/*

* Copyright (c) 2001-2009 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: 

* Define methods for asn1-encoding base class

*

*/

#include "base128enc.h"

#include "panic.h"

#include <asn1enc.h>

const TUint KMaxLowNumberFormTag = 30;

const TUint KMaxShortFormLength = 127;

EXPORT_C CASN1EncBase::CASN1EncBase(const TTagType aType, const TASN1Class aClass)

: iType(aType), iClass(aClass)

	{

	CalculateTagLengthDER();

	}

EXPORT_C CASN1EncBase::~CASN1EncBase()

	{

	}

EXPORT_C void CASN1EncBase::ConstructL()

	{

	ContentsLengthChanged();

	}

void CASN1EncBase::ContentsLengthChanged()

	{

	CalculateContentsLengthDER();

	CalculateLengthLengthDER();

	if (iParent)

		{

		iParent->ContentsLengthChanged();

		}

	}

// Set tagging scheme/tag/class

EXPORT_C void CASN1EncBase::SetTag(const TTagType aType, const TASN1Class aClass)

	{

	iType = aType;

	iClass = aClass;

	CalculateTagLengthDER();

	}

// Gives total number of octets in the DER encoding of this object

EXPORT_C TUint CASN1EncBase::LengthDER() const

	{

	return iTagLengthDER + iLengthLengthDER + iContentsLengthDER;

	}

// Writes entire DER encoding of this object into the given buffer

EXPORT_C void CASN1EncBase::WriteDERL(TDes8& aBuf, TUint& aPos) const

	{

	__ASSERT_ALWAYS(aBuf.Length() - STATIC_CAST(TInt, aPos) >= STATIC_CAST(TInt, LengthDER()),

		Panic(KErrDescriptorTooShort));

	WriteHelperL(aBuf, aPos, iTagLengthDER,      &CASN1EncBase::WriteTagDERL);

	WriteHelperL(aBuf, aPos, iLengthLengthDER,   &CASN1EncBase::WriteLengthDER);

	WriteHelperL(aBuf, aPos, iContentsLengthDER, &CASN1EncBase::WriteContentsDERL);

	}

// Internal helper method, used for efficiency

void CASN1EncBase::WriteHelperL(TDes8& aBuf, TUint& aPos, const TUint aLength,

									WriteFunc aWriteFunc) const

	{

	if (aLength)

		{

		// Get the middle bit of buffer we should be using

		TPtr8 ptr(&aBuf[aPos], aLength, aLength);

		// Call the function to actually write the data

		(this->*aWriteFunc)(ptr);

		aPos += aLength;

		}

	}

// Give number of octets in tag section

void CASN1EncBase::CalculateTagLengthDER()

	{

	if (iType <= KMaxLowNumberFormTag)

		{

		// Low tag number form

		iTagLengthDER = 1;

		}

	else

		{

		// High tag number form

		TASN1EncBase128DER encoder(iType);

		iTagLengthDER = encoder.LengthDER() + 1;

		}

	}

// Give number of octets in length section

// Only called after contents length is worked out

void CASN1EncBase::CalculateLengthLengthDER()

	{

	iLengthLengthDER = 1;

	if (iContentsLengthDER > KMaxShortFormLength)

		{

		// Long form - need number of octets in base256 representation

		// of length, plus 1.

		TUint working = iContentsLengthDER;

		do

			{

			++iLengthLengthDER;

			}

		while (working >>= 8);

		}

	}

// Writes the tag section into the given buffer

void CASN1EncBase::WriteTagDERL(TDes8& aBuf) const

	{

	// Write class - bits 7-8

	aBuf[0] = STATIC_CAST(TUint8, iClass << 6);

	// Write constructed/primitive flag in bit 6

	if (IsConstructed())

		{

		aBuf[0] |= 0x20;

		}

	// Write length

	if (iType <= KMaxLowNumberFormTag)

		{

		aBuf[0] |= iType;

		}

	else

		{

		// First byte signals more to come

		aBuf[0] |= 0x1F;

		// The rest we delegate

		TASN1EncBase128DER encoder(iType);

		TUint offset = 1;

		encoder.WriteDERL(aBuf, offset);

		}

	}

// Writes the length section into the given buffer

void CASN1EncBase::WriteLengthDER(TDes8& aBuf) const

	{

	if (iContentsLengthDER > KMaxShortFormLength)

		{

		// First byte is the number of other bytes, with top bit also set

		TUint octets = iLengthLengthDER - 1;

		// Cast takes 8 least sig bits

		aBuf[0] = STATIC_CAST(TUint8, octets);

		aBuf[0] |= 0x80;

		// Other bytes are base 256 representation of length, most significant first

		TUint working = iContentsLengthDER;

		do

			{

			// Cast to TUint8 takes 8 least sig bits

			aBuf[octets] = STATIC_CAST(TUint8, working);

			working >>= 8;

			}

		while (--octets);

		}

	else

		{

		// Short form, nice and easy - take least sig 8 bits with a cast

		aBuf[0] = STATIC_CAST(TUint8, iContentsLengthDER);

		}

	}

// Sets the parent (can only do this once)

void CASN1EncBase::SetParent(CASN1EncBase* aParent)

	{

	__ASSERT_ALWAYS(iParent == 0, Panic(KErrAlreadyHasParent));

	iParent = aParent;

	}