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CVJCompressor Class Reference

class CVJCompressor : public CVJCompressorIf

Van Jacobson TCP/IP header compressor (RFC 1144)

Inherits from

CVJCompressor
- CVJCompressorIf
  - CObject
    - CBase

Public Member Functions
	CVJCompressor()
	~CVJCompressor()
void	ConstructL(CVJCompFactory *, TUint, TBool)
TInt	VJCompressFrame(RMBufChain &)

Private Member Functions
TBool	CompressAck(TUint8 *, TUint8 , ThdrTCP , ThdrTCP )
TBool	CompressFrame(RMBufChain &, ThdrIP , ThdrTCP , TUint, ThdrIP , ThdrTCP )
TBool	CompressIPId(TUint8 *, TUint8 , ThdrIP , ThdrIP )
TBool	CompressPush(TUint8 , ThdrTCP )
TBool	CompressSeq(TUint8 *, TUint8 , ThdrTCP , ThdrTCP )
TBool	CompressSpecialCases(TUint8 *, TUint8 const , TUint8 , ThdrTCP , ThdrTCP , ThdrIP , ThdrIP *)
TBool	CompressUrgentPtr(TUint8 *, TUint8 , ThdrTCP , ThdrTCP )
TBool	CompressWindow(TUint8 *, TUint8 , ThdrTCP , ThdrTCP )
void	ConvertFrameToUncompVJ(ThdrIP *, TUint)
void	CopyInNewTxHeader(RMBufChain &, TUint8 *, TUint, TUint)
void	CopyTxHeader(ThdrIP *, TUint)
void	DecrementPacketLen(RMBufChain &, TUint)
void	EncodeDelta(TUint8 **, TInt16)
ThdrIP *	GetIPHeader(RMBufChain &)
TBool	GetStoredTxHeader(TUint , ThdrIP , ThdrTCP , ThdrIP , ThdrTCP *)
TUint8 *	GetTCPOpts(ThdrTCP *)
TBool	IPAddressesMatch(ThdrIP , ThdrIP )
TBool	IsDeltaCompressible(TUint32)
TBool	IsIPCompressible(ThdrIP , ThdrIP )
TBool	IsSameConnAsLast(TUint *, TUint)
TBool	IsTCPCompressible(ThdrTCP , ThdrTCP )
TBool	SendAsRawIP(ThdrIP , ThdrTCP )
void	SetFirstFewBytes(TUint8 , TBool, TUint8 , ThdrTCP , TUint)
TBool	SuitableForVJCompression(ThdrIP , ThdrTCP , TUint , ThdrIP , ThdrTCP *)
TBool	TCPPortsMatch(ThdrTCP , ThdrTCP )

Inherited Functions
	CBase::CBase()
	CBase::Delete(CBase *)
	CBase::operator new(TUint)
	CBase::operator new(TUint,TAny *)
	CBase::operator new(TUint,TLeave)
	CBase::operator new(TUint,TLeave,TUint)
	CBase::operator new(TUint,TUint)
	CBase::~CBase()
	CObject::AccessCount()const
	CObject::CObject()
	CObject::Close()
	CObject::Dec()
	CObject::Extension_(TUint,TAny &,TAny )
	CObject::FullName()const
	CObject::Inc()
	CObject::Name()const
	CObject::Open()
	CObject::Owner()const
	CObject::SetName(const TDesC *)
	CObject::SetNameL(const TDesC *)
	CObject::SetOwner(CObject *)
	CObject::UniqueID()const
	CObject::~CObject()
	CVJCompressorIf::CVJCompressorIf()
	CVJCompressorIf::~CVJCompressorIf()

Private Attributes
TBool	iCompressConnId
TUint	iLastTxConn
TVJCompHdr *	iLastTxHdr
TUint	iMaxVJSlots
TVJCompHdr *	iTxStates

Inherited Attributes
	CVJCompressorIf::iFactory

Constructor & Destructor Documentation

CVJCompressor()

CVJCompressor

(

)

~CVJCompressor()

~CVJCompressor

(

)

Member Functions Documentation

CompressAck(TUint8 **, TUint8 , ThdrTCP , ThdrTCP *)

TBool	CompressAck	(	TUint8 **	aVJPtr,
			TUint8 *	aChanges,
			ThdrTCP *	aTCPHeader,
			ThdrTCP *	aRetrievedTCPHdr
		)	[private]

Compresses the TCP Acknowledgement Number field.

