analyze.c

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

			consec = 0, discards[i + j] = 0;
		      else if (discards[i + j] == 0)
			consec = 0;
		      else
			consec++;
		      if (consec == 3)
			break;
		    }

		  /* I advances to the last line of the run.  */
		  i += length - 1;

		  /* Same thing, from end.  */
		  for (j = 0, consec = 0; j < length; j++)
		    {
		      if (j >= 8 && discards[i - j] == 1)
			break;
		      if (discards[i - j] == 2)
			consec = 0, discards[i - j] = 0;
		      else if (discards[i - j] == 0)
			consec = 0;
		      else
			consec++;
		      if (consec == 3)
			break;
		    }
		}
	    }
	}
    }

  /* Actually discard the lines. */
  for (f = 0; f < 2; f++)
    {
      char *discards = discarded[f];
      lin end = filevec[f].buffered_lines;
      lin j = 0;
      for (i = 0; i < end; ++i)
	if (minimal || discards[i] == 0)
	  {
	    filevec[f].undiscarded[j] = filevec[f].equivs[i];
	    filevec[f].realindexes[j++] = i;
	  }
	else
	  filevec[f].changed[i] = 1;
      filevec[f].nondiscarded_lines = j;
    }

  free (discarded[0]);
  free (equiv_count[0]);
}

/* Adjust inserts/deletes of identical lines to join changes
   as much as possible.

   We do something when a run of changed lines include a
   line at one end and have an excluded, identical line at the other.
   We are free to choose which identical line is included.
   `compareseq' usually chooses the one at the beginning,
   but usually it is cleaner to consider the following identical line
   to be the "change".  */

static void
shift_boundaries (struct file_data filevec[])
{
  int f;

  for (f = 0; f < 2; f++)
    {
      char *changed = filevec[f].changed;
      char *other_changed = filevec[1 - f].changed;
      lin const *equivs = filevec[f].equivs;
      lin i = 0;
      lin j = 0;
      lin i_end = filevec[f].buffered_lines;

      while (1)
	{
	  lin runlength, start, corresponding;

	  /* Scan forwards to find beginning of another run of changes.
	     Also keep track of the corresponding point in the other file.  */

	  while (i < i_end && !changed[i])
	    {
	      while (other_changed[j++])
		continue;
	      i++;
	    }

	  if (i == i_end)
	    break;

	  start = i;

	  /* Find the end of this run of changes.  */

	  while (changed[++i])
	    continue;
	  while (other_changed[j])
	    j++;

	  do
	    {
	      /* Record the length of this run of changes, so that
		 we can later determine whether the run has grown.  */
	      runlength = i - start;

	      /* Move the changed region back, so long as the
		 previous unchanged line matches the last changed one.
		 This merges with previous changed regions.  */

	      while (start && equivs[start - 1] == equivs[i - 1])
		{
		  changed[--start] = 1;
		  changed[--i] = 0;
		  while (changed[start - 1])
		    start--;
		  while (other_changed[--j])
		    continue;
		}

	      /* Set CORRESPONDING to the end of the changed run, at the last
		 point where it corresponds to a changed run in the other file.
		 CORRESPONDING == I_END means no such point has been found.  */
	      corresponding = other_changed[j - 1] ? i : i_end;

	      /* Move the changed region forward, so long as the
		 first changed line matches the following unchanged one.
		 This merges with following changed regions.
		 Do this second, so that if there are no merges,
		 the changed region is moved forward as far as possible.  */

	      while (i != i_end && equivs[start] == equivs[i])
		{
		  changed[start++] = 0;
		  changed[i++] = 1;
		  while (changed[i])
		    i++;
		  while (other_changed[++j])
		    corresponding = i;
		}
	    }
	  while (runlength != i - start);

	  /* If possible, move the fully-merged run of changes
	     back to a corresponding run in the other file.  */

	  while (corresponding < i)
	    {
	      changed[--start] = 1;
	      changed[--i] = 0;
	      while (other_changed[--j])
		continue;
	    }
	}
    }
}

/* Cons an additional entry onto the front of an edit script OLD.
   LINE0 and LINE1 are the first affected lines in the two files (origin 0).
   DELETED is the number of lines deleted here from file 0.
   INSERTED is the number of lines inserted here in file 1.

