wireshark/epan/dissectors/packet-per.c

/*
XXX all this offset>>3 and calculations of bytes in the tvb everytime
we put something in the tree is just silly.  should be replaced with some
proper helper routines
*/
/* packet-per.c
 * Routines for dissection of ASN.1 Aligned PER
 * 2003  Ronnie Sahlberg
 *
 * $Id$
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * This program 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 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <glib.h>
#include <epan/packet.h>

#include <stdio.h>
#include <string.h>

#include <epan/to_str.h>
#include <epan/prefs.h>
#include <epan/emem.h>
#include "packet-per.h"


static int proto_per = -1;
static int hf_per_GeneralString_length = -1;
static int hf_per_extension_bit = -1;
static int hf_per_extension_present_bit = -1;
static int hf_per_choice_index = -1;
static int hf_per_choice_extension_index = -1;
static int hf_per_enum_index = -1;
static int hf_per_enum_extension_index = -1;
static int hf_per_num_sequence_extensions = -1;
static int hf_per_small_number_bit = -1;
static int hf_per_optional_field_bit = -1;
static int hf_per_sequence_of_length = -1;
static int hf_per_object_identifier_length = -1;
static int hf_per_open_type_length = -1;
static int hf_per_octet_string_length = -1;
static int hf_per_bit_string_length = -1;
static int hf_per_const_int_len = -1;

static gint ett_per_sequence_of_item = -1;


/*
#define DEBUG_ENTRY(x) \
printf("#%u  %s   tvb:0x%08x\n",actx->pinfo->fd->num,x,(int)tvb);
*/
#define DEBUG_ENTRY(x) \
	;

#define BLEN(old_offset, offset) (((offset)>>3)!=((old_offset)>>3)?((offset)>>3)-((old_offset)>>3):1)

/* whether the PER helpers should put the internal PER fields into the tree
   or not.
*/
static gboolean display_internal_per_fields = FALSE;



static const true_false_string tfs_extension_present_bit = {
	"",
	""
};
static const true_false_string tfs_extension_bit = {
	"Extension bit is set",
	"Extension bit is clear"
};
static const true_false_string tfs_small_number_bit = {
	"The number is small, 0-63",
	"The number is large, >63"
};
static const true_false_string tfs_optional_field_bit = {
	"",
	""
};

void asn1_ctx_init(asn1_ctx_t *actx, asn1_enc_e encoding, gboolean aligned, packet_info *pinfo) {
  actx->encoding = encoding;
  actx->aligned = aligned;
  actx->pinfo = pinfo;
  actx->created_item = NULL;
  actx->value_ptr = NULL;
  actx->private_data = NULL;
}


#define BYTE_ALIGN_OFFSET(offset)		\
	if(offset&0x07){			\
		offset=(offset&0xfffffff8)+8;	\
	}

/* 10 Encoding procedures -------------------------------------------------- */

/* 10.2 Open type fields --------------------------------------------------- */
guint32 
dissect_per_open_type(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, per_type_fn type)
{
	guint32 type_length, end_offset;

	offset = dissect_per_length_determinant(tvb, offset, actx, tree, hf_per_open_type_length, &type_length);
	if (actx->aligned) BYTE_ALIGN_OFFSET(offset);
	end_offset = offset + type_length * 8;

	if (type) {
		type(tvb, offset, actx, tree, hf_index);
	} else {
		actx->created_item = proto_tree_add_text(tree, tvb, offset>>3, BLEN(offset, end_offset), "Unknown Open Type");
	}

	return end_offset;
}

/* 10.9 General rules for encoding a length determinant -------------------- 
	
	  NOTE 1 - (Tutorial) The procedures of this subclause are invoked when an explicit length field is needed 
				for some part of the encoding regardless of whether the length count is bounded above 
				(by PER-visible constraints) or not. The part of the encoding to which the length applies may 
				be a bit string (with the length count in bits), an octet string (with the length count in octets), 
				a known-multiplier character string (with the length count in characters), or a list of fields 
				(with the length count in components of a sequence-of or set-of).
	
	  NOTE 2 - (Tutorial) In the case of the ALIGNED variant if the length count is bounded above by an upper bound 
				that is less than 64K, then the constrained whole number encoding is used for the length. 
				For sufficiently small ranges the result is a bit-field, otherwise the unconstrained length ("n" say) 
				is encoded into an octet-aligned bit-field in one of three ways (in order of increasing size):
		a)	("n" less than 128) a single octet containing "n" with bit 8 set to zero;
		b)	("n" less than 16K) two octets containing "n" with bit 8 of the first octet set to 1 and bit 7 set to zero;
		c)	(large "n") a single octet containing a count "m" with bit 8 set to 1 and bit 7 set to 1. 
			The count "m" is one to four, and the length indicates that a fragment of the material follows 
			(a multiple "m" of 16K items). For all values of "m", the fragment is then followed by another length encoding
			for the remainder of the material.
	
	  NOTE 3 - (Tutorial) In the UNALIGNED variant, if the length count is bounded above by an upper bound that is less
			than 64K, then the constrained whole number encoding is used to encode the length in the minimum number of 
			bits necessary to represent the range. Otherwise, the unconstrained length ("n" say) is encoded into a bit 
			field in the manner described above in Note 2.

 */
guint32
dissect_per_length_determinant(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx _U_, proto_tree *tree, int hf_index, guint32 *length)
{
	guint8 byte;
	guint32 len;
	proto_item *pi;
	int num_bits;
	int i, bit;
	gboolean tmp;

	if(!length){
		length=&len;
	}

	/* byte aligned */
	if (actx->aligned){
		BYTE_ALIGN_OFFSET(offset);
		byte=tvb_get_guint8(tvb, offset>>3);
		offset+=8;
	}else{
		char *str;
		guint32 val;
		gint val_start;
		
		val_start = offset>>3;
		val = 0;
		str=ep_alloc(256);

		g_snprintf(str, 256, " ");
		for(bit=0;bit<((int)(offset&0x07));bit++){
			if(bit&&(!(bit%4))){
				strcat(str, " ");
			}
			strcat(str,".");
		}
		/* read the bits for the int */
		num_bits = 8;
		for(i=0;i<num_bits;i++){
			if(bit&&(!(bit%4))){
				strcat(str, " ");
			}
			if(bit&&(!(bit%8))){
				strcat(str, " ");
			}
			bit++;
			offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &tmp);
			val<<=1;
			if(tmp){
				val|=1;
				strcat(str, "1");
			} else {
				strcat(str, "0");
			}
		}
		if((val&0x80)==0){
			*length = val;
			if(hf_index!=-1){
				pi = proto_tree_add_uint(tree, hf_index, tvb, (offset>>3)-1, 1, *length);
				if (display_internal_per_fields)
					proto_item_append_text(pi," %s", str);
				else
					PROTO_ITEM_SET_HIDDEN(pi);
			}
		
			return offset;
		}
		PER_NOT_DECODED_YET("10.9 Unaligned");
		return offset;

	}

	/* 10.9.3.6 */
	if((byte&0x80)==0){
		*length=byte;
		if(hf_index!=-1){
			pi = proto_tree_add_uint(tree, hf_index, tvb, (offset>>3)-1, 1, *length);
			if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(pi);
		}
		return offset;
	}

