/* Support routines for GNU DIFF.
   Copyright (C) 1988, 1989 Free Software Foundation, Inc.

This file is part of GNU DIFF.

GNU DIFF is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 1, or (at your option)
any later version.

GNU DIFF is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU DIFF; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "diff.h"

/* Use when a system call returns non-zero status.
   TEXT should normally be the file name.  */

void
perror_with_name (text)
     char *text;
{
  fprintf (stderr, "%s: ", program);
  perror (text);
}

/* Use when a system call returns non-zero status and that is fatal.  */

void
pfatal_with_name (text)
     char *text;
{
  print_message_queue ();
  fprintf (stderr, "%s: ", program);
  perror (text);
  exit (2);
}

/* Print an error message from the format-string FORMAT
   with args ARG1 and ARG2.  */

void
error (format, arg, arg1)
     char *format;
     char *arg;
     char *arg1;
{
  fprintf (stderr, "%s: ", program);
  fprintf (stderr, format, arg, arg1);
  fprintf (stderr, "\n");
}

/* Print an error message containing the string TEXT, then exit.  */

void
fatal (message)
     char *message;
{
  print_message_queue ();
  error (message, "");
  exit (2);
}

/* Like printf, except if -l in effect then save the message and print later.
   This is used for things like "binary files differ" and "Only in ...".  */

void
message (format, arg1, arg2)
     char *format, *arg1, *arg2;
{
  if (paginate_flag)
    {
      struct msg *new = (struct msg *) xmalloc (sizeof (struct msg));
      if (msg_chain_end == 0)
	msg_chain = msg_chain_end = new;
      else
	{
	  msg_chain_end->next = new;
	  msg_chain_end = new;
	}
      new->format = format;
      new->arg1 = concat (arg1, "", "");
      new->arg2 = concat (arg2, "", "");
      new->next = 0;
    }
  else
    printf (format, arg1, arg2);
}

/* Output all the messages that were saved up by calls to `message'.  */

void
print_message_queue ()
{
  struct msg *m;

  for (m = msg_chain; m; m = m->next)
    printf (m->format, m->arg1, m->arg2);
}

/* Call before outputting the results of comparing files NAME0 and NAME1
   to set up OUTFILE, the stdio stream for the output to go to.

   Usually, OUTFILE is just stdout.  But when -l was specified
   we fork off a `pr' and make OUTFILE a pipe to it.
   `pr' then outputs to our stdout.  */

void
setup_output (name0, name1, depth)
     char *name0, *name1;
     int depth;
{
  char *name;

  /* Construct the header of this piece of diff.  */
  name = (char *) xmalloc (strlen (name0) + strlen (name1)
			   + strlen (switch_string) + 15);

  strcpy (name, "diff");
  strcat (name, switch_string);
  strcat (name, " ");
  strcat (name, name0);
  strcat (name, " ");
  strcat (name, name1);

  if (paginate_flag)
    {
      int pipes[2];
      int desc;

      /* For a `pr' and make OUTFILE a pipe to it.  */
      pipe (pipes);

      fflush (stdout);

      desc = vfork ();
      if (desc < 0)
	pfatal_with_name ("vfork");

      if (desc == 0)
	{
	  close (pipes[1]);
	  close (fileno (stdin));
	  if (dup2 (pipes[0], fileno (stdin)) < 0)
	    pfatal_with_name ("dup2");
	  close (pipes[0]);

	  if (execl (PR_FILE_NAME, PR_FILE_NAME, "-f", "-h", name, 0) < 0)
	    pfatal_with_name (PR_FILE_NAME);
	}
      else
	{
	  close (pipes[0]);
	  outfile = fdopen (pipes[1], "w");
	} 
    }
  else
    {

      /* If -l was not specified, output the diff straight to `stdout'.  */

      outfile = stdout;

      /* If handling multiple files (because scanning a directory),
	 print which files the following output is about.  */
      if (depth > 0)
	printf ("%s\n", name);
    }

  free (name);
}

/* Call after the end of output of diffs for one file.
   Close OUTFILE and get rid of the `pr' subfork.  */

void
finish_output ()
{
  if (outfile != stdout)
    {
      fclose (outfile);
      wait (0);
    }
}

/* Compare two lines (typically one from each input file)
   according to the command line options.
   Each line is described by a `struct line_def'.
   Return 1 if the lines differ, like `bcmp'.  */

int
line_cmp (s1, s2)
     struct line_def *s1, *s2;
{
  register char *t1, *t2;
  register char end_char = line_end_char;
  int savechar;

  /* Check first for exact identity.
     If that is true, return 0 immediately.
     This detects the common case of exact identity
     faster than complete comparison would.  */

  t1 = s1->text;
  t2 = s2->text;

  /* Alter the character following line 1 so it doesn't
     match that following line 2.  */
  savechar = s1->text[s1->length];
  s1->text[s1->length] = s2->text[s2->length] + 1;

  /* Now find the first mismatch; this won't go past the
     character we just changed.  */
  while (*t1++ == *t2++);

  /* Undo the alteration.  */
  s1->text[s1->length] = savechar;

  /* If the comparison stopped at the alteration,
     the two lines are identical.  */
  if (t1 == s1->text + s1->length + 1)
    return 0;

