diff3.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

      switch (ptr->correspond)
	{
	case DIFF_ALL:
	  x[0] = '\0';
	  dontprint = 3;	/* Print them all */
	  oddoneout = 3;	/* Nobody's odder than anyone else */
	  break;
	case DIFF_1ST:
	case DIFF_2ND:
	case DIFF_3RD:
	  oddoneout = rev_mapping[(int) ptr->correspond - (int) DIFF_1ST];

	  x[0] = oddoneout + '1';
	  x[1] = '\0';
	  dontprint = oddoneout==0;
	  break;
	default:
	  fatal ("internal error: invalid diff type passed to output");
	}
      fprintf (outputfile, "====%s\n", x);

      /* Go 0, 2, 1 if the first and third outputs are equivalent.  */
      for (i = 0; i < 3;
	   i = (oddoneout == 1 ? skew_increment[i] : i + 1))
	{
	  int realfile = mapping[i];
	  int
	    lowt = D_LOWLINE (ptr, realfile),
	    hight = D_HIGHLINE (ptr, realfile);

	  fprintf (outputfile, "%d:", i + 1);
	  switch (lowt - hight)
	    {
	    case 1:
	      fprintf (outputfile, "%da\n", lowt - 1);
	      break;
	    case 0:
	      fprintf (outputfile, "%dc\n", lowt);
	      break;
	    default:
	      fprintf (outputfile, "%d,%dc\n", lowt, hight);
	      break;
	    }

	  if (i == dontprint) continue;

	  if (lowt <= hight)
	    {
	      line = 0;
	      do
		{
		  fprintf (outputfile, line_prefix);
		  cp = D_RELNUM (ptr, realfile, line);
		  length = D_RELLEN (ptr, realfile, line);
		  fwrite (cp, sizeof (char), length, outputfile);
		}
	      while (++line < hight - lowt + 1);
	      if (cp[length - 1] != '\n')
		fprintf (outputfile, "\n\\ No newline at end of file\n");
	    }
	}
    }
}


/*
 * Output to OUTPUTFILE the lines of B taken from FILENUM.
 * Double any initial '.'s; yield nonzero if any initial '.'s were doubled.
 */
static int
dotlines (outputfile, b, filenum)
     FILE *outputfile;
     struct diff3_block *b;
     int filenum;
{
  int i;
  int leading_dot = 0;

  for (i = 0;
       i < D_NUMLINES (b, filenum);
       i++)
    {
      char *line = D_RELNUM (b, filenum, i);
      if (line[0] == '.')
	{
	  leading_dot = 1;
	  fprintf (outputfile, ".");
	}
      fwrite (line, sizeof (char),
	      D_RELLEN (b, filenum, i), outputfile);
    }

  return leading_dot;
}

/*
 * Output to OUTPUTFILE a '.' line.  If LEADING_DOT is nonzero,
 * also output a command that removes initial '.'s
 * starting with line START and continuing for NUM lines.
 */
static void
undotlines (outputfile, leading_dot, start, num)
     FILE *outputfile;
     int leading_dot, start, num;
{
  fprintf (outputfile, ".\n");
  if (leading_dot)
    if (num == 1)
      fprintf (outputfile, "%ds/^\\.//\n", start);
    else
      fprintf (outputfile, "%d,%ds/^\\.//\n", start, start + num - 1);
}

/*
 * This routine outputs a diff3 set of blocks as an ed script.  This
 * script applies the changes between file's 2 & 3 to file 1.  It
 * takes the precise format of the ed script to be output from global
 * variables set during options processing.  Note that it does
 * destructive things to the set of diff3 blocks it is passed; it
 * reverses their order (this gets around the problems involved with
 * changing line numbers in an ed script).
 *
 * Note that this routine has the same problem of mapping as the last
 * one did; the variable MAPPING maps from file number according to
 * the argument list to file number according to the diff passed.  All
 * files listed below are in terms of the argument list.
 * REV_MAPPING is the inverse of MAPPING.
 *
 * The arguments FILE0, FILE1 and FILE2 are the strings to print
 * as the names of the three files.  These may be the actual names,
 * or may be the arguments specified with -L.
 *
 * Returns 1 if conflicts were found.
 */

static int
output_diff3_edscript (outputfile, diff, mapping, rev_mapping,
		       file0, file1, file2)
     FILE *outputfile;
     struct diff3_block *diff;
     int const mapping[3], rev_mapping[3];
     char const *file0, *file1, *file2;
{
  int leading_dot;
  int conflicts_found = 0, conflict;
  struct diff3_block *b;

  for (b = reverse_diff3_blocklist (diff); b; b = b->next)
    {
      /* Must do mapping correctly.  */
      enum diff_type type
	= ((b->correspond == DIFF_ALL) ?
	   DIFF_ALL :
	   ((enum diff_type)
	    (((int) DIFF_1ST)
	     + rev_mapping[(int) b->correspond - (int) DIFF_1ST])));

