diff3.c

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

  else
    {
      D_LINEARRAY (result, FILE1) = 0;
      D_LENARRAY (result, FILE1) = 0;
    }

  numlines = D_NUMLINES (result, FILE2);
  if (numlines)
    {
      D_LINEARRAY (result, FILE2) = xcalloc (numlines, sizeof (char *));
      D_LENARRAY (result, FILE2) = xcalloc (numlines, sizeof (size_t));
    }
  else
    {
      D_LINEARRAY (result, FILE2) = 0;
      D_LENARRAY (result, FILE2) = 0;
    }

  /* Return */
  return result;
}

/* Compare two lists of lines of text.
   Return 1 if they are equivalent, 0 if not.  */

static bool
compare_line_list (char * const list1[], size_t const lengths1[],
		   char * const list2[], size_t const lengths2[],
		   lin nl)
{
  char * const *l1 = list1;
  char * const *l2 = list2;
  size_t const *lgths1 = lengths1;
  size_t const *lgths2 = lengths2;

  while (nl--)
    if (!*l1 || !*l2 || *lgths1 != *lgths2++
	|| memcmp (*l1++, *l2++, *lgths1++) != 0)
      return false;
  return true;
}

/* Input and parse two way diffs.  */

static struct diff_block *
process_diff (char const *filea,
	      char const *fileb,
	      struct diff_block **last_block)
{
  char *diff_contents;
  char *diff_limit;
  char *scan_diff;
  enum diff_type dt;
  lin i;
  struct diff_block *block_list, **block_list_end, *bptr;
  size_t too_many_lines = (PTRDIFF_MAX
			   / MIN (sizeof *bptr->lines[1],
				  sizeof *bptr->lengths[1]));

  diff_limit = read_diff (filea, fileb, &diff_contents);
  scan_diff = diff_contents;
  block_list_end = &block_list;
  bptr = 0; /* Pacify `gcc -W'.  */

  while (scan_diff < diff_limit)
    {
      bptr = xmalloc (sizeof *bptr);
      bptr->lines[0] = bptr->lines[1] = 0;
      bptr->lengths[0] = bptr->lengths[1] = 0;

      dt = process_diff_control (&scan_diff, bptr);
      if (dt == ERROR || *scan_diff != '\n')
	{
	  fprintf (stderr, _("%s: diff failed: "), program_name);
	  do
	    {
	      putc (*scan_diff, stderr);
	    }
	  while (*scan_diff++ != '\n');
	  exit (EXIT_TROUBLE);
	}
      scan_diff++;

      /* Force appropriate ranges to be null, if necessary */
      switch (dt)
	{
	case ADD:
	  bptr->ranges[0][0]++;
	  break;
	case DELETE:
	  bptr->ranges[1][0]++;
	  break;
	case CHANGE:
	  break;
	default:
	  fatal ("internal error: invalid diff type in process_diff");
	  break;
	}

      /* Allocate space for the pointers for the lines from filea, and
	 parcel them out among these pointers */
      if (dt != ADD)
	{
	  lin numlines = D_NUMLINES (bptr, 0);
	  if (too_many_lines <= numlines)
	    xalloc_die ();
	  bptr->lines[0] = xmalloc (numlines * sizeof *bptr->lines[0]);
	  bptr->lengths[0] = xmalloc (numlines * sizeof *bptr->lengths[0]);
	  for (i = 0; i < numlines; i++)
	    scan_diff = scan_diff_line (scan_diff,
					&(bptr->lines[0][i]),
					&(bptr->lengths[0][i]),
					diff_limit,
					'<');
	}

      /* Get past the separator for changes */
      if (dt == CHANGE)
	{
	  if (strncmp (scan_diff, "---\n", 4))
	    fatal ("invalid diff format; invalid change separator");
	  scan_diff += 4;
	}

      /* Allocate space for the pointers for the lines from fileb, and
	 parcel them out among these pointers */
      if (dt != DELETE)
	{
	  lin numlines = D_NUMLINES (bptr, 1);
	  if (too_many_lines <= numlines)
	    xalloc_die ();
	  bptr->lines[1] = xmalloc (numlines * sizeof *bptr->lines[1]);
	  bptr->lengths[1] = xmalloc (numlines * sizeof *bptr->lengths[1]);
	  for (i = 0; i < numlines; i++)
	    scan_diff = scan_diff_line (scan_diff,
					&(bptr->lines[1][i]),
					&(bptr->lengths[1][i]),
					diff_limit,
					'>');
	}