	/* 10.9.3.7 */
	if((byte&0xc0)==0x80){
		*length=(byte&0x3f);
		*length=((*length)<<8)+tvb_get_guint8(tvb, offset>>3);
		offset+=8;
		if(hf_index!=-1){
			pi = proto_tree_add_uint(tree, hf_index, tvb, (offset>>3)-2, 2, *length);
			if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(pi);
		}
		return offset;
	}
	PER_NOT_DECODED_YET("10.9.3.8.1");
	return offset;
}

/* 10.6   normally small non-negative whole number */
static guint32
dissect_per_normally_small_nonnegative_whole_number(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint32 *length)
{
	gboolean small_number;
	guint32 len;
	proto_item *pi;

DEBUG_ENTRY("dissect_per_normally_small_nonnegative_whole_number");
	if(!length){
		length=&len;
	}

	offset=dissect_per_boolean(tvb, offset, actx, tree, hf_per_small_number_bit, &small_number);
	if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
	if(!small_number){
		int i;
		/* 10.6.1 */
		*length=0;
		for(i=0;i<6;i++){
			offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &small_number);
			*length<<=1;
			if(small_number){
				*length|=1;
			}
		}
		if(hf_index!=-1){
			if((offset&0x07)<7){
				pi = proto_tree_add_uint(tree, hf_index, tvb, (offset>>3)-1, 1, *length);
			} else {
				pi = proto_tree_add_uint(tree, hf_index, tvb, (offset>>3), 1, *length);
			}
			if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(pi);
		}
		return offset;
	}

	/* 10.6.2 */
	offset=dissect_per_length_determinant(tvb, offset, actx, tree, hf_index, length);

	return offset;
}



/* this function reads a GeneralString */
/* currently based on pure guesswork since RFC2833 didnt tell me much
   i guess that the PER encoding for this is a normally-small-whole-number
   followed by a ascii string.

   based on pure guesswork.  it looks ok in the only capture i have where
   there is a 1 byte general string encoded
*/
guint32
dissect_per_GeneralString(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index)
{
	guint32 length;

	offset=dissect_per_length_determinant(tvb, offset, actx, tree, hf_per_GeneralString_length, &length);

	proto_tree_add_item(tree, hf_index, tvb, offset>>3, length, FALSE);

	offset+=length*8;

	return offset;
}

/* 17 Encoding the null type */
guint32
dissect_per_null(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx _U_, proto_tree *tree, int hf_index) {
  proto_item *ti_tmp;

  ti_tmp = proto_tree_add_item(tree, hf_index, tvb, offset>>8, 0, FALSE);
  proto_item_append_text(ti_tmp, ": NULL");

  return offset;
}

/* 19 this function dissects a sequence of */
static guint32
dissect_per_sequence_of_helper(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, per_type_fn func, int hf_index, guint32 length)
{
	guint32 i;

DEBUG_ENTRY("dissect_per_sequence_of_helper");
	for(i=0;i<length;i++){
		guint32 lold_offset=offset;
		proto_item *litem;
		proto_tree *ltree;

		litem=proto_tree_add_text(tree, tvb, offset>>3, 0, "Item %d", i);
		ltree=proto_item_add_subtree(litem, ett_per_sequence_of_item);

		offset=(*func)(tvb, offset, actx, ltree, hf_index);
		proto_item_set_len(litem, (offset>>3)!=(lold_offset>>3)?(offset>>3)-(lold_offset>>3):1);
	}

	return offset;
}
guint32
dissect_per_sequence_of(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *parent_tree, int hf_index, gint ett_index, const per_sequence_t *seq)
{
	proto_item *item;
	proto_tree *tree;
	guint32 old_offset=offset;
	guint32 length;
	header_field_info *hfi;

DEBUG_ENTRY("dissect_per_sequence_of");

	/* semi-constrained whole number for number of elements */
	/* each element encoded as 10.9 */

	offset=dissect_per_length_determinant(tvb, offset, actx, parent_tree, hf_per_sequence_of_length, &length);

	hfi = proto_registrar_get_nth(hf_index);
	if (IS_FT_UINT(hfi->type)) {
		item = proto_tree_add_uint(parent_tree, hf_index, tvb, offset>>3, 0, length);
		proto_item_append_text(item, (length==1)?" item":" items");
	} else {
		item=proto_tree_add_item(parent_tree, hf_index, tvb, offset>>3, 0, FALSE);
	}
	tree=proto_item_add_subtree(item, ett_index);

	offset=dissect_per_sequence_of_helper(tvb, offset, actx, tree, seq->func, *seq->p_id, length);


	proto_item_set_len(item, (offset>>3)!=(old_offset>>3)?(offset>>3)-(old_offset>>3):1);
	return offset;
}


/* dissect a constrained IA5String that consists of the full ASCII set,
   i.e. no FROM stuff limiting the alphabet
*/
guint32
dissect_per_IA5String(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len)
{
	offset=dissect_per_octet_string(tvb, offset, actx, tree, hf_index, min_len, max_len, NULL);

	return offset;
}

/* XXX we dont do >64k length strings   yet */
static guint32
dissect_per_restricted_character_string_sorted(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len, const char *alphabet, int alphabet_length, tvbuff_t **value_tvb)
{
	guint32 length;
	gboolean byte_aligned;
	guint8 *buf;
	guint char_pos;
	int bits_per_char;
	guint32 old_offset;

DEBUG_ENTRY("dissect_per_restricted_character_string");

	/* xx.x if the length is 0 bytes there will be no encoding */
	if(max_len==0){
		if (value_tvb) {
			*value_tvb = tvb_new_real_data(NULL, 0, 0); 
			tvb_set_child_real_data_tvbuff(tvb, *value_tvb);
		}
		return offset;
	}


	if (min_len == NO_BOUND) {
		min_len=0;
	}


	/* 27.5.2 depending of the alphabet length, find how many bits
	   are used to encode each character */
/* unaligned PER */
	if (actx->aligned){

		if(alphabet_length<=2){
			bits_per_char=1;
		} else if(alphabet_length<=4){
			bits_per_char=2;
		} else if(alphabet_length<=16){
			bits_per_char=4;
		} else {
			bits_per_char=8;
		}
	}else{
		if(alphabet_length<=2){
			bits_per_char=1;
		} else if(alphabet_length<=4){
			bits_per_char=2;
		} else if(alphabet_length<=8){
			bits_per_char=3;
		} else if(alphabet_length<=16){
			bits_per_char=4;
		} else if(alphabet_length<=32){
			bits_per_char=5;
		} else if(alphabet_length<=64){
			bits_per_char=6;
		} else if(alphabet_length<=128){
			bits_per_char=7;
		} else {
			bits_per_char=8;
		}
	}

	byte_aligned=TRUE;
	if((min_len==max_len)&&(max_len<=2)){
		byte_aligned=FALSE;
	}
	if ((max_len != NO_BOUND) && (max_len < 2)) {
		byte_aligned=FALSE;
	}