      /* If we aren't supposed to do this output block, skip it.  */
      switch (type)
	{
	default: continue;
	case DIFF_2ND: if (!show_2nd) continue; conflict = 1; break;
	case DIFF_3RD: if (overlap_only) continue; conflict = 0; break;
	case DIFF_ALL: if (simple_only) continue; conflict = flagging; break;
	}

      if (conflict)
	{
	  conflicts_found = 1;


	  /* Mark end of conflict.  */

	  fprintf (outputfile, "%da\n", D_HIGHLINE (b, mapping[FILE0]));
	  leading_dot = 0;
	  if (type == DIFF_ALL)
	    {
	      if (show_2nd)
		{
		  /* Append lines from FILE1.  */
		  fprintf (outputfile, "||||||| %s\n", file1);
		  leading_dot = dotlines (outputfile, b, mapping[FILE1]);
		}
	      /* Append lines from FILE2.  */
	      fprintf (outputfile, "=======\n");
	      leading_dot |= dotlines (outputfile, b, mapping[FILE2]);
	    }
	  fprintf (outputfile, ">>>>>>> %s\n", file2);
	  undotlines (outputfile, leading_dot,
		      D_HIGHLINE (b, mapping[FILE0]) + 2,
		      (D_NUMLINES (b, mapping[FILE1])
		       + D_NUMLINES (b, mapping[FILE2]) + 1));


	  /* Mark start of conflict.  */

	  fprintf (outputfile, "%da\n<<<<<<< %s\n",
		   D_LOWLINE (b, mapping[FILE0]) - 1,
		   type == DIFF_ALL ? file0 : file1);
	  leading_dot = 0;
	  if (type == DIFF_2ND)
	    {
	      /* Prepend lines from FILE1.  */
	      leading_dot = dotlines (outputfile, b, mapping[FILE1]);
	      fprintf (outputfile, "=======\n");
	    }
	  undotlines (outputfile, leading_dot,
		      D_LOWLINE (b, mapping[FILE0]) + 1,
		      D_NUMLINES (b, mapping[FILE1]));
	}
      else if (D_NUMLINES (b, mapping[FILE2]) == 0)
	/* Write out a delete */
	{
	  if (D_NUMLINES (b, mapping[FILE0]) == 1)
	    fprintf (outputfile, "%dd\n",
		     D_LOWLINE (b, mapping[FILE0]));
	  else
	    fprintf (outputfile, "%d,%dd\n",
		     D_LOWLINE (b, mapping[FILE0]),
		     D_HIGHLINE (b, mapping[FILE0]));
	}
      else
	/* Write out an add or change */
	{
	  switch (D_NUMLINES (b, mapping[FILE0]))
	    {
	    case 0:
	      fprintf (outputfile, "%da\n",
		       D_HIGHLINE (b, mapping[FILE0]));
	      break;
	    case 1:
	      fprintf (outputfile, "%dc\n",
		       D_HIGHLINE (b, mapping[FILE0]));
	      break;
	    default:
	      fprintf (outputfile, "%d,%dc\n",
		       D_LOWLINE (b, mapping[FILE0]),
		       D_HIGHLINE (b, mapping[FILE0]));
	      break;
	    }

	  undotlines (outputfile, dotlines (outputfile, b, mapping[FILE2]),
		      D_LOWLINE (b, mapping[FILE0]),
		      D_NUMLINES (b, mapping[FILE2]));
	}
    }
  if (finalwrite) fprintf (outputfile, "w\nq\n");
  return conflicts_found;
}

/*
 * Read from INFILE and output to OUTPUTFILE a set of diff3_ blocks DIFF
 * as a merged file.  This acts like 'ed file0 <[output_diff3_edscript]',
 * except that it works even for binary data or incomplete lines.
 *
 * As before, MAPPING maps from arg list file number to diff file number,
 * REV_MAPPING is its inverse,
 * and FILE0, FILE1, and FILE2 are the names of the files.
 *
 * Returns 1 if conflicts were found.
 */

static int
output_diff3_merge (infile, outputfile, diff, mapping, rev_mapping,
		    file0, file1, file2)
     FILE *infile, *outputfile;
     struct diff3_block *diff;
     int const mapping[3], rev_mapping[3];
     char const *file0, *file1, *file2;
{
  int c, i;
  int conflicts_found = 0, conflict;
  struct diff3_block *b;
  int linesread = 0;

  for (b = diff; b; b = b->next)
    {
      /* Must do mapping correctly.  */
      enum diff_type type
	= ((b->correspond == DIFF_ALL) ?
	   DIFF_ALL :
	   ((enum diff_type)
	    (((int) DIFF_1ST)
	     + rev_mapping[(int) b->correspond - (int) DIFF_1ST])));
      char const *format_2nd = "<<<<<<< %s\n";

