HuffmanEncoder Class Reference

#include <huffman.hpp>

Collaboration diagram for HuffmanEncoder:

Class Description

This class, together with sibling HuffmanDecoder implements the well known Huffman compression . The class uses type BitWriter to write the bit stream into an underlying BitBuffer.

The use of this class is quite straight forward:

• Create an instance of this class
• Feed the data to be compressed once to the algorithm using method CountSymbol
• Invoke method Generate
• Feed all data a second time using method Write.

Definition at line 31 of file huffman.hpp.

Inner Classes
struct	Symbol

Public Static Fields
static constexpr int	MAX_CODE_LENGTH = 64
static constexpr int	MAX_WORDS = 2
static constexpr int	WORD_SIZE = 32

Public Methods
	HuffmanEncoder (BitWriter &bitWriter)
ALIB_FORCE_INLINE void	CountSymbol (uint8_t symbol)
ALIB_API void	Generate ()
void	Write (uint8_t symbol)

Protected Fields
BitWriter &	bw
	The bit writer to use for encoding the data.
Symbol	symbols [256]
	The symbol table.

Constructor & Destructor Documentation

HuffmanEncoder()

HuffmanEncoder ( BitWriter &  bitWriter )

inline

Constructor.

Parameters

bitWriter

The bit writer to write the encoding information as well as the encoded symbols to. (Stored in field bw.)

Definition at line 73 of file huffman.hpp.

Member Function Documentation

CountSymbol()

ALIB_FORCE_INLINE void CountSymbol ( uint8_t  symbol )

inline

Counts a symbol. This method has to be invoked for each byte to compress later.

Parameters

symbol

The symbol to count.

Definition at line 83 of file huffman.hpp.

Generate()

ALIB_WARNINGS_ALLOW_UNSAFE_BUFFER_USAGE void Generate

(

)

Generates the huffman encoding table and writes this information to the bit writer.

Definition at line 104 of file huffman.cpp.

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Write()

void Write ( uint8_t  symbol )

inline

Writes the given symbol to the bit stream.

Parameters

symbol

The symbol to write.

Definition at line 100 of file huffman.hpp.

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Member Data Documentation

MAX_CODE_LENGTH

constexpr int MAX_CODE_LENGTH = 64

staticconstexpr

The maximum length of a huffman code. In theory, with 256 symbols, a maximum code length of 255 could occur. For this, each next symbol needed to have the double frequency than the previous. Hence, setting the value to 64, limits the encoded data size to 2^64 symbols, which should be more than enaugh for the next decades.

Definition at line 46 of file huffman.hpp.

MAX_WORDS

constexpr int MAX_WORDS = 2

staticconstexpr

Codes are stored in two (this constant) words of size 32.

Definition at line 36 of file huffman.hpp.

WORD_SIZE

constexpr int WORD_SIZE = 32

staticconstexpr

Codes are stored in two words of size 32 (this constant)

Definition at line 34 of file huffman.hpp.

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

• huffman.hpp
• huffman.cpp