util.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

	  /* Lowercase all letters if -i is specified.  */

	  if (ignore_case_flag)
	    {
	      if (ISUPPER (c1))
		c1 = tolower (c1);
	      if (ISUPPER (c2))
		c2 = tolower (c2);
	    }

	  if (c1 != c2)
	    break;
	}
      if (c1 == '\n')
	return 0;
    }

  return (1);
}

/* Find the consecutive changes at the start of the script START.
   Return the last link before the first gap.  */

struct change *
find_change (start)
     struct change *start;
{
  return start;
}

struct change *
find_reverse_change (start)
     struct change *start;
{
  return start;
}

/* Divide SCRIPT into pieces by calling HUNKFUN and
   print each piece with PRINTFUN.
   Both functions take one arg, an edit script.

   HUNKFUN is called with the tail of the script
   and returns the last link that belongs together with the start
   of the tail.

   PRINTFUN takes a subscript which belongs together (with a null
   link at the end) and prints it.  */

void
print_script (script, hunkfun, printfun)
     struct change *script;
     struct change * (*hunkfun) PARAMS((struct change *));
     void (*printfun) PARAMS((struct change *));
{
  struct change *next = script;

  while (next)
    {
      struct change *this, *end;

      /* Find a set of changes that belong together.  */
      this = next;
      end = (*hunkfun) (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;
#ifdef DEBUG
      debug_script (this);
#endif

      /* Print this hunk.  */
      (*printfun) (this);

      /* Reconnect the script so it will all be freed properly.  */
      end->link = next;
    }
}

/* Print the text of a single line LINE,
   flagging it with the characters in LINE_FLAG (which say whether
   the line is inserted, deleted, changed, etc.).  */

void
print_1_line (line_flag, line)
     char const *line_flag;
     char const * const *line;
{
  char const *text = line[0], *limit = line[1]; /* Help the compiler.  */
  FILE *out = outfile; /* Help the compiler some more.  */
  char const *flag_format = 0;

  /* If -T was specified, use a Tab between the line-flag and the text.
     Otherwise use a Space (as Unix diff does).
     Print neither space nor tab if line-flags are empty.  */

  if (line_flag && *line_flag)
    {
      flag_format = tab_align_flag ? "%s\t" : "%s ";
      fprintf (out, flag_format, line_flag);
    }

  output_1_line (text, limit, flag_format, line_flag);

  if ((!line_flag || line_flag[0]) && limit[-1] != '\n')
    fputc ('\n', out);
}

/* Output a line from TEXT up to LIMIT.  Without -t, output verbatim.
   With -t, expand white space characters to spaces, and if FLAG_FORMAT
   is nonzero, output it with argument LINE_FLAG after every
   internal carriage return, so that tab stops continue to line up.  */

void
output_1_line (text, limit, flag_format, line_flag)
     char const *text, *limit, *flag_format, *line_flag;
{
  if (!tab_expand_flag)
    fwrite (text, sizeof (char), limit - text, outfile);
  else
    {
      register FILE *out = outfile;
      register unsigned char c;
      register char const *t = text;
      register unsigned column = 0;

      while (t < limit)
	switch ((c = *t++))
	  {
	  case '\t':
	    {
	      unsigned spaces = TAB_WIDTH - column % TAB_WIDTH;
	      column += spaces;
	      do
		putc (' ', out);
	      while (--spaces);
	    }
	    break;

	  case '\r':
	    putc (c, out);
	    if (flag_format && t < limit && *t != '\n')
	      fprintf (out, flag_format, line_flag);
	    column = 0;
	    break;

	  case '\b':
	    if (column == 0)
	      continue;
	    column--;
	    putc (c, out);
	    break;

	  default:
	    if (ISPRINT (c))
	      column++;
	    putc (c, out);
	    break;
	  }
    }
}

int
change_letter (inserts, deletes)
     int inserts, deletes;
{
  if (!inserts)
    return 'd';
  else if (!deletes)
    return 'a';
  else
    return 'c';
}

/* Translate an internal line number (an index into diff's table of lines)
   into an actual line number in the input file.
   The internal line number is LNUM.  FILE points to the data on the file.

   Internal line numbers count from 0 starting after the prefix.
   Actual line numbers count from 1 within the entire file.  */

int
translate_line_number (file, lnum)
     struct file_data const *file;
     int lnum;
{
  return lnum + file->prefix_lines + 1;
}

void
translate_range (file, a, b, aptr, bptr)
     struct file_data const *file;
     int a, b;
     int *aptr, *bptr;
{
  *aptr = translate_line_number (file, a - 1) + 1;
  *bptr = translate_line_number (file, b + 1) - 1;
}

/* Print a pair of line numbers with SEPCHAR, translated for file FILE.
   If the two numbers are identical, print just one number.