Parameters

TUint8 ** aVJPtr	Pointer to the pointer within the VJ header to be modified; returns pointing one past the last header location used
TUint8 * aChanges	The VJ change mask to be updated
ThdrTCP * aTCPHeader	TCP header
ThdrTCP * aRetrievedTCPHdr	Cached TCP header from which to make a delta for aTCPHeader

CompressFrame(RMBufChain &, ThdrIP , ThdrTCP , TUint, ThdrIP , ThdrTCP )

TBool	CompressFrame	(	RMBufChain &	aPacket,
			ThdrIP *	aIPHeader,
			ThdrTCP *	aTCPHeader,
			TUint	aConnection,
			ThdrIP *	aRetrievedIPHdr,
			ThdrTCP *	aRetrievedTCPHdr
		)	[private]

Compresses a TCP/IP header if possible.

Parameters

RMBufChain & aPacket	MBuf chain containing packet
ThdrIP * aIPHeader	IP header
ThdrTCP * aTCPHeader	TCP header
TUint aConnection	VJ connection number
ThdrIP * aRetrievedIPHdr	Cached IP packet header
ThdrTCP * aRetrievedTCPHdr	Cached TCP packet header

CompressIPId(TUint8 **, TUint8 , ThdrIP , ThdrIP *)

TBool	CompressIPId	(	TUint8 **	aVJPtr,
			TUint8 *	aChanges,
			ThdrIP *	aIPHeader,
			ThdrIP *	aRetrievedIPHdr
		)	[private]

Compresses the IP Packet ID field.

Parameters

TUint8 ** aVJPtr	Pointer to the pointer within the VJ header to be modified; returns pointing one past the last header location used
TUint8 * aChanges	The VJ change mask to be updated
ThdrIP * aIPHeader	IP header
ThdrIP * aRetrievedIPHdr	Cached IP header from which to make a delta for aIPHeader

CompressPush(TUint8 , ThdrTCP )

TBool	CompressPush	(	TUint8 *	aChanges,
			ThdrTCP *	aTCPHeader
		)	[private]

Compresses the TCP Push flag.

Parameters

TUint8 * aChanges	The VJ change mask to be updated
ThdrTCP * aTCPHeader	TCP header

CompressSeq(TUint8 **, TUint8 , ThdrTCP , ThdrTCP *)

TBool	CompressSeq	(	TUint8 **	aVJPtr,
			TUint8 *	aChanges,
			ThdrTCP *	aTCPHeader,
			ThdrTCP *	aRetrievedTCPHdr
		)	[private]

Compresses the TCP Sequence Number field.

Parameters

TUint8 ** aVJPtr	Pointer to the pointer within the VJ header to be modified; returns pointing one past the last header location used
TUint8 * aChanges	The VJ change mask to be updated
ThdrTCP * aTCPHeader	TCP header
ThdrTCP * aRetrievedTCPHdr	Cached TCP header from which to make a delta for aTCPHeader

CompressSpecialCases(TUint8 **, TUint8 const, TUint8 , ThdrTCP , ThdrTCP , ThdrIP , ThdrIP )

TBool	CompressSpecialCases	(	TUint8 **	aVJPtr,
			TUint8 *const	aVJInitialDeltaPtr,
			TUint8 *	aChanges,
			ThdrTCP *	aTCPHeader,
			ThdrTCP *	aRetrievedTCPHdr,
			ThdrIP *	aIPHeader,
			ThdrIP *	aRetrievedIPHdr
		)	[private]

Compresses special case TCP/IP packets. See RFC 1144 sec. 3.2.3

Pre-condition: aChanges must reflect the compressed header except for the KVjCompMaskPush and KVjCompMaskIp bits which must be clear.

