path: root/contrib/patch/util.c

/* utility functions for `patch' */

/* $Id: util.c,v 1.24 1997/07/10 08:16:12 eggert Exp $ */

/*
Copyright 1986 Larry Wall
Copyright 1992, 1993, 1997 Free Software Foundation, Inc.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

This program 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; see the file COPYING.
If not, write to the Free Software Foundation,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

#define XTERN extern
#include <common.h>
#include <backupfile.h>
#include <quotearg.h>
#include <version.h>
#undef XTERN
#define XTERN
#include <util.h>

#include <maketime.h>
#include <partime.h>

#include <signal.h>
#if !defined SIGCHLD && defined SIGCLD
#define SIGCHLD SIGCLD
#endif
#if ! HAVE_RAISE
# define raise(sig) kill (getpid (), sig)
#endif

#ifdef __STDC__
# include <stdarg.h>
# define vararg_start va_start
#else
# define vararg_start(ap,p) va_start (ap)
# if HAVE_VARARGS_H
#  include <varargs.h>
# else
   typedef char *va_list;
#  define va_dcl int va_alist;
#  define va_start(ap) ((ap) = (va_list) &va_alist)
#  define va_arg(ap, t) (((t *) ((ap) += sizeof (t)))  [-1])
#  define va_end(ap)
# endif
#endif

static void makedirs PARAMS ((char *));

/* Move a file FROM to TO, renaming it if possible and copying it if necessary.
   If we must create TO, use MODE to create it.
   If FROM is null, remove TO (ignoring FROMSTAT).
   Back up TO if BACKUP is nonzero.  */

#ifdef __STDC__
/* If mode_t doesn't promote to itself, we can't use old-style definition.  */
void
move_file (char const *from, char *to, mode_t mode, int backup)
#else
void
move_file (from, to, mode, backup)
     char const *from;
     char *to;
     mode_t mode;
     int backup;
#endif
{
  struct stat to_st;
  int to_errno = ! backup ? -1 : stat (to, &to_st) == 0 ? 0 : errno;

  if (backup)
    {
      int try_makedirs_errno = 0;
      char *bakname;

      if (origprae || origbase)
	{
	  char const *p = origprae ? origprae : "";
	  char const *b = origbase ? origbase : "";
	  char const *o = base_name (to);
	  size_t plen = strlen (p);
	  size_t tlen = o - to;
	  size_t blen = strlen (b);
	  size_t osize = strlen (o) + 1;
	  bakname = xmalloc (plen + tlen + blen + osize);
	  memcpy (bakname, p, plen);
	  memcpy (bakname + plen, to, tlen);
	  memcpy (bakname + plen + tlen, b, blen);
	  memcpy (bakname + plen + tlen + blen, o, osize);
	  for (p += FILESYSTEM_PREFIX_LEN (p);  *p;  p++)
	    if (ISSLASH (*p))
	      {
		try_makedirs_errno = ENOENT;
		break;
	      }
	}
      else
	{
	  bakname = find_backup_file_name (to);
	  if (!bakname)
	    memory_fatal ();
	}

      if (to_errno)
	{
	  int fd;
	  if (debug & 4)
	    say ("creating empty unreadable file `%s'\n", bakname);
	  try_makedirs_errno = ENOENT;
	  unlink (bakname);
	  while ((fd = creat (bakname, 0)) < 0)
	    {
	      if (errno != try_makedirs_errno)
		pfatal ("can't create file `%s'", bakname);
	      makedirs (bakname);
	      try_makedirs_errno = 0;
	    }
	  if (close (fd) != 0)
	    pfatal ("can't close `%s'", bakname);
	}
      else
	{
	  if (debug & 4)
	    say ("renaming `%s' to `%s'\n", to, bakname);
	  while (rename (to, bakname) != 0)
	    {
	      if (errno != try_makedirs_errno)
		pfatal ("can't rename `%s' to `%s'", to, bakname);
	      makedirs (bakname);
	      try_makedirs_errno = 0;
	    }
	}

      free (bakname);
    }

  if (from)
    {
      if (debug & 4)
	say ("renaming `%s' to `%s'\n", from, to);

      if (rename (from, to) != 0)
	{
	  int to_dir_known_to_exist = 0;