	/* xx.x */
	length=max_len;
	if (max_len == NO_BOUND) {
		offset = dissect_per_length_determinant(tvb, offset, actx, tree, hf_per_octet_string_length, &length);
		/* the unconstrained strings are always byte aligned (27.6.3)*/
		byte_aligned=TRUE;
	} else if(min_len!=max_len){
		offset=dissect_per_constrained_integer(tvb, offset, actx,
			tree, hf_per_octet_string_length, min_len, max_len,
			&length, FALSE);
			if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
	}

	if(!length){
		/* there is no string at all, so dont do any byte alignment */
		/* byte_aligned=FALSE; */
		/* Advance offset to next 'element' */
		offset = offset + 1;	}

	if((byte_aligned)&&(actx->aligned)){
		BYTE_ALIGN_OFFSET(offset);
	}


	buf = g_malloc(length+1);
	old_offset=offset;
	for(char_pos=0;char_pos<length;char_pos++){
		guchar val;
		int i;
		gboolean bit;

		val=0;
		for(i=0;i<bits_per_char;i++){
			offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
			val=(val<<1)|bit;
		}
		/* ALIGNED PER does not do any remapping of chars if 
		   bitsperchar is 8 
		*/
		if(bits_per_char==8){
			buf[char_pos]=val;
		} else {
			if (val < alphabet_length){
				buf[char_pos]=alphabet[val];
			} else {
				buf[char_pos] = '?';	/* XXX - how to mark this? */
			}
		}
	}
	buf[char_pos]=0;
	proto_tree_add_string(tree, hf_index, tvb, (old_offset>>3), (offset>>3)-(old_offset>>3), (char*)buf);
	if (value_tvb) {
		*value_tvb = tvb_new_real_data(buf, length, length); 
		tvb_set_free_cb(*value_tvb, g_free);
		tvb_set_child_real_data_tvbuff(tvb, *value_tvb);
	} else {
		g_free(buf);
	}
	return offset;
}

static const char*
sort_alphabet(char *sorted_alphabet, const char *alphabet, int alphabet_length)
{
  int i, j;
  char c, c_max, c_min;
  char tmp_buf[256];

  if (!alphabet_length) return sorted_alphabet;
  memset(tmp_buf, 0, 256);
  c_min = c_max = alphabet[0];
  for (i=0; i<alphabet_length; i++) {
    c = alphabet[i];
    tmp_buf[(int)c] = 1;
    if (c > c_max) c_max = c;
    else if (c < c_min) c_min = c;
  }
  for (i=c_min,j=0; i<=c_max; i++) {
    if (tmp_buf[i]) sorted_alphabet[j++] = i;
  }
  return sorted_alphabet;
}

guint32
dissect_per_restricted_character_string(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len, const char *alphabet, int alphabet_length, tvbuff_t **value_tvb)
{
  const char *alphabet_ptr;
  char sorted_alphabet[128];

  if (alphabet_length > 127) {
    alphabet_ptr = alphabet;
  } else {
    alphabet_ptr = sort_alphabet(sorted_alphabet, alphabet, alphabet_length);
  }
  return dissect_per_restricted_character_string_sorted(tvb, offset, actx, tree, hf_index, min_len, max_len, alphabet_ptr, alphabet_length, value_tvb);
}

guint32
dissect_per_NumericString(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len)
{
	offset=dissect_per_restricted_character_string_sorted(tvb, offset, actx, tree, hf_index, min_len, max_len, 
		" 0123456789", 11, NULL);

	return offset;
}
guint32
dissect_per_PrintableString(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len)
{
	offset=dissect_per_restricted_character_string_sorted(tvb, offset, actx, tree, hf_index, min_len, max_len, 
		" '()+,-.*0123456789:=?ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz", 74, NULL);
	return offset;
}
guint32
dissect_per_VisibleString(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len)
{
	offset=dissect_per_restricted_character_string_sorted(tvb, offset, actx, tree, hf_index, min_len, max_len,
		" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~", 95, NULL);
	return offset;
}
guint32
dissect_per_BMPString(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len)
{
	guint32 length;
	static char *str;

	/* xx.x if the length is 0 bytes there will be no encoding */
	if(max_len==0){
		return offset;
	}


	if (min_len == NO_BOUND) {
		min_len = 0;
	}


	/* xx.x */
	length=max_len;
	if(min_len!=max_len){
		offset=dissect_per_constrained_integer(tvb, offset, actx,
			tree, hf_per_octet_string_length, min_len, max_len,
			&length, FALSE);
		if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
	}


	/* align to byte boundary */
	BYTE_ALIGN_OFFSET(offset);

	if(length>=1024){
		PER_NOT_DECODED_YET("BMPString too long");
		length=1024;
	}

	str = tvb_get_ephemeral_faked_unicode(tvb, offset>>3, length, FALSE);

	proto_tree_add_string(tree, hf_index, tvb, offset>>3, length*2, str);

	offset+=(length<<3)*2;

	return offset;
}


/* this function dissects a constrained sequence of */
guint32
dissect_per_constrained_sequence_of(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *parent_tree, int hf_index, gint ett_index, const per_sequence_t *seq, int min_len, int max_len)
{
	proto_item *item;
	proto_tree *tree;
	guint32 old_offset=offset;
	guint32 length;
	header_field_info *hfi;

DEBUG_ENTRY("dissect_per_constrained_sequence_of");

	/* 19.5 if min==max and min,max<64k ==> no length determinant */
	if((min_len==max_len) && (min_len<65536)){
		length=min_len;
		goto call_sohelper;
	}

	/* 19.6 ub>=64k or unset */
	if(max_len>=65536){
		/* semi-constrained whole number for number of elements */
		/* each element encoded as 10.9 */
		offset=dissect_per_length_determinant(tvb, offset, actx, parent_tree, hf_per_sequence_of_length, &length);
		length+=min_len;
		goto call_sohelper;
	}

	/* constrained whole number for number of elements */
	offset=dissect_per_constrained_integer(tvb, offset, actx,
		parent_tree, hf_per_sequence_of_length, min_len, max_len,
		&length, FALSE);
	if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);

call_sohelper:
	hfi = proto_registrar_get_nth(hf_index);
	if (IS_FT_UINT(hfi->type)) {
		item = proto_tree_add_uint(parent_tree, hf_index, tvb, offset>>3, 0, length);
		proto_item_append_text(item, (length==1)?" item":" items");
	} else {
		item=proto_tree_add_item(parent_tree, hf_index, tvb, offset>>3, 0, FALSE);
	}
	tree=proto_item_add_subtree(item, ett_index);

	offset=dissect_per_sequence_of_helper(tvb, offset, actx, tree, seq->func, *seq->p_id, length);


	proto_item_set_len(item, (offset>>3)!=(old_offset>>3)?(offset>>3)-(old_offset>>3):1);
	return offset;
}

/* this function dissects a constrained set of */
guint32
dissect_per_constrained_set_of(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *parent_tree, int hf_index, gint ett_index, const per_sequence_t *seq, int min_len, int max_len)
{
	/* for basic-per  a set-of is encoded in the same way as a sequence-of */
DEBUG_ENTRY("dissect_per_constrained_set_of");
	offset=dissect_per_constrained_sequence_of(tvb, offset, actx, parent_tree, hf_index, ett_index, seq, min_len, max_len);
	return offset;
}






/* this function dissects a set of */
guint32
dissect_per_set_of(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *parent_tree, int hf_index, gint ett_index, const per_sequence_t *seq)
{
	/* for basic-per  a set-of is encoded in the same way as a sequence-of */
DEBUG_ENTRY("dissect_per_set_of");
	offset=dissect_per_sequence_of(tvb, offset, actx, parent_tree, hf_index, ett_index, seq);
	return offset;
}




