/*

 * Copyright (c) 1998-2009 Nokia Corporation and/or its subsidiary(-ies).

 * All rights reserved.

 * This component and the accompanying materials are made available

 * under the terms of the License "Eclipse Public License v1.0"

 * which accompanies this distribution, and is available

 * at the URL "http://www.eclipse.org/legal/epl-v10.html".

 *

 * Initial Contributors:

 * Nokia Corporation - initial contribution.

 *

 * Contributors:

 *

 * Description: 

 * Implementation of the Standard Compression Scheme for Unicode.

 * This code is compiled only in the Unicode build.

 *

 */

 #ifdef _UNICODE

 #include <s32ucmp.h>

 #include <e32err.h>

 const TUint32 TUnicodeCompressionState::iStaticWindow[EStaticWindows] =

 	{

 	0x0000,		// tags

 	0x0080,		// Latin-1 supplement

 	0x0100,		// Latin Extended-A

 	0x0300,		// Combining Diacritics

 	0x2000,		// General Punctuation

 	0x2080,		// Currency Symbols

 	0x2100,		// Letterlike Symbols and Number Forms

 	0x3000		// CJK Symbols and Punctuation

 	};

 const TUint32 TUnicodeCompressionState::iDynamicWindowDefault[EDynamicWindows] =

 	{

 	0x0080,		// Latin-1 supplement

 	0x00C0,		// parts of Latin-1 supplement and Latin Extended-A

 	0x0400,		// Cyrillic

 	0x0600,		// Arabic

 	0x0900,		// Devanagari

 	0x3040,		// Hiragana

 	0x30A0,		// Katakana

 	0xFF00		// Fullwidth ASCII

 	};

 const TUint16 TUnicodeCompressionState::iSpecialBase[ESpecialBases] =

 	{

 	0x00C0,		// Latin 1 letters (not symbols) and some of Extended-A

 	0x0250,		// IPA extensions

 	0x0370,		// Greek

 	0x0530,		// Armenian

 	0x3040,		// Hiragana

 	0x30A0,		// Katakana

 	0xFF60		// Halfwidth katakana

 	};

 // Single-byte mode tag values

 const TUint8 SQ0 = 0x01;	// <byte>				quote from window 0

 const TUint8 SDX = 0x0B;	// <hbyte> <lbyte>		define window in expansion area

 const TUint8 SQU = 0x0E;	// <hbyte> <lbyte>		quote Unicode value

 const TUint8 SCU = 0x0F;	//						switch to Unicode mode

 const TUint8 SC0 = 0x10;	//						select dynamic window 0

 const TUint8 SD0 = 0x18;	// <byte>				set dynamic window 0 index to <byte> and select it

 // Unicode mode tag values

 const TUint8 UC0 = 0xE0;	//						select dynamic window 0 and switch to single-byte mode

 const TUint8 UD0 = 0xE8;	// <byte>				set dynamic window 0 index to <byte>, select it and switch to

 							//						single-byte mode

 const TUint8 UQU = 0xF0;	// <hbyte>, <lbyte>		quote Unicode value

 const TUint8 UDX = 0xF1;	// <hbyte>, <lbyte>		define window in expansion area and switch to single-byte mode

 TUnicodeCompressionState::TUnicodeCompressionState():

 	iUnicodeWords(0),

 	iMaxUnicodeWords(0),

 	iCompressedBytes(0),

 	iMaxCompressedBytes(0)

 	{

 	Reset();

 	}

 void TUnicodeCompressionState::Reset()

 	{

 	iUnicodeMode = FALSE;

 	iActiveWindowBase = 0x0080;

 	for (int i = 0; i < EDynamicWindows; i++)

 		iDynamicWindow[i] = iDynamicWindowDefault[i];

 	}

 // Return the index of the static window that contains this code, if any, or -1 if there is none.

 TInt TUnicodeCompressionState::StaticWindowIndex(TUint16 aCode)

 	{

 	for (TInt i = 0; i < EStaticWindows; i++)

 		if (aCode >= iStaticWindow[i] && aCode < iStaticWindow[i] + 128)

 			return i;

 	return -1;

 	}

 /*

 If aCode can be accommodated in one of the legal dynamic windows, return the index of that window

 in the offset table. If not return KErrNotFound.

