lsc::CLzwDecodingDict Class Reference

A dictionary for decoding an LZW bytestream. More...

#include <LSCLzwDecodingDict.h>

List of all members.

Classes
struct	LSN_LZW_DICT_ENTRY
Public Types
typedef LSUINT32	LSN_LZW_CODE
typedef struct lsc::CLzwDecodingDict::LSN_LZW_DICT_ENTRY *	LPLSN_LZW_DICT_ENTRY
typedef struct lsc::CLzwDecodingDict::LSN_LZW_DICT_ENTRY	LPCLSN_LZW_DICT_ENTRY
Public Member Functions
LSVOID LSE_CALL	Reset ()
LSVOID LSE_CALL	SetAllocator (CStdAllocator *_psaAllocator)
LSVOID LSE_CALL	InitializeDictionary (LSUINT32 _ui32Len, LSUINT32 _ui32MaxBits)
LSBOOL LSE_CALL	IsClearCode (LSN_LZW_CODE _lcCode) const
LSBOOL LSE_CALL	IsEndOfInputCode (LSN_LZW_CODE _lcCode) const
LSUINT32 LSE_CALL	GetTotal () const
LSBOOL LSE_CALL	AddCode (LSN_LZW_CODE _lcCode, LSUINT8 _ui8Char)
LSBOOL LSE_CALL	GetString (LSN_LZW_CODE _lcCode, CString &_sString) const
LSE_INLINE LSUINT32 LSE_CALL	GetBitsNeeded () const
Protected Member Functions
LSBOOL LSE_CALL	Alloc ()
LSUINT32 LSE_CALL	DeriveBitsNeeded () const
Protected Attributes
CAllocator	m_aAllocator
LPLSN_LZW_DICT_ENTRY	m_lpldeDictionary
LSUINT32	m_ui32Total
LSUINT32	m_ui32Alloc
LSUINT32	m_ui32RootLen
LSUINT32	m_ui32MaxSize
LSUINT32	m_ui32MaxBits
LSUINT32	m_ui32BitsNeeded

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Detailed Description

A dictionary for decoding an LZW bytestream.

Class CLzwDecodingDict Description: When decoding, the dictionary format for dictionary entries in the LZW compression scheme are different from when encoding. The codes are referenced only by code during decompression, allowing us to store the entries linearly during decompression. Our loop-up and usage functiosn for the codes are different from the ones used during encryption.

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Member Typedef Documentation

typedef struct lsc::CLzwDecodingDict::LSN_LZW_DICT_ENTRY * lsc::CLzwDecodingDict::LPLSN_LZW_DICT_ENTRY

A dictionary entry. The code of the item is its index in the array.

typedef LSUINT32 lsc::CLzwDecodingDict::LSN_LZW_CODE

A code.

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Member Function Documentation

LSBOOL LSE_CALL lsc::CLzwDecodingDict::AddCode	(	LSN_LZW_CODE	_lcCode,
		LSUINT8	_ui8Char
	)

Add a code to the dictionary. Fails if the dictionary is full.

Parameters:

_lcCode	The code to be added.
_ui8Char	The character associated with this code.

LSBOOL LSE_CALL lsc::CLzwDecodingDict::Alloc

(

)

[protected]

Allocate the full set of codes and initialize the roots.

Returns:

Returns false if allocation fails or if m_ui32RootLen is 0.

LSUINT32 LSE_CALL lsc::CLzwDecodingDict::DeriveBitsNeeded

(

)

const [protected]

Derive the total number of bits needed to read any code in the dictionary.

Returns:

Returns the number of bits needed for a code in the stream given the current size of the dictionary.

LSE_INLINE LSUINT32 LSE_CALL lsc::CLzwDecodingDict::GetBitsNeeded

(

)

const

Get the number of bits needed to access any code.

Returns:

Returns the minimum number of bits needed to access any code in the dictionary.

LSBOOL LSE_CALL lsc::CLzwDecodingDict::GetString	(	LSN_LZW_CODE	_lcCode,
		CString &	_sString
	)		const

Get a string from the dictionary. Translates all codes to characters and returns the length of the string. The string is returned in reverse order.

Parameters:

_lcCode	The code to translate into a byte string.
_sString	Upone return, this string contains the returned bytes.

Returns:

Returns true if the string was extracted successfully. If any unknown codes are encountered, false is returned.

LSUINT32 LSE_CALL lsc::CLzwDecodingDict::GetTotal

(

)

const

Get the size of the dictionary.

Returns:

Returns the number of codes in the dictionary.

LSVOID LSE_CALL lsc::CLzwDecodingDict::InitializeDictionary	(	LSUINT32	_ui32Len,
		LSUINT32	_ui32MaxBits
	)

Set the initial dictionary where each entry is a root.

Parameters:

_ui32Len	Number of root entries in the dictionary.
_ui32MaxBits	Maximum number of bits in any entry in the dictionary.

LSBOOL LSE_CALL lsc::CLzwDecodingDict::IsClearCode

(

LSN_LZW_CODE

_lcCode

)

const

Is the given code the clear code?

Parameters:

_lcCode

The code to be tested against the clear code.

Returns:

Returns true if the code is the clear code.

LSBOOL LSE_CALL lsc::CLzwDecodingDict::IsEndOfInputCode

(

LSN_LZW_CODE

_lcCode

)

const

Is the given code the end-of-input code?

Parameters:

_lcCode

The code to be tested against the end-of-input code.

Returns:

Returns true if the code is the end-of-input code.

LSVOID LSE_CALL lsc::CLzwDecodingDict::Reset

(

)

Reset everything. Deallocates all resources.

LSVOID LSE_CALL lsc::CLzwDecodingDict::SetAllocator

(

CStdAllocator *

_psaAllocator

)

Set the allocator. If different from the current allocator, the dictionary is reset.

Parameters:

_psaAllocator

The allocator to use by this class.

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Member Data Documentation

CAllocator lsc::CLzwDecodingDict::m_aAllocator [protected]

Our allocator.

LPLSN_LZW_DICT_ENTRY lsc::CLzwDecodingDict::m_lpldeDictionary [protected]

The dictionary.

LSUINT32 lsc::CLzwDecodingDict::m_ui32BitsNeeded [protected]

The bits needed for the current code.

LSUINT32 lsc::CLzwDecodingDict::m_ui32MaxBits [protected]

Maximum number of bits in an entry.

LSUINT32 lsc::CLzwDecodingDict::m_ui32MaxSize [protected]

Maximum size.

LSUINT32 lsc::CLzwDecodingDict::m_ui32RootLen [protected]

Size of the root.

LSUINT32 lsc::CLzwDecodingDict::m_ui32Total [protected]

The size of the dictionary.

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

• F:/My Projects/LSEngine/Modules/LSCompressionLib/Src/LZW/LSCLzwDecodingDict.h