OSB_LIB::Asn1Tag Class Reference

Collaboration diagram for OSB_LIB::Asn1Tag:

[legend]List of all members.

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Detailed Description

ASN.1 tag: Type identifier of encoded data.

ASN.1 uses tags to identify the type of encoded data. The class supports encoding, decoding and I/O of ASN.1 tags.

Encoding of tags:
+ Bits 8 and 7 of the frist byte contain the type class,
o universal: 00
o application: 01
o context: 10
o private: 11
+ Bit 6 of the first byte indicates if the type is primitive (0) or constructed (1).
+ Tag numbers less than 31 are coded in bits 5 to 1 of the tag's first byte.
+ For tag numbers greater or equal than 31 bits 5 to 1 of the tag's first byte are set to 11111. The actual number is stored in the subsequent bytes. These bytes contain the tag number in the 7 less significant bits and have bit 8 is set to 1 if more bytes with the tag number follow and bit 8 set to 0 for the final tag number byte. Examples:
o The value for the private tag 11, constructed type is 11101011 (binary) or 0xeb (hexadecimal).
o The application tag 195, primitive type is hexadecimal 0x5f8143.

Definition at line 90 of file asn1.h.

Public Types

• tcUniversal = 0x00

  universal tag
  

• tcApplication = 0x40

  application specific tag
  

• tcContext = 0x80

  context specific tag
  

• tcPrivate = 0xc0

  private tag
  

• enum TypeClass { tcUniversal = 0x00, tcApplication = 0x40, tcContext = 0x80, tcPrivate = 0xc0 }

  ASN.1 data type class. More...
  

Public Member Functions

• Asn1Tag (size_t val=tagNotSet)

  Constructor with encoded tag value.
  

• Asn1Tag (TypeClass typeClass, size_t tagNum, bool constructed)

  Constructor with type class, tag value and flag if the type is constructed.
  

• size_t value () const

  Tag value (incl. type class and composed flag).
  

• size_t tagNumber () const

  Tag number (excl. type class and composed flag).
  

• bool isSet () const

  Check if the tag is set.
  

• TypeClass typeClass () const

  Get the type class.
  

• bool isConstructed () const

  Check if type is constructed.
  

• size_t size () const

  Number of bytes needed for encoded form.
  

• Asn1Byte operator[] (size_t i) const

  Return encoded byte at position i.
  

• bool operator== (const Asn1Tag &rhs) const

  Equality operator.
  

• bool operator!= (const Asn1Tag &rhs) const

  Not-equal operator.
  

• bool operator< (const Asn1Tag &rhs) const

  Less than operator.
  

• size_t read (FILE *in)

  Read encoded ASN.1 tag from an input file.
  

• size_t get (const Asn1Byte *data, size_t dataSize)

  Get encoded ASN.1 tag from binary data.
  

• void encode (Asn1Data &dest) const

  Encode tag to binary data.
  

• std::string str () const

  Human readable output of an ASN.1 tag in hex format.
  

Static Public Attributes

• static const size_t tagNotSet = size_t(-1)

  Value of the tag if not set.
  

Private Member Functions

• void mkSize ()

  Compute size_.
  

Private Attributes

• size_t value_

  Tag value incl. type class and composed flag.
  

• size_t size_

  Number of bytes needed for encode format.
  

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Member Enumeration Documentation

enum OSB_LIB::Asn1Tag::TypeClass

ASN.1 data type class.

TypeClass defines the class of an ASN.1 data type. It is stored in bits 8 and 7 of the tag's first byte.

Enumerator:

tcUniversal	universal tag
tcApplication	application specific tag
tcContext	context specific tag
tcPrivate	private tag

Definition at line 98 of file asn1.h.

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Constructor & Destructor Documentation

OSB_LIB::Asn1Tag::Asn1Tag

(

size_t

val = tagNotSet

)

[explicit]

Constructor with encoded tag value.

Parameters:

val

Value of the encoded tag, incl. class and primitive/constructed.