      /* Place this block on the blocklist.  */
      *block_list_end = bptr;
      block_list_end = &bptr->next;
    }

  *block_list_end = 0;
  *last_block = bptr;
  return block_list;
}

/* Skip tabs and spaces, and return the first character after them.  */

static char *
skipwhite (char *s)
{
  while (*s == ' ' || *s == '\t')
    s++;
  return s;
}

/* Read a nonnegative line number from S, returning the address of the
   first character after the line number, and storing the number into
   *PNUM.  Return 0 if S does not point to a valid line number.  */

static char *
readnum (char *s, lin *pnum)
{
  unsigned char c = *s;
  lin num = 0;

  if (! ISDIGIT (c))
    return 0;

  do
    {
      num = c - '0' + num * 10;
      c = *++s;
    }
  while (ISDIGIT (c));

  *pnum = num;
  return s;
}

/* Parse a normal format diff control string.  Return the type of the
   diff (ERROR if the format is bad).  All of the other important
   information is filled into to the structure pointed to by db, and
   the string pointer (whose location is passed to this routine) is
   updated to point beyond the end of the string parsed.  Note that
   only the ranges in the diff_block will be set by this routine.

   If some specific pair of numbers has been reduced to a single
   number, then both corresponding numbers in the diff block are set
   to that number.  In general these numbers are interpreted as ranges
   inclusive, unless being used by the ADD or DELETE commands.  It is
   assumed that these will be special cased in a superior routine.   */

static enum diff_type
process_diff_control (char **string, struct diff_block *db)
{
  char *s = *string;
  enum diff_type type;

  /* Read first set of digits */
  s = readnum (skipwhite (s), &db->ranges[0][RANGE_START]);
  if (! s)
    return ERROR;

  /* Was that the only digit? */
  s = skipwhite (s);
  if (*s == ',')
    {
      s = readnum (s + 1, &db->ranges[0][RANGE_END]);
      if (! s)
	return ERROR;
    }
  else
    db->ranges[0][RANGE_END] = db->ranges[0][RANGE_START];

  /* Get the letter */
  s = skipwhite (s);
  switch (*s)
    {
    case 'a':
      type = ADD;
      break;
    case 'c':
      type = CHANGE;
      break;
    case 'd':
      type = DELETE;
      break;
    default:
      return ERROR;			/* Bad format */
    }
  s++;				/* Past letter */

  /* Read second set of digits */
  s = readnum (skipwhite (s), &db->ranges[1][RANGE_START]);
  if (! s)
    return ERROR;

  /* Was that the only digit? */
  s = skipwhite (s);
  if (*s == ',')
    {
      s = readnum (s + 1, &db->ranges[1][RANGE_END]);
      if (! s)
	return ERROR;
      s = skipwhite (s);		/* To move to end */
    }
  else
    db->ranges[1][RANGE_END] = db->ranges[1][RANGE_START];

  *string = s;
  return type;
}

static char *
read_diff (char const *filea,
	   char const *fileb,
	   char **output_placement)
{
  char *diff_result;
  size_t current_chunk_size, total;
  int fd, wstatus, status;
  int werrno = 0;
  struct stat pipestat;

#if HAVE_WORKING_FORK || HAVE_WORKING_VFORK

  char const *argv[9];
  char const **ap;
  int fds[2];
  pid_t pid;

  ap = argv;
  *ap++ = diff_program;
  if (text)
    *ap++ = "-a";
  if (strip_trailing_cr)
    *ap++ = "--strip-trailing-cr";
  *ap++ = "--horizon-lines=100";
  *ap++ = "--";
  *ap++ = filea;
  *ap++ = fileb;
  *ap = 0;

  if (pipe (fds) != 0)
    perror_with_exit ("pipe");

  pid = vfork ();
  if (pid == 0)
    {
      /* Child */
      close (fds[0]);
      if (fds[1] != STDOUT_FILENO)
	{
	  dup2 (fds[1], STDOUT_FILENO);
	  close (fds[1]);
	}

