io.c

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

               equal.  */
	    if (eqs[i].length == length)
	      {
		/* Reuse existing equivalence class if the lines are identical.
		   This detects the common case of exact identity
		   faster than lines_differ would.  */
		if (memcmp (eqline, ip, length) == 0)
		  break;
		if (!same_length_diff_contents_compare_anyway)
		  continue;
	      }
	    else if (!diff_length_compare_anyway)
	      continue;

	    if (! lines_differ (eqline, ip))
	      break;
	  }

      /* Maybe increase the size of the line table.  */
      if (line == alloc_lines)
	{
	  /* Double (alloc_lines - linbuf_base) by adding to alloc_lines.  */
	  if (PTRDIFF_MAX / 3 <= alloc_lines
	      || PTRDIFF_MAX / sizeof *cureqs <= 2 * alloc_lines - linbuf_base
	      || PTRDIFF_MAX / sizeof *linbuf <= alloc_lines - linbuf_base)
	    xalloc_die ();
	  alloc_lines = 2 * alloc_lines - linbuf_base;
	  cureqs = xrealloc (cureqs, alloc_lines * sizeof *cureqs);
	  linbuf += linbuf_base;
	  linbuf = xrealloc (linbuf,
			     (alloc_lines - linbuf_base) * sizeof *linbuf);
	  linbuf -= linbuf_base;
	}
      linbuf[line] = ip;
      cureqs[line] = i;
      ++line;
    }

  current->buffered_lines = line;

  for (i = 0;  ;  i++)
    {
      /* Record the line start for lines in the suffix that we care about.
	 Record one more line start than lines,
	 so that we can compute the length of any buffered line.  */
      if (line == alloc_lines)
	{
	  /* Double (alloc_lines - linbuf_base) by adding to alloc_lines.  */
	  if (PTRDIFF_MAX / 3 <= alloc_lines
	      || PTRDIFF_MAX / sizeof *cureqs <= 2 * alloc_lines - linbuf_base
	      || PTRDIFF_MAX / sizeof *linbuf <= alloc_lines - linbuf_base)
	    xalloc_die ();
	  alloc_lines = 2 * alloc_lines - linbuf_base;
	  linbuf += linbuf_base;
	  linbuf = xrealloc (linbuf,
			     (alloc_lines - linbuf_base) * sizeof *linbuf);
	  linbuf -= linbuf_base;
	}
      linbuf[line] = p;

      if (p == bufend)
	break;

      if (context <= i && no_diff_means_no_output)
	break;

      line++;

      while (*p++ != '\n')
	continue;
    }

  /* Done with cache in local variables.  */
  current->linbuf = linbuf;
  current->valid_lines = line;
  current->alloc_lines = alloc_lines;
  current->equivs = cureqs;
  equivs = eqs;
  equivs_alloc = eqs_alloc;
  equivs_index = eqs_index;
}

/* Prepare the text.  Make sure the text end is initialized.
   Make sure text ends in a newline,
   but remember that we had to add one.
   Strip trailing CRs, if that was requested.  */

static void
prepare_text (struct file_data *current)
{
  size_t buffered = current->buffered;
  char *p = FILE_BUFFER (current);
  char *dst;

  if (buffered == 0 || p[buffered - 1] == '\n')
    current->missing_newline = false;
  else
    {
      p[buffered++] = '\n';
      current->missing_newline = true;
    }

  if (!p)
    return;

  /* Don't use uninitialized storage when planting or using sentinels.  */
  memset (p + buffered, 0, sizeof (word));

  if (strip_trailing_cr && (dst = memchr (p, '\r', buffered)))
    {
      char const *src = dst;
      char const *srclim = p + buffered;

      do
	dst += ! ((*dst = *src++) == '\r' && *src == '\n');
      while (src < srclim);

      buffered -= src - dst;
    }

  current->buffered = buffered;
}

/* We have found N lines in a buffer of size S; guess the
   proportionate number of lines that will be found in a buffer of
   size T.  However, do not guess a number of lines so large that the
   resulting line table might cause overflow in size calculations.  */
static lin
guess_lines (lin n, size_t s, size_t t)
{
  size_t guessed_bytes_per_line = n < 10 ? 32 : s / (n - 1);
  lin guessed_lines = MAX (1, t / guessed_bytes_per_line);
  return MIN (guessed_lines, PTRDIFF_MAX / (2 * sizeof (char *) + 1) - 5) + 5;
}