 */

 TInt TUnicodeCompressionState::DynamicWindowOffsetIndex(TUint16 aCode)

 	{

 	if (aCode < 0x0080)

 		return KErrNotFound;

 	if (aCode >= 0x3400 && aCode <= 0xDFFF)

 		return KErrNotFound;

 	/*

 	Prefer sections that cross half-block boundaries. These are better adapted to actual text.

 	They are represented by offset indices 0xf9..0xff.

 	*/

 	for (int i = 0; i < ESpecialBases; i++)

 		if (aCode >= iSpecialBase[i] && aCode < iSpecialBase[i] + 128)

 			return 0xF9 + i;

 	/*

 	Offset indices 0x01..0x67 represent half blocks from 0x0080 to 0x3380 and

 	0x68..0xA7 represent half blocks from 0xE000 to 0xFF80.

 	*/

 	if (aCode >= 0xE000)

 		aCode -= 0xAC00;

 	return aCode / 0x80;

 	}

 // Return the base of the window represented by offset index <n>. Return 0 if the offset index is illegal.

 TUint32 TUnicodeCompressionState::DynamicWindowBase(TInt aOffsetIndex)

 	{

 	if (aOffsetIndex >= 0xF9 && aOffsetIndex <= 0xFF)

 		{

 		/*

 		WARNING: don't optimise the following two lines by replacing them with

 		'return iSpecialBase[aOffsetIndex - 0xF9];'. To do so would re-introduce an error

 		in ARM builds caused by optimisation and consequent erroneous fixing up

 		of the array base: see defect EDNGASR-4AGJQX in ER5U defects.

 		*/

 		int special_base_index = aOffsetIndex - 0xF9;

 		return iSpecialBase[special_base_index];

 		}

 	if (aOffsetIndex >= 0x01 && aOffsetIndex <= 0x67)

 		return aOffsetIndex * 0x80;

 	if (aOffsetIndex >= 0x68 && aOffsetIndex <= 0xA7)

 		return aOffsetIndex * 0x80 + 0xAC00;

 	return 0;

 	}

 TBool TUnicodeCompressionState::EncodeAsIs(TUint16 aCode)

 	{

 	return aCode == 0x0000 || aCode == 0x0009 || aCode == 0x000A || aCode == 0x000D ||

 		   (aCode >= 0x0020 && aCode <= 0x007F);

 	}

 void TUnicodeCompressionState::Panic(TPanic aPanic)

 	{

 		User::Panic(_L16("ucmp"),(TInt)aPanic);

 	}

 EXPORT_C TUnicodeCompressor::TUnicodeCompressor():

 	iInputBufferStart(0),

 	iInputBufferSize(0),

 	iOutputBufferStart(0),

 	iOutputBufferSize(0),

 	iDynamicWindowIndex(0),

 	iOutputStream(NULL),

 	iOutputPointer(NULL),

 	iInput(NULL)

 	{

 		// Clear coverity warning

 		memset(iOutputBuffer, 0, sizeof(iOutputBuffer));

 	}

 EXPORT_C void TUnicodeCompressor::CompressL(RWriteStream& aOutput,MUnicodeSource& aInput,

 											TInt aMaxOutputBytes,TInt aMaxInputWords,

 											TInt* aOutputBytes,TInt* aInputWords)

 	{

 	DoCompressL(&aOutput,NULL,&aInput,aMaxOutputBytes,aMaxInputWords,aOutputBytes,aInputWords);

 	}

 EXPORT_C void TUnicodeCompressor::CompressL(TUint8* aOutput,MUnicodeSource& aInput,

 											TInt aMaxOutputBytes,TInt aMaxInputWords,

 											TInt* aOutputBytes,TInt* aInputWords)

 	{

 	DoCompressL(NULL,aOutput,&aInput,aMaxOutputBytes,aMaxInputWords,aOutputBytes,aInputWords);

 	}

 EXPORT_C TInt TUnicodeCompressor::FlushL(RWriteStream& aOutput,TInt aMaxOutputBytes,TInt& aOutputBytes)

 	{

 	DoCompressL(&aOutput,NULL,NULL,aMaxOutputBytes,0,&aOutputBytes,NULL);

 	return iOutputBufferSize;