      /* The cast to (char **) is needed for portability to older
	 hosts with a nonstandard prototype for execvp.  */
      execvp (diff_program, (char **) argv);

      _exit (errno == ENOENT ? 127 : 126);
    }

  if (pid == -1)
    perror_with_exit ("fork");

  close (fds[1]);		/* Prevent erroneous lack of EOF */
  fd = fds[0];

#else

  FILE *fpipe;
  char const args[] = " --horizon-lines=100 -- ";
  char *command = xmalloc (quote_system_arg (0, diff_program)
			   + sizeof "-a"
			   + sizeof "--strip-trailing-cr"
			   + sizeof args - 1
			   + quote_system_arg (0, filea) + 1
			   + quote_system_arg (0, fileb) + 1);
  char *p = command;
  p += quote_system_arg (p, diff_program);
  if (text)
    {
      strcpy (p, " -a");
      p += 3;
    }
  if (strip_trailing_cr)
    {
      strcpy (p, " --strip-trailing-cr");
      p += 20;
    }
  strcpy (p, args);
  p += sizeof args - 1;
  p += quote_system_arg (p, filea);
  *p++ = ' ';
  p += quote_system_arg (p, fileb);
  *p = 0;
  errno = 0;
  fpipe = popen (command, "r");
  if (!fpipe)
    perror_with_exit (command);
  free (command);
  fd = fileno (fpipe);

#endif

  if (fstat (fd, &pipestat) != 0)
    perror_with_exit ("fstat");
  current_chunk_size = MAX (1, STAT_BLOCKSIZE (pipestat));
  diff_result = xmalloc (current_chunk_size);
  total = 0;

  for (;;)
    {
      size_t bytes_to_read = current_chunk_size - total;
      size_t bytes = block_read (fd, diff_result + total, bytes_to_read);
      total += bytes;
      if (bytes != bytes_to_read)
	{
	  if (bytes == SIZE_MAX)
	    perror_with_exit (_("read failed"));
	  break;
	}
      if (PTRDIFF_MAX / 2 <= current_chunk_size)
	xalloc_die ();
      current_chunk_size *= 2;
      diff_result = xrealloc (diff_result, current_chunk_size);
    }

  if (total != 0 && diff_result[total-1] != '\n')
    fatal ("invalid diff format; incomplete last line");

  *output_placement = diff_result;

#if ! (HAVE_WORKING_FORK || HAVE_WORKING_VFORK)

  wstatus = pclose (fpipe);
  if (wstatus == -1)
    werrno = errno;

#else

  if (close (fd) != 0)
    perror_with_exit ("close");
  if (waitpid (pid, &wstatus, 0) < 0)
    perror_with_exit ("waitpid");

#endif

  status = ! werrno && WIFEXITED (wstatus) ? WEXITSTATUS (wstatus) : INT_MAX;

  if (EXIT_TROUBLE <= status)
    error (EXIT_TROUBLE, werrno,
	   _(status == 126
	     ? "subsidiary program `%s' could not be invoked"
	     : status == 127
	     ? "subsidiary program `%s' not found"
	     : status == INT_MAX
	     ? "subsidiary program `%s' failed"
	     : "subsidiary program `%s' failed (exit status %d)"),
	   diff_program, status);

  return diff_result + total;
}


/* Scan a regular diff line (consisting of > or <, followed by a
   space, followed by text (including nulls) up to a newline.

   This next routine began life as a macro and many parameters in it
   are used as call-by-reference values.  */
static char *
scan_diff_line (char *scan_ptr, char **set_start, size_t *set_length,
		char *limit, char leadingchar)
{
  char *line_ptr;

  if (!(scan_ptr[0] == leadingchar
	&& scan_ptr[1] == ' '))
    fatal ("invalid diff format; incorrect leading line chars");

  *set_start = line_ptr = scan_ptr + 2;
  while (*line_ptr++ != '\n')
    continue;

  /* Include newline if the original line ended in a newline,
     or if an edit script is being generated.
     Copy any missing newline message to stderr if an edit script is being
     generated, because edit scripts cannot handle missing newlines.
     Return the beginning of the next line.  */