Re-implement iconv convertor as a regular filter.

* include/mailutils/filter.h (mu_iconv_filter): New extern.
* libmailutils/filter/iconvflt.c: New file.
* libmailutils/filter/Makefile.am (libfilter_la_SOURCES): Add iconvflt.c
* libmailutils/filter/filter.c (mu_filter_get_list): Register
mu_iconv_filter.

@@ -120,6 +120,7 @@ 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;
 extern mu_filter_record_t mu_linelen_filter;
+extern mu_filter_record_t mu_iconv_filter;
   
 enum mu_iconv_fallback_mode
   {

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

@@ -82,6 +82,7 @@ mu_filter_get_list (mu_list_t *plist)
       mu_list_append (filter_list, mu_header_filter);
       mu_list_append (filter_list, mu_linecon_filter);
       mu_list_append (filter_list, mu_linelen_filter);
+      mu_list_append (filter_list, mu_iconv_filter);
       /* FIXME: add the default encodings?  */
     }
   *plist = filter_list;

+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 2004, 2005, 2007, 2010 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/>. */
+
+/* Iconv filter: converts input between two charsets.
+   
+   This filter operates in decode mode only.  Initialization sequence
+   requires two arguments: the name of the input encoding and that
+   of the output encoding.  Optional third argument specifies what
+   to do when an illegal character sequence is encountered on input.
+   Possible values are:
+ 
+     none       - return failure and stop further conversions;
+     copy-pass  - copy the offending character to the output verbatim;
+     copy-octal - represent it as a C octal sequence (\NNN).
+
+   The default is "copy-octal", unless overridden by mu_default_fallback_mode
+   setting (which see).
+*/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <mailutils/stream.h>
+#include <mailutils/sys/stream.h>
+#include <mailutils/filter.h>
+#include <mailutils/errno.h>
+#include <mailutils/cstr.h>
+#include <mailutils/cctype.h>
+#include <mailutils/util.h>
+
+#ifdef HAVE_ICONV_H
+# include <iconv.h>
+#endif
+
+#ifndef ICONV_CONST
+# define ICONV_CONST
+#endif
+
+#ifndef HAVE_ICONV
+# undef iconv_open
+# define iconv_open(tocode, fromcode) ((iconv_t) -1)
+
+# undef iconv
+# define iconv(cd, inbuf, inbytesleft, outbuf, outbytesleft) (errno = EILSEQ, (size_t) -1)
+
+# undef iconv_close
+# define iconv_close(cd) 0
+
+#endif 
+
+struct _icvt_filter
+{
+  char *fromcode;
+  char *tocode;
+  enum mu_iconv_fallback_mode fallback_mode;
+  iconv_t cd;           /* Conversion descriptor */
+};
+
+static enum mu_filter_result
+_icvt_decoder (void *xd,
+	       enum mu_filter_command cmd,
+	       struct mu_filter_io *iobuf)
+{
+  struct _icvt_filter *_icvt = xd;
+  char *ip, *op;
+  size_t ilen, olen;
+  int rc;
+    
+  switch (cmd)
+    {
+    case mu_filter_init:
+      if (mu_c_strcasecmp (_icvt->fromcode, _icvt->tocode) == 0)
+	_icvt->cd = (iconv_t) -1;
+      else
+	{
+	  iconv_t cd = iconv_open (_icvt->tocode, _icvt->fromcode);
+	  if (cd == (iconv_t) -1)
+	    return mu_filter_failure;
+	  _icvt->cd = cd;
+	}
+      return mu_filter_ok;
+
+    case mu_filter_done:
+      iconv_close (_icvt->cd);
+      free (_icvt->fromcode);
+      free (_icvt->tocode);
+      return mu_filter_ok;
+
+    default:
+      break;
+    }
+
+  if (_icvt->cd == (iconv_t) -1)
+    {
+      size_t len = iobuf->isize;
+      if (len > iobuf->osize)
+	len = iobuf->osize;
+      memcpy (iobuf->output, iobuf->input, len);
+      iobuf->isize = len;
+      iobuf->osize = len;
+      return mu_filter_ok;
+    }
+  
+  ip = (char*) iobuf->input;
+  ilen = iobuf->isize;
+  op = iobuf->output;
+  olen = iobuf->osize;
+ again:
+  rc = iconv (_icvt->cd, &ip, &ilen, &op, &olen);
+  if (rc == -1)
+    {
+      switch (errno) 
+	{
+	case E2BIG:
+	  iobuf->osize += 16;
+	  return mu_filter_moreoutput;
+	
+	case EINVAL:
+	  /* An incomplete multibyte sequence is encountered in the input */
+	  if (ilen == iobuf->isize)
+	    {
+	      iobuf->isize++;
+	      return mu_filter_moreinput;
+	    }
+	  break;
+	  
+	case EILSEQ:
+	  switch (_icvt->fallback_mode)
+	    {
+	    case mu_fallback_none:
+	      return mu_filter_failure;
+	      
+	    case mu_fallback_copy_pass:
+	      *op++ = *ip++;
+	      ilen--;
+	      olen--;
+	      break;
+	      
+	    case mu_fallback_copy_octal:
+	      if (mu_isprint (*ip))
+		{
+		  *op++ = *ip++;
+		  ilen--;
+		  olen--;
+		}
+	      else
+		{
+		  if (olen < 4)
+		    {
+		      iobuf->osize = 4;
+		      return mu_filter_moreoutput;
+		    }
+		  sprintf (op, "\\%03o", *(unsigned char*)ip);
+		  op += 4;
+		  olen -= 4;
+		  ip++;
+		  ilen--;
+		}
+	    }
+	  if (ilen && olen)
+	    goto again;
+	  break;
+	      
+	default:
+	  return mu_filter_failure;
+	}
+    }
+
+  iobuf->isize = ip - iobuf->input;
+  iobuf->osize = op - iobuf->output;
+  return mu_filter_ok;
+}
+
+static int
+alloc_state (void **pret, int mode MU_ARG_UNUSED, int argc, const char **argv)
+{
+  struct _icvt_filter *flt;
+  const char *from;
+  const char *to;
+  enum mu_iconv_fallback_mode fallback_mode = mu_default_fallback_mode;
+  
+  if (argc < 3)
+    return EINVAL; /* FIXME: Provide some defaults? */
+  if (argc > 4)
+    return EINVAL;
+  
+  from = argv[1];
+  to = argv[2];
+
+  if (argc == 4)
+    {
+      const char *str = argv[3];
+      if (strcmp (str, "none") == 0)
+	fallback_mode = mu_fallback_none;
+      else if (strcmp (str, "copy-pass") == 0)
+	fallback_mode = mu_fallback_copy_pass;
+      else if (strcmp (str, "copy-octal") == 0)
+	fallback_mode = mu_fallback_copy_octal;
+      else
+	return EINVAL;
+    }
+
+  flt = calloc (1, sizeof (*flt));
+  if (!flt)
+    return ENOMEM;
+  flt->fromcode = strdup (from);
+  if (!flt->fromcode)
+    {
+      free (flt);
+      return ENOMEM;
+    }
+  flt->tocode = strdup (to);
+  if (!flt->tocode)
+    {
+      free (flt->fromcode);
+      free (flt);
+      return ENOMEM;
+    }
+  flt->fallback_mode = fallback_mode;
+  flt->cd = (iconv_t) -1;
+  *pret = flt;
+  return 0;
+}
+  
+static struct _mu_filter_record _iconv_filter = {
+  "ICONV",
+  alloc_state,
+  NULL,
+  _icvt_decoder  
+};
+
+mu_filter_record_t mu_iconv_filter = &_iconv_filter;