern char *ptsname(int);
    char *name = ptsname(fd);
    if (!name) return -1;
    strlcpy(buf, name, buflen);
    return 0;
}
# define HAVE_PTSNAME_R 1
#endif

#ifdef HAVE_FCHMOD
# define change_mode(name, fd, mode) fchmod(fd, mode)
#else
# define change_mode(name, fd, mode) chmod(name, mode)
#endif
#ifdef HAVE_FCHOWN
# define change_owner(name, fd, uid, gid) fchown(fd, uid, gid)
#else
# define change_owner(name, fd, uid, gid) chown(name, uid, gid)
#endif

#if defined(HAVE_POSIX_OPENPT) || defined(HAVE_OPENPTY) || defined(HAVE_PTSNAME_R)
static inline int
prevent_messages(const char *slavedevice, int fd, int nomesg)
{
    if (nomesg)
        return change_mode(slavedevice, fd, 0600);
    else
        return 0;
}
#endif

#if defined(I_PUSH) && !defined(__linux__) && !defined(_AIX)
static inline int
ioctl_I_PUSH(int fd, const char *const name)
{
    int ret = 0;
# if defined(I_FIND)
    ret = ioctl(fd, I_FIND, name);
# endif
    if (ret == 0) {
        ret = ioctl(fd, I_PUSH, name);
    }
    return ret;
}
#endif

static int
get_device_once(int *master, int *slave, char SlaveName[DEVICELEN], int nomesg, int fail)
{
#if defined(HAVE_POSIX_OPENPT)
    /* Unix98 PTY */
    int masterfd = -1, slavefd = -1;
    char *slavedevice;
    struct sigaction dfl, old;

    dfl.sa_handler = SIG_DFL;
    dfl.sa_flags = 0;
    sigemptyset(&dfl.sa_mask);

#if defined(__sun) || defined(__OpenBSD__) || (defined(__FreeBSD__) && __FreeBSD_version < 902000)
    /* workaround for Solaris 10: grantpt() doesn't work if FD_CLOEXEC is set.  [ruby-dev:44688] */
    /* FreeBSD 9.2 or later supports O_CLOEXEC
     * http://www.freebsd.org/cgi/query-pr.cgi?pr=162374 */
    if ((masterfd = posix_openpt(O_RDWR|O_NOCTTY)) == -1) goto error;
    if (sigaction(SIGCHLD, &dfl, &old) == -1) goto error;
    if (grantpt(masterfd) == -1) goto grantpt_error;
    rb_fd_fix_cloexec(masterfd);
#else
    {
        int flags = O_RDWR|O_NOCTTY;
# if defined(O_CLOEXEC)
        /* glibc posix_openpt() in GNU/Linux calls open("/dev/ptmx", flags) internally.
         * So version dependency on GNU/Linux is the same as O_CLOEXEC with open().
         * O_CLOEXEC is available since Linux 2.6.23.  Linux 2.6.18 silently ignore it. */
        flags |= O_CLOEXEC;
# endif
        if ((masterfd = posix_openpt(flags)) == -1) goto error;
    }
    rb_fd_fix_cloexec(masterfd);
    if (sigaction(SIGCHLD, &dfl, &old) == -1) goto error;
    if (grantpt(masterfd) == -1) goto grantpt_error;
#endif
    if (sigaction(SIGCHLD, &old, NULL) == -1) goto error;
    if (unlockpt(masterfd) == -1) goto error;
    if (ptsname_r(masterfd, SlaveName, DEVICELEN) != 0) goto error;
    slavedevice = SlaveName;
    if ((slavefd = rb_cloexec_open(slavedevice, O_RDWR|O_NOCTTY, 0)) == -1) goto error;
    if (prevent_messages(slavedevice, slavefd, nomesg) == -1) goto error;
    rb_update_max_fd(slavefd);

#if defined(I_PUSH) && !defined(__linux__) && !defined(_AIX)
    if (ioctl_I_PUSH(slavefd, "ptem") == -1) goto error;
    if (ioctl_I_PUSH(slavefd, "ldterm") == -1) goto error;
    if (ioctl_I_PUSH(slavefd, "ttcompat") == -1) goto error;
#endif