Parameters

TUint8 ** aVJPtr	Pointer to the pointer within the VJ header to be modified; returns pointing one past the last header location used
TUint8 *const aVJInitialDeltaPtr	Beginning of the compressed VJ header
TUint8 * aChanges	The VJ change mask to be updated
ThdrTCP * aTCPHeader	TCP header
ThdrTCP * aRetrievedTCPHdr	Cached TCP header from which to make a delta for aTCPHeader
ThdrIP * aIPHeader	IP header
ThdrIP * aRetrievedIPHdr	Cached IP header from which to make a delta for aIPHeader

CompressUrgentPtr(TUint8 **, TUint8 , ThdrTCP , ThdrTCP *)

TBool	CompressUrgentPtr	(	TUint8 **	aVJPtr,
			TUint8 *	aChanges,
			ThdrTCP *	aTCPHeader,
			ThdrTCP *	aRetrievedTCPHdr
		)	[private]

Compresses the TCP Urgent pointer field.

Parameters

TUint8 ** aVJPtr	Pointer to the pointer within the VJ header to be modified; returns pointing one past the last header location used
TUint8 * aChanges	The VJ change mask to be updated
ThdrTCP * aTCPHeader	TCP header
ThdrTCP * aRetrievedTCPHdr	Cached TCP header from which to make a delta for aTCPHeader

CompressWindow(TUint8 **, TUint8 , ThdrTCP , ThdrTCP *)

TBool	CompressWindow	(	TUint8 **	aVJPtr,
			TUint8 *	aChanges,
			ThdrTCP *	aTCPHeader,
			ThdrTCP *	aRetrievedTCPHdr
		)	[private]

Compresses the TCP Window field.

Parameters

TUint8 ** aVJPtr	Pointer to the pointer within the VJ header to be modified; returns pointing one past the last header location used
TUint8 * aChanges	The VJ change mask to be updated
ThdrTCP * aTCPHeader	TCP header
ThdrTCP * aRetrievedTCPHdr	Cached TCP header from which to make a delta for aTCPHeader

ConstructL(CVJCompFactory *, TUint, TBool)

void	ConstructL	(	CVJCompFactory *	aFactory,
			TUint	aMaxSlot,
			TBool	aCompressConnId
		)

Construct the CVJCompressor object.

Parameters

CVJCompFactory * aFactory	Factory that created this object
TUint aMaxSlot	Value of the highest VJ connection number to be sent
TBool aCompressConnId	Whether to compress the connection number

ConvertFrameToUncompVJ(ThdrIP *, TUint)

void	ConvertFrameToUncompVJ	(	ThdrIP *	aIPHeader,
			TUint	aConnection
		)	[private]

The frame is to be sent as an Uncompressed VJ frame, so set the connection number in place of the protocol type, and save the header.

Parameters

ThdrIP * aIPHeader	TCP/IP header
TUint aConnection	VJ connection number

CopyInNewTxHeader(RMBufChain &, TUint8 *, TUint, TUint)

void	CopyInNewTxHeader	(	RMBufChain &	aPacket,
			TUint8 *	aCompressedHdr,
			TUint	aOldHeaderLength,
			TUint	aNewHeaderLength
		)	[private]

Copies the compressed header into the packet.

Parameters

RMBufChain & aPacket	MBuf chain containing packet
TUint8 * aCompressedHdr	VJ compressed header
TUint aOldHeaderLength	Length of the current TCP/IP header in aPacket
TUint aNewHeaderLength	Length of VJ compressed header

CopyTxHeader(ThdrIP *, TUint)

void	CopyTxHeader	(	ThdrIP *	aIPHeader,
			TUint	aConnection
		)	[private]

Copies the given TCP/IP header into the storage slot for the given connection number.