	  if (errno == ENOENT
	      && (to_errno == -1 || to_errno == ENOENT))
	    {
	      makedirs (to);
	      to_dir_known_to_exist = 1;
	      if (rename (from, to) == 0)
		return;
	    }

	  if (errno == EXDEV)
	    {
	      if (! backup)
		{
		  if (unlink (to) == 0)
		    to_dir_known_to_exist = 1;
		  else if (errno != ENOENT)
		    pfatal ("can't remove `%s'", to);
		}
	      if (! to_dir_known_to_exist)
		makedirs (to);
	      copy_file (from, to, mode);
	      return;
	    }

	  pfatal ("can't rename `%s' to `%s'", from, to);
	}
    }
  else if (! backup)
    {
      if (debug & 4)
	say ("removing `%s'\n", to);
      if (unlink (to) != 0)
	pfatal ("can't remove `%s'", to);
    }
}

/* Create FILE with OPEN_FLAGS, and with MODE adjusted so that
   we can read and write the file and that the file is not executable.
   Return the file descriptor.  */
#ifdef __STDC__
/* If mode_t doesn't promote to itself, we can't use old-style definition.  */
int
create_file (char const *file, int open_flags, mode_t mode)
#else
int
create_file (file, open_flags, mode)
     char const *file;
     int open_flags;
     mode_t mode;
#endif
{
  int fd;
  mode |= S_IRUSR | S_IWUSR;
  mode &= ~ (S_IXUSR | S_IXGRP | S_IXOTH);
  if (! (O_CREAT && O_TRUNC))
    close (creat (file, mode));
  fd = open (file, O_CREAT | O_TRUNC | open_flags, mode);
  if (fd < 0)
    pfatal ("can't create `%s'", file);
  return fd;
}

/* Copy a file. */

#ifdef __STDC__
/* If mode_t doesn't promote to itself, we can't use old-style definition.  */
void
copy_file (char const *from, char const *to, mode_t mode)
#else
void
copy_file (from, to, mode)
     char const *from;
     char const *to;
     mode_t mode;
#endif
{
  int tofd;
  int fromfd;
  size_t i;

  if ((fromfd = open (from, O_RDONLY | O_BINARY)) < 0)
    pfatal ("can't reopen `%s'", from);
  tofd = create_file (to, O_WRONLY | O_BINARY, mode);
  while ((i = read (fromfd, buf, bufsize)) != 0)
    {
      if (i == -1)
	read_fatal ();
      if (write (tofd, buf, i) != i)
	write_fatal ();
    }
  if (close (fromfd) != 0)
    read_fatal ();
  if (close (tofd) != 0)
    write_fatal ();
}

static char const DEV_NULL[] = NULL_DEVICE;

static char const SCCSPREFIX[] = "s.";
static char const GET[] = "get ";
static char const GET_LOCKED[] = "get -e ";
static char const SCCSDIFF1[] = "get -p ";
static char const SCCSDIFF2[] = "|diff - %s";

static char const RCSSUFFIX[] = ",v";
static char const CHECKOUT[] = "co %s";
static char const CHECKOUT_LOCKED[] = "co -l %s";
static char const RCSDIFF1[] = "rcsdiff %s";

/* Return "RCS" if FILENAME is controlled by RCS,
   "SCCS" if it is controlled by SCCS, and 0 otherwise.
   READONLY is nonzero if we desire only readonly access to FILENAME.
   FILESTAT describes FILENAME's status or is 0 if FILENAME does not exist.
   If successful and if GETBUF is nonzero, set *GETBUF to a command
   that gets the file; similarly for DIFFBUF and a command to diff the file.
   *GETBUF and *DIFFBUF must be freed by the caller.  */
char const *
version_controller (filename, readonly, filestat, getbuf, diffbuf)
     char const *filename;
     int readonly;
     struct stat const *filestat;
     char **getbuf;
     char **diffbuf;
{
  struct stat cstat;
  char const *filebase = base_name (filename);
  char const *dotslash = *filename == '-' ? "./" : "";
  size_t dir_len = filebase - filename;
  size_t filenamelen = strlen (filename);
  size_t maxfixlen = sizeof "SCCS/" - 1 + sizeof SCCSPREFIX - 1;
  size_t maxtrysize = filenamelen + maxfixlen + 1;
  size_t quotelen = quote_system_arg (0, filename);
  size_t maxgetsize = sizeof GET_LOCKED + quotelen + maxfixlen;
  size_t maxdiffsize =
    (sizeof SCCSDIFF1 + sizeof SCCSDIFF2 + sizeof DEV_NULL - 1
     + 2 * quotelen + maxfixlen);
  char *trybuf = xmalloc (maxtrysize);
  char const *r = 0;

  strcpy (trybuf, filename);