   If DELETED is 0 then LINE0 is the number of the line before
   which the insertion was done; vice versa for INSERTED and LINE1.  */

static struct change *
add_change (lin line0, lin line1, lin deleted, lin inserted,
	    struct change *old)
{
  struct change *new = xmalloc (sizeof *new);

  new->line0 = line0;
  new->line1 = line1;
  new->inserted = inserted;
  new->deleted = deleted;
  new->link = old;
  return new;
}

/* Scan the tables of which lines are inserted and deleted,
   producing an edit script in reverse order.  */

static struct change *
build_reverse_script (struct file_data const filevec[])
{
  struct change *script = 0;
  char *changed0 = filevec[0].changed;
  char *changed1 = filevec[1].changed;
  lin len0 = filevec[0].buffered_lines;
  lin len1 = filevec[1].buffered_lines;

  /* Note that changedN[len0] does exist, and is 0.  */

  lin i0 = 0, i1 = 0;

  while (i0 < len0 || i1 < len1)
    {
      if (changed0[i0] | changed1[i1])
	{
	  lin line0 = i0, line1 = i1;

	  /* Find # lines changed here in each file.  */
	  while (changed0[i0]) ++i0;
	  while (changed1[i1]) ++i1;

	  /* Record this change.  */
	  script = add_change (line0, line1, i0 - line0, i1 - line1, script);
	}

      /* We have reached lines in the two files that match each other.  */
      i0++, i1++;
    }

  return script;
}

/* Scan the tables of which lines are inserted and deleted,
   producing an edit script in forward order.  */

static struct change *
build_script (struct file_data const filevec[])
{
  struct change *script = 0;
  char *changed0 = filevec[0].changed;
  char *changed1 = filevec[1].changed;
  lin i0 = filevec[0].buffered_lines, i1 = filevec[1].buffered_lines;

  /* Note that changedN[-1] does exist, and is 0.  */

  while (i0 >= 0 || i1 >= 0)
    {
      if (changed0[i0 - 1] | changed1[i1 - 1])
	{
	  lin line0 = i0, line1 = i1;

	  /* Find # lines changed here in each file.  */
	  while (changed0[i0 - 1]) --i0;
	  while (changed1[i1 - 1]) --i1;

	  /* Record this change.  */
	  script = add_change (i0, i1, line0 - i0, line1 - i1, script);
	}

      /* We have reached lines in the two files that match each other.  */
      i0--, i1--;
    }

  return script;
}

/* If CHANGES, briefly report that two files differed.
   Return 2 if trouble, CHANGES otherwise.  */
static int
briefly_report (int changes, struct file_data const filevec[])
{
  if (changes)
    {
      char const *label0 = file_label[0] ? file_label[0] : filevec[0].name;
      char const *label1 = file_label[1] ? file_label[1] : filevec[1].name;
      message ("Files %s and %s differ\n", label0, label1);
      if (! brief)
	changes = 2;
    }

  return changes;
}

/* Report the differences of two files.  */
int
diff_2_files (struct comparison *cmp)
{
  lin diags;
  int f;
  struct change *e, *p;
  struct change *script;
  int changes;


  /* If we have detected that either file is binary,
     compare the two files as binary.  This can happen
     only when the first chunk is read.
     Also, --brief without any --ignore-* options means
     we can speed things up by treating the files as binary.  */

  if (read_files (cmp->file, files_can_be_treated_as_binary))
    {
      /* Files with different lengths must be different.  */
      if (cmp->file[0].stat.st_size != cmp->file[1].stat.st_size
	  && (cmp->file[0].desc < 0 || S_ISREG (cmp->file[0].stat.st_mode))
	  && (cmp->file[1].desc < 0 || S_ISREG (cmp->file[1].stat.st_mode)))
	changes = 1;

      /* Standard input equals itself.  */
      else if (cmp->file[0].desc == cmp->file[1].desc)
	changes = 0;

      else
	/* Scan both files, a buffer at a time, looking for a difference.  */
	{
	  /* Allocate same-sized buffers for both files.  */
	  size_t lcm_max = PTRDIFF_MAX - 1;
	  size_t buffer_size =
	    buffer_lcm (sizeof (word),
			buffer_lcm (STAT_BLOCKSIZE (cmp->file[0].stat),
				    STAT_BLOCKSIZE (cmp->file[1].stat),
				    lcm_max),
			lcm_max);
	  for (f = 0; f < 2; f++)
	    cmp->file[f].buffer = xrealloc (cmp->file[f].buffer, buffer_size);

	  for (;; cmp->file[0].buffered = cmp->file[1].buffered = 0)
	    {
	      /* Read a buffer's worth from both files.  */
	      for (f = 0; f < 2; f++)
		if (0 <= cmp->file[f].desc)
		  file_block_read (&cmp->file[f],
				   buffer_size - cmp->file[f].buffered);

	      /* If the buffers differ, the files differ.  */
	      if (cmp->file[0].buffered != cmp->file[1].buffered
		  || memcmp (cmp->file[0].buffer,
			     cmp->file[1].buffer,
			     cmp->file[0].buffered))
		{
		  changes = 1;
		  break;
		}

	      /* If we reach end of file, the files are the same.  */
	      if (cmp->file[0].buffered != buffer_size)
		{
		  changes = 0;
		  break;
		}
	    }
	}

      changes = briefly_report (changes, cmp->file);
    }
  else
    {
      /* Allocate vectors for the results of comparison:
	 a flag for each line of each file, saying whether that line
	 is an insertion or deletion.
	 Allocate an extra element, always 0, at each end of each vector.  */

      size_t s = cmp->file[0].buffered_lines + cmp->file[1].buffered_lines + 4;
      char *flag_space = zalloc (s);
      cmp->file[0].changed = flag_space + 1;
      cmp->file[1].changed = flag_space + cmp->file[0].buffered_lines + 3;

