Package io.permazen.util

Class UnsignedIntEncoder

java.lang.Object

io.permazen.util.UnsignedIntEncoder

public final class UnsignedIntEncoder
extends Object

Encodes unsigned (i.e., non-negative) int values to/from self-delimited binary, preserving sort order, and such that the length of the encoding is optimized for values near zero and encoded values never begin with 0xff.

The encoding uses a simple prefixing format:

Encoding Format

Encoded Bytes	Value
0x00 ... 0xfa	Same
0xfb 0xWW	0xWW + 0xfb
0xfc 0xWW 0xXX	0xWWXX + 0xfb
0xfd 0xWW 0xXX 0xYY	0xWWXXYY + 0xfb
0xfe 0xWW 0xXX 0xYY 0xZZ	0xWWXXYYZZ + 0xfb
0xff	Illegal

Field Summary

Fields

Modifier and Type	Field	Description
static final int	MAX_ENCODED_LENGTH	Maximum possible length of an encoded value.
static final int	MIN_MULTI_BYTE_VALUE	Minimum value that triggers a multi-byte encoding.

Method Summary

Modifier and Type	Method	Description
static int	decode(ByteData data)	Decode the given value.
static int	decodeLength(int first)	Determine the length (in bytes) of an encoded value based on the first byte.
static ByteData	encode(int value)	Encode the given value.
static int	encodeLength(int value)	Determine the length (in bytes) of the encoded value.
static void	main(String[] args)	Test routine.
static int	read(ByteData.Reader reader)	Read and decode a value from the input.
static int	read(InputStream input)	Read and decode a value from the given InputStream.
static int	read(ByteBuffer buf)	Read and decode a value from the given ByteBuffer.
static void	skip(ByteData.Reader reader)	Skip a value from the input.
static void	write(ByteData.Writer writer, int value)	Encode the given value.
static void	write(OutputStream out, int value)	Encode the given value.
static void	write(ByteBuffer buf, int value)	Encode the given value.

Methods inherited from class java.lang.Object

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

Field Details

MAX_ENCODED_LENGTH

public static final int MAX_ENCODED_LENGTH

Maximum possible length of an encoded value.

See Also:

• Constant Field Values

MIN_MULTI_BYTE_VALUE

public static final int MIN_MULTI_BYTE_VALUE

Minimum value that triggers a multi-byte encoding.

See Also:

• Constant Field Values

Method Details

encode

public static ByteData encode(int value)

Encode the given value.

Parameters:

value - value to encode

Returns:

encoded value

Throws:

IllegalArgumentException - if value is negative

write

public static void write(ByteData.Writer writer,
 int value)

Encode the given value.

Parameters:

writer - destination for the encoded value

value - value to encode

Throws:

IllegalArgumentException - if value is negative

IllegalArgumentException - if writer is null

write

public static void write(OutputStream out,
 int value)
                  throws IOException

Encode the given value.

Parameters:

out - destination for the encoded value

value - value to encode

Throws:

IOException - if an I/O error occurs

IllegalArgumentException - if value is negative

IllegalArgumentException - if out is null

write

public static void write(ByteBuffer buf,
 int value)

Encode the given value.

Parameters:

buf - destination for the encoded value

value - value to encode

Throws:

IllegalArgumentException - if value is negative

BufferOverflowException - if buf overflows

ReadOnlyBufferException - if buf is read-only

IllegalArgumentException - if buf is null

encodeLength

public static int encodeLength(int value)

Determine the length (in bytes) of the encoded value.

Parameters:

value - value to encode

Returns:

the length of the encoded value, a value between one and MAX_ENCODED_LENGTH

Throws:

IllegalArgumentException - if value is negative

decode

public static int decode(ByteData data)

Decode the given value.

Parameters:

data - encoded value

Returns:

decoded value

Throws:

IllegalArgumentException - if data contains an invalid encoding, or extra trailing garbage

IllegalArgumentException - if data is null

read

public static int read(ByteData.Reader reader)

Read and decode a value from the input.

Parameters:

reader - input holding an encoded value

Returns:

the decoded value, always non-negative

Throws:

IllegalArgumentException - if the encoded value is truncated

IllegalArgumentException - if an invalid encoding is encountered

IllegalArgumentException - if reader is null

read

public static int read(InputStream input)
                throws IOException

Read and decode a value from the given InputStream.

Parameters:

input - input source for the encoded value

Returns:

the decoded value

Throws:

IOException - if an I/O error occurs

EOFException - if an unexpected EOF is encountered

IllegalArgumentException - if an invalid encoding is encountered

IllegalArgumentException - if input is null

read

public static int read(ByteBuffer buf)

Read and decode a value from the given ByteBuffer.

Parameters:

buf - input source for the encoded value

Returns:

the decoded value

Throws:

BufferUnderflowException - if buf underflows

IllegalArgumentException - if an invalid encoding is encountered

IllegalArgumentException - if buf is null

skip

public static void skip(ByteData.Reader reader)

Skip a value from the input.

Parameters:

reader - input holding an encoded value

Throws:

IllegalArgumentException - if reader is null

decodeLength

public static int decodeLength(int first)

Determine the length (in bytes) of an encoded value based on the first byte.

Parameters:

first - first byte of encoded value (in lower eight bits; other bits are ignored)

Returns:

the length of the encoded value (including first)

Throws:

IllegalArgumentException - if the lower eight bits of first equal 0xff

main

public static void main(String[] args)

Test routine.

Parameters:

args - command line arguments