/* 23 Encoding the object identifier type */
guint32
dissect_per_object_identifier(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx _U_, proto_tree *tree, int hf_index, tvbuff_t **value_tvb)
{
  guint length;
  char *str;
  proto_item *item = NULL;
  header_field_info *hfi;

DEBUG_ENTRY("dissect_per_object_identifier");

  offset = dissect_per_length_determinant(tvb, offset, actx, tree, hf_per_object_identifier_length, &length);
	
  hfi = proto_registrar_get_nth(hf_index);
  if (hfi->type == FT_OID) {
    item = proto_tree_add_item(tree, hf_index, tvb, offset>>3, length, FALSE);
  } else if (IS_FT_STRING(hfi->type)) {
    str = oid_to_str(tvb_get_ptr(tvb, offset>>3, length), length);
    item = proto_tree_add_string(tree, hf_index, tvb, offset>>3, length, str);
  } else {
    DISSECTOR_ASSERT_NOT_REACHED();
  }

  if (value_tvb)
    *value_tvb = tvb_new_subset(tvb, offset>>3, length, length);

  offset += 8 * length;

  return offset;
}

guint32
dissect_per_object_identifier_str(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, const char **value_string)
{
  tvbuff_t *value_tvb = NULL;
  guint length;

  offset = dissect_per_object_identifier(tvb, offset, actx, tree, hf_index, (value_string) ? &value_tvb : NULL);

  if (value_string) {
    if (value_tvb && (length = tvb_length(value_tvb))) {
      *value_string = oid_to_str(tvb_get_ptr(value_tvb, 0, length), length);
    } else {
      *value_string = "";
    }
  }

  return offset;
}



/* this function reads a single bit */
guint32
dissect_per_boolean(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx _U_, proto_tree *tree, int hf_index, gboolean *bool)
{
	guint8 ch, mask;
	gboolean value;
	header_field_info *hfi;

DEBUG_ENTRY("dissect_per_boolean");

	ch=tvb_get_guint8(tvb, offset>>3);
	mask=1<<(7-(offset&0x07));
	if(ch&mask){
		value=1;
	} else {
		value=0;
	}
	if(hf_index!=-1){
		char *str;
		hfi = proto_registrar_get_nth(hf_index);
		str=ep_alloc(256);
		g_snprintf(str, 256, "%c%c%c%c %c%c%c%c %s: %s",
			mask&0x80?'0'+value:'.',
			mask&0x40?'0'+value:'.',
			mask&0x20?'0'+value:'.',
			mask&0x10?'0'+value:'.',
			mask&0x08?'0'+value:'.',
			mask&0x04?'0'+value:'.',
			mask&0x02?'0'+value:'.',
			mask&0x01?'0'+value:'.',
			hfi->name,
			value?"True":"False"
		);
		actx->created_item = proto_tree_add_boolean_format(tree, hf_index, tvb, offset>>3, 1, value, str);
	} else {
		actx->created_item = NULL;
	}

	if(bool){
		*bool=value;
	}
	return offset+1;
}




/* we currently only handle integers up to 32 bits in length. */
guint32
dissect_per_integer(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, gint32 *value)
{
	guint32 i, length;
	gint32 val;
	proto_item *it=NULL;
	header_field_info *hfi;

	/* 12.2.6 b */
	offset=dissect_per_length_determinant(tvb, offset, actx, tree, -1, &length);
	/* gassert here? */
	if(length>4){
PER_NOT_DECODED_YET("too long integer");
		length=4;
	}

	val=0;
	for(i=0;i<length;i++){
		if(i==0){
			if(tvb_get_guint8(tvb, offset>>3)&0x80){
				/* negative number */
				val=0xffffffff;
			} else {
				/* positive number */
				val=0;
			}
		}
		val=(val<<8)|tvb_get_guint8(tvb,offset>>3);
		offset+=8;
	}

	hfi = proto_registrar_get_nth(hf_index);
	if (! hfi)
		THROW(ReportedBoundsError);
        if (IS_FT_INT(hfi->type)) {
		it=proto_tree_add_int(tree, hf_index, tvb, (offset>>3)-(length+1), length+1, val);
        } else if (IS_FT_UINT(hfi->type)) {
		it=proto_tree_add_uint(tree, hf_index, tvb, (offset>>3)-(length+1), length+1, val);
	} else {
		proto_tree_add_text(tree, tvb, (offset>>3)-(length+1), length+1, "Field is not an integer: %s", hfi->abbrev);
		REPORT_DISSECTOR_BUG("PER integer field that's not an FT_INT* or FT_UINT*");
	}


	actx->created_item = it;

	if(value){
		*value=val;
	}

	return offset;
}


/* this function reads a constrained integer  with or without a
   PER visible extension marker present

   has_extension==TRUE  would map to asn constructs such as:
		rfc-number	INTEGER (1..32768, ...)
   while has_extension==FALSE would map to:
		t35CountryCode	INTEGER (0..255)

   it only handles integers that fit inside a 32 bit integer
10.5.1 info only
10.5.2 info only
10.5.3 range=ub-lb+1
10.5.4 empty range
10.5.5 info only
	10.5.6 unaligned version
10.5.7 aligned version
10.5.7.1 decoding of 0-255 1-8 bits
10.5.7.2 decoding og 0-256 8 bits
10.5.7.3 decoding of 0-65535 16 bits
	10.5.7.4
*/
guint32
dissect_per_constrained_integer(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint32 min, guint32 max, guint32 *value, gboolean has_extension)
{
	proto_item *it=NULL;
	guint32 range, val;
	gint val_start, val_length;
	nstime_t timeval;
	header_field_info *hfi;
	int num_bits;
	int pad;
	gboolean tmp;

DEBUG_ENTRY("dissect_per_constrained_integer");
	if(has_extension){
		gboolean extension_present;
		offset=dissect_per_boolean(tvb, offset, actx, tree, hf_per_extension_present_bit, &extension_present);
		if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
		if(extension_present){
			offset = dissect_per_integer(tvb, offset, actx, tree, hf_index, (gint32*)value);
			return offset;
		}
	}

	hfi = proto_registrar_get_nth(hf_index);

	/* 10.5.3 Let "range" be defined as the integer value ("ub" - "lb"   1), and let the value to be encoded be "n". 
	 * 10.5.7	In the case of the ALIGNED variant the encoding depends on whether
	 *			d)	"range" is greater than 64K (the indefinite length case).
	 */
	if(((max-min)>65536)&&(actx->aligned)){
		/* just set range really big so it will fall through
		   to the bottom of the encoding */
		range=1000000;
	} else {
		/* Really ugly hack.
		 * We should really use guint64 as parameters for min/max.
		 * This is to prevent range from being 0 if
		 * the range for a signed integer spans the entire 32 bit range.
		 * Special case the 2 common cases when this can happen until
		 * a real fix is implemented.
		 */
		if( (max==0x7fffffff && min==0x80000000)
		||  (max==0xffffffff && min==0x00000000) ){
			range=0xffffffff;
		} else {
			range=max-min+1;
		}
	}

	num_bits=0;
	pad=0;
	val=0;
	timeval.secs=val; timeval.nsecs=0;
	/* 10.5.4 If "range" has the value 1, then the result of the encoding shall be an empty bit-field (no bits).*/

