org.snmp4j.agent.mo.snmp

Class RowCount

java.lang.Object

org.snmp4j.agent.mo.snmp.RowCount

All Implemented Interfaces:

Cloneable, Comparable<org.snmp4j.smi.Variable>, org.snmp4j.asn1.BERSerializable, org.snmp4j.smi.Variable

public class RowCount
extends Object
implements org.snmp4j.smi.Variable

The RowCount class implements a Variable that counts the rows of a table and returns the number of rows as value. This class is a dynamic Variable, which means it needs to be cloned when serialized. When cloned, a Gauge32 instance with the row count of the source table will be created.

Since:

3.2.1

Author:

Frank Fock

Field Summary

Fields inherited from interface org.snmp4j.smi.Variable

serialVersionUID

Constructor Summary

Constructors

Constructor and Description
RowCount() Creates a RowCount which returns zero always.
RowCount(MOTable moTable) Creates a row counting Gauge32 variable for the specified MOTable.

Method Summary

Modifier and Type	Method and Description
Object	clone() Clones this variable.
int	compareTo(org.snmp4j.smi.Variable o)
void	decodeBER(org.snmp4j.asn1.BERInputStream inputStream) Decodes a Variable from an InputStream.
void	encodeBER(OutputStream outputStream) Encodes a Variable to an OutputStream.
void	fromSubIndex(org.snmp4j.smi.OID subIndex, boolean impliedLength) Sets the value of this Variable from the supplied (sub-)index.
int	getBERLength() Returns the length of this BERSerializable object in bytes when encoded according to the Basic Encoding Rules (BER).
int	getBERPayloadLength() Returns the length of the payload of this BERSerializable object in bytes when encoded according to the Basic Encoding Rules (BER).
int	getSyntax() Gets the ASN.1 syntax identifier value of this SNMP variable.
String	getSyntaxString() Gets a textual description of this Variable.
long	getValue() Gets the number of rows in the associated table as unsigned long value.
boolean	isDynamic() Indicates whether this variable is dynamic.
boolean	isException() Checks whether this variable represents an exception like noSuchObject, noSuchInstance, and endOfMibView.
int	toInt() Returns an integer representation of this variable if such a representation exists.
long	toLong() Returns a long representation of this variable if such a representation exists.
org.snmp4j.smi.OID	toSubIndex(boolean impliedLength) Converts the value of this Variable to a (sub-)index value.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.snmp4j.smi.Variable

equals, hashCode, toString

Constructor Detail

RowCount

public RowCount()

Creates a RowCount which returns zero always.

RowCount

public RowCount(MOTable moTable)

Creates a row counting Gauge32 variable for the specified MOTable.

Parameters:

moTable - a table instance whose rows should be counted by this variable.

Method Detail

getValue

public long getValue()

Gets the number of rows in the associated table as unsigned long value.

Returns:

the number of rows in the associated table (greater or equal to zero). Zero is returned if a null table is associated.

compareTo

public int compareTo(org.snmp4j.smi.Variable o)

Specified by:

compareTo in interface Comparable<org.snmp4j.smi.Variable>

Specified by:

compareTo in interface org.snmp4j.smi.Variable

clone

public Object clone()

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.

Specified by:

clone in interface org.snmp4j.smi.Variable

Overrides:

clone in class Object

Returns:

a new instance of this Variable with the same value.

getSyntax

public int getSyntax()

Gets the ASN.1 syntax identifier value of this SNMP variable.

Specified by:

getSyntax in interface org.snmp4j.smi.Variable

Returns:

an integer value < 128 for regular SMI objects and a value >= 128 for exception values like noSuchObject, noSuchInstance, and endOfMibView.

isException

public boolean isException()

Checks whether this variable represents an exception like noSuchObject, noSuchInstance, and endOfMibView.

Specified by:

isException in interface org.snmp4j.smi.Variable

Returns:

true if the syntax of this variable is an instance of Null and its syntax equals one of the following:

• SMIConstants.EXCEPTION_NO_SUCH_OBJECT
• SMIConstants.EXCEPTION_NO_SUCH_INSTANCE
• SMIConstants.EXCEPTION_END_OF_MIB_VIEW

toInt

public int toInt()

Returns an integer representation of this variable if such a representation exists.

Specified by:

toInt in interface org.snmp4j.smi.Variable

Returns:

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.

toLong

public long toLong()

Returns a long representation of this variable if such a representation exists.

Specified by:

toLong in interface org.snmp4j.smi.Variable

Returns:

a long value.

Throws:

UnsupportedOperationException - if a long representation does not exists for this Variable.

getSyntaxString

public String getSyntaxString()

Gets a textual description of this Variable.

Specified by:

getSyntaxString in interface org.snmp4j.smi.Variable

Returns:

a textual description like 'Integer32' as used in the Structure of Management Information (SMI) modules. '?' is returned if the syntax is unknown.

toSubIndex

public org.snmp4j.smi.OID toSubIndex(boolean impliedLength)

Converts the value of this Variable to a (sub-)index value.

Specified by:

toSubIndex in interface org.snmp4j.smi.Variable

Parameters:

impliedLength - specifies if the sub-index has an implied length. This parameter applies to variable length variables only (e.g. OctetString and OID). For other variables it has no effect.

Returns:

an OID that represents this value as an (sub-)index.

Throws:

UnsupportedOperationException - if this variable cannot be used in an index.

fromSubIndex

public void fromSubIndex(org.snmp4j.smi.OID subIndex,
                         boolean impliedLength)

Sets the value of this Variable from the supplied (sub-)index.

Specified by:

fromSubIndex in interface org.snmp4j.smi.Variable

Parameters:

subIndex - the sub-index OID.

impliedLength - specifies if the sub-index has an implied length. This parameter applies to variable length variables only (e.g. OctetString and OID). For other variables it has no effect.

Throws:

UnsupportedOperationException - if this variable cannot be used in an index.

isDynamic

public boolean isDynamic()

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 getBERLength() for encoding enclosing SEQUENCES and the actual encoding of the Variable itself with encodeBER(java.io.OutputStream) changes to the value need to be blocked by synchronization. In order to ensure proper synchronization if a Variable is dynamic, modifications of the variables content need to synchronize on the 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);
      }
    }
 

Specified by:

isDynamic in interface org.snmp4j.smi.Variable

Returns:

true because the variable might change its value between two calls to getBERLength() and encodeBER(java.io.OutputStream).

getBERLength

public int getBERLength()

Returns the length of this BERSerializable object in bytes when encoded according to the Basic Encoding Rules (BER).

Specified by:

getBERLength in interface org.snmp4j.asn1.BERSerializable

Returns:

the BER encoded length of this variable.

getBERPayloadLength

public int getBERPayloadLength()

Returns the length of the payload of this BERSerializable object in bytes when encoded according to the Basic Encoding Rules (BER).

Specified by:

getBERPayloadLength in interface org.snmp4j.asn1.BERSerializable

Returns:

the BER encoded length of this variable.

decodeBER

public void decodeBER(org.snmp4j.asn1.BERInputStream inputStream)
               throws IOException

Decodes a Variable from an InputStream.

Specified by:

decodeBER in interface org.snmp4j.asn1.BERSerializable

Parameters:

inputStream - an InputStream containing a BER encoded byte stream.

Throws:

IOException - if the stream could not be decoded by using BER rules.

encodeBER

public void encodeBER(OutputStream outputStream)
               throws IOException

Encodes a Variable to an OutputStream.

Specified by:

encodeBER in interface org.snmp4j.asn1.BERSerializable

Parameters:

outputStream - an OutputStream.

Throws:

IOException - if an error occurs while writing to the stream.