Parameters

ThdrIP * aIPHeader	TCP/IP header
TUint aConnection	VJ connection number

DecrementPacketLen(RMBufChain &, TUint)

void	DecrementPacketLen	(	RMBufChain &	aPacket,
			TUint	SizeDecrease
		)	[private]

There is a header prepended to the frame, one element is the length which has now changed, so change it

Parameters

RMBufChain & aPacket	MBuf chain containing packet
TUint SizeDecrease	Amount by which to reduce the length metadata

EncodeDelta(TUint8 **, TInt16)

void	EncodeDelta	(	TUint8 **	aVJCompHeader,
			TInt16	aValue
		)	[private]

Encodes a delta value in VJ compressed format.

Parameters

TUint8 ** aVJCompHeader	Pointer to pointer into VJ header buffer to store encoded value; returns with pointer incremented one past end of value
TInt16 aValue	Value to store

GetIPHeader(RMBufChain &)

ThdrIP *

GetIPHeader

(

RMBufChain &

aChain

)

[private]

Get the IP Header even though there is a buffer of Info on the front. This is used in VJ, to avoid the awful hack in the main receive path. PRR 20-11-97

Parameters

RMBufChain & aChain

MBuf chain containing packet

GetStoredTxHeader(TUint , ThdrIP , ThdrTCP , ThdrIP , ThdrTCP *)

TBool	GetStoredTxHeader	(	TUint *	aConnection,
			ThdrIP *	aIPHeader,
			ThdrTCP *	aTCPHeader,
			ThdrIP *	aRetrievedIPHdr,
			ThdrTCP *	aRetrievedTCPHdr
		)	[private]

Retrieves a packet header from the VJ connection cache. The packet must match on the IP source and destination address and on the TCP source and destination port numbers.

Parameters

TUint * aConnection	Returns the matching VJ connection number
ThdrIP * aIPHeader	IP packet header
ThdrTCP * aTCPHeader	TCP header
ThdrIP * aRetrievedIPHdr	Returns the cached IP packet header
ThdrTCP * aRetrievedTCPHdr	Returns the cached TCP packet header

GetTCPOpts(ThdrTCP *)

TUint8 *

GetTCPOpts

(

ThdrTCP *

aTCPHeader

)

const [private, inline]

Returns a pointer to the start of the TCP options (if there are any).

Parameters

ThdrTCP * aTCPHeader

TCP header

IPAddressesMatch(ThdrIP , ThdrIP )

TBool	IPAddressesMatch	(	ThdrIP *	aIPHeader,
			ThdrIP *	aNotherIPHdr
		)	[private]

Compares the addresses in two IP headers.

Parameters

ThdrIP * aIPHeader	First IP header
ThdrIP * aNotherIPHdr	Second IP header

IsDeltaCompressible(TUint32)

TBool

IsDeltaCompressible

(

TUint32

aDelta

)

const [private, inline]

Tests if the delta value is compressible into the 16 bit VJ delta format. The aDelta value actually needs a 33 bit signed integer to hold the entire possible range, but the twos complement math works out if it's just stored as a 32 bit unsigned integer.

Parameters

TUint32 aDelta

Delta value to test

IsIPCompressible(ThdrIP , ThdrIP )

TBool	IsIPCompressible	(	ThdrIP *	aIPHeader,
			ThdrIP *	aRetrievedIPHdr
		)	[private]

Compares two IP headers to see if the seldom-changing fields match.

Parameters

ThdrIP * aIPHeader	First IP packet header
ThdrIP * aRetrievedIPHdr	Second IP packet header

IsSameConnAsLast(TUint *, TUint)

TBool	IsSameConnAsLast	(	TUint *	aCompressedHdrLen,
			TUint	aConnection
		)	[private]

Determines whether the given VJ connection number is the same as that of the last compressed packet sent and returns the size of the compressed header.

