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/*
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* Copyright (c) 2002-2007 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 "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: Bit manipulator.
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*
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*/
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#include "TSatBitOP.h"
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#include "SatLog.h"
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const TUint8 KBitsInByte( 8 );
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const TUint8 KBitsInWord( 16 );
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const TUint8 KHighBitInByte( 7 );
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const TUint8 KHighBitInWord( 15 );
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// -----------------------------------------------------------------------------
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// Extracts bits from bit sequence. First bit is 0 index.
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// The lsb of extracted bits is set to 0 bit.
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// -----------------------------------------------------------------------------
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//
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TUint8 TSatBitOP::ExtractBits(
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TInt aBitIndex,
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TUint8 aBitCount,
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const TDesC8& aBytes )
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{
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LOG( DETAILED, "SATENGINE: TSatBitOP::ExtractBits calling" )
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// Calculate the byte where aBitIndex is pointing.
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const TInt byteIndex( static_cast<TInt>( aBitIndex / KBitsInByte ) );
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if ( byteIndex > 0 ) // aBitIndex is pointing other than first byte.
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{
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LOG( DETAILED, "SATENGINE: TSatBitOP::ExtractBits byteIndex > 0" )
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// Change the aBitIndex to point the bits 0 to 7, because
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// we know which byte it is indexing.
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aBitIndex -= byteIndex * KBitsInByte;
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}
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TUint8 result( 0 );
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// Check if the bits to be extracted is in two bytes.
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// ie. Part of the bits is in one byte and another
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// part is in the following byte.
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const TUint8 lastBit( static_cast<TUint8>( aBitIndex + aBitCount ) );
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LOG2( DETAILED, "SATENGINE: TSatBitOP::ExtractBits lastBit: %i", lastBit )
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if ( lastBit > KBitsInByte )
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{
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// The bits to be extracted reside in two bytes.
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// Take the bytes.
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const TUint16 word( static_cast<TUint16>(
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( aBytes[byteIndex] << KBitsInByte ) + aBytes[byteIndex + 1] ) );
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// Create the mask, which extracts the bits.
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const TUint16 mask(
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CreateMask16Bit( static_cast<TUint8>( aBitIndex ), aBitCount ) );
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// Extract the bits from the word.
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// Result will be shifted so that the lsb bit of the extracted bits
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// will be in bit 0.
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result =
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static_cast<TUint8>( ( word & mask ) >> ( KBitsInWord - lastBit ) );
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}
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else
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{
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// Bits can be extracted from single byte.
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// Create the mask.
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const TUint8 mask(
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CreateMask8Bit( static_cast<TUint8>( aBitIndex ), aBitCount ) );
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const TUint8 byte( aBytes[byteIndex] );
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// Mask the bits and move the lsb of the extracted bits to 0 bit.
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// Result will be shifted so that the lsb bit of the extracted bits
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// will be in bit 0.
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result =
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static_cast<TUint8>( ( byte & mask ) >> ( KBitsInByte - lastBit ) );
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}
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LOG( DETAILED, "SATENGINE: TSatBitOP::ExtractBits exiting" )
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return result;
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}
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// -----------------------------------------------------------------------------
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// Creates a 8-bit mask of ones.
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// -----------------------------------------------------------------------------
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//
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TUint8 TSatBitOP::CreateMask8Bit( TUint8 aBitIndex, TUint8 aCount )
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{
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LOG( DETAILED, "SATENGINE: TSatBitOP::CreateMask8Bit calling" )
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// Change aBitIndex to use normal indexing of bits, because
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// 0 in aBitIndex means MSB.
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aBitIndex = static_cast<TUint8>( KHighBitInByte - aBitIndex );
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TUint8 result( 0 );
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TInt i ( 0 );
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for ( i = 0; i < aCount; i++ )
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{
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result |= static_cast<TUint8>( 1 << aBitIndex );
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aBitIndex--;
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}
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LOG2( DETAILED, "SATENGINE: TSatBitOP::CreateMask8Bit i: %i", i )
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LOG2( DETAILED, "SATENGINE: TSatBitOP::CreateMask8Bit exiting, \
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result: %i", result )
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return result;
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}
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// -----------------------------------------------------------------------------
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// Creates a 16-bit mask of ones.
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// -----------------------------------------------------------------------------
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//
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TUint16 TSatBitOP::CreateMask16Bit( TUint8 aBitIndex, TUint8 aCount )
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{
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LOG( DETAILED, "SATENGINE: TSatBitOP::CreateMask16Bit calling" )
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// Change aBitIndex to use normal indexing of bits, because
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// 0 in aBitIndex means MSB.
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aBitIndex = static_cast<TUint8>( KHighBitInWord - aBitIndex );
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TUint16 result( 0 );
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TInt i ( 0 );
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for ( i = 0; i < aCount; i++ )
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{
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result |= static_cast<TUint16>( 1 << aBitIndex );
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aBitIndex--;
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}
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LOG2( DETAILED, "SATENGINE: TSatBitOP::CreateMask16Bit i: %i", i )
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LOG2( DETAILED, "SATENGINE: TSatBitOP::CreateMask16Bit exiting, \
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result: %i", result )
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return result;
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}
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