Implement a "line continuation" filter.

Line continuation filter removes from its input any sequence of '\\\n'
(a backslash followed by a newline).  It is useful for reading various
UNIX configuration files.

* include/mailutils/filter.h (mu_linecon_filter): New extern.
* libmailutils/filter/linecon.c: New file.
* libmailutils/filter/Makefile.am (libfilter_la_SOURCES): Add linecon.c
* libmailutils/filter/filter.c (mu_filter_get_list): Register mu_linecon_filter.
* libmailutils/tests/linecon.at: New test.
* libmailutils/tests/Makefile.am (TESTSUITE_AT): Add linecon.at
* libmailutils/tests/testsuite.at: Include linecon.at

@@ -110,6 +110,7 @@ extern mu_filter_record_t mu_rfc_2047_B_filter;
 extern mu_filter_record_t mu_from_filter;
 extern mu_filter_record_t mu_inline_comment_filter;
 extern mu_filter_record_t mu_header_filter;
+extern mu_filter_record_t mu_linecon_filter;
 
 enum mu_iconv_fallback_mode
   {

@@ -29,6 +29,7 @@ libfilter_la_SOURCES =\
  fromflt.c\
  header.c\
  inline-comment.c\
+ linecon.c\
  linelenflt.c\
  qpflt.c
 

@@ -80,6 +80,7 @@ mu_filter_get_list (mu_list_t *plist)
       mu_list_append (filter_list, mu_from_filter);
       mu_list_append (filter_list, mu_inline_comment_filter);
       mu_list_append (filter_list, mu_header_filter);
+      mu_list_append (filter_list, mu_linecon_filter);
       /* FIXME: add the default encodings?  */
     }
   *plist = filter_list;

+/* Simple inline comment filter for GNU Mailutils.
+   Copyright (C) 2010 Free Software Foundation, Inc.
+
+   GNU Mailutils 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 3, or (at your option)
+   any later version.
+
+   GNU Mailutils 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 Mailutils.  If not, see <http://www.gnu.org/licenses/>. */
+
+/* linecon - a line continuation filter.
+
+   This filter has only decode mode.  It removes from the input
+   backslashes immediately followed by a newline, thus implementing
+   a familiar UNIX line-continuation facility. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <stdlib.h>
+#include <mailutils/errno.h>
+#include <mailutils/filter.h>
+#include <mailutils/cctype.h>
+
+static enum mu_filter_result
+_linecon_decoder (void *xd, enum mu_filter_command cmd,
+		  struct mu_filter_io *iobuf)
+{
+  int *escaped = xd;
+  const unsigned char *iptr, *iend;
+  char *optr, *oend;
+
+  switch (cmd)
+    {
+    case mu_filter_init:
+      *escaped = 0;
+      return mu_filter_ok;
+      
+    case mu_filter_done:
+      return mu_filter_ok;
+      
+    default:
+      break;
+    }
+  
+  iptr = (const unsigned char *) iobuf->input;
+  iend = iptr + iobuf->isize;
+  optr = iobuf->output;
+  oend = optr + iobuf->osize;
+
+  while (iptr < iend && optr < oend)
+    {
+      int c = *iptr++;
+      switch (c)
+	{
+	case '\\':
+	  *escaped = 1;
+	  continue;
+
+	case '\n':
+	  if (*escaped)
+	    {
+	      *escaped = 0;
+	      continue;
+	    }
+	  *optr++ = c;
+	  break;
+
+	default:
+	  if (*escaped)
+	    {
+	      *escaped = 0;
+	      *optr++ = '\\';
+	      if (optr == oend)
+		{
+		  iptr--;
+		  break;
+		}
+	    }
+	  *optr++ = c;
+	}
+    }
+
+  iobuf->isize = iptr - (const unsigned char *) iobuf->input;
+  iobuf->osize = optr - iobuf->output;
+  return mu_filter_ok;
+}
+
+static int
+alloc_state (void **pret, int mode MU_ARG_UNUSED, int argc, const char **argv)
+{
+  *pret = malloc (sizeof (int));
+  if (!*pret)
+    return ENOMEM;
+  return 0;
+}
+
+static struct _mu_filter_record _linecon_filter = {
+  "LINECON",
+  0,
+  alloc_state,
+  NULL,
+  _linecon_decoder,
+};
+
+mu_filter_record_t mu_linecon_filter = &_linecon_filter;

@@ -69,6 +69,7 @@ TESTSUITE_AT = \
  fromflt.at\
  hdrflt.at\
  inline-comment.at\
+ linecon.at\
  list.at\
  mailcap.at\
  prop.at\

+# This file is part of GNU Mailutils. -*- Autotest -*-
+# Copyright (C) 2010 Free Software Foundation, Inc.
+#
+# GNU Mailutils 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 3, or (at
+# your option) any later version.
+#
+# GNU Mailutils 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 Mailutils.  If not, see <http://www.gnu.org/licenses/>.
+
+AT_SETUP([linecon filter])
+AT_KEYWORDS([filter decode linecon])
+sed 's/\$//' > input <<EOT
+input line 1
+input line 2
+a very\
+ long logical\
+ line spl\
+it over several physical\
+ ones
+a li\ne with \escapes
+backslash followed by a space \ $
+EOT
+sed 's/\$//' > expout <<EOT
+input line 1
+input line 2
+a very long logical line split over several physical ones
+a li\ne with \escapes
+backslash followed by a space \ $
+EOT
+
+AT_CHECK([fltst linecon decode read < input],
+[0],
+[expout])
+
+AT_CHECK([fltst linecon decode write < input],
+[0],
+[expout])
+
+AT_CLEANUP
+
+
+

@@ -67,4 +67,5 @@ m4_include([wicket.at])
 m4_include([prop.at])
 m4_include([inline-comment.at])
 m4_include([hdrflt.at])
+m4_include([linecon.at])