 	}

 EXPORT_C TInt TUnicodeCompressor::FlushL(TUint8* aOutput,TInt aMaxOutputBytes,TInt& aOutputBytes)

 	{

 	DoCompressL(NULL,aOutput,NULL,aMaxOutputBytes,0,&aOutputBytes,NULL);

 	return iOutputBufferSize;

 	}

 EXPORT_C TInt TUnicodeCompressor::CompressedSizeL(MUnicodeSource& aInput,TInt aInputWords)

 	{

 	TInt bytes;

 	TUnicodeCompressor c;

 	c.DoCompressL(NULL,NULL,&aInput,KMaxTInt,aInputWords,&bytes,NULL);

 	return bytes;

 	}

 // Compress until input or output is exhausted or an exception occurs.

 void TUnicodeCompressor::DoCompressL(RWriteStream* aOutputStream,TUint8* aOutputPointer,MUnicodeSource* aInput,

 									 TInt aMaxOutputBytes,TInt aMaxInputWords,

 									 TInt* aOutputBytes,TInt* aInputWords)

 	{

 	iOutputStream = aOutputStream;

 	iOutputPointer = aOutputPointer;

 	iInput = aInput;

 	iMaxCompressedBytes = aMaxOutputBytes;

 	iMaxUnicodeWords = aMaxInputWords;

 	iCompressedBytes = iUnicodeWords = 0;

 	FlushOutputBufferL();

 	if (iInput)

 		{

 		while (iUnicodeWords < iMaxUnicodeWords && iCompressedBytes < iMaxCompressedBytes)

 			{

 			TUint16 x = iInput->ReadUnicodeValueL();

 			TAction action(x);

 			iInputBuffer[(iInputBufferStart + iInputBufferSize) % EMaxInputBufferSize] = action;

 			iInputBufferSize++;

 			iUnicodeWords++;

 			if (iInputBufferSize == EMaxInputBufferSize)

 				WriteRunL();

 			}

 		}

 	FlushInputBufferL();

 	if (aOutputBytes)

 		*aOutputBytes = iCompressedBytes;

 	if (aInputWords)

 		*aInputWords = iUnicodeWords;

 	}

 TUnicodeCompressor::TAction::TAction(TUint16 aCode):

 	iCode(aCode)

 	{

 	if (TUnicodeCompressionState::EncodeAsIs(aCode))

 		iTreatment = EPlainASCII;

 	else

 		{

 		iTreatment = TUnicodeCompressionState::DynamicWindowOffsetIndex(aCode);

 		if (iTreatment == -1)

 			{

 			iTreatment = TUnicodeCompressionState::StaticWindowIndex(aCode);

 			if (iTreatment == -1)

 				iTreatment = EPlainUnicode;

 			else

 				iTreatment += EFirstStatic;

 			}

 		}

 	}

 void TUnicodeCompressor::WriteCharacterFromBuffer()

 	{

 	const TAction& action = iInputBuffer[iInputBufferStart];

 	iInputBufferSize--;

 	iInputBufferStart = (iInputBufferStart + 1) % EMaxInputBufferSize;

 	WriteCharacter(action);

 	}

 void TUnicodeCompressor::FlushInputBufferL()

 	{

 	while (iInputBufferSize > 0 && iCompressedBytes < iMaxCompressedBytes)

 		WriteRunL();

 	}

 void TUnicodeCompressor::WriteRunL()

 	{

 	// Write out any leading characters that can be passed through.

 	if (!iUnicodeMode)

 		while (iInputBufferSize > 0)

 			{

 			const TAction& action = iInputBuffer[iInputBufferStart];

 			if (action.iTreatment == TAction::EPlainASCII ||

 				(action.iCode >= iActiveWindowBase && action.iCode < iActiveWindowBase + 128))

 				WriteCharacterFromBuffer();

 			else

 				break;

 			}

 	// Write a run of characters that cannot be passed through.

 	int i;

 	if (iInputBufferSize > 0)

 		{

 		/*

 		Find a run of characters with the same treatment and select that treatment

 		if the run has more than one character.