Parameters

TUint * aCompressedHdrLen	Returns the length of the compressed header
TUint aConnection	VJ connection number

IsTCPCompressible(ThdrTCP , ThdrTCP )

TBool	IsTCPCompressible	(	ThdrTCP *	aTCPHeader,
			ThdrTCP *	aRetrievedTCPHdr
		)	[private]

Compares two TCP headers to see if the options, ECN & reserved bits match. Everything else in the TCP header is handled specially by the VJ compression algorithm.

Parameters

ThdrTCP * aTCPHeader	First TCP header
ThdrTCP * aRetrievedTCPHdr	Second TCP header

SendAsRawIP(ThdrIP , ThdrTCP )

TBool	SendAsRawIP	(	ThdrIP *	aIPHeader,
			ThdrTCP *	aTCPHeader
		)	[private]

Determines if the packet must bypass VJ compression altogether. This happens with fragmented IP packets and certain TCP flags.

Parameters

ThdrIP * aIPHeader	First IP packet header
ThdrTCP * aTCPHeader	TCP header

SetFirstFewBytes(TUint8 *, TBool, TUint8 **, ThdrTCP *, TUint)

void	SetFirstFewBytes	(	TUint8 *	aChanges,
			TBool	aNewConnection,
			TUint8 **	aVJHeader,
			ThdrTCP *	aTCPHeader,
			TUint	aConnection
		)	[private]

Sets the change mask, connection number (if necessary) and TCP checksum bytes in the VJ compressed header.

Parameters

TUint8 * aChanges	The VJ change mask to be copied and potentially modified
TBool aNewConnection	Whether this is a new connection, requiring the number in the header
TUint8 ** aVJHeader	Pointer to the pointer to the VJ header to be modified
ThdrTCP * aTCPHeader	TCP header
TUint aConnection	VJ connection number

SuitableForVJCompression(ThdrIP , ThdrTCP , TUint , ThdrIP , ThdrTCP *)

TBool	SuitableForVJCompression	(	ThdrIP *	aIPHeader,
			ThdrTCP *	aTCPHeader,
			TUint *	aConnection,
			ThdrIP *	aRetrievedIPHdr,
			ThdrTCP *	aRetrievedTCPHdr
		)	[private]

Sees if a packet header is stored in the VJ connection cache.

Parameters

ThdrIP * aIPHeader	IP packet header
ThdrTCP * aTCPHeader	TCP header
TUint * aConnection	Returns the matching VJ connection number
ThdrIP * aRetrievedIPHdr	Returns the cached IP packet header
ThdrTCP * aRetrievedTCPHdr	Returns the cached TCP packet header

TCPPortsMatch(ThdrTCP , ThdrTCP )

TBool	TCPPortsMatch	(	ThdrTCP *	aHeader,
			ThdrTCP *	aNotherHdr
		)	[private]

Compares the TCP port numbers TCP headers.

Parameters

ThdrTCP * aHeader	First TCP header
ThdrTCP * aNotherHdr	Second TCP header

VJCompressFrame(RMBufChain &)

TInt

VJCompressFrame

(

RMBufChain &

aPacket

)

[virtual]

Takes a packet and transforms it for sending. It may end up VJ compressed, VJ uncompressed or untouched.

Parameters

RMBufChain & aPacket

MBuf chain containing packet

Member Data Documentation

TBool iCompressConnId

TBool

iCompressConnId

[private]

Whether VJ was configured to compress the connection number

TUint iLastTxConn

TUint

iLastTxConn

[private]

Connection number of the last packet compressed

TVJCompHdr * iLastTxHdr

TVJCompHdr *

iLastTxHdr

[private]

Pointer to the last element in the LRU circular list

TUint iMaxVJSlots

TUint

iMaxVJSlots

[private]

Maximum number of VJ connections

TVJCompHdr * iTxStates

TVJCompHdr *

iTxStates

[private]

Pointer to start of array of VJ connections

CVJCompressor Class Reference

Inherits from

Constructor & Destructor Documentation

CVJCompressor()

~CVJCompressor()

Member Functions Documentation

CompressAck(TUint8 **, TUint8 *, ThdrTCP *, ThdrTCP *)

