Package org.apache.directory.api.asn1.ber.tlv

Class IntegerDecoder

java.lang.Object

org.apache.directory.api.asn1.ber.tlv.IntegerDecoder

public final class IntegerDecoder
extends Object

Parse and decode an Integer value.

Author:

Apache Directory Project

Field Summary

Fields

Modifier and Type	Field	Description
private static int[]	MASK	A mask used to get only the necessary bytes

Constructor Summary

Constructors

Modifier	Constructor	Description
private	IntegerDecoder()

Method Summary

Modifier and Type	Method	Description
static int	parse(BerValue value)	Parse a byte buffer and send back an integer
static int	parse(BerValue value, int min, int max)	Parse a byte buffer and send back an integer, controlling that this number is in a specified interval.
private static int	parseInt(BerValue value)	Helper method used to parse the integer.

Methods inherited from class java.lang.Object

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

Field Detail

MASK

private static final int[] MASK

A mask used to get only the necessary bytes

Constructor Detail

IntegerDecoder

private IntegerDecoder()

Method Detail

parse

public static int parse(BerValue value,
                        int min,
                        int max)
                 throws IntegerDecoderException

Parse a byte buffer and send back an integer, controlling that this number is in a specified interval.

Parameters:

value - The Value containing the byte[] to parse

min - Lowest value allowed, included

max - Highest value allowed, included

Returns:

An integer

Throws:

IntegerDecoderException - Thrown if the byte[] does not contains an integer

parse

public static int parse(BerValue value)
                 throws IntegerDecoderException

Parse a byte buffer and send back an integer

Parameters:

value - The byte buffer to parse

Returns:

An integer

Throws:

IntegerDecoderException - Thrown if the byte stream does not contains an integer

parseInt

private static int parseInt(BerValue value)
                     throws IntegerDecoderException

Helper method used to parse the integer. We don't check any minimal or maximal bound. An BER encoded int can be either positive or negative. It uses the minimum number of bytes necessary to encode the value. The high order bit gives the sign of the integer : if it's 1, then it's a negative value, otherwise it's a positive value. Integer with a high order bit set to 1 but prefixed by a 0x00 are positive. If the integer is negative, then the 2 complement value is stored
Here are a few samples :

• 0x02 0x01 0x00 : integer 0
• 0x02 0x01 0x01 : integer 1
• 0x02 0x01 0x7F : integer 127
• 0x02 0x01 0x80 : integer -128
• 0x02 0x01 0x81 : integer -127
• 0x02 0x01 0xFF : integer -1
• 0x02 0x02 0x00 0x80 : integer 128
• 0x02 0x02 0x00 0x81 : integer 129
• 0x02 0x02 0x00 0xFF : integer 255

and so on...

Parameters:

value - the BER PDU to parse

Returns:

The decoded value

Throws:

IntegerDecoderException - If the BER contains an invalid integer value