cryptoservices/certificateandkeymgmt/asn1/base128enc.cpp
author Dremov Kirill (Nokia-D-MSW/Tampere) <kirill.dremov@nokia.com>
Thu, 10 Sep 2009 14:01:51 +0300
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/*
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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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* Implementation for TASN1EncBase128 class.
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*
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*/
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#include "base128enc.h"
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TASN1EncBase128DER::TASN1EncBase128DER(TUint aInt) : iInt(aInt), iLengthDER(0)
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	{
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	CalculateLengthDER();
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	}
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TUint TASN1EncBase128DER::LengthDER() const
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	{
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	return iLengthDER;
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	}
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void TASN1EncBase128DER::CalculateLengthDER()
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	{
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	iLengthDER = 1;
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	TUint working = iInt;
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	while (working >>= 7)
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		{
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		++iLengthDER;
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		}
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	}
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void TASN1EncBase128DER::WriteDERL(TDes8& aBuf, TUint& aPos) const
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	{
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	__ASSERT_DEBUG(aBuf.Length() - aPos >= STATIC_CAST(TUint8, iLengthDER), 
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		User::Leave(KErrBadDescriptor));
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	TInt last = aPos + iLengthDER - 1;
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	TUint working = iInt;
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	for (TUint cursor = last; cursor >= aPos; --cursor)
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		{
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		// Cast takes least significant 8 bits only (actually, we only need 7)
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		aBuf[cursor] = STATIC_CAST(TUint8, working);
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		aBuf[cursor] |= 0x80; // Top bit always set to 1...
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		working >>= 7;
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		}
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	// ...except top bit on last byte is 0
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	aBuf[last] &= 0x7F;
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	aPos += iLengthDER;
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	}