sdiff.c

制作2.6内核的CLFS时 使用的diffutils-2.8.7.tar.gz包

	int i;

	for (i = 0;  diffargv[i];  i++)
	  cmdsize += quote_system_arg (0, diffargv[i]) + 1;
	command = p = xmalloc (cmdsize);
	for (i = 0;  diffargv[i];  i++)
	  {
	    p += quote_system_arg (p, diffargv[i]);
	    *p++ = ' ';
	  }
	p[-1] = 0;
	errno = 0;
	diffout = popen (command, "r");
	if (! diffout)
	  perror_fatal (command);
	free (command);
      }
#else
      {
	int diff_fds[2];
# if HAVE_WORKING_VFORK
	sigset_t procmask;
	sigset_t blocked;
# endif

	if (pipe (diff_fds) != 0)
	  perror_fatal ("pipe");

# if HAVE_WORKING_VFORK
	/* Block SIGINT and SIGPIPE.  */
	sigemptyset (&blocked);
	sigaddset (&blocked, SIGINT);
	sigaddset (&blocked, SIGPIPE);
	sigprocmask (SIG_BLOCK, &blocked, &procmask);
# endif
	diffpid = vfork ();
	if (diffpid < 0)
	  perror_fatal ("fork");
	if (! diffpid)
	  {
	    /* Alter the child's SIGINT and SIGPIPE handlers;
	       this may munge the parent.
	       The child ignores SIGINT in case the user interrupts the editor.
	       The child does not ignore SIGPIPE, even if the parent does.  */
	    if (initial_handler (handler_index_of_SIGINT) != SIG_IGN)
	      signal_handler (SIGINT, SIG_IGN);
	    signal_handler (SIGPIPE, SIG_DFL);
# if HAVE_WORKING_VFORK
	    /* Stop blocking SIGINT and SIGPIPE in the child.  */
	    sigprocmask (SIG_SETMASK, &procmask, 0);
# endif
	    close (diff_fds[0]);
	    if (diff_fds[1] != STDOUT_FILENO)
	      {
		dup2 (diff_fds[1], STDOUT_FILENO);
		close (diff_fds[1]);
	      }

	    execvp (diffargv[0], (char **) diffargv);
	    _exit (errno == ENOENT ? 127 : 126);
	  }

# if HAVE_WORKING_VFORK
	/* Restore the parent's SIGINT and SIGPIPE behavior.  */
	if (initial_handler (handler_index_of_SIGINT) != SIG_IGN)
	  signal_handler (SIGINT, catchsig);
	if (initial_handler (handler_index_of_SIGPIPE) != SIG_IGN)
	  signal_handler (SIGPIPE, catchsig);
	else
	  signal_handler (SIGPIPE, SIG_IGN);

	/* Stop blocking SIGINT and SIGPIPE in the parent.  */
	sigprocmask (SIG_SETMASK, &procmask, 0);
# endif

	close (diff_fds[1]);
	diffout = fdopen (diff_fds[0], "r");
	if (! diffout)
	  perror_fatal ("fdopen");
      }
#endif

      lf_init (&diff_filt, diffout);
      lf_init (&lfilt, left);
      lf_init (&rfilt, right);

      interact_ok = interact (&diff_filt, &lfilt, lname, &rfilt, rname, out);

      ck_fclose (left);
      ck_fclose (right);
      ck_fclose (out);

      {
	int wstatus;
	int werrno = 0;

#if ! (HAVE_WORKING_FORK || HAVE_WORKING_VFORK)
	wstatus = pclose (diffout);
	if (wstatus == -1)
	  werrno = errno;
#else
	ck_fclose (diffout);
	while (waitpid (diffpid, &wstatus, 0) < 0)
	  if (errno == EINTR)
	    checksigs ();
	  else
	    perror_fatal ("waitpid");
	diffpid = 0;
#endif

	if (tmpname)
	  {
	    unlink (tmpname);
	    tmpname = 0;
	  }

	if (! interact_ok)
	  exiterr ();