    *master = masterfd;
    *slave = slavefd;
    return 0;

  grantpt_error:
    sigaction(SIGCHLD, &old, NULL);
  error:
    if (slavefd != -1) close(slavefd);
    if (masterfd != -1) close(masterfd);
    if (fail) {
        rb_raise(rb_eRuntimeError, "can't get Master/Slave device");
    }
    return -1;
#elif defined HAVE_OPENPTY
/*
 * Use openpty(3) of 4.3BSD Reno and later,
 * or the same interface function.
 */
    if (openpty(master, slave, SlaveName,
                (struct termios *)0, (struct winsize *)0) == -1) {
        if (!fail) return -1;
        rb_raise(rb_eRuntimeError, "openpty() failed");
    }
    rb_fd_fix_cloexec(*master);
    rb_fd_fix_cloexec(*slave);
    if (prevent_messages(SlaveName, *slave, nomesg) == -1) {
        close(*master);
        close(*slave);
        if (!fail) return -1;
        rb_raise(rb_eRuntimeError, "can't chmod slave pty");
    }

    return 0;

#elif defined HAVE__GETPTY
    /* SGI IRIX */
    char *name;
    mode_t mode = nomesg ? 0600 : 0622;

    if (!(name = _getpty(master, O_RDWR, mode, 0))) {
        if (!fail) return -1;
        rb_raise(rb_eRuntimeError, "_getpty() failed");
    }
    rb_fd_fix_cloexec(*master);

    *slave = rb_cloexec_open(name, O_RDWR, 0);
    /* error check? */
    rb_update_max_fd(*slave);
    strlcpy(SlaveName, name, DEVICELEN);

    return 0;
#elif defined(HAVE_PTSNAME)
    /* System V */
    int	 masterfd = -1, slavefd = -1;
    char *slavedevice;
    void (*s)();

    extern int unlockpt(int);
    extern int grantpt(int);

#if defined(__sun)
    /* workaround for Solaris 10: grantpt() doesn't work if FD_CLOEXEC is set.  [ruby-dev:44688] */
    if((masterfd = open("/dev/ptmx", O_RDWR, 0)) == -1) goto error;
    s = signal(SIGCHLD, SIG_DFL);
    if(grantpt(masterfd) == -1) goto error;
    rb_fd_fix_cloexec(masterfd);
#else
    if((masterfd = rb_cloexec_open("/dev/ptmx", O_RDWR, 0)) == -1) goto error;
    rb_update_max_fd(masterfd);
    s = signal(SIGCHLD, SIG_DFL);
    if(grantpt(masterfd) == -1) goto error;
#endif
    signal(SIGCHLD, s);
    if(unlockpt(masterfd) == -1) goto error;
    if (ptsname_r(masterfd, SlaveName, DEVICELEN) != 0) goto error;
    slavedevice = SlaveName;
    if((slavefd = rb_cloexec_open(slavedevice, O_RDWR, 0)) == -1) goto error;
    if (prevent_messages(slavedevice, slavefd, nomesg) == -1) goto error;
    rb_update_max_fd(slavefd);
#if defined(I_PUSH) && !defined(__linux__) && !defined(_AIX)
    if(ioctl_I_PUSH(slavefd, "ptem") == -1) goto error;
    if(ioctl_I_PUSH(slavefd, "ldterm") == -1) goto error;
    ioctl_I_PUSH(slavefd, "ttcompat");
#endif
    *master = masterfd;
    *slave = slavefd;
    return 0;

  error:
    if (slavefd != -1) close(slavefd);
    if (masterfd != -1) close(masterfd);
    if (fail) rb_raise(rb_eRuntimeError, "can't get Master/Slave device");
    return -1;
#else
    /* BSD */
    int	 masterfd = -1, slavefd = -1;
    int  i;
    char MasterName[DEVICELEN];

#define HEX1(c) \
        c"0",c"1",c"2",c"3",c"4",c"5",c"6",c"7", \
        c"8",c"9",c"a",c"b",c"c",c"d",c"e",c"f"