	/* something is really wrong if range is 0 */
	DISSECTOR_ASSERT(range!=0);

	if(range==1){
		val_start = offset>>3; val_length = 0;
		val = min; 
	} else if((range<=255)||(!actx->aligned)) {
		/* 10.5.7.1 
		 * 10.5.6	In the case of the UNALIGNED variant the value ("n" - "lb") shall be encoded
		 * as a non-negative  binary integer in a bit field as specified in 10.3 with the minimum
		 * number of bits necessary to represent the range.
		 */
		char *str;
		int i, bit, length;
		guint32 mask,mask2;
		/* We only handle 32 bit integers */
		mask  = 0x80000000;
		mask2 = 0x7fffffff;
		i = 32;
		while ((range & mask)== 0){
			i = i - 1;
			mask = mask>>1;
			mask2 = mask2>>1;
		}
		if ((range & mask2) == 0)
			i = i-1;

		num_bits = i;
		length=1;
		if(range<=2){
			num_bits=1;
		}

		/* prepare the string */
		str=ep_alloc(256);
		g_snprintf(str, 256, "%s: ", hfi->name);
		for(bit=0;bit<((int)(offset&0x07));bit++){
			if(bit&&(!(bit%4))){
				strcat(str, " ");
			}
			strcat(str,".");
		}
		/* read the bits for the int */
		for(i=0;i<num_bits;i++){
			if(bit&&(!(bit%4))){
				strcat(str, " ");
			}
			if(bit&&(!(bit%8))){
				length+=1;
				strcat(str, " ");
			}
			bit++;
			offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &tmp);
			val<<=1;
			if(tmp){
				val|=1;
				strcat(str, "1");
			} else {
				strcat(str, "0");
			}
		}
		for(;bit%8;bit++){
			if(bit&&(!(bit%4))){
				strcat(str, " ");
			}
			strcat(str,".");
		}
		val_start = (offset-num_bits)>>3; val_length = length;
		val+=min;
		if (display_internal_per_fields)
			proto_tree_add_text(tree, tvb, val_start,val_length,"Range = %u Bitfield length %u, %s",range, num_bits, str);
	} else if(range==256){
		/* 10.5.7.2 */
		num_bits=8;
		pad=7-(offset&0x07);

		/* in the aligned case, align to byte boundary */
		BYTE_ALIGN_OFFSET(offset);
		val=tvb_get_guint8(tvb, offset>>3);
		offset+=8;

		val_start = (offset>>3)-1; val_length = 1;
		val+=min;
	} else if(range<=65536){
		/* 10.5.7.3 */
		num_bits=16;
		pad=7-(offset&0x07);

		/* in the aligned case, align to byte boundary */
		BYTE_ALIGN_OFFSET(offset);
		val=tvb_get_guint8(tvb, offset>>3);
		val<<=8;
		offset+=8;
		val|=tvb_get_guint8(tvb, offset>>3);
		offset+=8;

		val_start = (offset>>3)-2; val_length = 2;
		val+=min;
	} else {
		int i,num_bytes;
		gboolean bit;

		/* 10.5.7.4 */
		/* 12.2.6 */
		offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
		num_bytes=bit;
		offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
		num_bytes=(num_bytes<<1)|bit;

		num_bytes++;  /* lower bound for length determinant is 1 */
		if (display_internal_per_fields)
			proto_tree_add_uint(tree, hf_per_const_int_len, tvb, (offset>>3), 1, num_bytes);

		/* byte aligned */
		BYTE_ALIGN_OFFSET(offset);
		val=0;
		for(i=0;i<num_bytes;i++){
			val=(val<<8)|tvb_get_guint8(tvb,offset>>3);
			offset+=8;
		}
		val_start = (offset>>3)-(num_bytes+1); val_length = num_bytes+1;
		val+=min;
	}

	timeval.secs = val;
	if (IS_FT_UINT(hfi->type)) {
		it = proto_tree_add_uint(tree, hf_index, tvb, val_start, val_length, val);
	} else if (IS_FT_INT(hfi->type)) {
		it = proto_tree_add_int(tree, hf_index, tvb, val_start, val_length, val);
	} else if (IS_FT_TIME(hfi->type)) {
		it = proto_tree_add_time(tree, hf_index, tvb, val_start, val_length, &timeval);
	} else {
		THROW(ReportedBoundsError);
	}
	actx->created_item = it;
	if (value) *value = val;
	return offset;}

/* 13 Enemerated */
guint32
dissect_per_enumerated(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint32 root_num, guint32 *value, gboolean has_extension, guint32 ext_num, guint32 *value_map)
{

	proto_item *it=NULL;
	guint32 enum_index, val;
	guint32 start_offset = offset;
	gboolean extension_present = FALSE;
	header_field_info *hfi;

	if (has_extension) {
		/* Extension bit */
		offset = dissect_per_boolean(tvb, offset, actx, tree, hf_per_extension_present_bit, &extension_present);
		if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
	}

	if (!extension_present) {
		/* 13.2  */
		offset = dissect_per_constrained_integer(tvb, offset, actx, tree, hf_per_enum_index, 0, root_num - 1, &enum_index, FALSE);
		if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
	} else {
		/* 13.3  */
		if (ext_num == 1) {
			/* 10.5.4	If "range" has the value 1,
			 * then the result of the encoding shall be
			 * an empty bit-field (no bits).
			 */
			enum_index = 0;
		} else {
			/* 13.3 ".. and the value shall be added to the field-list as a
			 * normally small non-negative whole number whose value is the 
			 * enumeration index of the additional enumeration and with "lb" set to 0.."
			 *
			 * Byte align after reading Extension bit 
			 *
			 */
			BYTE_ALIGN_OFFSET(offset);
			offset = dissect_per_normally_small_nonnegative_whole_number(tvb, offset, actx, tree, hf_per_enum_extension_index, &enum_index);
		}
		enum_index += root_num;
	}
    val = (value_map && (enum_index<(root_num+ext_num))) ? value_map[enum_index] : enum_index;
	hfi = proto_registrar_get_nth(hf_index);
	if (IS_FT_UINT(hfi->type)) {
		it = proto_tree_add_uint(tree, hf_index, tvb, start_offset>>3, BLEN(start_offset, offset), val);
	} else {
		THROW(ReportedBoundsError);
	}
	actx->created_item = it;
	if (value) *value = val;
	return offset;
}

/* 22 Encoding the choice type */
guint32
dissect_per_choice(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, gint ett_index, const per_choice_t *choice, guint32 *value)
{
	gboolean extension_present, extension_flag;
	int extension_root_entries;
	int extension_addition_entries;
	guint32 choice_index;
	int i, index, cidx;
	guint32 ext_length;
	guint32 old_offset = offset;
	proto_item *choice_item = NULL;
	proto_tree *choice_tree = NULL;

DEBUG_ENTRY("dissect_per_choice");

	/* 22.5 */
	if (choice[0].extension == ASN1_NO_EXTENSIONS){
		extension_present = FALSE;
		extension_flag = FALSE;
	} else {
		extension_present = TRUE;
		offset = dissect_per_boolean(tvb, offset, actx, tree, hf_per_extension_bit, &extension_flag);
		if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
	}