   Args A and B are internal line numbers.
   We print the translated (real) line numbers.  */

void
print_number_range (sepchar, file, a, b)
     int sepchar;
     struct file_data *file;
     int a, b;
{
  int trans_a, trans_b;
  translate_range (file, a, b, &trans_a, &trans_b);

  /* Note: we can have B < A in the case of a range of no lines.
     In this case, we should print the line number before the range,
     which is B.  */
  if (trans_b > trans_a)
    fprintf (outfile, "%d%c%d", trans_a, sepchar, trans_b);
  else
    fprintf (outfile, "%d", trans_b);
}

/* Look at a hunk of edit script and report the range of lines in each file
   that it applies to.  HUNK is the start of the hunk, which is a chain
   of `struct change'.  The first and last line numbers of file 0 are stored in
   *FIRST0 and *LAST0, and likewise for file 1 in *FIRST1 and *LAST1.
   Note that these are internal line numbers that count from 0.

   If no lines from file 0 are deleted, then FIRST0 is LAST0+1.

   Also set *DELETES nonzero if any lines of file 0 are deleted
   and set *INSERTS nonzero if any lines of file 1 are inserted.
   If only ignorable lines are inserted or deleted, both are
   set to 0.  */

void
analyze_hunk (hunk, first0, last0, first1, last1, deletes, inserts)
     struct change *hunk;
     int *first0, *last0, *first1, *last1;
     int *deletes, *inserts;
{
  int l0, l1, show_from, show_to;
  int i;
  int trivial = ignore_blank_lines_flag || ignore_regexp_list;
  struct change *next;

  show_from = show_to = 0;

  *first0 = hunk->line0;
  *first1 = hunk->line1;

  next = hunk;
  do
    {
      l0 = next->line0 + next->deleted - 1;
      l1 = next->line1 + next->inserted - 1;
      show_from += next->deleted;
      show_to += next->inserted;

      for (i = next->line0; i <= l0 && trivial; i++)
	if (!ignore_blank_lines_flag || files[0].linbuf[i][0] != '\n')
	  {
	    struct regexp_list *r;
	    char const *line = files[0].linbuf[i];
	    int len = files[0].linbuf[i + 1] - line;

	    for (r = ignore_regexp_list; r; r = r->next)
	      if (0 <= re_search (&r->buf, line, len, 0, len, 0))
		break;	/* Found a match.  Ignore this line.  */
	    /* If we got all the way through the regexp list without
	       finding a match, then it's nontrivial.  */
	    if (!r)
	      trivial = 0;
	  }

      for (i = next->line1; i <= l1 && trivial; i++)
	if (!ignore_blank_lines_flag || files[1].linbuf[i][0] != '\n')
	  {
	    struct regexp_list *r;
	    char const *line = files[1].linbuf[i];
	    int len = files[1].linbuf[i + 1] - line;

	    for (r = ignore_regexp_list; r; r = r->next)
	      if (0 <= re_search (&r->buf, line, len, 0, len, 0))
		break;	/* Found a match.  Ignore this line.  */
	    /* If we got all the way through the regexp list without
	       finding a match, then it's nontrivial.  */
	    if (!r)
	      trivial = 0;
	  }
    }
  while ((next = next->link) != 0);

  *last0 = l0;
  *last1 = l1;

  /* If all inserted or deleted lines are ignorable,
     tell the caller to ignore this hunk.  */

  if (trivial)
    show_from = show_to = 0;

  *deletes = show_from;
  *inserts = show_to;
}

/* malloc a block of memory, with fatal error message if we can't do it. */

VOID *
xmalloc (size)
     size_t size;
{
  register VOID *value;

  if (size == 0)
    size = 1;

  value = (VOID *) malloc (size);

  if (!value)
    fatal ("memory exhausted");
  return value;
}

/* realloc a block of memory, with fatal error message if we can't do it. */

VOID *
xrealloc (old, size)
     VOID *old;
     size_t size;
{
  register VOID *value;

  if (size == 0)
    size = 1;

  value = (VOID *) realloc (old, size);

  if (!value)
    fatal ("memory exhausted");
  return value;
}

/* Concatenate three strings, returning a newly malloc'd string.  */

char *
concat (s1, s2, s3)
     char const *s1, *s2, *s3;
{
  size_t len = strlen (s1) + strlen (s2) + strlen (s3);
  char *new = xmalloc (len + 1);
  sprintf (new, "%s%s%s", s1, s2, s3);
  return new;
}

/* Yield the newly malloc'd pathname
   of the file in DIR whose filename is FILE.  */

char *
dir_file_pathname (dir, file)
     char const *dir, *file;
{
  char const *p = filename_lastdirchar (dir);
  return concat (dir, "/" + (p && !p[1]), file);
}

void
debug_script (sp)
     struct change *sp;
{
  fflush (stdout);
  for (; sp; sp = sp->link)
    fprintf (stderr, "%3d %3d delete %d insert %d\n",
	     sp->line0, sp->line1, sp->deleted, sp->inserted);
  fflush (stderr);
}