JASS::compress_integer_elias_delta Class Reference

Elias delta encoding of integers. More...

#include <compress_integer_elias_delta.h>

Inheritance diagram for JASS::compress_integer_elias_delta:

Collaboration diagram for JASS::compress_integer_elias_delta:

Public Member Functions
virtual size_t	encode (void *encoded, size_t encoded_buffer_length, const integer *source, size_t source_integers)
	Encode a sequence of integers returning the number of bytes used for the encoding, or 0 if the encoded sequence doesn't fit in the buffer. More...
virtual void	decode (integer *decoded, size_t integers_to_decode, const void *source, size_t source_length)
	Decode a sequence of integers encoded with this codex. More...
Public Member Functions inherited from JASS::compress_integer
	compress_integer ()
	Constructor.
virtual	~compress_integer ()
	Destructor.

Static Public Member Functions
static void	unittest (void)
	Unit test this class.
Static Public Member Functions inherited from JASS::compress_integer
static size_t	d1_encode (integer *encoded, const integer *source, size_t source_integers)
	Convert an array of integers into an array of D1 (delta, d-gap) encoded integers. More...
static size_t	d1_decode (integer *decoded, const integer *source, size_t source_integers)
	Convert a D1 encoded array of integers into an array of integers. More...
static size_t	dn_encode (integer *encoded, const integer *source, size_t source_integers, size_t n=1)
	Convert an array of integers into an array of Dn (delta, d-gap) encoded integers with a gap of n. More...
static size_t	dn_decode (integer *decoded, const integer *source, size_t source_integers, size_t n=1)
	Convert a Dn encoded array of integers into an array of integers. More...
static void	unittest_one (compress_integer &encoder, const std::vector< uint32_t > &sequence)
	Test one sequence to make sure it encodes and decodes to the same thing. Assert if not. More...
static void	unittest (compress_integer &compressor, uint32_t staring_from=0)
	Unit test this class, assert on failure. More...

Additional Inherited Members
Public Types inherited from JASS::compress_integer
typedef uint32_t	integer
	This class and descendants will work on integers of this size. Do not change without also changing JASS_COMPRESS_INTEGER_BITS_PER_INTEGER.

Detailed Description

Elias delta encoding of integers.

To quote the Wikipedia (https://en.wikipedia.org/wiki/Elias_delta_coding):

To code a number X ≥ 1: Let N = floor(log2 X) be the highest power of 2 in X, so 2^N ≤ X < 2^(N+1). Let L = floor(log2 N+1) be the highest power of 2 in N+1, so 2^L ≤ N+1 < 2^(L+1). Write L zeros, followed by the L+1-bit binary representation of N+1, followed by all but the leading bit (i.e. the last N bits) of X. An equivalent way to express the same process: Separate X into the highest power of 2 it contains (2^N) and the remaining N binary digits. Encode N+1 with Elias gamma coding. Append the remaining N binary digits to this representation of N+1.

See: P. Elias (1975). "Universal codeword sets and representations of the integers". IEEE Transactions on Information Theory. 21 (2): 194–203. doi:10.1109/tit.1975.1055349.

Member Function Documentation

decode()

void JASS::compress_integer_elias_delta::decode ( integer *  decoded, size_t  integers_to_decode, const void *  source, size_t  source_length  )

virtual

Decode a sequence of integers encoded with this codex.

Parameters

decoded	[out] The sequence of decoded integers.
integers_to_decode	[in] The minimum number of integers to decode (it may decode more).
source	[in] The encoded integers.
source_length	[in] The length (in bytes) of the source buffer.

bits used in the second word if we cross a word boundary (and not kept from block to block)

Implements JASS::compress_integer.

encode()

size_t JASS::compress_integer_elias_delta::encode ( void *  encoded, size_t  encoded_buffer_length, const integer *  source, size_t  source_integers  )

virtual

Encode a sequence of integers returning the number of bytes used for the encoding, or 0 if the encoded sequence doesn't fit in the buffer.

Parameters

encoded	[out] The sequence of bytes that is the encoded sequence.
encoded_buffer_length	[in] The length (in bytes) of the output buffer, encoded.
source	[in] The sequence of integers to encode.
source_integers	[in] The length (in integers) of the source buffer.

Returns

The number of bytes used to encode the integer sequence, or 0 on error (i.e. overflow).

Implements JASS::compress_integer.

---

The documentation for this class was generated from the following files:

• source/compress_integer_elias_delta.h
• source/compress_integer_elias_delta.cpp