#if defined(_IBMESA)  /* AIX/ESA */
    static const char MasterDevice[] = "/dev/ptyp%s";
    static const char SlaveDevice[] = "/dev/ttyp%s";
    static const char deviceNo[][3] = {
        HEX1("0"), HEX1("1"), HEX1("2"), HEX1("3"),
        HEX1("4"), HEX1("5"), HEX1("6"), HEX1("7"),
        HEX1("8"), HEX1("9"), HEX1("a"), HEX1("b"),
        HEX1("c"), HEX1("d"), HEX1("e"), HEX1("f"),
    };
#else /* 4.2BSD */
    static const char MasterDevice[] = "/dev/pty%s";
    static const char SlaveDevice[] = "/dev/tty%s";
    static const char deviceNo[][3] = {
        HEX1("p"), HEX1("q"), HEX1("r"), HEX1("s"),
    };
#endif
#undef HEX1
    for (i = 0; i < numberof(deviceNo); i++) {
        const char *const devno = deviceNo[i];
        snprintf(MasterName, sizeof MasterName, MasterDevice, devno);
        if ((masterfd = rb_cloexec_open(MasterName,O_RDWR,0)) >= 0) {
            rb_update_max_fd(masterfd);
            *master = masterfd;
            snprintf(SlaveName, DEVICELEN, SlaveDevice, devno);
            if ((slavefd = rb_cloexec_open(SlaveName,O_RDWR,0)) >= 0) {
                rb_update_max_fd(slavefd);
                *slave = slavefd;
                if (change_owner(SlaveName, slavefd, getuid(), getgid()) != 0) goto error;
                if (change_mode(SlaveName, slavefd, nomesg ? 0600 : 0622) != 0) goto error;
                return 0;
            }
            close(masterfd);
        }
    }
  error:
    if (slavefd != -1) close(slavefd);
    if (masterfd != -1) close(masterfd);
    if (fail) rb_raise(rb_eRuntimeError, "can't get %s", SlaveName);
    return -1;
#endif
}

static void
getDevice(int *master, int *slave, char SlaveName[DEVICELEN], int nomesg)
{
    if (get_device_once(master, slave, SlaveName, nomesg, 0)) {
        rb_gc();
        get_device_once(master, slave, SlaveName, nomesg, 1);
    }
}

static VALUE
pty_close_pty(VALUE assoc)
{
    VALUE io;
    int i;

    for (i = 0; i < 2; i++) {
        io = rb_ary_entry(assoc, i);
        if (RB_TYPE_P(io, T_FILE)) {
            /* it's OK to call rb_io_close again even if it's already closed */
            rb_io_close(io);
        }
    }
    return Qnil;
}

/*
 * call-seq:
 *   PTY.open => [master_io, slave_file]
 *   PTY.open {|(master_io, slave_file)| ... } => block value
 *
 * Allocates a pty (pseudo-terminal).
 *
 * In the block form, yields an array of two elements (<tt>master_io, slave_file</tt>)
 * and the value of the block is returned from +open+.
 *
 * The IO and File are both closed after the block completes if they haven't
 * been already closed.
 *
 *   PTY.open {|master, slave|
 *     p master      #=> #<IO:masterpty:/dev/pts/1>
 *     p slave      #=> #<File:/dev/pts/1>
 *     p slave.path #=> "/dev/pts/1"
 *   }
 *
 * In the non-block form, returns a two element array, <tt>[master_io,
 * slave_file]</tt>.
 *
 *   master, slave = PTY.open
 *   # do something with master for IO, or the slave file
 *
 * The arguments in both forms are:
 *
 * +master_io+::    the master of the pty, as an IO.
 * +slave_file+::   the slave of the pty, as a File.  The path to the
 *		    terminal device is available via +slave_file.path+
 *
 * IO#raw! is usable to disable newline conversions:
 *
 *   require 'io/console'
 *   PTY.open {|m, s|
 *     s.raw!
 *     # ...
 *   }
 *
 */
static VALUE
pty_open(VALUE klass)
{
    int master_fd, slave_fd;
    char slavename[DEVICELEN];

    getDevice(&master_fd, &slave_fd, slavename, 1);

    VALUE master_path = rb_obj_freeze(rb_sprintf("masterpty:%s", slavename));
    VALUE master_io = rb_io_open_descriptor(rb_cIO, master_fd, FMODE_READWRITE | FMODE_SYNC | FMODE_DUPLEX, master_path, RUBY_IO_TIMEOUT_DEFAULT, NULL);

    VALUE slave_path = rb_obj_freeze(rb_str_new_cstr(slavename));
    VALUE slave_file = rb_io_open_descriptor(rb_cFile, slave_fd, FMODE_READWRITE | FMODE_SYNC | FMODE_DUPLEX | FMODE_TTY, slave_path, RUBY_IO_TIMEOUT_DEFAULT, NULL);

