New filter "c-escape".

* libmailutils/filter/c-escape.c: New file.
* include/mailutils/filter.h (mu_c_escape_filter): New extern.
* libmailutils/filter/Makefile.am (libfilter_la_SOURCES): Add c-escape.c
* libmailutils/filter/filter.c (mu_filter_get_list): Add
mu_c_escape_filter to the list.

@@ -123,6 +123,7 @@ extern mu_filter_record_t mu_header_filter;
 extern mu_filter_record_t mu_linecon_filter;
 extern mu_filter_record_t mu_linelen_filter;
 extern mu_filter_record_t mu_iconv_filter;
+extern mu_filter_record_t mu_c_escape_filter;
   
 enum mu_iconv_fallback_mode
   {

@@ -20,6 +20,7 @@ noinst_LTLIBRARIES = libfilter.la
 libfilter_la_SOURCES =\
  base64.c\
  binflt.c\
+ c-escape.c\
  crlfdot.c\
  crlfflt.c\
  decode.c\

+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 2011 Free Software Foundation, Inc.
+
+   This library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 3 of the License, or (at your option) any later version.
+
+   This library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General
+   Public License along with this library.  If not, see 
+   <http://www.gnu.org/licenses/>. */
+
+/* A C-escape filter.
+   In encode mode, replaces control characters with their C escapes.
+   For example, newline (ASCII 10) becomes \n, horizontal tab (ASCII 9)
+   becomes \t etc.
+   In decode mode, the reverse operation is performed, i.e. each C escape
+   is replaced with the corresponding character.  Unrecognized escape
+   sequences are copied verbatim.
+
+   FIXME: Only named escapes are supported.
+*/
+   
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <mailutils/errno.h>
+#include <mailutils/filter.h>
+#include <mailutils/wordsplit.h>
+#include <mailutils/cctype.h>
+
+/* Move min(isize,osize) bytes from iptr to optr, replacing each
+   escapable control character with its escape sequence. */
+static enum mu_filter_result
+_c_escape_encoder (void *xd MU_ARG_UNUSED,
+		   enum mu_filter_command cmd,
+		   struct mu_filter_io *iobuf)
+{
+  size_t i, j;
+  const unsigned char *iptr;
+  size_t isize;
+  char *optr;
+  size_t osize;
+  
+  switch (cmd)
+    {
+    case mu_filter_init:
+    case mu_filter_done:
+      return mu_filter_ok;
+    default:
+      break;
+    }
+  
+  iptr = (const unsigned char *) iobuf->input;
+  isize = iobuf->isize;
+  optr = iobuf->output;
+  osize = iobuf->osize;
+
+  for (i = j = 0; i < isize && j < osize; i++)
+    {
+      unsigned char c = *iptr++;
+
+      if (mu_iscntrl (c))
+	{
+	  int x;
+
+	  x = mu_wordsplit_c_quote_char (c);
+	  if (x == -1)
+	    optr[j++] = c;
+	  else if (j + 1 == osize)
+	    {
+	      if (i == 0)
+		{
+		  iobuf->osize = 2;
+		  return mu_filter_moreoutput;
+		}
+	      break;
+	    }
+	  else
+	    {
+	      optr[j++] = '\\';
+	      optr[j++] = x;
+	    }
+	}
+      else
+	optr[j++] = c;
+    }
+  iobuf->isize = i;
+  iobuf->osize = j;
+  return mu_filter_ok;
+}
+
+/* Move min(isize,osize) bytes from iptr to optr, replacing each escape
+   sequence with its ASCII code. */
+static enum mu_filter_result
+_c_escape_decoder (void *xd MU_ARG_UNUSED,
+		   enum mu_filter_command cmd,
+		   struct mu_filter_io *iobuf)
+{
+  size_t i, j;
+  const unsigned char *iptr;
+  size_t isize;
+  char *optr;
+  size_t osize;
+  
+  switch (cmd)
+    {
+    case mu_filter_init:
+    case mu_filter_done:
+      return mu_filter_ok;
+    default:
+      break;
+    }
+  
+  iptr = (const unsigned char *) iobuf->input;
+  isize = iobuf->isize;
+  optr = iobuf->output;
+  osize = iobuf->osize;
+
+  for (i = j = 0; i < isize && j < osize; i++)
+    {
+      unsigned char c = *iptr++;
+      if (c == '\\')
+	{
+	  int x;
+	  if (i + 1 == isize)
+	    break;
+	  c = *iptr++;
+	  i++;
+	  x = mu_wordsplit_c_unquote_char (c);
+	  optr[j++] = (x == -1) ? c : x;
+	}
+      else
+	optr[j++] = c;
+    }
+
+  iobuf->isize = i;
+  iobuf->osize = j;
+  return mu_filter_ok;
+}
+
+static struct _mu_filter_record _c_escape_filter = {
+  "C-escape",
+  NULL,
+  _c_escape_encoder,
+  _c_escape_decoder,
+};
+
+mu_filter_record_t mu_c_escape_filter = &_c_escape_filter;
+

@@ -83,6 +83,7 @@ mu_filter_get_list (mu_list_t *plist)
       mu_list_append (filter_list, mu_linecon_filter);
       mu_list_append (filter_list, mu_linelen_filter);
       mu_list_append (filter_list, mu_iconv_filter);
+      mu_list_append (filter_list, mu_c_escape_filter);
       /* FIXME: add the default encodings?  */
     }
   *plist = filter_list;

 ;; Default components file for GNU MH.
 ;; Lines beginning with ; are ignored.  Rest of lines is copied verbatim.
-To:
-cc:
-Subject:
+To: 
+cc: 
+Subject: 
 --------