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