/* Given a vector of two file_data objects, find the identical
   prefixes and suffixes of each object.  */

static void
find_identical_ends (struct file_data filevec[])
{
  word *w0, *w1;
  char *p0, *p1, *buffer0, *buffer1;
  char const *end0, *beg0;
  char const **linbuf0, **linbuf1;
  lin i, lines;
  size_t n0, n1;
  lin alloc_lines0, alloc_lines1;
  lin buffered_prefix, prefix_count, prefix_mask;
  lin middle_guess, suffix_guess;

  slurp (&filevec[0]);
  prepare_text (&filevec[0]);
  if (filevec[0].desc != filevec[1].desc)
    {
      slurp (&filevec[1]);
      prepare_text (&filevec[1]);
    }
  else
    {
      filevec[1].buffer = filevec[0].buffer;
      filevec[1].bufsize = filevec[0].bufsize;
      filevec[1].buffered = filevec[0].buffered;
      filevec[1].missing_newline = filevec[0].missing_newline;
    }

  /* Find identical prefix.  */

  w0 = filevec[0].buffer;
  w1 = filevec[1].buffer;
  p0 = buffer0 = (char *) w0;
  p1 = buffer1 = (char *) w1;
  n0 = filevec[0].buffered;
  n1 = filevec[1].buffered;

  if (p0 == p1)
    /* The buffers are the same; sentinels won't work.  */
    p0 = p1 += n1;
  else
    {
      /* Insert end sentinels, in this case characters that are guaranteed
	 to make the equality test false, and thus terminate the loop.  */

      if (n0 < n1)
	p0[n0] = ~p1[n0];
      else
	p1[n1] = ~p0[n1];

      /* Loop until first mismatch, or to the sentinel characters.  */

      /* Compare a word at a time for speed.  */
      while (*w0 == *w1)
	w0++, w1++;

      /* Do the last few bytes of comparison a byte at a time.  */
      p0 = (char *) w0;
      p1 = (char *) w1;
      while (*p0 == *p1)
	p0++, p1++;

      /* Don't mistakenly count missing newline as part of prefix.  */
      if (ROBUST_OUTPUT_STYLE (output_style)
	  && ((buffer0 + n0 - filevec[0].missing_newline < p0)
	      !=
	      (buffer1 + n1 - filevec[1].missing_newline < p1)))
	p0--, p1--;
    }

  /* Now P0 and P1 point at the first nonmatching characters.  */

  /* Skip back to last line-beginning in the prefix,
     and then discard up to HORIZON_LINES lines from the prefix.  */
  i = horizon_lines;
  while (p0 != buffer0 && (p0[-1] != '\n' || i--))
    p0--, p1--;

  /* Record the prefix.  */
  filevec[0].prefix_end = p0;
  filevec[1].prefix_end = p1;

  /* Find identical suffix.  */

  /* P0 and P1 point beyond the last chars not yet compared.  */
  p0 = buffer0 + n0;
  p1 = buffer1 + n1;

  if (! ROBUST_OUTPUT_STYLE (output_style)
      || filevec[0].missing_newline == filevec[1].missing_newline)
    {
      end0 = p0;	/* Addr of last char in file 0.  */

      /* Get value of P0 at which we should stop scanning backward:
	 this is when either P0 or P1 points just past the last char
	 of the identical prefix.  */
      beg0 = filevec[0].prefix_end + (n0 < n1 ? 0 : n0 - n1);

