iaik.asn1
Class UTF8String

java.lang.Object
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  +--iaik.asn1.ASN1Object
        |
        +--iaik.asn1.UTF8String

public class UTF8String

extends ASN1Object

This class implements the ASN.1 character string type "UTF8String". UTF8String is a simple ASN.1 string type identified by the UNIVERSAL TAG number 12.

UTF-8 (UCS transformation format 8) is an encoding format that has been developed for handling UCS-2/UCS-4 multi-octet character sets by applications that operate on 7, 8 bit characters. UTF-8 is specified by ISO 10646 in RFC 2279.

RFC 2279 gives an algorithm for transforming UCS-4/UCS-2 multi octet characters into UTF-8 octet sequences. This class can be used for UTF-8 encoding UCS-2/Unicode character strings according to the following rules:

• Characters in the range of 0x0000 to 0x007F (US-ASCII) are encoded as a single octet having a zero (0) bit in its highest position: 0xxxxxxx.
• Characters in the range of 0x0080 to 0x07EF are encoded as two octets according to 110xxxxx 10xxxxxx, where x denote the bits of the given character to be inserted from the right
• Characters in the range of 0x0800 to 0xFFFF are encoded as three octets according to 1110xxxx 10xxxxxx 10xxxxxx, where x denote the bits of the given character to be inserted from the right

Characters out of range will raise a CodingException.

When creating a new UTF8String object the value to be represented has to be supplied as Java String type:

 String s = ...;
 UTF8String UTF8String = new UTF8String(s);
 

When calling the getValue method for getting the inherent string value from an ASN.1 UTF8String instance, a Java object of type String is returned:

 String s = (String)UTF8String.getValue();
 

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.

See Also:

ASN1Object, ASN

Fields inherited from class iaik.asn1.ASN1Object

asnType, encode_listener, stream_mode

Constructor Summary

protected	UTF8String() Creates an empty UTF8String.
	UTF8String(java.lang.String value) Creates a new ASN.1 UTF8String object for the given String value.

Method Summary

protected void	decode(int length, java.io.InputStream is) Decodes an UTF8String value from the given InputStream.
protected void	encode(java.io.OutputStream os) DER encodes this UTF8String ASN1Object and writes the result to the given output stream.
java.lang.Object	getValue() Returns the value of this UTF8String as a String object.
void	setValue(java.lang.Object object) Sets the value of this UTF8String.
java.lang.String	toString() Returns a string that represents the contents of this UTF8String.

Methods inherited from class iaik.asn1.ASN1Object

addComponent, addEncodeListener, countComponents, encodeObject, getAsnType, getComponentAt, indefiniteLength, isA, isConstructed, setIndefiniteLength, setIndefiniteRecursive

Methods inherited from class java.lang.Object

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

Constructor Detail

UTF8String

protected UTF8String()

Creates an empty UTF8String.

UTF8String

public UTF8String(java.lang.String value)

Creates a new ASN.1 UTF8String object for the given String value.

Parameters:

value - the String value this UTF8String object should be initialized with

Method Detail

getValue

public java.lang.Object getValue()

Returns the value of this UTF8String as a String object.

Overrides:

getValue in class ASN1Object

Returns:

the value of this UTF8String as a String object

setValue

public void setValue(java.lang.Object object)

Sets the value of this UTF8String.

The supplied value has to be a Java object of type String.

Overrides:

setValue in class ASN1Object

Parameters:

object - the Java String value to be set for this UTF8String

encode

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

DER encodes this UTF8String ASN1Object and writes the result to the given output stream.

This is a protected method and will not be used by an application for DER encoding an UTF8String 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.

Overrides:

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 UTF8String 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 UTF8String.

This is a protected method and will not be used by an application for decoding a DER encoded UTF8String. 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 UTF8String object and internally calls this decode method for actually reading the value. No check is performed if the received value actually is composed only of characters belonging to the UTF8String character set!

Overrides:

decode in class ASN1Object

Parameters:

length - the already decoded length, i.e. number of the bytes representing the value of the UTF8String to be decoded

is - the input stream from which the DER encoded 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 UTF8String.

Overrides:

toString in class ASN1Object

Returns:

the string representation

See Also:

ASN1Object.toString()