Package org.firebirdsql.extern.decimal

Class DenselyPackedDecimalCodec

java.lang.Object

org.firebirdsql.extern.decimal.DenselyPackedDecimalCodec

public final class DenselyPackedDecimalCodec
extends java.lang.Object

Provides conversion between Densely Packed Decimal encoding and BigInteger.

Densely packed decimals are encoded in groups of three digits, which are encoded in 10 bits per group.

See: A Summary of Densely Packed Decimal encoding

The implementation is tied to the needs of the IEEE-754 decimal encoding and decoding of this library, so it may be quirky for other purposes.

This implementation can be made to behave as for n * 3 digits by constructing it for n * 3 + 1 digits and calling decodeValue(int, int, byte[]) with 0 for the second parameter (firstDigit).

Author:

Mark Rotteveel

Constructor Summary

Constructors

Constructor	Description
DenselyPackedDecimalCodec(int numberOfDigits)	Creates a densely packed decimal coder for the specified number of digits.

Method Summary

Modifier and Type	Method	Description
java.math.BigInteger	decodeValue(int signum, int firstDigit, byte[] decBytes)	Decodes a densely packed decimal from a byte array to a BigInteger.
java.math.BigInteger	decodeValue(int signum, int firstDigit, byte[] decBytes, int lsbIndex)	Decodes a densely packed decimal from a byte array to a BigInteger.
int	encodeValue(java.math.BigInteger value, byte[] decBytes)	Encodes a BigInteger to a densely packed decimal in a byte array.
int	encodeValue(java.math.BigInteger value, byte[] decBytes, int lsbIndex)	Encodes a BigInteger to a densely packed decimal in a byte array.

Methods inherited from class java.lang.Object

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

Constructor Detail

DenselyPackedDecimalCodec

public DenselyPackedDecimalCodec(int numberOfDigits)

Creates a densely packed decimal coder for the specified number of digits.

Current implementation only supports decoding and encoding n * 3 + 1 number of digits with n > 0, where the most significant digit is provided by the caller during decoding.

Parameters:

numberOfDigits - Number of digits that this coder will decode or encode

Throws:

java.lang.IllegalArgumentException - When numberOfDigits is not n * 3 + 1 with n > 0

Method Detail

decodeValue

public java.math.BigInteger decodeValue(int signum,
                                        int firstDigit,
                                        byte[] decBytes)

Decodes a densely packed decimal from a byte array to a BigInteger.

Digits are read from the end of the array to the front.

Parameters:

signum - Signum value (values other than Signum.NEGATIVE are considered positive!)

firstDigit - First, most significant, digit (0 <= firstDigit <= 9)

decBytes - Byte array with the densely packed decimal, with the least significant byte at index length - 1

Returns:

A BigInteger with the decoded value

Throws:

java.lang.IllegalArgumentException - When firstDigit is out of range, or decBytes is too small for the necessary number of bytes

See Also:

decodeValue(int, int, byte[], int)

decodeValue

public java.math.BigInteger decodeValue(int signum,
                                        int firstDigit,
                                        byte[] decBytes,
                                        int lsbIndex)

Decodes a densely packed decimal from a byte array to a BigInteger.

Digits are read from lsbIndex of the array to the front.

Parameters:

signum - Signum value (values other than Signum.NEGATIVE are considered positive!)

firstDigit - First, most significant, digit (0 <= firstDigit <= 9)

decBytes - Byte array with the densely packed decimal, with the least significant byte at index lsbIndex

lsbIndex - Index of the least significant byte (or the last byte)

Returns:

A BigInteger with the decoded value

Throws:

java.lang.IndexOutOfBoundsException - If lsbIndex is not valid for decBytes

java.lang.IllegalArgumentException - When firstDigit is out of range, or lsbIndex is too small for the necessary number of bytes

encodeValue

public int encodeValue(java.math.BigInteger value,
                       byte[] decBytes)

Encodes a BigInteger to a densely packed decimal in a byte array.

Digits are written from the end of the array to the front. The most significant digit is not encoded into the array, but instead returned to the caller.

Parameters:

value - BigInteger with the value to encode

decBytes - Target byte array for the densely packed decimal, with the least significant byte to be written at index length - 1. The implementation assumes the array is zero-filled for the bits to be populated by this method.

Returns:

First, most significant, digit (0 <= firstDigit <= 9) to be encoded separately

Throws:

java.lang.IndexOutOfBoundsException - If lsbIndex is not valid for decBytes

java.lang.IllegalArgumentException - When lsbIndex is too small for the necessary number of bytes

See Also:

encodeValue(BigInteger, byte[], int)

encodeValue

public int encodeValue(java.math.BigInteger value,
                       byte[] decBytes,
                       int lsbIndex)

Encodes a BigInteger to a densely packed decimal in a byte array.

Digits are written from lsbIndex of the array to the front. The most significant digit is not encoded into the array, but instead returned to the caller.

Parameters:

value - BigInteger with the value to encode

decBytes - Target byte array for the densely packed decimal, with the least significant byte to be written at index lsbIndex. The implementation assumes the array is zero-filled for the bits to be populated by this method.

lsbIndex - Index for the least significant byte (or the last byte)

Returns:

First, most significant, digit (0 <= firstDigit <= 9) to be encoded separately

Throws:

java.lang.IndexOutOfBoundsException - If lsbIndex is not valid for decBytes

java.lang.IllegalArgumentException - When lsbIndex is too small for the necessary number of bytes