perdecoder.cxx

asn格式文件的编译器

/*
 * PERDecoder.cxx
 *
 * Abstract Syntax Notation 1 Encoding Rules
 *
 * Copyright (c) 1993-1998 Equivalence Pty. Ltd.
 *
 * Copyright (c) 2001 Institute for Information Industry, Taiwan, Republic of China 
 * (http://www.iii.org.tw/iiia/ewelcome.htm)
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is Portable Windows Library.
 *
 * The Initial Developer of the Original Code is Equivalence Pty. Ltd.
 *
 * Portions are Copyright (C) 1993 Free Software Foundation, Inc.
 * All Rights Reserved.
 *
 * Contributor(s): Huang-Ming Huang
 *
 * The code is adapted from asner.cxx of PWLib, but the dependancy on PWLib has
 * been removed.
 *
 * $Log: PERDecoder.cxx,v $
 * Revision 1.6  2002/07/10 07:25:48  btrummer
 * Minor simplification at the end of PERDecoder::decodeChoicePreamle().
 *
 * Revision 1.5  2002/07/03 08:15:30  btrummer
 * Fixed the assignment to beginPosition in PERDecoder::setPosition().
 *
 * Revision 1.4  2002/07/03 06:26:38  btrummer
 * Introduced an upper bound for the size of strings and arrays,
 * like PWLib's PERDecoder does. Otherwise, broken data may make the
 * PERDecoder allocate hundrets of Megabytes RAM...
 *
 * Revision 1.3  2002/07/02 04:45:13  mangelo
 * Modify for VC.Net and GCC 3.1
 *
 * Revision 1.2  2001/10/05 19:10:42  mangelo
 * Added Log
 *
 * 2001/07/16 Huang-Ming Huang
 * Optional components of SEQUENCE is now created on demand.
 *
 * 2001/06/26 Huang-Ming Huang 
 * Version 2.1 Reimplemented to minimize the code size.
 *
 * 2001/05/01
 * Fixed problem with en/decoding more than 16 extension fields in a sequence 
 *   in accordance with PWLib asner.cxx Revision 1.41.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "asn1.h"

namespace ASN1 {

// When resizing strings or vectors, these values will be used as upper limit.
static unsigned MaximumArraySize = 128;
static unsigned MaximumStringSize = 16*1024;

extern unsigned CountBits(unsigned range);

bool PERDecoder::decodeBitMap(std::vector<char>& bitData, unsigned nBit)
{
  unsigned theBits;
  int idx = 0;
  unsigned bitsLeft = nBit;
  while (bitsLeft >= 8) {
    if (!decodeMultiBit(8, theBits))
      return false;
    bitData[idx++] = (unsigned char)theBits;
    bitsLeft -= 8;
  }

  if (bitsLeft > 0) {
    if (!decodeMultiBit(bitsLeft, theBits))
      return false;
    bitData[idx] = (unsigned char)(theBits << (8-bitsLeft));
  }
  return true;
}

inline bool PERDecoder::atEnd() 
{ 
    return beginPosition >= endPosition; 
}


bool PERDecoder::do_visit(Null& value)
{
  return true;
}

bool PERDecoder::do_visit(BOOLEAN& value)
{
  if (atEnd())
    return false;

  // X.931 Section 11
  value = decodeSingleBit();
  return true;
}

bool PERDecoder::do_visit(INTEGER& integer)
{
  // X.931 Sections 12

  unsigned value;
  if ((integer.getConstraintType() == ExtendableConstraint && decodeSingleBit()) 
	  || integer.getConstraintType() < FixedConstraint) { //  12.1
    unsigned len;
    if (decodeLength(0, INT_MAX, len) != 0)
      return false;
    if (!decodeMultiBit(len*8, value))
		return false;

	if (!integer.constrained() && (value & 1 << ((len*8)-1) ) ) // negative value
		value = (0xFFFFFFFF << (len*8)) | value;

	integer = value;
    return true;
  }

  if ((unsigned)integer.getLowerLimit() != integer.getUpperLimit())  // 12.2.1
    if (decodeUnsigned(integer.getLowerLimit(), integer.getUpperLimit(), value) == 0) // 12.2.2 which devolves to 10.5
	{
		integer = value;
		return true;
	}

  integer = integer.getLowerLimit();
  return true;
}

bool PERDecoder::do_visit(ENUMERATED& value)
{
  // X.691 Section 13

  unsigned v;
  if (value.extendable()) {  // 13.3
	if (decodeSingleBit()) {
      unsigned len = 0;
      if ( decodeSmallUnsigned(len) &&
             len > 0 &&
             decodeUnsigned(0, len-1, v) == 0)
	  {
		  value.setFromInt(v);
		  return true;
	  }
	}
  }