      /* If we aren't supposed to do this output block, skip it.  */
      switch (type)
	{
	default: continue;
	case DIFF_2ND: if (!show_2nd) continue; conflict = 1; break;
	case DIFF_3RD: if (overlap_only) continue; conflict = 0; break;
	case DIFF_ALL: if (simple_only) continue; conflict = flagging;
	  format_2nd = "||||||| %s\n";
	  break;
	}

      /* Copy I lines from file 0.  */
      i = D_LOWLINE (b, FILE0) - linesread - 1;
      linesread += i;
      while (0 <= --i)
	do
	  {
	    c = getc (infile);
	    if (c == EOF)
	      if (ferror (infile))
		perror_with_exit ("input file");
	      else if (feof (infile))
		fatal ("input file shrank");
	    putc (c, outputfile);
	  }
	while (c != '\n');

      if (conflict)
	{
	  conflicts_found = 1;

	  if (type == DIFF_ALL)
	    {
	      /* Put in lines from FILE0 with bracket.  */
	      fprintf (outputfile, "<<<<<<< %s\n", file0);
	      for (i = 0;
		   i < D_NUMLINES (b, mapping[FILE0]);
		   i++)
		fwrite (D_RELNUM (b, mapping[FILE0], i), sizeof (char),
			D_RELLEN (b, mapping[FILE0], i), outputfile);
	    }

	  if (show_2nd)
	    {
	      /* Put in lines from FILE1 with bracket.  */
	      fprintf (outputfile, format_2nd, file1);
	      for (i = 0;
		   i < D_NUMLINES (b, mapping[FILE1]);
		   i++)
		fwrite (D_RELNUM (b, mapping[FILE1], i), sizeof (char),
			D_RELLEN (b, mapping[FILE1], i), outputfile);
	    }

	  fprintf (outputfile, "=======\n");
	}

      /* Put in lines from FILE2.  */
      for (i = 0;
	   i < D_NUMLINES (b, mapping[FILE2]);
	   i++)
	fwrite (D_RELNUM (b, mapping[FILE2], i), sizeof (char),
		D_RELLEN (b, mapping[FILE2], i), outputfile);

      if (conflict)
	fprintf (outputfile, ">>>>>>> %s\n", file2);

      /* Skip I lines in file 0.  */
      i = D_NUMLINES (b, FILE0);
      linesread += i;
      while (0 <= --i)
	while ((c = getc (infile)) != '\n')
	  if (c == EOF)
	    if (ferror (infile))
	      perror_with_exit ("input file");
	    else if (feof (infile))
	      {
		if (i || b->next)
		  fatal ("input file shrank");
		return conflicts_found;
	      }
    }
  /* Copy rest of common file.  */
  while ((c = getc (infile)) != EOF || !(ferror (infile) | feof (infile)))
    putc (c, outputfile);
  return conflicts_found;
}

/*
 * Reverse the order of the list of diff3 blocks.
 */
static struct diff3_block *
reverse_diff3_blocklist (diff)
     struct diff3_block *diff;
{
  register struct diff3_block *tmp, *next, *prev;

  for (tmp = diff, prev = 0;  tmp;  tmp = next)
    {
      next = tmp->next;
      tmp->next = prev;
      prev = tmp;
    }

  return prev;
}

static size_t
myread (fd, ptr, size)
     int fd;
     char *ptr;
     size_t size;
{
  size_t result = read (fd, ptr, size);
  if (result == -1)
    perror_with_exit ("read failed");
  return result;
}

static VOID *
xmalloc (size)
     size_t size;
{
  VOID *result = (VOID *) malloc (size ? size : 1);
  if (!result)
    fatal ("memory exhausted");
  return result;
}

static VOID *
xrealloc (ptr, size)
     VOID *ptr;
     size_t size;
{
  VOID *result = (VOID *) realloc (ptr, size ? size : 1);
  if (!result)
    fatal ("memory exhausted");
  return result;
}

static void
fatal (string)
     char const *string;
{
  fprintf (stderr, "%s: %s\n", program_name, string);
  exit (2);
}

static void
perror_with_exit (string)
     char const *string;
{
  int e = errno;
  fprintf (stderr, "%s: ", program_name);
  errno = e;
  perror (string);
  exit (2);
}