 		*/

 		int treatment = iInputBuffer[iInputBufferStart].iTreatment;

 		int next_treatment = treatment;

 		int run_size = 1;

 		for (i = 1; i < iInputBufferSize; i++)

 			{

 			int index = (iInputBufferStart + i) % EMaxInputBufferSize;

 			next_treatment = iInputBuffer[index].iTreatment;

 			if (next_treatment != treatment)

 				break;

 			run_size++;

 			}

 		if (run_size > 1)

 			SelectTreatment(treatment);

 		for (i = 0; i < run_size; i++)

 			WriteCharacterFromBuffer();

 		}

 	FlushOutputBufferL();

 	}

 void TUnicodeCompressor::FlushOutputBufferL()

 	{

 	while (iOutputBufferSize > 0 &&	iCompressedBytes < iMaxCompressedBytes)

 		{

 		TUint8 byte = iOutputBuffer[iOutputBufferStart];

 		if (iOutputPointer)

 			*iOutputPointer++ = byte;

 		else if (iOutputStream)

 			iOutputStream->WriteUint8L(byte);

 		iCompressedBytes++;

 		iOutputBufferSize--;

 		iOutputBufferStart = (iOutputBufferStart + 1) % EMaxOutputBufferSize;

 		}

 	}

 void TUnicodeCompressor::SelectTreatment(TInt aTreatment)

 	{

 	if (aTreatment == TAction::EPlainUnicode)

 		{

 		// Switch to Unicode mode if not there already.

 		if (!iUnicodeMode)

 			{

 			WriteByte(SCU);

 			iUnicodeMode = TRUE;

 			}

 		return;

 		}

 	if (aTreatment == TAction::EPlainASCII)

 		{

 		// Switch to single-byte mode, using the current dynamic window, if not there already.

 		if (iUnicodeMode)

 			{

 			WriteByte(UC0 + iDynamicWindowIndex);

 			iUnicodeMode = FALSE;

 			}

 		return;

 		}

 	if (aTreatment >= TAction::EFirstDynamic && aTreatment <= TAction::ELastDynamic)

 		{

 		TUint32 base = DynamicWindowBase(aTreatment);

 		// Switch to the appropriate dynamic window if it is available; if not, redefine and select dynamic window 4.

 		for (int i = 0; i < EDynamicWindows; i++)

 			if (base == iDynamicWindow[i])

 				{

 				if (iUnicodeMode)

 					WriteByte(UC0 + i);

 				else if (i != iDynamicWindowIndex)

 					WriteByte(SC0 + i);

 				iUnicodeMode = FALSE;

 				iDynamicWindowIndex = i;

 				iActiveWindowBase = base;

 				return;

 				}

 		if (iUnicodeMode)

 			WriteByte(UD0 + 4);

 		else

 			WriteByte(SD0 + 4);

 		iDynamicWindowIndex = 4;

 		iUnicodeMode = FALSE;

 		WriteByte(aTreatment);

 		iDynamicWindow[4] = base;

 		iActiveWindowBase = base;

 		return;

 		}

 	}

 // Write a character without changing mode or window.

 void TUnicodeCompressor::WriteCharacter(const TAction& aAction)

 	{

 	if (iUnicodeMode)

 		WriteUCharacter(aAction.iCode);

 	else

 		WriteSCharacter(aAction);

 	}

 void TUnicodeCompressor::WriteUCharacter(TUint16 aCode)

 	{

 	// Emit the 'quote Unicode' tag if the character would conflict with a tag.

 	if (aCode >= 0xE000 && aCode <= 0xF2FF)

 		WriteByte(UQU);

 	// Write the Unicode value big-end first.

 	WriteByte((aCode >> 8) & 0xFF);

 	WriteByte(aCode & 0xFF);

 	}

 void TUnicodeCompressor::WriteByte(TUint aByte)

 	{

 	if (iOutputBufferSize >= EMaxOutputBufferSize)

 		Panic(EOutputBufferOverflow); //Panic here is ok as this is a programming error

 	iOutputBuffer[(iOutputBufferStart + iOutputBufferSize) % EMaxOutputBufferSize] = (TUint8)aByte;

 	iOutputBufferSize++;

 	}

 void TUnicodeCompressor::WriteSCharacter(const TAction& aAction)