	check_child_status (werrno, wstatus, EXIT_FAILURE, diffargv[0]);
	untrapsig (0);
	checksigs ();
	exit (WEXITSTATUS (wstatus));
      }
    }
  return EXIT_SUCCESS;			/* Fool `-Wall'.  */
}

static void
diffarg (char const *a)
{
  static size_t diffargs, diffarglim;

  if (diffargs == diffarglim)
    {
      if (! diffarglim)
	diffarglim = 16;
      else if (PTRDIFF_MAX / (2 * sizeof *diffargv) <= diffarglim)
	xalloc_die ();
      else
	diffarglim *= 2;
      diffargv = xrealloc (diffargv, diffarglim * sizeof *diffargv);
    }
  diffargv[diffargs++] = a;
}

/* Signal handling */

static bool volatile ignore_SIGINT;
static int volatile signal_received;
static bool sigs_trapped;

static void
catchsig (int s)
{
#if ! HAVE_SIGACTION
  signal (s, SIG_IGN);
#endif
  if (! (s == SIGINT && ignore_SIGINT))
    signal_received = s;
}

#if HAVE_SIGACTION
static struct sigaction catchaction;

static void
signal_handler (int sig, void (*handler) (int))
{
  catchaction.sa_handler = handler;
  sigaction (sig, &catchaction, 0);
}
#endif

static void
trapsigs (void)
{
  int i;

#if HAVE_SIGACTION
  catchaction.sa_flags = SA_RESTART;
  sigemptyset (&catchaction.sa_mask);
  for (i = 0;  i < NUM_SIGS;  i++)
    sigaddset (&catchaction.sa_mask, sigs[i]);
#endif

  for (i = 0;  i < NUM_SIGS;  i++)
    {
#if HAVE_SIGACTION
      sigaction (sigs[i], 0, &initial_action[i]);
#else
      initial_action[i] = signal (sigs[i], SIG_IGN);
#endif
      if (initial_handler (i) != SIG_IGN)
	signal_handler (sigs[i], catchsig);
    }

#ifdef SIGCHLD
  /* System V fork+wait does not work if SIGCHLD is ignored.  */
  signal (SIGCHLD, SIG_DFL);
#endif

  sigs_trapped = true;
}

/* Untrap signal S, or all trapped signals if S is zero.  */
static void
untrapsig (int s)
{
  int i;

  if (sigs_trapped)
    for (i = 0;  i < NUM_SIGS;  i++)
      if ((! s || sigs[i] == s)  &&  initial_handler (i) != SIG_IGN)
	{
#if HAVE_SIGACTION
	  sigaction (sigs[i], &initial_action[i], 0);
#else
	  signal (sigs[i], initial_action[i]);
#endif
	}
}

/* Exit if a signal has been received.  */
static void
checksigs (void)
{
  int s = signal_received;
  if (s)
    {
      cleanup (0);

      /* Yield an exit status indicating that a signal was received.  */
      untrapsig (s);
      kill (getpid (), s);

      /* That didn't work, so exit with error status.  */
      exit (EXIT_TROUBLE);
    }
}

static void
give_help (void)
{
  fprintf (stderr, "%s", _("\
ed:\tEdit then use both versions, each decorated with a header.\n\
eb:\tEdit then use both versions.\n\
el:\tEdit then use the left version.\n\
er:\tEdit then use the right version.\n\
e:\tEdit a new version.\n\
l:\tUse the left version.\n\
r:\tUse the right version.\n\
s:\tSilently include common lines.\n\
v:\tVerbosely include common lines.\n\
q:\tQuit.\n\
"));
}

static int
skip_white (void)
{
  int c;
  for (;;)
    {
      c = getchar ();
      if (! isspace (c) || c == '\n')
	break;
      checksigs ();
    }
  if (ferror (stdin))
    perror_fatal (_("read failed"));
  return c;
}

static void
flush_line (void)
{
  int c;
  while ((c = getchar ()) != '\n' && c != EOF)
    continue;
  if (ferror (stdin))
    perror_fatal (_("read failed"));
}