Parameters

CompressFrame(RMBufChain &, ThdrIP *, ThdrTCP *, TUint, ThdrIP *, ThdrTCP *)

Parameters

CompressIPId(TUint8 **, TUint8 *, ThdrIP *, ThdrIP *)

Parameters

CompressPush(TUint8 *, ThdrTCP *)

Parameters

CompressSeq(TUint8 **, TUint8 *, ThdrTCP *, ThdrTCP *)

Parameters

CompressSpecialCases(TUint8 **, TUint8 *const, TUint8 *, ThdrTCP *, ThdrTCP *, ThdrIP *, ThdrIP *)

Parameters

CompressUrgentPtr(TUint8 **, TUint8 *, ThdrTCP *, ThdrTCP *)

Parameters

CompressWindow(TUint8 **, TUint8 *, ThdrTCP *, ThdrTCP *)

Parameters

ConstructL(CVJCompFactory *, TUint, TBool)

Parameters

ConvertFrameToUncompVJ(ThdrIP *, TUint)

Parameters

CopyInNewTxHeader(RMBufChain &, TUint8 *, TUint, TUint)

Parameters

CopyTxHeader(ThdrIP *, TUint)

Parameters

DecrementPacketLen(RMBufChain &, TUint)

Parameters

EncodeDelta(TUint8 **, TInt16)

Parameters

GetIPHeader(RMBufChain &)

Parameters

GetStoredTxHeader(TUint *, ThdrIP *, ThdrTCP *, ThdrIP *, ThdrTCP *)

Parameters

GetTCPOpts(ThdrTCP *)

Parameters

IPAddressesMatch(ThdrIP *, ThdrIP *)

Parameters

IsDeltaCompressible(TUint32)

Parameters

IsIPCompressible(ThdrIP *, ThdrIP *)

Parameters

IsSameConnAsLast(TUint *, TUint)

Parameters

IsTCPCompressible(ThdrTCP *, ThdrTCP *)

Parameters

SendAsRawIP(ThdrIP *, ThdrTCP *)

Parameters

SetFirstFewBytes(TUint8 *, TBool, TUint8 **, ThdrTCP *, TUint)

Parameters

SuitableForVJCompression(ThdrIP *, ThdrTCP *, TUint *, ThdrIP *, ThdrTCP *)

Parameters

TCPPortsMatch(ThdrTCP *, ThdrTCP *)

Parameters

VJCompressFrame(RMBufChain &)

Parameters

Member Data Documentation

TBool iCompressConnId

TUint iLastTxConn

TVJCompHdr * iLastTxHdr

TUint iMaxVJSlots

TVJCompHdr * iTxStates

CompressAck(TUint8 **, TUint8 , ThdrTCP , ThdrTCP *)

CompressFrame(RMBufChain &, ThdrIP , ThdrTCP , TUint, ThdrIP , ThdrTCP )

CompressIPId(TUint8 **, TUint8 , ThdrIP , ThdrIP *)

CompressPush(TUint8 , ThdrTCP )

CompressSeq(TUint8 **, TUint8 , ThdrTCP , ThdrTCP *)

CompressSpecialCases(TUint8 **, TUint8 const, TUint8 , ThdrTCP , ThdrTCP , ThdrIP , ThdrIP )

CompressUrgentPtr(TUint8 **, TUint8 , ThdrTCP , ThdrTCP *)

CompressWindow(TUint8 **, TUint8 , ThdrTCP , ThdrTCP *)

GetStoredTxHeader(TUint , ThdrIP , ThdrTCP , ThdrIP , ThdrTCP *)

IPAddressesMatch(ThdrIP , ThdrIP )

IsIPCompressible(ThdrIP , ThdrIP )

IsTCPCompressible(ThdrTCP , ThdrTCP )

SendAsRawIP(ThdrIP , ThdrTCP )

SuitableForVJCompression(ThdrIP , ThdrTCP , TUint , ThdrIP , ThdrTCP *)

TCPPortsMatch(ThdrTCP , ThdrTCP )