      /* Scan back until chars don't match or we reach that point.  */
      for (; p0 != beg0; p0--, p1--)
	if (*p0 != *p1)
	  {
	    /* Point at the first char of the matching suffix.  */
	    beg0 = p0;
	    break;
	  }

      /* Are we at a line-beginning in both files?  If not, add the rest of
	 this line to the main body.  Discard up to HORIZON_LINES lines from
	 the identical suffix.  Also, discard one extra line,
	 because shift_boundaries may need it.  */
      i = horizon_lines + !((buffer0 == p0 || p0[-1] == '\n')
			    &&
			    (buffer1 == p1 || p1[-1] == '\n'));
      while (i-- && p0 != end0)
	while (*p0++ != '\n')
	  continue;

      p1 += p0 - beg0;
    }

  /* Record the suffix.  */
  filevec[0].suffix_begin = p0;
  filevec[1].suffix_begin = p1;

  /* Calculate number of lines of prefix to save.

     prefix_count == 0 means save the whole prefix;
     we need this for options like -D that output the whole file,
     or for enormous contexts (to avoid worrying about arithmetic overflow).
     We also need it for options like -F that output some preceding line;
     at least we will need to find the last few lines,
     but since we don't know how many, it's easiest to find them all.

     Otherwise, prefix_count != 0.  Save just prefix_count lines at start
     of the line buffer; they'll be moved to the proper location later.
     Handle 1 more line than the context says (because we count 1 too many),
     rounded up to the next power of 2 to speed index computation.  */

  if (no_diff_means_no_output && ! function_regexp.fastmap
      && context < LIN_MAX / 4 && context < n0)
    {
      middle_guess = guess_lines (0, 0, p0 - filevec[0].prefix_end);
      suffix_guess = guess_lines (0, 0, buffer0 + n0 - p0);
      for (prefix_count = 1;  prefix_count <= context;  prefix_count *= 2)
	continue;
      alloc_lines0 = (prefix_count + middle_guess
		      + MIN (context, suffix_guess));
    }
  else
    {
      prefix_count = 0;
      alloc_lines0 = guess_lines (0, 0, n0);
    }

  prefix_mask = prefix_count - 1;
  lines = 0;
  linbuf0 = xmalloc (alloc_lines0 * sizeof *linbuf0);
  p0 = buffer0;

  /* If the prefix is needed, find the prefix lines.  */
  if (! (no_diff_means_no_output
	 && filevec[0].prefix_end == p0
	 && filevec[1].prefix_end == p1))
    {
      end0 = filevec[0].prefix_end;
      while (p0 != end0)
	{
	  lin l = lines++ & prefix_mask;
	  if (l == alloc_lines0)
	    {
	      if (PTRDIFF_MAX / (2 * sizeof *linbuf0) <= alloc_lines0)
		xalloc_die ();
	      alloc_lines0 *= 2;
	      linbuf0 = xrealloc (linbuf0, alloc_lines0 * sizeof *linbuf0);
	    }
	  linbuf0[l] = p0;
	  while (*p0++ != '\n')
	    continue;
	}
    }
  buffered_prefix = prefix_count && context < lines ? context : lines;

  /* Allocate line buffer 1.  */

  middle_guess = guess_lines (lines, p0 - buffer0, p1 - filevec[1].prefix_end);
  suffix_guess = guess_lines (lines, p0 - buffer0, buffer1 + n1 - p1);
  alloc_lines1 = buffered_prefix + middle_guess + MIN (context, suffix_guess);
  if (alloc_lines1 < buffered_prefix
      || PTRDIFF_MAX / sizeof *linbuf1 <= alloc_lines1)
    xalloc_die ();
  linbuf1 = xmalloc (alloc_lines1 * sizeof *linbuf1);

  if (buffered_prefix != lines)
    {
      /* Rotate prefix lines to proper location.  */
      for (i = 0;  i < buffered_prefix;  i++)
	linbuf1[i] = linbuf0[(lines - context + i) & prefix_mask];
      for (i = 0;  i < buffered_prefix;  i++)
	linbuf0[i] = linbuf1[i];
    }

