// Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies).

 // All rights reserved.

 // This component and the accompanying materials are made available

 // under the terms of "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:

 //

 #include "parsers.h"

 // The ID3 tag has a 10 byte header.

 static const TInt KID3HeaderSize = 10;

 //

 // Checks if an ID3 header is present at the current

 // reader position, and skips over it if it is.

 // Returns ETrue if a header was found, EFalse otherwise.

 //

 TBool TID3Parser::ReadAndSkipID3L(CReader& aReader)

 	{

 	TBuf8<KID3HeaderSize> header;

 	TUint8 a;

 	TUint8 b;

 	TUint8 c;

 	TUint8 d;

 	header.SetLength(KID3HeaderSize);

 	aReader.ReadBytesL(header);

 	do

 		{

 		// Look for the ID3 header.

 		if ((header[0] != 'I') || (header[1] != 'D') || (header[2] != '3'))

 			{

 			break;

 			}

 		// The last 4 bits of byte[5] should be zero.

 		if ((header[5] & 0x0f))	// [00001111]

 			{

 			break;

 			}

 		// Read the tag size. It's stored in a sync-safe manner

 		// (the highest bit is never set so it won't be confused

 		// with a frame-sync). If the highest bit is set, it's invalid.

 		a = header[6];

 		b = header[7];

 		c = header[8];

 		d = header[9];

 		// OR the values together and check that the highest bit of

 		// the result isn't set. Saves on doing four individual checks.

 		if ((a | b | c | d) & 0x80) // [10000000]

 			{

 			break;

 			}

 		// Convert from sync-safe format to normal format.

 		// [0aaaaaaa][0bbbbbbb][0ccccccc][0ddddddd] is changed to

 		// [0000aaaa][aaabbbbb][bbcccccc][cddddddd]

 		//

 		// Copy bit[0] of c into bit[7] of d.

 		d |= ((c & 0x01) << 7);

 		c >>= 1;

 		// Copy bit[1,0] of b into bit[7,6] of c.

 		c |= ((b & 0x03) << 6);

 		b >>= 2;

 		// Copy bit[2,1,0] of a into bit[7,6,5] of b.

 		b |= ((a & 0x07) << 5);

 		a >>= 3;

 		TInt length = MAKE_INT32(a, b, c, d);

 		aReader.SeekL(length);

 		return ETrue;

 		}

 	while (EFalse);

 	// It's not an ID3 header.

 	// Undo the header read.

 	aReader.SeekL(-KID3HeaderSize);

 	return EFalse;

 	}