com.sun.sgs.impl.util
Class Int30

java.lang.Object
  com.sun.sgs.impl.util.Int30

public final class Int30
extends Object

Provides utilities for reading and writing 30-bit integers in a compressed format that is smaller for smaller integers. Does not support negative integers or values above 2^30 - 1 or 1073741823.

The high order two bits of the first byte specify the number of additional bytes beyond the first byte that will be needed to store the entire integer. The bottom 6 bits of the first byte hold the highest order bits of the integer, with the following bytes holding the remaining bytes.

Values less than 2^6 are represented by just storing the value in a single byte, since the top two marking bits are zero:

• 53 (0x35) => 0x35

Values less than 2^14 are represented in two bytes, with the top two bits of the first byte set to 01 binary:

• 4000 (0xfa0) => 0x4f 0xa0

Values less than 2^22 take three bytes, with 10 binary in the top bits, and less than 2^30 take four, with 11 binary in the top bits:

• 123456 (0x1e240) => 0x81 0xe2 0x40
• 123456789 (0x75bcd15) => 0xc7 0x5b 0xcd 0x15
• 456789012 (0x1b3a0c14) => 0xdb 0x3a 0x0c 0x14

Field Summary

static int

MAX_VALUE The maximum integer that can be encoded.

Method Summary

static int	read(InputStream in) Reads a 30-bit integer from an input stream.
static void	write(int n, OutputStream out) Writes a 30-bit integer to an output stream.

Methods inherited from class java.lang.Object

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

Field Detail

MAX_VALUE

public static final int MAX_VALUE

The maximum integer that can be encoded.

See Also:

Constant Field Values

Method Detail

write

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

Writes a 30-bit integer to an output stream.

Parameters:

n - the integer

out - the output stream

Throws:

IllegalArgumentException - if n is less than 0 or greater than 1073741823

IOException - if an I/O error occurs

read

public static int read(InputStream in)
                throws IOException

Reads a 30-bit integer from an input stream.

Parameters:

in - the input stream

Returns:

the integer

Throws:

IOException - if an I/O error occurs