  /* Not exactly identical, but perhaps they match anyway
     when case or whitespace is ignored.  */

  if (ignore_case_flag || ignore_space_change_flag || ignore_all_space_flag)
    {
      t1 = s1->text;
      t2 = s2->text;

      while (1)
	{
	  register char c1 = *t1++;
	  register char c2 = *t2++;

	  /* Ignore horizontal whitespace if -b or -w is specified.  */

	  if (ignore_all_space_flag)
	    {
	      /* For -w, just skip past any spaces or tabs.  */
	      while (c1 == ' ' || c1 == '\t') c1 = *t1++;
	      while (c2 == ' ' || c2 == '\t') c2 = *t2++;
	    }
	  else if (ignore_space_change_flag)
	    {
	      /* For -b, advance past any sequence of whitespace in line 1
		 and consider it just one Space, or nothing at all
		 if it is at the end of the line.  */
	      if (c1 == ' ' || c1 == '\t')
		{
		  while (1)
		    {
		      c1 = *t1++;
		      if (c1 == end_char)
			break;
		      if (c1 != ' ' && c1 != '\t')
			{
			  --t1;
			  c1 = ' ';
			  break;
			}
		    }
		}

	      /* Likewise for line 2.  */
	      if (c2 == ' ' || c2 == '\t')
		{
		  while (1)
		    {
		      c2 = *t2++;
		      if (c2 == end_char)
			break;
		      if (c2 != ' ' && c2 != '\t')
			{
			  --t2;
			  c2 = ' ';
			  break;
			}
		    }
		}
	    }

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

	  if (ignore_case_flag)
	    {
	      if (islower (c1))
		c1 = toupper (c1);
	      if (islower (c2))
		c2 = toupper (c2);
	    }

	  if (c1 != c2)
	    break;
	  if (c1 == end_char)
	    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) ();
     void (*printfun) ();
{
  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 = NULL;
#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 *line_flag;
     struct line_def *line;
{
  fprintf (outfile, "%s", line_flag);

  /* 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[0] != 0)
    {
      if (tab_align_flag)
	fprintf (outfile, "\t");
      else
	fprintf (outfile, " ");
    }

  /* Now output the contents of the line.
     If -t was specified, expand tabs to spaces.
     Otherwise output verbatim.  */

  if (tab_expand_flag)
    {
      register int column = 0;
      register int i;
      for (i = 0; i <= line->length; i++)
	{
	  register char c = line->text[i];
	  if (c == '\t')
	    {
	      putc (' ', outfile);
	      column++;
	      while (column & 7)
		{
		  putc (' ', outfile);
		  column++;
		}
	    }
	  else if (c == '\b')
	    {
	      column--;
	      putc (c, outfile);
	    }
	  else
	    {
	      column++;
	      putc (c, outfile);
	    }
	}
    }
  else
    fwrite (line->text, sizeof (char), line->length + 1, outfile);

  if (line_end_char != '\n')
    putc ('\n', outfile);
}

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 within the current chunk.
   Actual line numbers count from 1 within the entire file;
   in addition, they include lines ignored for comparison purposes.

   The `ltran' feature is no longer in use.  */

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

void
translate_range (file, a, b, aptr, bptr)
     struct file_data *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)
     char 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 f0, l0, f1, l1, show_from, show_to;
  int i;
  int nontrivial = !(ignore_blank_lines_flag || ignore_regexp);
  struct change *next;

  show_from = show_to = 0;

  f0 = hunk->line0;
  f1 = hunk->line1;

  for (next = hunk; next; next = next->link)
    {
      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 && ! nontrivial; i++)
	if ((!ignore_blank_lines_flag || files[0].linbuf[i].length > 1)
	    && (!ignore_regexp
		|| 0 > re_search (&ignore_regexp_compiled,
				  files[0].linbuf[i].text,
				  files[0].linbuf[i].length, 0,
				  files[0].linbuf[i].length, 0)))
	  nontrivial = 1;

      for (i = next->line1; i <= l1 && ! nontrivial; i++)
	if ((!ignore_blank_lines_flag || files[1].linbuf[i].length > 1)
	    && (!ignore_regexp
		|| 0 > re_search (&ignore_regexp_compiled,
				  files[1].linbuf[i].text,
				  files[1].linbuf[i].length, 0,
				  files[1].linbuf[i].length, 0)))
	  nontrivial = 1;
    }

  *first0 = f0;
  *last0 = l0;
  *first1 = f1;
  *last1 = l1;

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

  if (!nontrivial)
    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)
     unsigned size;
{
  register void *value = (void *) malloc (size);

  if (!value)
    fatal ("virtual 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;
     unsigned int size;
{
  register void *value = (void *) realloc (old, size);

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

void *
xcalloc (nitems, size)
     int nitems, size;
{
  void *value = (void *) calloc (nitems, size);

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

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

char *
concat (s1, s2, s3)
     char *s1, *s2, *s3;
{
  int len = strlen (s1) + strlen (s2) + strlen (s3);
  char *new = (char *) xmalloc (len + 1);
  strcpy (new, s1);
  strcat (new, s2);
  strcat (new, s3);
  return new;
}

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);
}