    VALUE assoc = rb_assoc_new(master_io, slave_file);

    if (rb_block_given_p()) {
        return rb_ensure(rb_yield, assoc, pty_close_pty, assoc);
    }

    return assoc;
}

static VALUE
pty_detach_process(VALUE v)
{
    struct pty_info *info = (void *)v;
#ifdef WNOHANG
    int st;
    if (rb_waitpid(info->child_pid, &st, WNOHANG) <= 0)
        return Qnil;
#endif
    rb_detach_process(info->child_pid);
    return Qnil;
}

/*
 * call-seq:
 *   PTY.spawn([env,] command_line)  { |r, w, pid| ... }
 *   PTY.spawn([env,] command_line)  => [r, w, pid]
 *   PTY.spawn([env,] command, arguments, ...)  { |r, w, pid| ... }
 *   PTY.spawn([env,] command, arguments, ...)  => [r, w, pid]
 *
 * Spawns the specified command on a newly allocated pty. You can also use the
 * alias ::getpty.
 *
 * The command's controlling tty is set to the slave device of the pty
 * and its standard input/output/error is redirected to the slave device.
 *
 * +env+ is an optional hash that provides additional environment variables to the spawned pty.
 *
 *   # sets FOO to "bar"
 *   PTY.spawn({"FOO"=>"bar"}, "printenv", "FOO") do |r, w, pid|
 *     p r.read #=> "bar\r\n"
 *   ensure
 *     r.close; w.close; Process.wait(pid)
 *   end
 *   # unsets FOO
 *   PTY.spawn({"FOO"=>nil}, "printenv", "FOO") do |r, w, pid|
 *     p r.read #=> ""
 *   ensure
 *     r.close; w.close; Process.wait(pid)
 *   end
 *
 * +command+ and +command_line+ are the full commands to run, given a String.
 * Any additional +arguments+ will be passed to the command.
 *
 * === Return values
 *
 * In the non-block form this returns an array of size three,
 * <tt>[r, w, pid]</tt>.
 *
 * In the block form these same values will be yielded to the block:
 *
 * +r+:: A readable IO that contains the command's
 *       standard output and standard error
 * +w+:: A writable IO that is the command's standard input
 * +pid+:: The process identifier for the command.
 *
 * === Clean up
 *
 * This method does not clean up like closing IOs or waiting for child
 * process, except that the process is detached in the block form to
 * prevent it from becoming a zombie (see Process.detach).  Any other
 * cleanup is the responsibility of the caller.  If waiting for +pid+,
 * be sure to close both +r+ and +w+ before doing so; doing it in the
 * reverse order may cause deadlock on some OSes.
 */
static VALUE
pty_getpty(int argc, VALUE *argv, VALUE self)
{
    VALUE res;
    struct pty_info info;
    char SlaveName[DEVICELEN];

    establishShell(argc, argv, &info, SlaveName);

    VALUE pty_path = rb_obj_freeze(rb_str_new_cstr(SlaveName));
    VALUE rport = rb_io_open_descriptor(
        rb_cFile, info.fd, FMODE_READABLE, pty_path, RUBY_IO_TIMEOUT_DEFAULT, NULL
    );

    int wpty_fd = rb_cloexec_dup(info.fd);
    if (wpty_fd == -1) {
        rb_sys_fail("dup()");
    }
    VALUE wport = rb_io_open_descriptor(
        rb_cFile, wpty_fd, FMODE_WRITABLE | FMODE_TRUNC | FMODE_CREATE | FMODE_SYNC,
        pty_path, RUBY_IO_TIMEOUT_DEFAULT, NULL
    );

    res = rb_ary_new2(3);
    rb_ary_store(res, 0, rport);
    rb_ary_store(res, 1, wport);
    rb_ary_store(res,2,PIDT2NUM(info.child_pid));

    if (rb_block_given_p()) {
        rb_ensure(rb_yield, res, pty_detach_process, (VALUE)&info);
        return Qnil;
    }
    return res;
}

NORETURN(static void raise_from_check(rb_pid_t pid, int status));
static void
raise_from_check(rb_pid_t pid, int status)
{
    const char *state;
    VALUE msg;
    VALUE exc;

#if defined(WIFSTOPPED)
#elif defined(IF_STOPPED)
#define WIFSTOPPED(status) IF_STOPPED(status)
#else
---->> Either IF_STOPPED or WIFSTOPPED is needed <<----
#endif /* WIFSTOPPED | IF_STOPPED */
    if (WIFSTOPPED(status)) { /* suspend */
        state = "stopped";
    }
    else if (kill(pid, 0) == 0) {
        state = "changed";
    }
    else {
        state = "exited";
    }
    msg = rb_sprintf("pty - %s: %ld", state, (long)pid);
    exc = rb_exc_new_str(eChildExited, msg);
    rb_iv_set(exc, "status", rb_last_status_get());
    rb_exc_raise(exc);
}

