lsc Namespace Reference

Classes
class	CLzwDecodingDict
	A dictionary for decoding an LZW bytestream. More...
class	CLzwEncodingDict
	A dictionary for the encoding of a bytestream using the LZW algorithm. More...
class	CMisc
	Various types of specialized compression routines. More...
class	CZLib
	A primitive and light-weight implementation of a zlib inflation routine. More...
Typedefs
typedef lsstd::CBitStream	Parent
Functions
LSVOID LSE_CALL	SetAllocator (CAllocator *_paAllocator)
CAllocator *LSE_CALL	GetAllocator ()
virtual LSVOID *LSE_CALL	ReAlloc (LSVOID *_pvOriginal, LSUINT32 _ui32Total) const
virtual LSVOID LSE_CALL	Free (LSVOID *_pvOriginal) const
LSVOID LSE_CALL	SetAllocator (CStdAllocator *_psaAllocator)
LSUINT32 LSE_CALL	Decode (const CBitStream &_bsStream, LSUINT32 _ui32DictionaryStartingSize, LSUINT32 _ui32MaxBits, lsstd::IStream &_sStream, LSBOOL _bResetDictionary=false)
LSUINT32 LSE_CALL	Encode (const LSUINT8 *_pui8Bytes, LSUINT64 _ui64Size, LSUINT32 _ui32DictionaryStartingSize, LSUINT32 _ui32MaxBits, CBitStream &_bsStream, LSBOOL _bResetDictionary=false, LSUINT32 _ui32PrevBits=0UL, LSUINT32 _ui32MaxSize=~0UL)
LSBOOL LSE_CALL	EndStream (CBitStream &_bsStream) const
Variables
F	__pad0__
CAllocator *	m_paAllocator
CLzwDecodingDict	m_lddDict
CLzwEncodingDict	m_ledDict

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Detailed Description

Copyright L. Spiro 2011 All rights reserved.

Written by: Shawn (L. Spiro) Wilcoxen

This code may not be sold or traded for any personal gain without express written consent. You may use this code in your own projects and modify it to suit your needs as long as this disclaimer remains intact. You may not take credit for having written this code.

Description: Extends the lsstd::CBitStream class with memory-manager functionality.

Copyright L. Spiro 2011 All rights reserved.

Written by: Shawn (L. Spiro) Wilcoxen

This code may not be sold or traded for any personal gain without express written consent. You may use this code in your own projects and modify it to suit your needs as long as this disclaimer remains intact. You may not take credit for having written this code.

Description: Decodes a bitstream previously encoded with CLzwEncoder::Encode().

Copyright L. Spiro 2011 All rights reserved.

Written by: Shawn (L. Spiro) Wilcoxen

This code may not be sold or traded for any personal gain without express written consent. You may use this code in your own projects and modify it to suit your needs as long as this disclaimer remains intact. You may not take credit for having written this code.

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.

Copyright L. Spiro 2011 All rights reserved.

Written by: Shawn (L. Spiro) Wilcoxen

This code may not be sold or traded for any personal gain without express written consent. You may use this code in your own projects and modify it to suit your needs as long as this disclaimer remains intact. You may not take credit for having written this code.

Description: Encodes a stream of bytes into an LZW compressed stream of bits.

Copyright L. Spiro 2011 All rights reserved.

Written by: Shawn (L. Spiro) Wilcoxen

This code may not be sold or traded for any personal gain without express written consent. You may use this code in your own projects and modify it to suit your needs as long as this disclaimer remains intact. You may not take credit for having written this code.

Description: Description: When encoding bytes, the dictionary for the LZW algorithm is stored differently from when the bytes are being decoded. During encryption, codes are referenced via (code+char) combination which requires a hash look-up. For this reason, we cannot store the codes in such a way that index = code. During decoding, however, codes are referenced only by code, so we are able to store the codes linearly such that index = code. This saves space over the encoding algorithm and gives us cause to keep the two dictionaries separate. The dictionary is created with a maximum size at the beginning, which depends on the maximum number of bits a code may have. This class can output variable-sized codes or predefined-sized codes as per the desires of the user. Variable-sized codes simply means that the smallest number of bits needed to access any code in the dictionary are output instead of using a fixed size such as 15 bits for every code. This is the typical method for encoding.

Copyright L. Spiro 2011 All rights reserved.

Written by: Shawn (L. Spiro) Wilcoxen

This code may not be sold or traded for any personal gain without express written consent. You may use this code in your own projects and modify it to suit your needs as long as this disclaimer remains intact. You may not take credit for having written this code.

Description: Various types of specialized compression routines. Data often gets compressed better when routines are specialized towards that type of data. For example, if a normal is assumed to be unit-length, only 65 bits are needed to hold it, instead of 96. An array of index data usually starts with low numbers and gradually builds into higher numbers. Only a few bits of data are needed to hold the first several numbers.