 	{

 	// Characters in the range 0x0020..0x007F, plus nul, tab, cr, and lf, can be emitted as their low bytes.

 	if (aAction.iTreatment == TAction::EPlainASCII)

 		{

 		WriteByte(aAction.iCode);

 		return;

 		}

 	// Characters in a static window can be written using SQ<n> plus a byte in the range 0x00-0x7F

 	if (aAction.iTreatment >= TAction::EFirstStatic && aAction.iTreatment <= TAction::ELastStatic)

 		{

 		int window = aAction.iTreatment - TAction::EFirstStatic;

 		WriteByte(SQ0 + window);

 		WriteByte(aAction.iCode);

 		return;

 		}

 	// Characters in the current dynamic window can be written as a byte in the range 0x80-0xFF.

 	if (aAction.iCode >= iActiveWindowBase && aAction.iCode < iActiveWindowBase + 128)

 		{

 		WriteByte(aAction.iCode - iActiveWindowBase + 0x80);

 		return;

 		}

 	// Characters in another dynamic window can be written using SQ<n> plus a byte in the range 0x80-0xFF

 	int i;

 	for (i = 0; i < EDynamicWindows; i++)

 		if (aAction.iCode >= iDynamicWindow[i] && aAction.iCode < iDynamicWindow[i] + 128)

 			{

 			WriteByte(SQ0 + i);

 			WriteByte(aAction.iCode - iDynamicWindow[i] + 0x80);

 			return;

 			}

 	// Other characters can be quoted.

 	WriteByte(SQU);

 	WriteByte((aAction.iCode >> 8) & 0xFF);

 	WriteByte(aAction.iCode & 0xFF);

 	return;

 	}

 EXPORT_C TUnicodeExpander::TUnicodeExpander():

 	iInputBufferStart(0),

 	iInputBufferSize(0),

 	iOutputBufferStart(0),

 	iOutputBufferSize(0),

 	iOutput(NULL),

 	iInputStream(NULL),

 	iInputPointer(NULL)

 	{

 		// Clear coverity warnings

 		memset(iInputBuffer, 0, sizeof(iInputBuffer));

 		memset(iOutputBuffer, 0, sizeof(iOutputBuffer));

 	}

 EXPORT_C void TUnicodeExpander::ExpandL(MUnicodeSink& aOutput,RReadStream& aInput,

 										TInt aMaxOutputWords,TInt aMaxInputBytes,

 										TInt* aOutputWords,TInt* aInputBytes)

 	{

 	DoExpandL(&aOutput,&aInput,NULL,aMaxOutputWords,aMaxInputBytes,aOutputWords,aInputBytes);

 	}

 EXPORT_C void TUnicodeExpander::ExpandL(MUnicodeSink& aOutput,const TUint8* aInput,

 										TInt aMaxOutputWords,TInt aMaxInputBytes,

 										TInt* aOutputWords,TInt* aInputBytes)

 	{

 	DoExpandL(&aOutput,NULL,aInput,aMaxOutputWords,aMaxInputBytes,aOutputWords,aInputBytes);

 	}

 EXPORT_C TInt TUnicodeExpander::FlushL(MUnicodeSink& aOutput,TInt aMaxOutputWords,TInt& aOutputWords)

 	{

 	DoExpandL(&aOutput,NULL,NULL,aMaxOutputWords,0,&aOutputWords,NULL);

 	return iOutputBufferSize;

 	}

 EXPORT_C TInt TUnicodeExpander::ExpandedSizeL(RReadStream& aInput,TInt aInputBytes)

 	{

 	TInt words;

 	TUnicodeExpander e;

 	e.DoExpandL(NULL,&aInput,NULL,KMaxTInt,aInputBytes,&words,NULL);

 	return words;

 	}

 EXPORT_C TInt TUnicodeExpander::ExpandedSizeL(const TUint8* aInput,TInt aInputBytes)

 	{

 	TInt words;

 	TUnicodeExpander e;

 	e.DoExpandL(NULL,NULL,aInput,KMaxTInt,aInputBytes,&words,NULL);

 	return words;

 	}

 // Expand until input or output is exhausted or an exception occurs.

 void TUnicodeExpander::DoExpandL(MUnicodeSink* aOutput,RReadStream* aInputStream,const TUint8* aInputPointer,