/*
 * call-seq:
 *   PTY.check(pid, raise = false) => Process::Status or nil
 *   PTY.check(pid, true)          => nil or raises PTY::ChildExited
 *
 * Checks the status of the child process specified by +pid+.
 * Returns +nil+ if the process is still alive.
 *
 * If the process is not alive, and +raise+ was true, a PTY::ChildExited
 * exception will be raised. Otherwise it will return a Process::Status
 * instance.
 *
 * +pid+:: The process id of the process to check
 * +raise+:: If +true+ and the process identified by +pid+ is no longer
 *           alive a PTY::ChildExited is raised.
 *
 */
static VALUE
pty_check(int argc, VALUE *argv, VALUE self)
{
    VALUE pid, exc;
    rb_pid_t cpid;
    int status;
    const int flag =
#ifdef WNOHANG
        WNOHANG|
#endif
#ifdef WUNTRACED
        WUNTRACED|
#endif
        0;

    rb_scan_args(argc, argv, "11", &pid, &exc);
    cpid = rb_waitpid(NUM2PIDT(pid), &status, flag);
    if (cpid == -1 || cpid == 0) return Qnil;

    if (!RTEST(exc)) return rb_last_status_get();
    raise_from_check(cpid, status);

    UNREACHABLE_RETURN(Qnil);
}

static VALUE cPTY;

/*
 * Document-class: PTY::ChildExited
 *
 * Thrown when PTY::check is called for a pid that represents a process that
 * has exited.
 */

/*
 * Document-class: PTY
 *
 * Creates and manages pseudo terminals (PTYs).  See also
 * https://en.wikipedia.org/wiki/Pseudo_terminal
 *
 * PTY allows you to allocate new terminals using ::open or ::spawn a new
 * terminal with a specific command.
 *
 * == Example
 *
 * In this example we will change the buffering type in the +factor+ command,
 * assuming that factor uses stdio for stdout buffering.
 *
 * If IO.pipe is used instead of PTY.open, this code deadlocks because factor's
 * stdout is fully buffered.
 *
 *   # start by requiring the standard library PTY
 *   require 'pty'
 *
 *   master, slave = PTY.open
 *   read, write = IO.pipe
 *   pid = spawn("factor", :in=>read, :out=>slave)
 *   read.close	    # we dont need the read
 *   slave.close    # or the slave
 *
 *   # pipe "42" to the factor command
 *   write.puts "42"
 *   # output the response from factor
 *   p master.gets #=> "42: 2 3 7\n"
 *
 *   # pipe "144" to factor and print out the response
 *   write.puts "144"
 *   p master.gets #=> "144: 2 2 2 2 3 3\n"
 *   write.close # close the pipe
 *
 *   # The result of read operation when pty slave is closed is platform
 *   # dependent.
 *   ret = begin
 *           master.gets     # FreeBSD returns nil.
 *         rescue Errno::EIO # GNU/Linux raises EIO.
 *           nil
 *         end
 *   p ret #=> nil
 *
 * == License
 *
 * (c) Copyright 1998 by Akinori Ito.
 *
 * This software may be redistributed freely for this purpose, in full
 * or in part, provided that this entire copyright notice is included
 * on any copies of this software and applications and derivations thereof.
 *
 * This software is provided on an "as is" basis, without warranty of any
 * kind, either expressed or implied, as to any matter including, but not
 * limited to warranty of fitness of purpose, or merchantability, or
 * results obtained from use of this software.
 */

void
Init_pty(void)
{
    cPTY = rb_define_module("PTY");
#if 1
    rb_define_module_function(cPTY,"get""pty",pty_getpty,-1);
#else  /* for RDoc */
    /* show getpty as an alias of spawn */
    VALUE sPTY = rb_singleton_class(cPTY);
    rb_define_alias(sPTY, "getpty", "spawn");
#endif
    rb_define_module_function(cPTY,"spawn",pty_getpty,-1);
    rb_define_singleton_method(cPTY,"check",pty_check,-1);
    rb_define_singleton_method(cPTY,"open",pty_open,0);

    eChildExited = rb_define_class_under(cPTY,"ChildExited",rb_eRuntimeError);
    rb_define_method(eChildExited,"status",echild_status,0);
}