#define try1(f,a1)    (sprintf (trybuf + dir_len, f, a1),    stat (trybuf, &cstat) == 0)
#define try2(f,a1,a2) (sprintf (trybuf + dir_len, f, a1,a2), stat (trybuf, &cstat) == 0)

  /* Check that RCS file is not working file.
     Some hosts don't report file name length errors.  */

  if ((try2 ("RCS/%s%s", filebase, RCSSUFFIX)
       || try1 ("RCS/%s", filebase)
       || try2 ("%s%s", filebase, RCSSUFFIX))
      && ! (filestat
	    && filestat->st_dev == cstat.st_dev
	    && filestat->st_ino == cstat.st_ino))
    {
      if (getbuf)
	{
	  char *p = *getbuf = xmalloc (maxgetsize);
	  sprintf (p, readonly ? CHECKOUT : CHECKOUT_LOCKED, dotslash);
	  p += strlen (p);
	  p += quote_system_arg (p, filename);
	  *p = '\0';
	}

      if (diffbuf)
	{
	  char *p = *diffbuf = xmalloc (maxdiffsize);
	  sprintf (p, RCSDIFF1, dotslash);
	  p += strlen (p);
	  p += quote_system_arg (p, filename);
	  *p++ = '>';
	  strcpy (p, DEV_NULL);
	}

      r = "RCS";
    }
  else if (try2 ("SCCS/%s%s", SCCSPREFIX, filebase)
	   || try2 ("%s%s", SCCSPREFIX, filebase))
    {
      if (getbuf)
	{
	  char *p = *getbuf = xmalloc (maxgetsize);
	  sprintf (p, readonly ? GET : GET_LOCKED);
	  p += strlen (p);
	  p += quote_system_arg (p, trybuf);
	  *p = '\0';
	}

      if (diffbuf)
	{
	  char *p = *diffbuf = xmalloc (maxdiffsize);
	  strcpy (p, SCCSDIFF1);
	  p += sizeof SCCSDIFF1 - 1;
	  p += quote_system_arg (p, trybuf);
	  sprintf (p, SCCSDIFF2, dotslash);
	  p += strlen (p);
	  p += quote_system_arg (p, filename);
	  *p++ = '>';
	  strcpy (p, DEV_NULL);
	}

      r = "SCCS";
    }

  free (trybuf);
  return r;
}

/* Get FILENAME from version control system CS.  The file already exists if
   EXISTS is nonzero.  Only readonly access is needed if READONLY is nonzero.
   Use the command GETBUF to actually get the named file.
   Store the resulting file status into *FILESTAT.
   Return nonzero if successful.  */
int
version_get (filename, cs, exists, readonly, getbuf, filestat)
     char const *filename;
     char const *cs;
     int exists;
     int readonly;
     char const *getbuf;
     struct stat *filestat;
{
  if (patch_get < 0)
    {
      ask ("Get file `%s' from %s%s? [y] ", filename,
	   cs, readonly ? "" : " with lock");
      if (*buf == 'n')
	return 0;
    }

  if (dry_run)
    {
      if (! exists)
	fatal ("can't do dry run on nonexistent version-controlled file `%s'; invoke `%s' and try again",
	       filename, getbuf);
    }
  else
    {
      if (verbosity == VERBOSE)
	say ("Getting file `%s' from %s%s...\n", filename,
	     cs, readonly ? "" : " with lock");
      if (systemic (getbuf) != 0)
	fatal ("can't get file `%s' from %s", filename, cs);
      if (stat (filename, filestat) != 0)
	pfatal ("%s", filename);
    }
  
  return 1;
}

/* Allocate a unique area for a string. */

char *
savebuf (s, size)
     register char const *s;
     register size_t size;
{
  register char *rv;

  assert (s && size);
  rv = malloc (size);

  if (! rv)
    {
      if (! using_plan_a)
	memory_fatal ();
    }
  else
    memcpy (rv, s, size);

  return rv;
}

char *
savestr(s)
     char const *s;
{
  return savebuf (s, strlen (s) + 1);
}

void
remove_prefix (p, prefixlen)
     char *p;
     size_t prefixlen;
{
  char const *s = p + prefixlen;
  while ((*p++ = *s++))
    continue;
}