	/* count the number of entries in the extension root and extension addition */
	extension_root_entries = 0;
	extension_addition_entries = 0;
	for (i=0; choice[i].p_id; i++) {
		switch(choice[i].extension){
			case ASN1_NO_EXTENSIONS:
			case ASN1_EXTENSION_ROOT:
				extension_root_entries++;
				break;
			case ASN1_NOT_EXTENSION_ROOT:
				extension_addition_entries++;
				break;
		}
	}

	if (!extension_flag) {  /* 22.6, 22.7 */
		if (extension_root_entries == 1) {  /* 22.5 */
			choice_index = 0;
		} else {
			offset = dissect_per_constrained_integer(tvb, offset, actx,
				tree, hf_per_choice_index, 0, extension_root_entries - 1,
				&choice_index, FALSE);
			if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
		}

		index = -1; cidx = choice_index;
		for (i=0; choice[i].p_id; i++) {
			if(choice[i].extension != ASN1_NOT_EXTENSION_ROOT){
				if (!cidx) { index = i; break; }
				cidx--;
			}
		}
	} else {  /* 22.8 */
		offset = dissect_per_normally_small_nonnegative_whole_number(tvb, offset, actx, tree, hf_per_choice_extension_index, &choice_index);
		offset = dissect_per_length_determinant(tvb, offset, actx, tree, hf_per_open_type_length, &ext_length);

		index = -1; cidx = choice_index;
		for (i=0; choice[i].p_id; i++) {
			if(choice[i].extension == ASN1_NOT_EXTENSION_ROOT){
				if (!cidx) { index = i; break; }
				cidx--;
			}
		}
	}

	if (index != -1) {
		choice_item = proto_tree_add_uint(tree, hf_index, tvb, old_offset>>3, 0, choice[index].value);
		choice_tree = proto_item_add_subtree(choice_item, ett_index);
		if (!extension_flag) {
			offset = choice[index].func(tvb, offset, actx, choice_tree, *choice[index].p_id);
		} else {
			choice[index].func(tvb, offset, actx, choice_tree, *choice[index].p_id);
			offset += ext_length * 8;
		}
		proto_item_set_len(choice_item, BLEN(old_offset, offset));
	} else {
		if (!extension_flag) {
			PER_NOT_DECODED_YET("unknown extension root index in choice");
		} else {
			offset += ext_length * 8;
			proto_tree_add_text(tree, tvb, old_offset>>3, BLEN(old_offset, offset), "Choice no. %d in extension", choice_index);
			PER_NOT_DECODED_YET("unknown choice extension");
		}
	}

	if (value) *value = choice[index].value;

	return offset;
}


static const char *
index_get_optional_name(const per_sequence_t *sequence, int index)
{
	int i;
	header_field_info *hfi;

	for(i=0;sequence[i].p_id;i++){
		if((sequence[i].extension!=ASN1_NOT_EXTENSION_ROOT)&&(sequence[i].optional==ASN1_OPTIONAL)){
			if (index == 0) {
				hfi = proto_registrar_get_nth(*sequence[i].p_id);
				return (hfi) ? hfi->name : "<unknown filed>";
			}
			index--;
		}
	}
	return "<unknown type>";
}

static const char *
index_get_extension_name(const per_sequence_t *sequence, int index)
{
	int i;
	header_field_info *hfi;

	for(i=0;sequence[i].p_id;i++){
		if(sequence[i].extension==ASN1_NOT_EXTENSION_ROOT){
			if (index == 0) {
				hfi = proto_registrar_get_nth(*sequence[i].p_id);
				return (hfi) ? hfi->name : "<unknown filed>";
			}
			index--;
		}
	}
	return "<unknown type>";
}

static const char *
index_get_field_name(const per_sequence_t *sequence, int index)
{
	header_field_info *hfi;

	hfi = proto_registrar_get_nth(*sequence[index].p_id);
	return (hfi) ? hfi->name : "<unknown filed>";
}

/* this functions decodes a SEQUENCE
   it can only handle SEQUENCES with at most 32 DEFAULT or OPTIONAL fields
18.1 extension bit
18.2 optinal/default items in root
18.3 we ignore the case where n>64K
18.4 the root sequence
	   18.5
	   18.6
	   18.7
	   18.8
	   18.9
*/
guint32
dissect_per_sequence(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *parent_tree, int hf_index, gint ett_index, const per_sequence_t *sequence)
{
	gboolean extension_present, extension_flag, optional_field_flag;
	proto_item *item;
	proto_tree *tree;
	guint32 old_offset=offset;
	guint32 i, num_opts;
	guint32 optional_mask;

DEBUG_ENTRY("dissect_per_sequence");

	item=proto_tree_add_item(parent_tree, hf_index, tvb, offset>>3, 0, FALSE);
	tree=proto_item_add_subtree(item, ett_index);


	/* first check if there should be an extension bit for this CHOICE.
	   we do this by just checking the first choice arm
	 */
	/* 18.1 */
	extension_flag=0;
	if(sequence[0].extension==ASN1_NO_EXTENSIONS){
		extension_present=0;
	} else {
		extension_present=1;
		offset=dissect_per_boolean(tvb, offset, actx, tree, hf_per_extension_bit, &extension_flag);
		if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
	}
	/* 18.2 */
	num_opts=0;
	for(i=0;sequence[i].p_id;i++){
		if((sequence[i].extension!=ASN1_NOT_EXTENSION_ROOT)&&(sequence[i].optional==ASN1_OPTIONAL)){
			num_opts++;
		}
	}

	optional_mask=0;
	for(i=0;i<num_opts;i++){
		offset=dissect_per_boolean(tvb, offset, actx, tree, hf_per_optional_field_bit, &optional_field_flag);
		if (tree) {
			proto_item_append_text(actx->created_item, " (%s %s present)",
				index_get_optional_name(sequence, i), optional_field_flag?"is":"is NOT");
		}
		if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
		optional_mask<<=1;
		if(optional_field_flag){
			optional_mask|=0x01;
		}
	}


	/* 18.4 */
	for(i=0;sequence[i].p_id;i++){
		if( (sequence[i].extension==ASN1_NO_EXTENSIONS)
		||  (sequence[i].extension==ASN1_EXTENSION_ROOT) ){
			if(sequence[i].optional==ASN1_OPTIONAL){
				gboolean is_present;
				is_present=(1<<(num_opts-1))&optional_mask;
				num_opts--;
				if(!is_present){
					continue;
				}
			}
			if(sequence[i].func){
				offset=sequence[i].func(tvb, offset, actx, tree, *sequence[i].p_id);
			} else {
				PER_NOT_DECODED_YET(index_get_field_name(sequence, i));
			}
		}
	}


	if(extension_flag){
		gboolean extension_bit;
		guint32 num_known_extensions;
		guint32 num_extensions;
		guint32 extension_mask;

		offset=dissect_per_normally_small_nonnegative_whole_number(tvb, offset, actx, tree, hf_per_num_sequence_extensions, &num_extensions);
		/* the X.691 standard is VERY unclear here.
		   there is no mention that the lower bound lb for this
		   (apparently) semiconstrained value is 1,
		   apart from the NOTE: comment in 18.8 that this value can
		   not be 0.
		   In my book, there is a semantic difference between having
		   a comment that says that the value can not be zero
		   and stating that the lb is 1.
		   I dont know if this is right or not but it makes
		   some of the very few captures I have decode properly.