  if (decodeUnsigned(0, value.getMaximum(), v)==0)	  // 13.2
  {
	  value.setFromInt(v);
	  return true;
  }
  return false;
}


bool PERDecoder::do_visit(OBJECT_IDENTIFIER& value)
{
  // X.691 Section 23

  unsigned dataLen;
  if (decodeLength(0, 255, dataLen) < 0)
    return false;

  beginPosition += dataLen;
  if (atEnd()) return false;

  return value.decodeCommon(beginPosition-dataLen, dataLen);
}

bool PERDecoder::do_visit(BIT_STRING& value)
{
  // X.691 Section 15

  if (decodeConstrainedLength(value, value.totalBits) < 0)
    return false;

  if (value.totalBits > MaximumStringSize)
    return false;

  value.resize(value.totalBits);

  if (value.size() == 0)
    return true;   // 15.7

  if (value.size() > getBitsLeft())
    return false;

  if (value.size() > 16 && aligned()) {
    unsigned nBytes = (value.size()+7)/8;
    return decodeBlock(&*(value.bitData.begin()), nBytes) == nBytes;   // 15.9
  }

  return decodeBitMap( value.bitData, value.size());
}

bool PERDecoder::do_visit(OCTET_STRING& value)
{
  // X.691 Section 16

  unsigned nBytes;
  if (decodeConstrainedLength(value, nBytes) < 0)
    return false;

  if (nBytes > MaximumStringSize)
    return false;

  value.resize(nBytes);   // 16.5

  unsigned theBits;
  switch (nBytes) {
    case 0 :
      break;

    case 1 :  // 16.6
	  if (!decodeMultiBit(8, theBits))
        return false;
      value[0] = (char)theBits;
      break;

    case 2 :  // 16.6
      if (!decodeMultiBit(8, theBits))
        return false;
      value[0] = (char)theBits;
      if (!decodeMultiBit(8, theBits))
        return false;
      value[1] = (char)theBits;

      break;

    default: // 16.7
      return decodeBlock(&(*value.begin()), nBytes) == nBytes;
  }

  return true;
}

bool PERDecoder::do_visit(AbstractString& value)
{
  // X.691 Section 26

  unsigned len;
  if (decodeConstrainedLength(value, len) < 0)
    return false;

  unsigned nBits = value.getNumBits(aligned());

  if (len > MaximumStringSize)
    return false;

  value.resize(len);
  if (value.getConstraintType() == Unconstrained || value.getUpperLimit()*nBits > 16) {
    if (nBits == 8)
	{
	  if (decodeBlock(&(*value.begin()), len) != len)
		  value.resize(0);
	  return value.size() == len;
	}

    if (aligned())
      byteAlign();
  }


  unsigned i;
  for (i = 0; i < (unsigned)len; i++) {
	unsigned theBits;
    if (!decodeMultiBit(nBits, theBits))
      return false;
    if (nBits >= value.getCanonicalSetBits() && value.getCanonicalSetBits() > 4)
      value[i] = (char)theBits;
    else
      value[i] = value.getCharacterSet()[theBits];
  }
  return true;
}

bool PERDecoder::do_visit(BMPString& value)
{
  // X.691 Section 26

  unsigned len;
  if (decodeConstrainedLength(value, len) < 0)
    return false;

  if (len > MaximumStringSize)
    return false;

  value.resize(len);

  unsigned nBits = value.getNumBits(aligned());

  if ((value.getConstraintType() == Unconstrained || value.getUpperLimit()*nBits > 16) && aligned())
    byteAlign();

  for (unsigned i = 0; i < (unsigned)len; i++) {
      unsigned theBits;
      if (!decodeMultiBit(nBits, theBits))
          return false;
      value[i] = (wchar_t)(theBits + value.getFirstChar());
  }
  return true;
}

bool PERDecoder::decodeChoicePreamle(CHOICE& value, memento_type& nextPosition)
{
  // X.691 Section 22
  if (atEnd()) {
    return false;
  }

  bool ok = true;
  unsigned choiceID;

  if (value.extendable()) {
    if (decodeSingleBit()) {
      if (!decodeSmallUnsigned(choiceID))
        return false;
      choiceID += value.getNumChoices();
      unsigned len;
      if (decodeLength(0, INT_MAX, len) != 0)
        return false;
      nextPosition.bytePosition = beginPosition + len;
      nextPosition.bitPosition = 8;
      return value.select(choiceID);
    }
  }

  if (value.getNumChoices() < 2)
    choiceID = 0;
  else {
    if (decodeUnsigned(0, value.getNumChoices()-1, choiceID) < 0)
      return false;
  }

  nextPosition.bytePosition = 0;
  return value.select(choiceID);
}