/* interpret an edit command */
static bool
edit (struct line_filter *left, char const *lname, lin lline, lin llen,
      struct line_filter *right, char const *rname, lin rline, lin rlen,
      FILE *outfile)
{
  for (;;)
    {
      int cmd0, cmd1;
      bool gotcmd = false;

      cmd1 = 0; /* Pacify `gcc -W'.  */

      while (! gotcmd)
	{
	  if (putchar ('%') != '%')
	    perror_fatal (_("write failed"));
	  ck_fflush (stdout);

	  cmd0 = skip_white ();
	  switch (cmd0)
	    {
	    case 'l': case 'r': case 's': case 'v': case 'q':
	      if (skip_white () != '\n')
		{
		  give_help ();
		  flush_line ();
		  continue;
		}
	      gotcmd = true;
	      break;

	    case 'e':
	      cmd1 = skip_white ();
	      switch (cmd1)
		{
		case 'b': case 'd': case 'l': case 'r':
		  if (skip_white () != '\n')
		    {
		      give_help ();
		      flush_line ();
		      continue;
		    }
		  gotcmd = true;
		  break;
		case '\n':
		  gotcmd = true;
		  break;
		default:
		  give_help ();
		  flush_line ();
		  continue;
		}
	      break;

	    case EOF:
	      if (feof (stdin))
		{
		  gotcmd = true;
		  cmd0 = 'q';
		  break;
		}
	      /* Fall through.  */
	    default:
	      flush_line ();
	      /* Fall through.  */
	    case '\n':
	      give_help ();
	      continue;
	    }
	}

      switch (cmd0)
	{
	case 'l':
	  lf_copy (left, llen, outfile);
	  lf_skip (right, rlen);
	  return true;
	case 'r':
	  lf_copy (right, rlen, outfile);
	  lf_skip (left, llen);
	  return true;
	case 's':
	  suppress_common_lines = true;
	  break;
	case 'v':
	  suppress_common_lines = false;
	  break;
	case 'q':
	  return false;
	case 'e':
	  {
	    int fd;

	    if (tmpname)
	      tmp = fopen (tmpname, "w");
	    else
	      {
		if ((fd = temporary_file ()) < 0)
		  perror_fatal ("mkstemp");
		tmp = fdopen (fd, "w");
	      }

	    if (! tmp)
	      perror_fatal (tmpname);

	    switch (cmd1)
	      {
	      case 'd':
		if (llen)
		  {
		    if (llen == 1)
		      fprintf (tmp, "--- %s %ld\n", lname, (long int) lline);
		    else
		      fprintf (tmp, "--- %s %ld,%ld\n", lname,
			       (long int) lline,
			       (long int) (lline + llen - 1));
		  }
		/* Fall through.  */
	      case 'b': case 'l':
		lf_copy (left, llen, tmp);
		break;

	      default:
		lf_skip (left, llen);
		break;
	      }

	    switch (cmd1)
	      {
	      case 'd':
		if (rlen)
		  {
		    if (rlen == 1)
		      fprintf (tmp, "+++ %s %ld\n", rname, (long int) rline);
		    else
		      fprintf (tmp, "+++ %s %ld,%ld\n", rname,
			       (long int) rline,
			       (long int) (rline + rlen - 1));
		  }
		/* Fall through.  */
	      case 'b': case 'r':
		lf_copy (right, rlen, tmp);
		break;

	      default:
		lf_skip (right, rlen);
		break;
	      }

	    ck_fclose (tmp);

	    {
	      int wstatus;
	      int werrno = 0;
	      ignore_SIGINT = true;
	      checksigs ();

	      {
#if ! (HAVE_WORKING_FORK || HAVE_WORKING_VFORK)
		char *command =
		  xmalloc (quote_system_arg (0, editor_program)
			   + 1 + strlen (tmpname) + 1);
		sprintf (command + quote_system_arg (command, editor_program),
			 " %s", tmpname);
		wstatus = system (command);
		if (wstatus == -1)
		  werrno = errno;
		free (command);
#else
		pid_t pid;

		pid = vfork ();
		if (pid == 0)
		  {
		    char const *argv[3];
		    int i = 0;

		    argv[i++] = editor_program;
		    argv[i++] = tmpname;
		    argv[i] = 0;

		    execvp (editor_program, (char **) argv);
		    _exit (errno == ENOENT ? 127 : 126);
		  }

		if (pid < 0)
		  perror_fatal ("fork");

		while (waitpid (pid, &wstatus, 0) < 0)
		  if (errno == EINTR)
		    checksigs ();
		  else
		    perror_fatal ("waitpid");
#endif
	      }

	      ignore_SIGINT = false;
	      check_child_status (werrno, wstatus, EXIT_SUCCESS,
				  editor_program);
	    }