OSB_LIB::Asn1Tag::Asn1Tag	(	TypeClass	typeClass,
		size_t	tagNum,
		bool	constructed
	)

Constructor with type class, tag value and flag if the type is constructed.

Remarks:

Copy constructor, assignment and destructor by compiler.

Parameters:

	typeClass	The type class.
	tagNum	The tag number.
	constructed	Flag if type is constructed.

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Member Function Documentation

void OSB_LIB::Asn1Tag::encode

(

Asn1Data &

dest

)

const

Encode tag to binary data.

Parameters:

dest

Buffer to populate.

size_t OSB_LIB::Asn1Tag::get	(	const Asn1Byte *	data,
		size_t	dataSize
	)

Get encoded ASN.1 tag from binary data.

Parameters:

	data	Array with binary data.
	dataSize	Size of binary data.

Returns:

size_t(-1) in case of an error,
else the number of bytes used for the tag.

bool OSB_LIB::Asn1Tag::isConstructed

(

)

const [inline]

Check if type is constructed.

Definition at line 320 of file asn1.h.

bool OSB_LIB::Asn1Tag::isSet

(

)

const [inline]

Check if the tag is set.

Definition at line 304 of file asn1.h.

References tagNotSet, and value_.

void OSB_LIB::Asn1Tag::mkSize

(

)

[inline, private]

Compute size_.

bool OSB_LIB::Asn1Tag::operator!=

(

const Asn1Tag &

rhs

)

const [inline]

Not-equal operator.

Definition at line 331 of file asn1.h.

References value_.

bool OSB_LIB::Asn1Tag::operator<

(

const Asn1Tag &

rhs

)

const [inline]

Less than operator.

Definition at line 336 of file asn1.h.

References value_.

bool OSB_LIB::Asn1Tag::operator==

(

const Asn1Tag &

rhs

)

const [inline]

Equality operator.

Definition at line 326 of file asn1.h.

References value_.

Asn1Byte OSB_LIB::Asn1Tag::operator[]

(

size_t

i

)

const

Return encoded byte at position i.

size_t OSB_LIB::Asn1Tag::read

(

FILE *

in

)

Read encoded ASN.1 tag from an input file.

If a read error on the input file occurs, the tag value is not set.

Parameters:

in

Input file to read from.

Returns:

Number of bytes read from the input.

size_t OSB_LIB::Asn1Tag::size

(

)

const [inline]

Number of bytes needed for encoded form.

Definition at line 309 of file asn1.h.

References size_.

std::string OSB_LIB::Asn1Tag::str

(

)

const

Human readable output of an ASN.1 tag in hex format.

The returned string is empty if the tag is not set.

Remarks:

Use the member function encode(...) to get the binary ASN.1 data.

size_t OSB_LIB::Asn1Tag::tagNumber

(

)

const

Tag number (excl. type class and composed flag).

Asn1Tag::TypeClass OSB_LIB::Asn1Tag::typeClass

(

)

const [inline]

Get the type class.

Definition at line 314 of file asn1.h.

References tcPrivate.

size_t OSB_LIB::Asn1Tag::value

(

)

const [inline]

Tag value (incl. type class and composed flag).

Definition at line 299 of file asn1.h.

References value_.

Referenced by OSB_LIB::Asn1Info::tagValue().

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Member Data Documentation

size_t OSB_LIB::Asn1Tag::size_ [private]

Number of bytes needed for encode format.

Definition at line 197 of file asn1.h.

Referenced by size().

const size_t OSB_LIB::Asn1Tag::tagNotSet = size_t(-1) [static]

Value of the tag if not set.

Definition at line 106 of file asn1.h.

Referenced by isSet().

size_t OSB_LIB::Asn1Tag::value_ [private]

Tag value incl. type class and composed flag.

Definition at line 195 of file asn1.h.

Referenced by isSet(), operator!=(), operator<(), operator==(), and value().

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The documentation for this class was generated from the following file:

• asn1.h

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