#if !HAVE_VPRINTF
#define vfprintf my_vfprintf
static int vfprintf PARAMS ((FILE *, char const *, va_list));
static int
vfprintf (stream, format, args)
     FILE *stream;
     char const *format;
     va_list args;
{
#if !HAVE_DOPRNT && HAVE__DOPRINTF
# define _doprnt _doprintf
#endif
#if HAVE_DOPRNT || HAVE__DOPRINTF
  _doprnt (format, args, stream);
  return ferror (stream) ? -1 : 0;
#else
  int *a = (int *) args;
  return fprintf (stream, format,
		  a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9]);
#endif
}
#endif /* !HAVE_VPRINTF */

/* Terminal output, pun intended. */

#ifdef __STDC__
void
fatal (char const *format, ...)
#else
/*VARARGS1*/ void
fatal (format, va_alist)
     char const *format;
     va_dcl
#endif
{
  va_list args;
  fprintf (stderr, "%s: **** ", program_name);
  vararg_start (args, format);
  vfprintf (stderr, format, args);
  va_end (args);
  putc ('\n', stderr);
  fflush (stderr);
  fatal_exit (0);
}

void
memory_fatal ()
{
  fatal ("out of memory");
}

void
read_fatal ()
{
  pfatal ("read error");
}

void
write_fatal ()
{
  pfatal ("write error");
}

/* Say something from patch, something from the system, then silence . . . */

#ifdef __STDC__
void
pfatal (char const *format, ...)
#else
/*VARARGS1*/ void
pfatal (format, va_alist)
     char const *format;
     va_dcl
#endif
{
  int errnum = errno;
  va_list args;
  fprintf (stderr, "%s: **** ", program_name);
  vararg_start (args, format);
  vfprintf (stderr, format, args);
  va_end (args);
  fflush (stderr); /* perror bypasses stdio on some hosts.  */
  errno = errnum;
  perror (" ");
  fflush (stderr);
  fatal_exit (0);
}

/* Tell the user something.  */

#ifdef __STDC__
void
say (char const *format, ...)
#else
/*VARARGS1*/ void
say (format, va_alist)
     char const *format;
     va_dcl
#endif
{
  va_list args;
  vararg_start (args, format);
  vfprintf (stdout, format, args);
  va_end (args);
  fflush (stdout);
}

/* Get a response from the user, somehow or other. */

#ifdef __STDC__
void
ask (char const *format, ...)
#else
/*VARARGS1*/ void
ask (format, va_alist)
     char const *format;
     va_dcl
#endif
{
  static int ttyfd = -2;
  int r;
  va_list args;

  vararg_start (args, format);
  vfprintf (stdout, format, args);
  va_end (args);
  fflush (stdout);

  if (ttyfd == -2)
    {
      /* If standard output is not a tty, don't bother opening /dev/tty,
	 since it's unlikely that stdout will be seen by the tty user.
	 The isatty test also works around a bug in GNU Emacs 19.34 under Linux
	 which makes a call-process `patch' hang when it reads from /dev/tty.
	 POSIX.2 requires that we read /dev/tty, though.  */
      ttyfd = (posixly_correct || isatty (STDOUT_FILENO)
	       ? open (TTY_DEVICE, O_RDONLY)
	       : -1);
    }

  if (ttyfd < 0)
    {
      /* No terminal at all -- default it.  */
      printf ("\n");
      buf[0] = '\n';
      buf[1] = '\0';
    }
  else
    {
      size_t s = 0;
      while ((r = read (ttyfd, buf + s, bufsize - 1 - s)) == bufsize - 1 - s
	     && buf[bufsize - 2] != '\n')
	{
	  s = bufsize - 1;
	  bufsize *= 2;
	  buf = realloc (buf, bufsize);
	  if (!buf)
	    memory_fatal ();
	}
      if (r == 0)
	printf ("EOF\n");
      else if (r < 0)
	{
	  perror ("tty read");
	  fflush (stderr);
	  close (ttyfd);
	  ttyfd = -1;
	  r = 0;
	}
      buf[s + r] = '\0';
    }
}

