iaik.asn1

Class INTEGER

java.lang.Object

iaik.asn1.ASN1Object

iaik.asn1.INTEGER

All Implemented Interfaces:

java.lang.Cloneable

public class INTEGER
extends ASN1Object

This class implements the native ASN.1 type "INTEGER". INTEGER is a simple non-string ASN.1 type identified by the UNIVERSAL TAG number 2. An ASN.1 INTEGER object may represent any arbitrary integer value.

When creating a new ASN.1 INTEGER object, an application may supply the integer value either as Java int value or as Java BigInteger object,e.g.:

 int value = ...;
 INTEGER asn1Integer = new INTEGER(value);
 //or
 BigInteger value = ...;
 INTEGER asn1Integer = new INTEGER(value);
 

When calling the getValue method for getting the inherent value from an ASN.1 INTEGER instance, a Java object of type BigInteger is returned:

 BigInteger Value = (BigInteger)asn1Integer.getValue();
 int value = Value.intValue();
 

DER en/decoding generally is done by means of the several methods of the DerCoder class; decoding alternatively may be performed by using the DerInputStream utility.

Version:

File Revision 18

See Also:

ASN1Object, ASN

Field Summary

Fields inherited from class iaik.asn1.ASN1Object

asnType, constructed, encode_listener, indefinite_length, isStringType, stream_mode

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	INTEGER() Creates an empty INTEGER.
	INTEGER(java.math.BigInteger value) Creates a new ASN.1 INTEGER object for the given Java BigInteger value.
	INTEGER(int value) Creates a new ASN.1 INTEGER object for the given Java int value.

Method Summary

Methods

Modifier and Type	Method and Description
static void	checkForMinumumLengthEncoding(boolean check) Decide whether to check if the INTEGER value is encoded in the minimum number of octets.
protected void	decode(int length, java.io.InputStream is) Decodes an INTEGER value from the given InputStream.
protected void	encode(java.io.OutputStream os) DER encodes this INTEGER ASN1Object and writes the result to the given OutputStream.
java.math.BigInteger	getBigIntegerValue(boolean makePositive) Returns the value as BigInteger.
java.lang.Object	getValue() Returns the value of this INTEGER as a BigInteger object.
void	setIndefiniteLength(boolean indefiniteLength) Does nothing (primitive INTEGER is encoded with definite length in any case).
void	setValue(java.lang.Object value) Sets the value of this INTEGER.
java.lang.String	toString() Returns a string that represents the contents of this INTEGER ASN1Object.

Methods inherited from class iaik.asn1.ASN1Object

addComponent, addEncodeListener, clone, countComponents, encodeObject, getAsnType, getComponentAt, indefiniteLength, isA, isConstructed, isStringType

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

INTEGER

protected INTEGER()

Creates an empty INTEGER.

INTEGER

public INTEGER(java.math.BigInteger value)

Creates a new ASN.1 INTEGER object for the given Java BigInteger value.

Parameters:

value - the BigInteger value this INTEGER object should represent

INTEGER

public INTEGER(int value)

Creates a new ASN.1 INTEGER object for the given Java int value.

Parameters:

value - the int value this INTEGER object should represent

Method Detail

checkForMinumumLengthEncoding

public static void checkForMinumumLengthEncoding(boolean check)

Decide whether to check if the INTEGER value is encoded in the minimum number of octets.

If the correctness of the encoding shall be checked an exception is thrown when decoding an INTEGER value containing more than only one octets and all bits of the first octet and bit 8 of the second octest are all zero bits or all one bits.

According to the ASN.1 specification (ITU-T X.690) minimum length encoding is required for INTEGER values, both for BER and DER. However, for compatibility reasons the minimum length value check is disabled by default except for when using DerCoder#decode(byte[] coding, boolean ensureDER) with ensureDER set to true.

Parameters:

check - whether to check for minumum length encoding (default: false)

getValue

public java.lang.Object getValue()

Returns the value of this INTEGER as a BigInteger object.

Specified by:

getValue in class ASN1Object

Returns:

the value of this INTEGER as a BigInteger object

getBigIntegerValue

public java.math.BigInteger getBigIntegerValue(boolean makePositive)

Returns the value as BigInteger. For cryptographic components, like, e.g. the modulus of a RSA public key a positive INTEGER is required. However, implementations may not correctly encoded INTEGER values. If the most significant bit of the modulus is set, the INTEGER representation has to be padded with a leading zero to indicate the positive value.

Parameters:

makePositive - whether to make the value positive (

Returns:

the (positive) BigInteger value

setValue

public void setValue(java.lang.Object value)

Sets the value of this INTEGER. The supplied value has to be a Java object of type BigInteger.

Specified by:

setValue in class ASN1Object

Parameters:

value - the Java BigInteger value to be set for this INTEGER object

setIndefiniteLength

public void setIndefiniteLength(boolean indefiniteLength)

Does nothing (primitive INTEGER is encoded with definite length in any case).

Overrides:

setIndefiniteLength in class ASN1Object

Parameters:

indefiniteLength - ignored

encode

protected void encode(java.io.OutputStream os)
               throws java.io.IOException

DER encodes this INTEGER ASN1Object and writes the result to the given OutputStream. This is a protected method and will not be used by an application for DER encoding an INTEGER object. An application will call one of the encode methods of the DerCoder class for performing the encoding, and the DerCoder internally will call this encode method.

Specified by:

encode in class ASN1Object

Parameters:

os - the output stream to which to write the data

Throws:

java.io.IOException - if an I/O error occurs while writing to the stream

decode

protected void decode(int length,
          java.io.InputStream is)
               throws java.io.IOException

Decodes an INTEGER value from the given InputStream. The given input stream carries DER encoded data, and the next length bytes to be read represent the value of an ASN.1 object of type INTEGER.

This is a protected method and will not be used by an application for decoding a DER encoded INTEGER. An application will call one of the decode methods of the DerCoder class for performing the decoding. The DerCoder then determines the number of bytes (length) occupied by the value of this INTEGER object and internally calls this decode method for actually reading the value.

Specified by:

decode in class ASN1Object

Parameters:

length - the already decoded length, i.e. number of the bytes representing the value of the INTEGER to be decoded

is - the input stream from which the DER decoded data is read in

Throws:

java.io.IOException - if there is a problem with the InputStream

toString

public java.lang.String toString()

Returns a string that represents the contents of this INTEGER ASN1Object.

Overrides:

toString in class ASN1Object

Returns:

the string representation