Hello!
I have made the path. It works. But I'm not sure that it's consistent
with ASN.1-standard... Here http://luca.ntop.org/Teaching/Appunti/asn1.html
in "3.1 Primitive, definite-length method. Identifier octets. High-tag-
number form.":
Two or more octets. First octet is as in low-tag-number form, except
that bits 5-1 all have value "1." Second and following octets give the
tag number, base 128, most significant digit first, with as few digits
as possible, and with the bit 8 of each octet except the last set to
"1."
The problem is in my application first octet doesn't correspond to
rule above: bits 5-1 not all have value "1".(This tag of 2 byte length
is from ICAO standard and I can't change its length.)
Path:
**********************asn.h**********************
//! BER General Decoder
class CRYPTOPP_DLL BERGeneralDecoder : public Store
{
public:
explicit BERGeneralDecoder(BufferedTransformation &inQueue, byte
asnTag);
explicit BERGeneralDecoder(BERGeneralDecoder &inQueue, byte
asnTag);
explicit BERGeneralDecoder(BufferedTransformation &inQueue, byte
hiAsnTag, byte loAsnTag);
explicit BERGeneralDecoder(BERGeneralDecoder &inQueue, byte
hiAsnTag, byte loAsnTag);
~BERGeneralDecoder();
bool IsDefiniteLength() const {return m_definiteLength;}
lword RemainingLength() const {assert(m_definiteLength); return
m_length;}
bool EndReached() const;
byte PeekByte() const;
void CheckByte(byte b);
size_t TransferTo2(BufferedTransformation &target, lword
&transferBytes, const std::string &channel=DEFAULT_CHANNEL, bool
blocking=true);
size_t CopyRangeTo2(BufferedTransformation &target, lword &begin,
lword end=LWORD_MAX, const std::string &channel=DEFAULT_CHANNEL, bool
blocking=true) const;
// call this to denote end of sequence
void MessageEnd();
protected:
BufferedTransformation &m_inQueue;
bool m_finished, m_definiteLength;
lword m_length;
private:
void Init(byte asnTag);
void Init(byte hiAsnTag, byte loAsnTag);
void StoreInitialize(const NameValuePairs ¶meters) {assert
(false);}
lword ReduceLength(lword delta);
};
*************************************************
*********************asn.cpp*********************
BERGeneralDecoder::BERGeneralDecoder(BufferedTransformation &inQueue,
byte hiAsnTag, byte loAsnTag)
: m_inQueue(inQueue), m_finished(false)
{
Init(hiAsnTag, loAsnTag);
}
BERGeneralDecoder::BERGeneralDecoder(BERGeneralDecoder &inQueue, byte
hiAsnTag, byte loAsnTag)
: m_inQueue(inQueue), m_finished(false)
{
Init(hiAsnTag, loAsnTag);
}
void BERGeneralDecoder::Init(byte hiAsnTag, byte loAsnTag)
{
byte b;
if (!m_inQueue.Get(b) || b != hiAsnTag)
BERDecodeError();
if (!m_inQueue.Get(b) || b != loAsnTag)
BERDecodeError();
if (!BERLengthDecode(m_inQueue, m_length, m_definiteLength))
BERDecodeError();
if (!m_definiteLength && !(loAsnTag & CONSTRUCTED))
BERDecodeError(); // cannot be primitive and have
indefinite length
}
*************************************************
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