  /* Initialize line buffer 1 from line buffer 0.  */
  for (i = 0; i < buffered_prefix; i++)
    linbuf1[i] = linbuf0[i] - buffer0 + buffer1;

  /* Record the line buffer, adjusted so that
     linbuf[0] points at the first differing line.  */
  filevec[0].linbuf = linbuf0 + buffered_prefix;
  filevec[1].linbuf = linbuf1 + buffered_prefix;
  filevec[0].linbuf_base = filevec[1].linbuf_base = - buffered_prefix;
  filevec[0].alloc_lines = alloc_lines0 - buffered_prefix;
  filevec[1].alloc_lines = alloc_lines1 - buffered_prefix;
  filevec[0].prefix_lines = filevec[1].prefix_lines = lines;
}

/* If 1 < k, then (2**k - prime_offset[k]) is the largest prime less
   than 2**k.  This table is derived from Chris K. Caldwell's list
   <http://www.utm.edu/research/primes/lists/2small/>.  */

static unsigned char const prime_offset[] =
{
  0, 0, 1, 1, 3, 1, 3, 1, 5, 3, 3, 9, 3, 1, 3, 19, 15, 1, 5, 1, 3, 9, 3,
  15, 3, 39, 5, 39, 57, 3, 35, 1, 5, 9, 41, 31, 5, 25, 45, 7, 87, 21,
  11, 57, 17, 55, 21, 115, 59, 81, 27, 129, 47, 111, 33, 55, 5, 13, 27,
  55, 93, 1, 57, 25
};

/* Verify that this host's size_t is not too wide for the above table.  */

verify (enough_prime_offsets,
	sizeof (size_t) * CHAR_BIT <= sizeof prime_offset);

/* Given a vector of two file_data objects, read the file associated
   with each one, and build the table of equivalence classes.
   Return nonzero if either file appears to be a binary file.
   If PRETEND_BINARY is nonzero, pretend they are binary regardless.  */

bool
read_files (struct file_data filevec[], bool pretend_binary)
{
  int i;
  bool skip_test = text | pretend_binary;
  bool appears_binary = pretend_binary | sip (&filevec[0], skip_test);

  if (filevec[0].desc != filevec[1].desc)
    appears_binary |= sip (&filevec[1], skip_test | appears_binary);
  else
    {
      filevec[1].buffer = filevec[0].buffer;
      filevec[1].bufsize = filevec[0].bufsize;
      filevec[1].buffered = filevec[0].buffered;
    }
  if (appears_binary)
    {
      set_binary_mode (filevec[0].desc, true);
      set_binary_mode (filevec[1].desc, true);
      return true;
    }

  find_identical_ends (filevec);

  equivs_alloc = filevec[0].alloc_lines + filevec[1].alloc_lines + 1;
  if (PTRDIFF_MAX / sizeof *equivs <= equivs_alloc)
    xalloc_die ();
  equivs = xmalloc (equivs_alloc * sizeof *equivs);
  /* Equivalence class 0 is permanently safe for lines that were not
     hashed.  Real equivalence classes start at 1.  */
  equivs_index = 1;

  /* Allocate (one plus) a prime number of hash buckets.  Use a prime
     number between 1/3 and 2/3 of the value of equiv_allocs,
     approximately.  */
  for (i = 9; (size_t) 1 << i < equivs_alloc / 3; i++)
    continue;
  nbuckets = ((size_t) 1 << i) - prime_offset[i];
  if (PTRDIFF_MAX / sizeof *buckets <= nbuckets)
    xalloc_die ();
  buckets = zalloc ((nbuckets + 1) * sizeof *buckets);
  buckets++;

  for (i = 0; i < 2; i++)
    find_and_hash_each_line (&filevec[i]);

  filevec[0].equiv_max = filevec[1].equiv_max = equivs_index;

  free (equivs);
  free (buckets - 1);

  return false;
}