Copyright L. Spiro 2011 All rights reserved.

Written by: Shawn (L. Spiro) Wilcoxen

This code may not be sold or traded for any personal gain without express written consent. You may use this code in your own projects and modify it to suit your needs as long as this disclaimer remains intact. You may not take credit for having written this code.

Description: A primitive and light-weight implementation of a zlib inflation routine. This class cannot be used to compress/deflate data.

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Function Documentation

LSUINT32 LSE_CALL lsc::Decode	(	const CBitStream &	_bsStream,
		LSUINT32	_ui32DictionaryStartingSize,
		LSUINT32	_ui32MaxBits,
		lsstd::IStream &	_sStream,
		LSBOOL	_bResetDictionary = false
	)

Decode raw bytes of LZW compressed data.

Parameters:

_bsStream	Bitstream containing data compressed with the LZW algorithm.
_ui32DictionaryStartingSize	Starting size of the dictionary.
_ui32MaxBits	Maximum bits possible in the dictionary.
_sStream	The stream to hold the decoded bytes.
_bResetDictionary	If true, the dictionary is reset for the decoding of this chunk of bytes. This is optional so as to allow breaking up the decoding into multiple chunks.

Returns:

Returns the number of bits needed to read the next code from the input buffer. This can be used in a subsequent call to Decode() to continue decoding data over several chunks. If 0 is returned, an error occurred.

LSUINT32 LSE_CALL lsc::Encode	(	const LSUINT8 *	_pui8Bytes,
		LSUINT64	_ui64Size,
		LSUINT32	_ui32DictionaryStartingSize,
		LSUINT32	_ui32MaxBits,
		CBitStream &	_bsStream,
		LSBOOL	_bResetDictionary = false,
		LSUINT32	_ui32PrevBits = 0UL,
		LSUINT32	_ui32MaxSize = ~0UL
	)

Encode an array of bytes. The encoded data is output at the current position in the given bitstream. This allows multiple encodings to be packed together into the same stream.

Parameters:

_pui8Bytes	Pointer to the bytes to encode.
_ui64Size	Size of the buffer to which _pui8Bytes points.
_ui32DictionaryStartingSize	Starting size of the dictionary.
_ui32MaxBits	Maximum bits possible in the dictionary.
_bsStream	Stream to which the compressed bits are to be written.
_bResetDictionary	If true, the dictionary will be reset and the first code output to the bitstream will be a dictionary-reset code of _ui32PrevBits bits.
_ui32PrevBits	If bits were already compressed to _bsStream, this informs this function of the size of the next command, in bits, that would be read from the stream if decompressing. This is required if _bsStream is not empty.
_ui32MaxSize	Size at which to stop compression. If the size of the compressed data exceeds this amount then compression is ended.

Returns:

Returns the size of the next command that would be written to _bsStream if compression were to continue. This can be used in a subsequent call to Encode(). On error, 0UL is returned.

LSBOOL LSE_CALL lsc::EndStream

(

CBitStream &

_bsStream

)

const

Append a bit stream with a stream-end code using the current dictionary. If the dictionary is empty the function fails.

Parameters:

_bsStream

The stream to which to append the end-of-stream code.

Returns:

Returns true if there is a dictionary and the append succeeded.

virtual LSVOID LSE_CALL lsc::Free

(

LSVOID *

_pvOriginal

)

const [protected, virtual]

Free bytes. Overrides the base definition to allow usage of our allocator, if not NULL.

Parameters:

_pvOriginal

Pointer to the data, allocated with ReAlloc() to free.

CAllocator* LSE_CALL lsc::GetAllocator

(

)

Get our allocator.

Returns:

Returns the allocator assigned to this object.

Gets our allocator.

Returns:

Returns our allocator.

Get our allocator.

Returns:

Returns a pointer to the allocator used by this object.

virtual LSVOID* LSE_CALL lsc::ReAlloc	(	LSVOID *	_pvOriginal,
		LSUINT32	_ui32Total
	)		const [protected, virtual]

Re-allocate bytes. Overrides the base definition to allow usage of our allocator, if not NULL.

Parameters:

_pvOriginal	Address to re-alloate. Pass NULL to allocate new data.
_ui32Total	Total number of bytes to allocate.

Returns:

Returns the re-allocated bytes or NULL upon failure.

LSVOID LSE_CALL lsc::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.

LSVOID LSE_CALL lsc::SetAllocator

(

CAllocator *

_paAllocator

)

Set the allocator. Causes all data in the bit stream to be lost if the allocator is not the same as the only already set.

Parameters:

_paAllocator

The allocator to use by this class.

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Variable Documentation

CLzwDecodingDict lsc::m_lddDict

Our dictionary.

CLzwEncodingDict lsc::m_ledDict

The dictionary we use.

CAllocator* lsc::m_paAllocator

Our allocator.