      /* Some lines are obviously insertions or deletions
	 because they don't match anything.  Detect them now, and
	 avoid even thinking about them in the main comparison algorithm.  */

      discard_confusing_lines (cmp->file);

      /* Now do the main comparison algorithm, considering just the
	 undiscarded lines.  */

      xvec = cmp->file[0].undiscarded;
      yvec = cmp->file[1].undiscarded;
      diags = (cmp->file[0].nondiscarded_lines
	       + cmp->file[1].nondiscarded_lines + 3);
      fdiag = xmalloc (diags * (2 * sizeof *fdiag));
      bdiag = fdiag + diags;
      fdiag += cmp->file[1].nondiscarded_lines + 1;
      bdiag += cmp->file[1].nondiscarded_lines + 1;

      /* Set TOO_EXPENSIVE to be approximate square root of input size,
	 bounded below by 256.  */
      too_expensive = 1;
      for (;  diags != 0;  diags >>= 2)
	too_expensive <<= 1;
      too_expensive = MAX (256, too_expensive);

      files[0] = cmp->file[0];
      files[1] = cmp->file[1];

      compareseq (0, cmp->file[0].nondiscarded_lines,
		  0, cmp->file[1].nondiscarded_lines, minimal);

      free (fdiag - (cmp->file[1].nondiscarded_lines + 1));

      /* Modify the results slightly to make them prettier
	 in cases where that can validly be done.  */

      shift_boundaries (cmp->file);

      /* Get the results of comparison in the form of a chain
	 of `struct change's -- an edit script.  */

      if (output_style == OUTPUT_ED)
	script = build_reverse_script (cmp->file);
      else
	script = build_script (cmp->file);

      /* Set CHANGES if we had any diffs.
	 If some changes are ignored, we must scan the script to decide.  */
      if (ignore_blank_lines || ignore_regexp.fastmap)
	{
	  struct change *next = script;
	  changes = 0;

	  while (next && changes == 0)
	    {
	      struct change *this, *end;
	      lin first0, last0, first1, last1;

	      /* Find a set of changes that belong together.  */
	      this = next;
	      end = find_change (next);

	      /* Disconnect them from the rest of the changes, making them
		 a hunk, and remember the rest for next iteration.  */
	      next = end->link;
	      end->link = 0;

	      /* Determine whether this hunk is really a difference.  */
	      if (analyze_hunk (this, &first0, &last0, &first1, &last1))
		changes = 1;

	      /* Reconnect the script so it will all be freed properly.  */
	      end->link = next;
	    }
	}
      else
	changes = (script != 0);

      if (brief)
	changes = briefly_report (changes, cmp->file);
      else
	{
	  if (changes | !no_diff_means_no_output)
	    {
	      /* Record info for starting up output,
		 to be used if and when we have some output to print.  */
	      setup_output (file_label[0] ? file_label[0] : cmp->file[0].name,
			    file_label[1] ? file_label[1] : cmp->file[1].name,
			    cmp->parent != 0);

	      switch (output_style)
		{
		case OUTPUT_CONTEXT:
		  print_context_script (script, false);
		  break;

		case OUTPUT_UNIFIED:
		  print_context_script (script, true);
		  break;

		case OUTPUT_ED:
		  print_ed_script (script);
		  break;

		case OUTPUT_FORWARD_ED:
		  pr_forward_ed_script (script);
		  break;

		case OUTPUT_RCS:
		  print_rcs_script (script);
		  break;

		case OUTPUT_NORMAL:
		  print_normal_script (script);
		  break;

		case OUTPUT_IFDEF:
		  print_ifdef_script (script);
		  break;

		case OUTPUT_SDIFF:
		  print_sdiff_script (script);
		  break;

		default:
		  abort ();
		}

	      finish_output ();
	    }
	}

      free (cmp->file[0].undiscarded);

      free (flag_space);

      for (f = 0; f < 2; f++)
	{
	  free (cmp->file[f].equivs);
	  free (cmp->file[f].linbuf + cmp->file[f].linbuf_base);
	}

      for (e = script; e; e = p)
	{
	  p = e->link;
	  free (e);
	}

      if (! ROBUST_OUTPUT_STYLE (output_style))
	for (f = 0; f < 2; ++f)
	  if (cmp->file[f].missing_newline)
	    {
	      error (0, 0, "%s: %s\n",
		     file_label[f] ? file_label[f] : cmp->file[f].name,
		     _("No newline at end of file"));
	      changes = 2;
	    }
    }

  if (cmp->file[0].buffer != cmp->file[1].buffer)
    free (cmp->file[0].buffer);
  free (cmp->file[1].buffer);

  return changes;
}