/* Return nonzero if it OK to reverse a patch.  */

#ifdef __STDC__
int
ok_to_reverse (char const *format, ...)
#else
ok_to_reverse (format, va_alist)
     char const *format;
     va_dcl
#endif
{
  int r = 0;

  if (noreverse || ! (force && verbosity == SILENT))
    {
      va_list args;
      vararg_start (args, format);
      vfprintf (stdout, format, args);
      va_end (args);
    }

  if (noreverse)
    {
      printf ("  Skipping patch.\n");
      skip_rest_of_patch = TRUE;
      r = 0;
    }
  else if (force)
    {
      if (verbosity != SILENT)
	printf ("  Applying it anyway.\n");
      r = 0;
    }
  else if (batch)
    {
      say (reverse ? "  Ignoring -R.\n" : "  Assuming -R.\n");
      r = 1;
    }
  else
    {
      ask (reverse ? "  Ignore -R? [n] " : "  Assume -R? [n] ");
      r = *buf == 'y';
      if (! r)
	{
	  ask ("Apply anyway? [n] ");
	  if (*buf != 'y')
	    {
	      if (verbosity != SILENT)
		say ("Skipping patch.\n");
	      skip_rest_of_patch = TRUE;
	    }
	}
    }

  return r;
}

/* How to handle certain events when not in a critical region. */

#define NUM_SIGS (sizeof (sigs) / sizeof (*sigs))
static int const sigs[] = {
#ifdef SIGHUP
       SIGHUP,
#endif
#ifdef SIGPIPE
       SIGPIPE,
#endif
#ifdef SIGTERM
       SIGTERM,
#endif
#ifdef SIGXCPU
       SIGXCPU,
#endif
#ifdef SIGXFSZ
       SIGXFSZ,
#endif
       SIGINT
};

#if !HAVE_SIGPROCMASK
#define sigset_t int
#define sigemptyset(s) (*(s) = 0)
#ifndef sigmask
#define sigmask(sig) (1 << ((sig) - 1))
#endif
#define sigaddset(s, sig) (*(s) |= sigmask (sig))
#define sigismember(s, sig) ((*(s) & sigmask (sig)) != 0)
#ifndef SIG_BLOCK
#define SIG_BLOCK 0
#endif
#ifndef SIG_UNBLOCK
#define SIG_UNBLOCK (SIG_BLOCK + 1)
#endif
#ifndef SIG_SETMASK
#define SIG_SETMASK (SIG_BLOCK + 2)
#endif
#define sigprocmask(how, n, o) \
  ((how) == SIG_BLOCK \
   ? ((o) ? *(o) = sigblock (*(n)) : sigblock (*(n))) \
   : (how) == SIG_UNBLOCK \
   ? sigsetmask (((o) ? *(o) = sigblock (0) : sigblock (0)) & ~*(n)) \
   : (o ? *(o) = sigsetmask (*(n)) : sigsetmask (*(n))))
#if !HAVE_SIGSETMASK
#define sigblock(mask) 0
#define sigsetmask(mask) 0
#endif
#endif

static sigset_t initial_signal_mask;
static sigset_t signals_to_block;

#if ! HAVE_SIGACTION
static RETSIGTYPE fatal_exit_handler PARAMS ((int)) __attribute__ ((noreturn));
static RETSIGTYPE
fatal_exit_handler (sig)
     int sig;
{
  signal (sig, SIG_IGN);
  fatal_exit (sig);
}
#endif

void
set_signals(reset)
int reset;
{
  int i;
#if HAVE_SIGACTION
  struct sigaction initial_act, fatal_act;
  fatal_act.sa_handler = fatal_exit;
  sigemptyset (&fatal_act.sa_mask);
  fatal_act.sa_flags = 0;
#define setup_handler(sig) sigaction (sig, &fatal_act, (struct sigaction *) 0)
#else
#define setup_handler(sig) signal (sig, fatal_exit_handler)
#endif

