org.snmp4j.smi.Variable Maven / Gradle / Ivy
/*_############################################################################
_##
_## SNMP4J - Variable.java
_##
_## Copyright (C) 2003-2018 Frank Fock and Jochen Katz (SNMP4J.org)
_##
_## Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
_##
_## Unless required by applicable law or agreed to in writing, software
_## distributed under the License is distributed on an "AS IS" BASIS,
_## WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
_## See the License for the specific language governing permissions and
_## limitations under the License.
_##
_##########################################################################*/
package org.snmp4j.smi;
import org.snmp4j.asn1.BERSerializable;
/**
* The {@code Variable} interface defines common attributes of all SNMP variables.
*
* Before version 1.8, Variable has been an abstract class which has been renamed to {@link AbstractVariable}.
*
* @author Frank Fock
* @version 1.8
* @since 1.8
*/
public interface Variable extends Cloneable, Comparable, BERSerializable {
/**
* This definition of a serialVersionUID for the Variable interface has been made for backward compatibility with
* SNMP4J 1.7.x or earlier serialized Variable instances.
*/
long serialVersionUID = 1395840752909725320L;
boolean equals(Object o);
int compareTo(Variable o);
int hashCode();
/**
* Clones this variable. Cloning can be used by the SNMP4J API to better support concurrency by creating a clone for
* internal processing. The content of this object is independent to the content of the clone. Thus, changes to the
* clone will have no effect to this object.
*
* @return a new instance of this {@code Variable} with the same value.
*/
Object clone();
/**
* Gets the ASN.1 syntax identifier value of this SNMP variable.
*
* @return an integer value < 128 for regular SMI objects and a value >= 128 for exception values like
* noSuchObject, noSuchInstance, and endOfMibView.
*/
int getSyntax();
/**
* Checks whether this variable represents an exception like noSuchObject, noSuchInstance, and endOfMibView.
*
* @return {@code true} if the syntax of this variable is an instance of {@code Null} and its syntax equals one of
* the following:
*
* - {@link SMIConstants#EXCEPTION_NO_SUCH_OBJECT}
* - {@link SMIConstants#EXCEPTION_NO_SUCH_INSTANCE}
* - {@link SMIConstants#EXCEPTION_END_OF_MIB_VIEW}
*
*/
boolean isException();
/**
* Gets a string representation of the variable.
*
* @return a string representation of the variable's value.
*/
String toString();
/**
* Returns an integer representation of this variable if such a representation exists.
*
* @return an integer value (if the native representation of this variable would be a long, then the long value will
* be casted to int).
* @throws UnsupportedOperationException
* if an integer representation does not exists for this Variable.
*/
int toInt();
/**
* Returns a long representation of this variable if such a representation exists.
*
* @return a long value.
* @throws UnsupportedOperationException
* if a long representation does not exists for this Variable.
*/
long toLong();
/**
* Gets a textual description of this Variable.
*
* @return a textual description like 'Integer32' as used in the Structure of Management Information (SMI) modules.
* '?' is returned if the syntax is unknown.
*/
String getSyntaxString();
/**
* Converts the value of this {@code Variable} to a (sub-)index value.
*
* @param impliedLength
* specifies if the sub-index has an implied length. This parameter applies to variable length variables
* only (e.g. {@link OctetString} and {@link OID}). For other variables it has no effect.
*
* @return an OID that represents this value as an (sub-)index.
* @throws UnsupportedOperationException
* if this variable cannot be used in an index.
*/
OID toSubIndex(boolean impliedLength);
/**
* Sets the value of this {@code Variable} from the supplied (sub-)index.
*
* @param subIndex
* the sub-index OID.
* @param impliedLength
* specifies if the sub-index has an implied length. This parameter applies to variable length variables
* only (e.g. {@link OctetString} and {@link OID}). For other variables it has no effect.
*
* @throws UnsupportedOperationException
* if this variable cannot be used in an index.
*/
void fromSubIndex(OID subIndex, boolean impliedLength);
/**
* Indicates whether this variable is dynamic. If a variable is dynamic, precautions have to be taken when a
* Variable is serialized using BER encoding, because between determining the length with {@link #getBERLength()}
* for encoding enclosing SEQUENCES and the actual encoding of the Variable itself with {@link #encodeBER} changes
* to the value need to be blocked by synchronization. In order to ensure proper synchronization if a {@code
* Variable} is dynamic, modifications of the variables content need to synchronize on the {@code Variable}
* instance. This can be achieved for the standard SMI Variable implementations for example by
*
* public static modifyVariable(Integer32 variable, int value)
* synchronize(variable) {
* variable.setValue(value);
* }
* }
*
*
* @return {@code true} if the variable might change its value between two calls to {@link #getBERLength()} and
* {@link #encodeBER} and {@code false} if the value is immutable or if its value does not change while
* serialization because of measures taken by the implementor (i.e. variable cloning).
*/
boolean isDynamic();
}