/*+
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* Copyright (c) 2001-2009 Nokia Corporation and/or its subsidiary(-ies).+
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* All rights reserved.+
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* This component and the accompanying materials are made available+
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* under the terms of the License "Eclipse Public License v1.0"+
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* which accompanies this distribution, and is available+
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* at the URL "http://www.eclipse.org/legal/epl-v10.html".+
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*+
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* Initial Contributors:+
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* Nokia Corporation - initial contribution.+
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*+
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* Contributors:+
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*+
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* Description: +
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* Define methods for asn1-encoding base class+
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*+
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*/+
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+
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+
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#include "base128enc.h"+
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#include "panic.h"+
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+
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#include <asn1enc.h>+
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+
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const TUint KMaxLowNumberFormTag = 30;+
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const TUint KMaxShortFormLength = 127;+
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+
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+
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EXPORT_C CASN1EncBase::CASN1EncBase(const TTagType aType, const TASN1Class aClass)+
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: iType(aType), iClass(aClass)+
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	{+
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	CalculateTagLengthDER();+
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	}+
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+
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+
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EXPORT_C CASN1EncBase::~CASN1EncBase()+
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	{+
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	}+
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+
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+
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EXPORT_C void CASN1EncBase::ConstructL()+
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	{+
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	ContentsLengthChanged();+
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	}+
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+
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+
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void CASN1EncBase::ContentsLengthChanged()+
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	{+
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	CalculateContentsLengthDER();+
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	CalculateLengthLengthDER();+
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+
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	if (iParent)+
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		{+
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		iParent->ContentsLengthChanged();+
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		}+
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	}+
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+
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+
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// Set tagging scheme/tag/class+
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EXPORT_C void CASN1EncBase::SetTag(const TTagType aType, const TASN1Class aClass)+
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	{+
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	iType = aType;+
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	iClass = aClass;+
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+
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	CalculateTagLengthDER();+
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	}+
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+
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+
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// Gives total number of octets in the DER encoding of this object+
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EXPORT_C TUint CASN1EncBase::LengthDER() const+
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	{+
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	return iTagLengthDER + iLengthLengthDER + iContentsLengthDER;+
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	}+
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	+
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+
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// Writes entire DER encoding of this object into the given buffer+
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EXPORT_C void CASN1EncBase::WriteDERL(TDes8& aBuf, TUint& aPos) const+
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	{+
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	__ASSERT_ALWAYS(aBuf.Length() - STATIC_CAST(TInt, aPos) >= STATIC_CAST(TInt, LengthDER()),+
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		Panic(KErrDescriptorTooShort));+
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+
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	WriteHelperL(aBuf, aPos, iTagLengthDER,      &CASN1EncBase::WriteTagDERL);+
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	WriteHelperL(aBuf, aPos, iLengthLengthDER,   &CASN1EncBase::WriteLengthDER);+
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	WriteHelperL(aBuf, aPos, iContentsLengthDER, &CASN1EncBase::WriteContentsDERL);+
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	}+
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+
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+
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// Internal helper method, used for efficiency+
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void CASN1EncBase::WriteHelperL(TDes8& aBuf, TUint& aPos, const TUint aLength,+
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									WriteFunc aWriteFunc) const+
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	{+
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	if (aLength)+
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		{+
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		// Get the middle bit of buffer we should be using+
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		TPtr8 ptr(&aBuf[aPos], aLength, aLength);+
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		+
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		// Call the function to actually write the data+
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		(this->*aWriteFunc)(ptr);+
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		+
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		aPos += aLength;+
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		}+
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	}+
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+
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+
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// Give number of octets in tag section+
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void CASN1EncBase::CalculateTagLengthDER()+
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	{+
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	if (iType <= KMaxLowNumberFormTag)+
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		{+
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		// Low tag number form+
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		iTagLengthDER = 1;+
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		}+
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	else+
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		{+
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		// High tag number form+
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		TASN1EncBase128DER encoder(iType);+
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		iTagLengthDER = encoder.LengthDER() + 1;+
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		}+
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	}+
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+
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+
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// Give number of octets in length section+
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// Only called after contents length is worked out+
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void CASN1EncBase::CalculateLengthLengthDER()+
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	{+
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	iLengthLengthDER = 1;+
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	if (iContentsLengthDER > KMaxShortFormLength)+
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		{+
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		// Long form - need number of octets in base256 representation+
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		// of length, plus 1.+
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+
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		TUint working = iContentsLengthDER;+
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		do+
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			{+
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			++iLengthLengthDER;+
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			}+
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		while (working >>= 8);+
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		}+
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	}+
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+
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+
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// Writes the tag section into the given buffer+
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void CASN1EncBase::WriteTagDERL(TDes8& aBuf) const+
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	{+
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	// Write class - bits 7-8+
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	aBuf[0] = STATIC_CAST(TUint8, iClass << 6);+
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+
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	// Write constructed/primitive flag in bit 6+
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	if (IsConstructed())+
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		{+
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		aBuf[0] |= 0x20;+
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		}+
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+
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	// Write length+
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	if (iType <= KMaxLowNumberFormTag)+
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		{+
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		aBuf[0] |= iType;+
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		}+
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	else+
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		{+
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		// First byte signals more to come+
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		aBuf[0] |= 0x1F;+
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+
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		// The rest we delegate+
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		TASN1EncBase128DER encoder(iType);+
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		TUint offset = 1;+
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		encoder.WriteDERL(aBuf, offset);+
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		}+
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	}+
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+
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+
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// Writes the length section into the given buffer+
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void CASN1EncBase::WriteLengthDER(TDes8& aBuf) const+
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	{+
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	if (iContentsLengthDER > KMaxShortFormLength)+
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		{+
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		// First byte is the number of other bytes, with top bit also set+
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		TUint octets = iLengthLengthDER - 1;+
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+
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		// Cast takes 8 least sig bits+
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		aBuf[0] = STATIC_CAST(TUint8, octets);+
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		aBuf[0] |= 0x80;+
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+
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		// Other bytes are base 256 representation of length, most significant first+
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		TUint working = iContentsLengthDER;+
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		do+
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			{+
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			// Cast to TUint8 takes 8 least sig bits+
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			aBuf[octets] = STATIC_CAST(TUint8, working);+
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			working >>= 8;+
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			}+
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		while (--octets);+
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		}+
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	else+
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		{+
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		// Short form, nice and easy - take least sig 8 bits with a cast+
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		aBuf[0] = STATIC_CAST(TUint8, iContentsLengthDER);+
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		}+
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	}+
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+
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+
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// Sets the parent (can only do this once)+
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void CASN1EncBase::SetParent(CASN1EncBase* aParent)+
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	{+
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	__ASSERT_ALWAYS(iParent == 0, Panic(KErrAlreadyHasParent));+
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	iParent = aParent;+
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	}+
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