org.apache.cassandra.utils.vint

Class VIntCoding

java.lang.Object

org.apache.cassandra.utils.vint.VIntCoding

public class VIntCoding
extends java.lang.Object

Borrows idea from https://developers.google.com/protocol-buffers/docs/encoding#varints

Field Summary

Fields

Modifier and Type	Field and Description
protected static io.netty.util.concurrent.FastThreadLocal<byte[]>	encodingBuffer
static int	MAX_SIZE

Constructor Summary

Constructors

Constructor and Description
VIntCoding()

Method Summary

Modifier and Type	Method and Description
static int	computeUnsignedVIntSize(java.nio.ByteBuffer input, int readerIndex) Computes size of an unsigned vint that starts at readerIndex of the provided ByteBuf.
static int	computeUnsignedVIntSize(java.nio.ByteBuffer input, int readerIndex, int readerLimit)
static int	computeUnsignedVIntSize(long value) Compute the number of bytes that would be needed to encode an unsigned varint.
static int	computeVIntSize(long param) Compute the number of bytes that would be needed to encode a varint.
static long	decodeZigZag64(long n) Decode a ZigZag-encoded 64-bit value.
static int	encodeExtraBytesToRead(int extraBytesToRead)
static long	encodeZigZag64(long n) Encode a ZigZag-encoded 64-bit value.
static int	firstByteValueMask(int extraBytesToRead)
static long	getUnsignedVInt(java.nio.ByteBuffer input, int readerIndex) Note this method is the same as readUnsignedVInt(DataInput), except that we do *not* block if there are not enough bytes in the buffer to reconstruct the value.
static long	getUnsignedVInt(java.nio.ByteBuffer input, int readerIndex, int readerLimit)
static int	numberOfExtraBytesToRead(int firstByte)
static long	readUnsignedVInt(java.io.DataInput input)
static long	readVInt(java.io.DataInput input)
static void	skipUnsignedVInt(DataInputPlus input)
static void	writeUnsignedVInt(long value, java.nio.ByteBuffer output)
static void	writeUnsignedVInt(long value, java.io.DataOutput output)
static void	writeVInt(long value, java.io.DataOutput output)

Methods inherited from class java.lang.Object

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

Field Detail

MAX_SIZE

public static final int MAX_SIZE

See Also:

Constant Field Values

encodingBuffer

protected static final io.netty.util.concurrent.FastThreadLocal<byte[]> encodingBuffer

Constructor Detail

VIntCoding

public VIntCoding()

Method Detail

readUnsignedVInt

public static long readUnsignedVInt(java.io.DataInput input)
                             throws java.io.IOException

Throws:

java.io.IOException

skipUnsignedVInt

public static void skipUnsignedVInt(DataInputPlus input)
                             throws java.io.IOException

Throws:

java.io.IOException

getUnsignedVInt

public static long getUnsignedVInt(java.nio.ByteBuffer input,
                                   int readerIndex)

Note this method is the same as readUnsignedVInt(DataInput), except that we do *not* block if there are not enough bytes in the buffer to reconstruct the value. WARNING: this method is only safe for vints we know to be representable by a positive long value.

Returns:

-1 if there are not enough bytes in the input to read the value; else, the vint unsigned value.

getUnsignedVInt

public static long getUnsignedVInt(java.nio.ByteBuffer input,
                                   int readerIndex,
                                   int readerLimit)

computeUnsignedVIntSize

public static int computeUnsignedVIntSize(java.nio.ByteBuffer input,
                                          int readerIndex)

Computes size of an unsigned vint that starts at readerIndex of the provided ByteBuf.

Returns:

-1 if there are not enough bytes in the input to calculate the size; else, the vint unsigned value size in bytes.

computeUnsignedVIntSize

public static int computeUnsignedVIntSize(java.nio.ByteBuffer input,
                                          int readerIndex,
                                          int readerLimit)

readVInt

public static long readVInt(java.io.DataInput input)
                     throws java.io.IOException

Throws:

java.io.IOException

firstByteValueMask

public static int firstByteValueMask(int extraBytesToRead)

encodeExtraBytesToRead

public static int encodeExtraBytesToRead(int extraBytesToRead)

numberOfExtraBytesToRead

public static int numberOfExtraBytesToRead(int firstByte)

writeUnsignedVInt

@Inline
public static void writeUnsignedVInt(long value,
                                             java.io.DataOutput output)
                                      throws java.io.IOException

Throws:

java.io.IOException

writeUnsignedVInt

@Inline
public static void writeUnsignedVInt(long value,
                                             java.nio.ByteBuffer output)

writeVInt

@Inline
public static void writeVInt(long value,
                                     java.io.DataOutput output)
                              throws java.io.IOException

Throws:

java.io.IOException

decodeZigZag64

public static long decodeZigZag64(long n)

Decode a ZigZag-encoded 64-bit value. ZigZag encodes signed integers into values that can be efficiently encoded with varint. (Otherwise, negative values must be sign-extended to 64 bits to be varint encoded, thus always taking 10 bytes on the wire.)

Parameters:

n - An unsigned 64-bit integer, stored in a signed int because Java has no explicit unsigned support.

Returns:

A signed 64-bit integer.

encodeZigZag64

public static long encodeZigZag64(long n)

Encode a ZigZag-encoded 64-bit value. ZigZag encodes signed integers into values that can be efficiently encoded with varint. (Otherwise, negative values must be sign-extended to 64 bits to be varint encoded, thus always taking 10 bytes on the wire.)

Parameters:

n - A signed 64-bit integer.

Returns:

An unsigned 64-bit integer, stored in a signed int because Java has no explicit unsigned support.

computeVIntSize

public static int computeVIntSize(long param)

Compute the number of bytes that would be needed to encode a varint.

computeUnsignedVIntSize

public static int computeUnsignedVIntSize(long value)

Compute the number of bytes that would be needed to encode an unsigned varint.