Package org.eclipse.rdf4j.rio.hdt

Class VByte

java.lang.Object

org.eclipse.rdf4j.rio.hdt.VByte

public class VByte
extends Object

Variable byte encoding for numbers.

A variable number of bytes is used to encode (unsigned) numeric values, the first bit (MSB) of each byte indicates if there are more bytes to read, the other 7 bits are used to encode the value.

In this implementation, the MSB is set to 1 if this byte is the last one.

E.g: 10000001 is value 1, 00000001 10000001 is 128 (decimal). Note that the value is stored little-endian, so in this example 10000001 00000001.

Author:

Bart.Hanssens

See Also:

• Variable byte codes

Constructor Summary

Constructors

Constructor	Description
VByte()

Method Summary

Modifier and Type	Method	Description
static long	decode(byte[] bytes, int len)	Decode a series of encoded bytes, with a maximum of 8 bytes
static long	decode(InputStream is)	Decode a maximum of 8 bytes from the input stream.
static long	decodeFrom(byte[] b, int start)	Decode a maximum of 8 bytes from a byte array.
static int	encodedLength(long value)	Calculate the number of bytes needed for encoding a value
static boolean	hasNext(byte b)	Checks if the most significant bit is set.

Methods inherited from class java.lang.Object

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

Constructor Details

VByte

public VByte()

Method Details

hasNext

public static boolean hasNext(byte b)

Checks if the most significant bit is set. If this bit is zero, then the next byte must also be read to decode the number.

Parameters:

b -

Returns:

true if there is a next byte

decode

public static long decode(byte[] bytes,
 int len)

Decode a series of encoded bytes, with a maximum of 8 bytes

Parameters:

bytes - byte array

len - number of bytes to decode

Returns:

long value

decode

public static long decode(InputStream is)
                   throws IOException

Decode a maximum of 8 bytes from the input stream.

Parameters:

is - input stream

Returns:

decode value

Throws:

IOException

decodeFrom

public static long decodeFrom(byte[] b,
 int start)

Decode a maximum of 8 bytes from a byte array.

Parameters:

b - byte array

start - starting position

Returns:

decode value

encodedLength

public static int encodedLength(long value)

Calculate the number of bytes needed for encoding a value

Parameters:

value - numeric value

Returns:

number of bytes