  if (!reset)
    {
#ifdef SIGCHLD
      /* System V fork+wait does not work if SIGCHLD is ignored.  */
      signal (SIGCHLD, SIG_DFL);
#endif
      sigemptyset (&signals_to_block);
      for (i = 0;  i < NUM_SIGS;  i++)
	{
	  int ignoring_signal;
#if HAVE_SIGACTION
	  if (sigaction (sigs[i], (struct sigaction *) 0, &initial_act) != 0)
	    continue;
	  ignoring_signal = initial_act.sa_handler == SIG_IGN;
#else
	  ignoring_signal = signal (sigs[i], SIG_IGN) == SIG_IGN;
#endif
	  if (! ignoring_signal)
	    {
	      sigaddset (&signals_to_block, sigs[i]);
	      setup_handler (sigs[i]);
	    }
	}
    }
  else
    {
      /* Undo the effect of ignore_signals.  */
#if HAVE_SIGPROCMASK || HAVE_SIGSETMASK
      sigprocmask (SIG_SETMASK, &initial_signal_mask, (sigset_t *) 0);
#else
      for (i = 0;  i < NUM_SIGS;  i++)
	if (sigismember (&signals_to_block, sigs[i]))
	  setup_handler (sigs[i]);
#endif
    }
}

/* How to handle certain events when in a critical region. */

void
ignore_signals()
{
#if HAVE_SIGPROCMASK || HAVE_SIGSETMASK
  sigprocmask (SIG_BLOCK, &signals_to_block, &initial_signal_mask);
#else
  int i;
  for (i = 0;  i < NUM_SIGS;  i++)
    if (sigismember (&signals_to_block, sigs[i]))
      signal (sigs[i], SIG_IGN);
#endif
}

void
exit_with_signal (sig)
     int sig;
{
  sigset_t s;
  signal (sig, SIG_DFL);
  sigemptyset (&s);
  sigaddset (&s, sig);
  sigprocmask (SIG_UNBLOCK, &s, (sigset_t *) 0);
  raise (sig);
  exit (2);
}

int
systemic (command)
     char const *command;
{
  if (debug & 8)
    say ("+ %s\n", command);
  fflush (stdout);
  return system (command);
}

#if !HAVE_MKDIR
/* These mkdir and rmdir substitutes are good enough for `patch';
   they are not general emulators.  */

static int doprogram PARAMS ((char const *, char const *));
static int mkdir PARAMS ((char const *, mode_t));
static int rmdir PARAMS ((char const *));

static int
doprogram (program, arg)
     char const *program;
     char const *arg;
{
  int result;
  static char const DISCARD_OUTPUT[] = " 2>/dev/null";
  size_t program_len = strlen (program);
  char *cmd = xmalloc (program_len + 1 + quote_system_arg (0, arg)
		       + sizeof DISCARD_OUTPUT);
  char *p = cmd;
  strcpy (p, program);
  p += program_len;
  *p++ = ' ';
  p += quote_system_arg (p, arg);
  strcpy (p, DISCARD_OUTPUT);
  result = systemic (cmd);
  free (cmd);
  return result;
}

#ifdef __STDC__
/* If mode_t doesn't promote to itself, we can't use old-style definition.  */
static int
mkdir (char const *path, mode_t mode)
#else
static int
mkdir (path, mode)
     char const *path;
     mode_t mode; /* ignored */
#endif
{
  return doprogram ("mkdir", path);
}

static int
rmdir (path)
     char const *path;
{
  int result = doprogram ("rmdir", path);
  errno = EEXIST;
  return result;
}
#endif

/* Replace '/' with '\0' in FILENAME if it marks a place that
   needs testing for the existence of directory.  Return the address
   of the last location replaced, or 0 if none were replaced.  */
static char *replace_slashes PARAMS ((char *));
static char *
replace_slashes (filename)
     char *filename;
{
  char *f;
  char *last_location_replaced = 0;
  char const *component_start;

  for (f = filename + FILESYSTEM_PREFIX_LEN (filename);  ISSLASH (*f);  f++)
    continue;

  component_start = f;

  for (; *f; f++)
    if (ISSLASH (*f))
      {
	char *slash = f;

	/* Treat multiple slashes as if they were one slash.  */
	while (ISSLASH (f[1]))
	  f++;

	/* Ignore slashes at the end of the path.  */
	if (! f[1])
	  break;