		   It could also be that the captures I have are generated by
		   a broken implementation.
		   If this is wrong and you dont report it as a bug
		   then it wont get fixed!
		*/
		num_extensions+=1;

		extension_mask=0;
		for(i=0;i<num_extensions;i++){
			offset=dissect_per_boolean(tvb, offset, actx, tree, hf_per_extension_present_bit, &extension_bit);
			if (tree) {
				proto_item_append_text(actx->created_item, " (%s %s present)",
					index_get_extension_name(sequence, i), extension_bit?"is":"is NOT");
			}
			if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);

			extension_mask=(extension_mask<<1)|extension_bit;
		}

		/* find how many extensions we know about */
		num_known_extensions=0;
		for(i=0;sequence[i].p_id;i++){
			if(sequence[i].extension==ASN1_NOT_EXTENSION_ROOT){
				num_known_extensions++;
			}
		}

		/* decode the extensions one by one */
		for(i=0;i<num_extensions;i++){
			guint32 length;
			guint32 new_offset;
			guint32 extension_index;
			guint32 j,k;

			if(!((1L<<(num_extensions-1-i))&extension_mask)){
				/* this extension is not encoded in this PDU */
				continue;
			}

			offset=dissect_per_length_determinant(tvb, offset, actx, tree, hf_per_open_type_length, &length);

			if(i>=num_known_extensions){
				/* we dont know how to decode this extension */
				offset+=length*8;
				PER_NOT_DECODED_YET("unknown sequence extension");
				continue;
			}

			extension_index=0;
			for(j=0,k=0;sequence[j].p_id;j++){
				if(sequence[j].extension==ASN1_NOT_EXTENSION_ROOT){
					if(k==i){
						extension_index=j;
						break;
					}
					k++;
				}
			}

			if(sequence[extension_index].func){
				new_offset=sequence[extension_index].func(tvb, offset, actx, tree, *sequence[extension_index].p_id);
			} else {
				PER_NOT_DECODED_YET(index_get_field_name(sequence, extension_index));
			}
			offset+=length*8;

		}
	}

	proto_item_set_len(item, (offset>>3)!=(old_offset>>3)?(offset>>3)-(old_offset>>3):1);
	actx->created_item = item;
	return offset;
}



/* 15 Encoding the bitstring type

   max_len or min_len == NO_BOUND means there is no lower/upper constraint

*/
guint32
dissect_per_bit_string(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len, gboolean has_extension, tvbuff_t **value_tvb)
{
	gint val_start, val_length;
	guint32 length;
	header_field_info *hfi;

	hfi = (hf_index==-1) ? NULL : proto_registrar_get_nth(hf_index);

DEBUG_ENTRY("dissect_per_bit_string");
	/* 15.8 if the length is 0 bytes there will be no encoding */
	if(max_len==0) {
		return offset;
	}

	if (min_len == NO_BOUND) {
		min_len = 0;
	}

	/* 15.9 if length is fixed and less than or equal to sixteen bits*/
	if((min_len==max_len)&&(max_len<=16)){
		static guint8 bytes[4];
		int i;
		guint32 old_offset=offset;
		gboolean bit;

		bytes[0]=bytes[1]=bytes[2]=0;
		if(min_len<=8){
			for(i=0;i<min_len;i++){
				offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
				bytes[0]=(bytes[0]<<1)|bit;
			}
		}
		if(min_len>8){
			for(i=0;i<8;i++){
				offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
				bytes[0]=(bytes[0]<<1)|bit;
			}
			for(i=8;i<min_len;i++){
				offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
				bytes[1]=(bytes[1]<<1)|bit;
			}
		}
		if (hfi) {
			proto_tree_add_bytes(tree, hf_index, tvb, old_offset>>3, (min_len+7)/8, bytes);
		}
		return offset;
	}


	/* 15.10 if length is fixed and less than to 64kbits*/
	if((min_len==max_len)&&(min_len<65536)){
		/* align to byte */
		BYTE_ALIGN_OFFSET(offset);
		val_start = offset>>3;
		val_length = (min_len+7)/8;
		if (hfi) {
			proto_tree_add_item(tree, hf_index, tvb, offset>>3, (min_len+7)/8, FALSE);
		}
		offset+=min_len;
		return offset;
	}

	/* 15.11 */
	if (max_len != NO_BOUND) {
		offset=dissect_per_constrained_integer(tvb, offset, actx,
			tree, hf_per_bit_string_length, min_len, max_len,
			&length, has_extension);
			if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
	} else {
		offset=dissect_per_length_determinant(tvb, offset, actx, tree, hf_per_bit_string_length, &length);
	}
	if(length){
		/* align to byte */
		BYTE_ALIGN_OFFSET(offset);
		if (hfi) {
			proto_tree_add_item(tree, hf_index, tvb, offset>>3, (length+7)/8, FALSE);
		}
	}
	val_start = offset>>3;
	val_length = (length+7)/8;
	offset+=length;

	if (value_tvb)
		*value_tvb = tvb_new_subset(tvb, val_start, val_length, val_length);

	return offset;
}


/* this fucntion dissects an OCTET STRING
	16.1
	16.2
	16.3
	16.4
	16.5
	16.6
	16.7
	16.8

   max_len or min_len == NO_BOUND means there is no lower/upper constraint

   hf_index can either be a FT_BYTES or an FT_STRING
*/
guint32
dissect_per_octet_string(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len, tvbuff_t **value_tvb)
{
	proto_item *it = NULL;
	gint val_start, val_length;
	guint32 length;
	header_field_info *hfi;
	static guint8 bytes[4];
	guint8 *pbytes = NULL;
	tvbuff_t *out_tvb = NULL;

	hfi = (hf_index==-1) ? NULL : proto_registrar_get_nth(hf_index);

DEBUG_ENTRY("dissect_per_octet_string");

	if (min_len == NO_BOUND) {
		min_len = 0;
	}
	if (max_len==0) {  /* 16.5 if the length is 0 bytes there will be no encoding */
		val_start = offset>>3; 
		val_length = 0;

	} else if((min_len==max_len)&&(max_len<=2)) {  /* 16.6 if length is fixed and less than or equal to two bytes*/
		guint32 i, old_offset=offset;
		gboolean bit;

		for(i=0;i<8;i++){
			offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
			bytes[0]=(bytes[0]<<1)|bit;
		}
		if(min_len==2){
			for(i=0;i<8;i++){
				offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
				bytes[1]=(bytes[1]<<1)|bit;
			}
		}
		bytes[min_len]=0;
		pbytes = bytes;
		val_start = old_offset>>3; 
		val_length = min_len+((offset&0x07)?1:0);

	} else if ((min_len==max_len)&&(min_len<65536)) {  /* 16.7 if length is fixed and less than to 64k*/

		/* align to byte */
		if (actx->aligned){
			BYTE_ALIGN_OFFSET(offset);			 
			val_start = offset>>3;
			val_length = min_len;
			offset+=min_len*8;
		}else{
			guint8 *buff;
			guint32 i = 0;
			guint32 j = 0;
			gboolean bit;

			val_start = offset>>3;
			buff = ep_alloc(min_len);
			while (j < (guint32)min_len){
				for(i=0;i<8;i++){
					offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
					buff[j]=(buff[j]<<1)|bit;
				}
				j = j+1;
			}
			pbytes = buff;
			val_length = min_len;
			/* XXX should we return a new tvb with the octetstring? */
		}