	    {
	      char buf[SDIFF_BUFSIZE];
	      size_t size;
	      tmp = ck_fopen (tmpname, "r");
	      while ((size = ck_fread (buf, SDIFF_BUFSIZE, tmp)) != 0)
		{
		  checksigs ();
		  ck_fwrite (buf, size, outfile);
		}
	      ck_fclose (tmp);
	    }
	    return true;
	  }
	default:
	  give_help ();
	  break;
	}
    }
}

/* Alternately reveal bursts of diff output and handle user commands.  */
static bool
interact (struct line_filter *diff,
	  struct line_filter *left, char const *lname,
	  struct line_filter *right, char const *rname,
	  FILE *outfile)
{
  lin lline = 1, rline = 1;

  for (;;)
    {
      char diff_help[256];
      int snarfed = lf_snarf (diff, diff_help, sizeof diff_help);

      if (snarfed <= 0)
	return snarfed != 0;

      checksigs ();

      if (diff_help[0] == ' ')
	puts (diff_help + 1);
      else
	{
	  char *numend;
	  uintmax_t val;
	  lin llen, rlen, lenmax;
	  errno = 0;
	  llen = val = strtoumax (diff_help + 1, &numend, 10);
	  if (llen < 0 || llen != val || errno || *numend != ',')
	    fatal (diff_help);
	  rlen = val = strtoumax (numend + 1, &numend, 10);
	  if (rlen < 0 || rlen != val || errno || *numend)
	    fatal (diff_help);

	  lenmax = MAX (llen, rlen);

	  switch (diff_help[0])
	    {
	    case 'i':
	      if (suppress_common_lines)
		lf_skip (diff, lenmax);
	      else
		lf_copy (diff, lenmax, stdout);

	      lf_copy (left, llen, outfile);
	      lf_skip (right, rlen);
	      break;

	    case 'c':
	      lf_copy (diff, lenmax, stdout);
	      if (! edit (left, lname, lline, llen,
			  right, rname, rline, rlen,
			  outfile))
		return false;
	      break;

	    default:
	      fatal (diff_help);
	    }

	  lline += llen;
	  rline += rlen;
	}
    }
}

/* Return true if DIR is an existing directory.  */
static bool
diraccess (char const *dir)
{
  struct stat buf;
  return stat (dir, &buf) == 0 && S_ISDIR (buf.st_mode);
}

#ifndef P_tmpdir
# define P_tmpdir "/tmp"
#endif
#ifndef TMPDIR_ENV
# define TMPDIR_ENV "TMPDIR"
#endif

/* Open a temporary file and return its file descriptor.  Put into
   tmpname the address of a newly allocated buffer that holds the
   file's name.  Use the prefix "sdiff".  */
static int
temporary_file (void)
{
  char const *tmpdir = getenv (TMPDIR_ENV);
  char const *dir = tmpdir ? tmpdir : P_tmpdir;
  char *buf = xmalloc (strlen (dir) + 1 + 5 + 6 + 1);
  int fd;
  int e;
  sigset_t procmask;
  sigset_t blocked;
  sprintf (buf, "%s/sdiffXXXXXX", dir);
  sigemptyset (&blocked);
  sigaddset (&blocked, SIGINT);
  sigprocmask (SIG_BLOCK, &blocked, &procmask);
  fd = mkstemp (buf);
  e = errno;
  if (0 <= fd)
    tmpname = buf;
  sigprocmask (SIG_SETMASK, &procmask, 0);
  errno = e;
  return fd;
}