 								 TInt aMaxOutputWords,TInt aMaxInputBytes,

 								 TInt* aOutputWords,TInt* aInputBytes)

 	{

 	iOutput = aOutput;

 	iInputStream = aInputStream;

 	iInputPointer = aInputPointer;

 	iMaxUnicodeWords = aMaxOutputWords;

 	iMaxCompressedBytes = aMaxInputBytes;

 	iUnicodeWords = iCompressedBytes = 0;

 	iInputBufferStart = 0;

 	FlushOutputBufferL();

 	if (iInputPointer || iInputStream)

 		{

 		while (iUnicodeWords + iOutputBufferSize < iMaxUnicodeWords && iCompressedBytes < iMaxCompressedBytes)

 			HandleByteL();

 		}

 	if (aOutputWords)

 		*aOutputWords = iUnicodeWords;

 	if (aInputBytes)

 		*aInputBytes = iCompressedBytes;

 	}

 void TUnicodeExpander::HandleByteL()

 	{

 	TUint8 byte;

 	TBool handled = FALSE;

 	if (ReadByteL(byte))

 		{

 		if (iUnicodeMode)

 			handled = HandleUByteL(byte);

 		else

 			handled = HandleSByteL(byte);

 		}

 	iInputBufferStart = 0;

 	if (handled)

 		iInputBufferSize = 0;

 	FlushOutputBufferL();

 	}

 void TUnicodeExpander::FlushOutputBufferL()

 	{

 	while (iOutputBufferSize > 0 &&	iUnicodeWords < iMaxUnicodeWords)

 		{

 		if (iOutput)

 			iOutput->WriteUnicodeValueL(iOutputBuffer[iOutputBufferStart]);

 		iUnicodeWords++;

 		iOutputBufferSize--;

 		iOutputBufferStart = (iOutputBufferStart + 1) % EMaxOutputBufferSize;

 		}

 	}

 TBool TUnicodeExpander::HandleSByteL(TUint8 aByte)

 	{

 	// 'Pass-through' codes.

 	if (TUnicodeCompressionState::EncodeAsIs(aByte))

 		{

 		WriteChar(aByte);

 		return TRUE;

 		}

 	// Codes 0x80-0xFF select a character from the active window.

 	if (aByte >= 0x80)

 		{

 		WriteChar32(iActiveWindowBase + aByte - 0x80);

 		return TRUE;

 		}

 	// SQU: quote a Unicode character.

 	if (aByte == SQU)

 		return QuoteUnicodeL();

 	// SCU: switch to Unicode mode.

 	if (aByte == SCU)

 		{

 		iUnicodeMode = TRUE;

 		return TRUE;

 		}

 	// SQn: quote from window n.

 	if (aByte >= SQ0 && aByte <= SQ0 + 7)

 		{

 		int window = aByte - SQ0;

 		TUint8 byte;

 		if (ReadByteL(byte))

 			{

 			TUint32 c = byte;

 			if (c <= 0x7F)

 				c += iStaticWindow[window];

 			else

 				c += iDynamicWindow[window] - 0x80;

 			WriteChar32(c);

 			return TRUE;

 			}

 		else

 			return FALSE;

 		}

 	// SCn: switch to dynamic window n.

 	if (aByte >= SC0 && aByte <= SC0 + 7)

 		{

 		iActiveWindowBase = iDynamicWindow[aByte - SC0];

 		return TRUE;

 		}

 	// SDn: define dynamic window n and switch to it.

 	if (aByte >= SD0 && aByte <= SD0 + 7)

 		return DefineWindowL(aByte - SD0);

 	// SDX: define window in the expansion space.

 	if (aByte == SDX)

 		return DefineExpansionWindowL();

 	User::Leave(KErrCorrupt);

 	return FALSE;

 	}

 TBool TUnicodeExpander::HandleUByteL(TUint8 aByte)

 	{

 	// Plain Unicode; get the low byte and emit the Unicode value.

 	if (aByte <= 0xDF || aByte >= 0xF3)

 		{

 		TUint8 lo;

 		if (ReadByteL(lo))

 			{

 			TUint16 c = (TUint16)((aByte << 8) | lo);