	} else {  /* 16.8 */
		if(max_len>0) {  
			offset = dissect_per_constrained_integer(tvb, offset, actx, tree,
				hf_per_octet_string_length, min_len, max_len,
				&length, FALSE);
				if (!display_internal_per_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
		} else {
			offset = dissect_per_length_determinant(tvb, offset, actx, tree, 
				hf_per_octet_string_length, &length);
		}

		if(length){
			/* align to byte */
			if (actx->aligned){
				BYTE_ALIGN_OFFSET(offset);
				val_start = offset>>3; 
				offset+=length*8;
			}else{
				guint8 *buff;
				guint32 i = 0;
				guint32 j = 0;
				gboolean bit;

				val_start = offset>>3;
				buff = g_malloc(length);
				while (j < length){
					for(i=0;i<8;i++){
						offset=dissect_per_boolean(tvb, offset, actx, tree, -1, &bit);
						buff[j]=(buff[j]<<1)|bit;
					}
				j = j+1;
				}
				pbytes = buff;
				out_tvb = tvb_new_real_data(buff,length,length);
				/* Arrange that the allocated packet data copy be freed when the
				 * tvbuff is freed. 
				 */
				tvb_set_free_cb(out_tvb, g_free );
				tvb_set_child_real_data_tvbuff(tvb,out_tvb);
				add_new_data_source(actx->pinfo, out_tvb, "PER unaligned decoded OCTET STRING");
			}
		} else {
			val_start = offset>>3; 
		}
		val_length = length;
	}

	if (hfi) {
		if (IS_FT_UINT(hfi->type)||IS_FT_INT(hfi->type)) {
			if (IS_FT_UINT(hfi->type))
				it = proto_tree_add_uint(tree, hf_index, tvb, val_start, val_length, val_length);
			else
				it = proto_tree_add_int(tree, hf_index, tvb, val_start, val_length, val_length);
			proto_item_append_text(it, plurality(val_length, " octet", " octets"));
		} else {
			if (pbytes) {
				if(IS_FT_STRING(hfi->type)){
					proto_tree_add_string(tree, hf_index, tvb, val_start, val_length, (char*)pbytes);
				} else if (hfi->type==FT_BYTES) {
					proto_tree_add_bytes(tree, hf_index, tvb, val_start, val_length, pbytes);
				} else {
					THROW(ReportedBoundsError);
				}
			} else {
				proto_tree_add_item(tree, hf_index, tvb, val_start, val_length, FALSE);
			}
		}
	}

	if (value_tvb)
		*value_tvb = (out_tvb) ? out_tvb : tvb_new_subset(tvb, val_start, val_length, val_length);

	return offset;
}



void
proto_register_per(void)
{
	static hf_register_info hf[] =
	{
	{ &hf_per_num_sequence_extensions,
		{ "Number of Sequence Extensions", "per.num_sequence_extensions", FT_UINT32, BASE_DEC,
		NULL, 0, "Number of extensions encoded in this sequence", HFILL }},
	{ &hf_per_choice_index,
		{ "Choice Index", "per.choice_index", FT_UINT32, BASE_DEC,
		NULL, 0, "Which index of the Choice within extension root is encoded", HFILL }},
	{ &hf_per_choice_extension_index,
		{ "Choice Extension Index", "per.choice_extension_index", FT_UINT32, BASE_DEC,
		NULL, 0, "Which index of the Choice within extension addition is encoded", HFILL }},
	{ &hf_per_enum_index,
		{ "Enumerated Index", "per.enum_index", FT_UINT32, BASE_DEC,
		NULL, 0, "Which index of the Enumerated within extension root is encoded", HFILL }},
	{ &hf_per_enum_extension_index,
		{ "Enumerated Extension Index", "per.enum_extension_index", FT_UINT32, BASE_DEC,
		NULL, 0, "Which index of the Enumerated within extension addition is encoded", HFILL }},
	{ &hf_per_GeneralString_length,
		{ "GeneralString Length", "per.generalstring_length", FT_UINT32, BASE_DEC,
		NULL, 0, "Length of the GeneralString", HFILL }},
	{ &hf_per_extension_bit,
		{ "Extension Bit", "per.extension_bit", FT_BOOLEAN, 8,
		TFS(&tfs_extension_bit), 0x01, "The extension bit of an aggregate", HFILL }},
	{ &hf_per_extension_present_bit,
		{ "Extension Present Bit", "per.extension_present_bit", FT_BOOLEAN, 8,
		TFS(&tfs_extension_present_bit), 0x01, "Whether this optional extension is present or not", HFILL }},
	{ &hf_per_small_number_bit,
		{ "Small Number Bit", "per.small_number_bit", FT_BOOLEAN, 8,
		TFS(&tfs_small_number_bit), 0x01, "The small number bit for a section 10.6 integer", HFILL }},
	{ &hf_per_optional_field_bit,
		{ "Optional Field Bit", "per.optional_field_bit", FT_BOOLEAN, 8,
		TFS(&tfs_optional_field_bit), 0x01, "This bit specifies the presence/absence of an optional field", HFILL }},
	{ &hf_per_sequence_of_length,
		{ "Sequence-Of Length", "per.sequence_of_length", FT_UINT32, BASE_DEC,
		NULL, 0, "Number of items in the Sequence Of", HFILL }},
	{ &hf_per_object_identifier_length,
		{ "Object Length", "per.object_length", FT_UINT32, BASE_DEC,
		NULL, 0, "Length of the object identifier", HFILL }},
	{ &hf_per_open_type_length,
		{ "Open Type Length", "per.open_type_length", FT_UINT32, BASE_DEC,
		NULL, 0, "Length of an open type encoding", HFILL }},
	{ &hf_per_octet_string_length,
		{ "Octet String Length", "per.octet_string_length", FT_UINT32, BASE_DEC,
		NULL, 0, "Number of bytes in the Octet String", HFILL }},
	{ &hf_per_bit_string_length,
		{ "Bit String Length", "per.bit_string_length", FT_UINT32, BASE_DEC,
		NULL, 0, "Number of bits in the Bit String", HFILL }},
	{ &hf_per_const_int_len,
		{ "Constrained Integer Length", "per._const_int_len", FT_UINT32, BASE_DEC,
		NULL, 0, "Number of bytes in the Constrained Integer", HFILL }},
	};
	static gint *ett[] =
	{
		&ett_per_sequence_of_item
	};
	module_t *per_module;

	proto_per = proto_register_protocol("Packed Encoding Rules (ASN.1 X.691)", "PER", "per");
	proto_register_field_array(proto_per, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));

	proto_set_cant_toggle(proto_per);

	per_module = prefs_register_protocol(proto_per, NULL);
	prefs_register_bool_preference(per_module, "display_internal_per_fields",
		"Display the internal PER fields in the tree",
		"Whether the dissector should put the internal PER data in the tree or if it should hide it",
		&display_internal_per_fields);

}

void
proto_reg_handoff_per(void)
{
}