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/* braces.c -- code for doing word expansion in curly braces. */

/* Copyright (C) 1987,1989 Free Software Foundation, Inc.

This file is part of GNU Bash, the Bourne Again SHell.

Bash 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.

Bash 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 Bash; see the file COPYING.  If not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */

/* Stuff in curly braces gets expanded after variable and command
   substitution, but before filename globbing. 

   (Actually, this should be true for the sake of efficiency, but it
   isn't because of quoting hacks.  Once I rebuild quoting it will be
   true. */

/* Thanks to Chet Ramey (chet@cwjcc@cwru.edu) for his approach. */

#include "general.h"
#define brace_whitespace(c) (!(c) || (c) == ' ' || (c) == '\t' || (c) == '\n')
#ifndef NULL
#define NULL (char *)0x0
#endif

/* Basic idea:

   Segregate the text into 3 sections: preamble (stuff before an open brace),
   postamble (stuff after the matching close brace) and amble (stuff after
   preamble, and before postamble).  Expand amble, and then tack on the
   expansions to preamble.  Expand postamble, and tack on the expansions to
   the result so far.
 */

static int brace_gobbler ();
static char **expand_amble (), **array_concat (), **copy_array ();

/* Return an array of strings; the brace expansion of TEXT. */
char **
brace_expand (text)
     char *text;
{
  register int start;
  char *preamble, *postamble, *amble;
  char **tack, **result;
  int i, c;

  /* Find the text of the preamble. */
  i = 0;
  c = brace_gobbler (text, &i, '{');

  preamble = (char *)xmalloc (i + 1);
  strncpy (preamble, text, i);
  preamble[i] = '\0';

  result = (char **)xmalloc (2 * sizeof (char *));
  result[0] = preamble;
  result[1] = (char *)NULL;
  
  /* Special case.  If we never found an exciting character, then
     the preamble is all of the text, so just return that. */
  if (c != '{')
    return (result);

  /* Find the amble.  This is the stuff inside this set of braces. */
  start = ++i;
  c = brace_gobbler (text, &i, '}');

  /* What if there isn't a matching close brace? */
  if (!c)
    {
      report_error ("Missing `}'");
      free (preamble);
      result[0] = savestring (text);
      return (result);
    }

  amble = (char *)xmalloc (1 + (i - start));
  strncpy (amble, &text[start], (i - start));
  amble[i - start] = '\0';

  postamble = &text[i + 1];

  tack = expand_amble (amble);
  result = array_concat (result, tack);
  free (amble);
  free_array (tack);

  tack = brace_expand (postamble);
  result = array_concat (result, tack);
  free_array (tack);

  return (result);
}

/* Expand the text found inside of braces.  We simply try to split the
   text at commas into separate strings.  We then brace expand each
   slot which needs it, until there are no more slots which need it. */
static char **
expand_amble (text)
     char *text;
{
  char **result, **partial;
  char *tem;
  int start, i, c;

  result = (char **)NULL;

  for (start = 0, i = 0, c = 1; c; start = ++i)
    {
      c = brace_gobbler (text, &i, ',');
      tem = (char *)xmalloc (1 + (i - start));
      strncpy (tem, &text[start], (i - start));
      tem[i- start] = '\0';

      partial = brace_expand (tem);

      if (!result)
	result = partial;
      else
	{
	  register int lr = array_len (result);
	  register int lp = array_len (partial);
	  register int j;

	  result = (char **)xrealloc (result, (1 + lp + lr) * sizeof (char *));

	  for (j = 0; j < lp; j++)
	    result[lr + j] = partial[j];

	  result[lr + j] = (char *)NULL;
	  free (partial);
	}
      free (tem);
    }
  return (result);
}

/* Start at INDEX, and skip characters in TEXT.  Set INDEX to the
   index of the character matching SATISFY.  This understands about
   quoting.  Return the character that caused us to stop searching;
   this is either the same as SATISFY, or 0. */
static int
brace_gobbler (text, index, satisfy)
     char *text;
     int *index;
     int satisfy;
{
  register int i, c, quoted, level;

  level = quoted = 0;

  for (i = *index; c = text[i]; i++)
    {
      if (quoted)
	{
	  if ((quoted == '\\') || (c == quoted))
	    quoted = 0;
	  continue;
	}

      if (c == '"' || c == '\'' || c == '\\')
	{
	  quoted = c;
	  continue;
	}
      
      if (c == satisfy && !level && !quoted)
	{
	  /* We ignore an open brace surrounded by whitespace, and also
	     an open brace followed immediately by a close brace, that
	     was preceded with whitespace.  */
	  if (c == '{' &&
	      ((!i || brace_whitespace (text[i - 1])) &&
	       (brace_whitespace (text[i + 1]) || text[i + 1] == '}')))
	    continue;
#ifdef SHELL
	  if (c != '{' || (!i || (text[i - 1] != '$')))
#endif
	    break;
	}

      if (c == '{')
	level++;
      else if (c == '}' && level)
	level--;
    }

  *index = i;
  return (c);
}

/* Return a new array of strings which is the result of appending each
   string in ARR2 to each string in ARR1.  The resultant array is
   len (arr1) * len (arr2) long.  For convenience, ARR1 (and its contents)
   are free ()'ed.  ARR1 can be NULL, in that case, a new version of ARR2
   is returned. */
static char **
array_concat (arr1, arr2)
     char **arr1, **arr2;
{
  register int i, j, len, len1, len2;
  register char **result;

  if (!arr1)
    return (copy_array (arr2));

  if (!arr2)
    return (arr1);

  len1 = array_len (arr1);
  len2 = array_len (arr2);

  result = (char **)xmalloc ((1 + (len1 * len2)) * sizeof (char *));

  len = 0;
  for (i = 0; i < len1; i++)
    {
      int strlen_1 = strlen (arr1[i]);

      for (j = 0; j < len2; j++)
	{
	  result[len] =
	    (char *)xmalloc (1 + strlen_1 + strlen (arr2[j]));
	  strcpy (result[len], arr1[i]);
	  strcpy (result[len] + strlen_1, arr2[j]);
	  len++;
	}
      free (arr1[i]);
    }
  free (arr1);

  result[len] = (char *)NULL;
  return (result);
}

static char **
copy_array (array)
     char **array;
{
  register int i;
  char **new;


  if (!array)
    return (array);

  new = (char **)xmalloc ((1 + array_len (array)) * sizeof (char *));

  for (i = 0; array[i]; i++)
    new[i] = savestring (array[i]);

  new[i] = (char *)NULL;

  return (new);
}
  

#ifdef TEST

#include <stdio.h>

fatal_error (format, arg1, arg2)
     char *format, *arg1, *arg2;
{
  report_error (format, arg1, arg2);
  exit (1);
}

report_error (format, arg1, arg2)
     char *format, *arg1, *arg2;
{
  fprintf (stderr, format, arg1, arg2);
  fprintf (stderr, "\n");
}

main ()
{
  char example[256];

  for (;;)
    {
      char **result;
      int i;

      fprintf (stderr, "brace_expand> ");

      if ((!fgets (example, 256, stdin)) ||
	  (strncmp (example, "quit", 4) == 0))
	break;

      if (strlen (example))
	example[strlen (example) - 1] = '\0';

      result = brace_expand (example);

      for (i = 0; result[i]; i++)
	printf ("%s\n", result[i]);

      free_array (result);
    }
}

\f


/*
 * Local variables:
 * compile-command: "gcc -g -Bstatic -DTEST -o brace_expand braces.c general.o"
 * end:
 */

#endif  /* TEST */
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