 			WriteChar(c);

 			return TRUE;

 			}

 		else

 			return FALSE;

 		}

 	// Quote a Unicode character that would otherwise conflict with a tag.

 	if (aByte == UQU)

 		return QuoteUnicodeL();

 	// UCn: change to single byte mode and select window n.

 	if (aByte >= UC0 && aByte <= UC0 + 7)

 		{

 		iUnicodeMode = FALSE;

 		iActiveWindowBase = iDynamicWindow[aByte - UC0];

 		return TRUE;

 		}

 	// UDn: define dynamic window n and switch to it.

 	if (aByte >= UD0 && aByte <= UD0 + 7)

 		return DefineWindowL(aByte - UD0);

 	// UDX: define window in the expansion space.

 	if (aByte == UDX)

 		return DefineExpansionWindowL();

 	User::Leave(KErrCorrupt);

 	return FALSE;

 	}

 TBool TUnicodeExpander::QuoteUnicodeL()

 	{

 	TUint8 hi, lo;

 	if (ReadByteL(hi) && ReadByteL(lo))

 		{

 		TUint16 c = (TUint16)((hi << 8) | lo);

 		WriteChar(c);

 		return TRUE;

 		}

 	else

 		return FALSE;

 	}

 TBool TUnicodeExpander::DefineWindowL(TInt aIndex)

 	{

 	TUint8 window;

 	if (ReadByteL(window))

 		{

 		iUnicodeMode = FALSE;

 		iActiveWindowBase = DynamicWindowBase(window);

 		iDynamicWindow[aIndex] = iActiveWindowBase;

 		return TRUE;

 		}

 	else

 		return FALSE;

 	}

 TBool TUnicodeExpander::DefineExpansionWindowL()

 	{

 	TUint8 hi, lo;

 	if (ReadByteL(hi) && ReadByteL(lo))

 		{

 		iUnicodeMode = FALSE;

 		iActiveWindowBase = 0x10000 + (0x80 * ((hi & 0x1F) * 0x100 + lo));

 		iDynamicWindow[hi >> 5] = iActiveWindowBase;

 		return TRUE;

 		}

 	else

 		return FALSE;

 	}

 // Read either from the buffer (in the case of restarting after source finished in mid-operation) or from the source.

 TBool TUnicodeExpander::ReadByteL(TUint8& aByte)

 	{

 	if (iInputBufferStart < iInputBufferSize)

 		{

 		aByte = iInputBuffer[iInputBufferStart++];

 		return TRUE;

 		}

 	else if (iCompressedBytes < iMaxCompressedBytes)

 		{

 		if (iInputPointer)

 			aByte = *iInputPointer++;

 		else

 			aByte = iInputStream->ReadUint8L();

 		iInputBuffer[iInputBufferStart++] = aByte;

 		iInputBufferSize = iInputBufferStart;

 		iCompressedBytes++;

 		return TRUE;

 		}

 	else

 		return FALSE;

 	}

 void TUnicodeExpander::WriteChar(TUint16 aChar)

 	{

 	if (iOutputBufferSize >= EMaxOutputBufferSize)

 		Panic(EOutputBufferOverflow); //Panic here is ok since this is a programming error

 	iOutputBuffer[(iOutputBufferStart + iOutputBufferSize) % EMaxOutputBufferSize] = aChar;

 	iOutputBufferSize++;

 	}

 // Write a Unicode character; write using surrogates if in the range 0x10000..0x10FFFF.

 void TUnicodeExpander::WriteChar32(TUint aChar)

 	{

 	if (aChar <= 0xFFFF)

 		WriteChar((TUint16)aChar);

 	else if (aChar <= 0x10FFFF)

 		{

 		aChar -= 0x10000;									// reduce to 20-bit value in the range 0x0..0xFFFFF

 		WriteChar((TUint16)(0xD800 + (aChar >> 10)));		// first high surrogate + high 10 bits

 		WriteChar((TUint16)(0xDC00 + (aChar & 0x03FF)));	// first low surrogate + low 10 bits

 		}

 	else

 		//Panic to be kept here as impossible to test this case (nor the one before). Biggest value that can be passed is 0xFFFFF 

 		Panic(ENotUnicode);

 	}

 #endif // _UNICODE