	/* "." and ".." need not be tested.  */
	if (! (slash - component_start <= 2
	       && component_start[0] == '.' && slash[-1] == '.'))
	  {
	    *slash = '\0';
	    last_location_replaced = slash;
	  }

	component_start = f + 1;
      }

  return last_location_replaced;
}

/* Make sure we'll have the directories to create a file.
   Ignore the last element of `filename'.  */

static void
makedirs (filename)
     register char *filename;
{
  register char *f;
  register char *flim = replace_slashes (filename);

  if (flim)
    {
      /* Create any missing directories, replacing NULs by '/'s.
	 Ignore errors.  We may have to keep going even after an EEXIST,
	 since the path may contain ".."s; and when there is an EEXIST
	 failure the system may return some other error number.
	 Any problems will eventually be reported when we create the file.  */
      for (f = filename;  f <= flim;  f++)
	if (!*f)
	  {
	    mkdir (filename,
		   S_IRUSR|S_IWUSR|S_IXUSR
		   |S_IRGRP|S_IWGRP|S_IXGRP
		   |S_IROTH|S_IWOTH|S_IXOTH);
	    *f = '/';
	  }
    }
}

/* Remove empty ancestor directories of FILENAME.
   Ignore errors, since the path may contain ".."s, and when there
   is an EEXIST failure the system may return some other error number.  */
void
removedirs (filename)
     char *filename;
{
  size_t i;

  for (i = strlen (filename);  i != 0;  i--)
    if (ISSLASH (filename[i])
	&& ! (ISSLASH (filename[i - 1])
	      || (filename[i - 1] == '.'
		  && (i == 1
		      || ISSLASH (filename[i - 2])
		      || (filename[i - 2] == '.'
			  && (i == 2
			      || ISSLASH (filename[i - 3])))))))
      {
	filename[i] = '\0';
	if (rmdir (filename) == 0 && verbosity == VERBOSE)
	  say ("Removed empty directory `%s'.\n", filename);
	filename[i] = '/';
      }
}

static time_t initial_time;

void
init_time ()
{
  time (&initial_time);
}

/* Make filenames more reasonable. */

char *
fetchname (at, strip_leading, pstamp)
char *at;
int strip_leading;
time_t *pstamp;
{
    char *name;
    register char *t;
    int sleading = strip_leading;
    time_t stamp = (time_t) -1;

    while (ISSPACE ((unsigned char) *at))
	at++;
    if (debug & 128)
	say ("fetchname %s %d\n", at, strip_leading);

    name = at;
    /* Strip off up to `sleading' leading slashes and null terminate.  */
    for (t = at;  *t;  t++)
      {
	if (ISSLASH (*t))
	  {
	    while (ISSLASH (t[1]))
	      t++;
	    if (--sleading >= 0)
		name = t+1;
	  }
	else if (ISSPACE ((unsigned char) *t))
	  {
	    if (set_time | set_utc)
	      stamp = str2time (t, initial_time, set_utc ? 0L : TM_LOCAL_ZONE);
	    else
	      {
		/* The head says the file is nonexistent if the timestamp
		   is the epoch; but the listed time is local time, not UTC,
		   and POSIX.1 allows local time to be 24 hours away from UTC.
		   So match any time within 24 hours of the epoch.
		   Use a default time zone 24 hours behind UTC so that any
		   non-zoned time within 24 hours of the epoch is valid.  */
		stamp = str2time (t, initial_time, -24L * 60 * 60);
		if (0 <= stamp && stamp <= 2 * 24L * 60 * 60)
		  stamp = 0;
	      }

	    *t = '\0';
	    break;
	  }
      }

    if (!*name)
      return 0;

    /* Allow files to be created by diffing against /dev/null.  */
    if (strcmp (at, "/dev/null") == 0)
      {
	if (pstamp)
	  *pstamp = 0;
	return 0;
      }

    if (pstamp)
      *pstamp = stamp;

    return savestr (name);
}

GENERIC_OBJECT *
xmalloc (size)
     size_t size;
{
  register GENERIC_OBJECT *p = malloc (size);
  if (!p)
    memory_fatal ();
  return p;
}

void
Fseek (stream, offset, ptrname)
     FILE *stream;
     file_offset offset;
     int ptrname;
{
  if (file_seek (stream, offset, ptrname) != 0)
    pfatal ("fseek");
}