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Add support in dicformat for skipping storing CD prefixes and suffixes that are correct.

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This commit is contained in:
Natalia Portillo
2018-07-31 23:27:08 +01:00
parent daab885f2a
commit 9aab686e93
9 changed files with 833 additions and 118 deletions
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123
DiscImageChef.DiscImages/DiscImageChef/CdEcc.cs Normal file
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// /***************************************************************************
// The Disc Image Chef
// ----------------------------------------------------------------------------
//
// Filename : ClauniaSubchannelTransform.cs
// Author(s) : Natalia Portillo <claunia@claunia.com>
//
// Component : Disk image plugins.
//
// --[ Description ] ----------------------------------------------------------
//
// Contains the CD ECC algorithm.
//
// --[ License ] --------------------------------------------------------------
//
// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 2.1 of the
// License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, see <http://www.gnu.org/licenses/>.
//
// ----------------------------------------------------------------------------
// Copyright © 2011-2018 Natalia Portillo
// ECC algorithm from ECM(c) 2002-2011 Neill Corlett
// ****************************************************************************/
using System;
namespace DiscImageChef.DiscImages
{
public partial class DiscImageChef
{
byte[] eccBTable;
byte[] eccFTable;
uint[] edcTable;
void EccInit()
{
eccFTable = new byte[256];
eccBTable = new byte[256];
edcTable = new uint[256];
for(uint i = 0; i < 256; i++)
{
uint edc = i;
uint j = (uint)((i << 1) ^ ((i & 0x80) == 0x80 ? 0x11D : 0));
eccFTable[i] = (byte)j;
eccBTable[i ^ j] = (byte)i;
for(j = 0; j < 8; j++) edc = (edc >> 1) ^ ((edc & 1) > 0 ? 0xD8018001 : 0);
edcTable[i] = edc;
}
}
bool SuffixIsCorrect(byte[] channel)
{
if(channel[0x814] != 0x00 || // reserved (8 bytes)
channel[0x815] != 0x00 || channel[0x816] != 0x00 || channel[0x817] != 0x00 || channel[0x818] != 0x00 ||
channel[0x819] != 0x00 || channel[0x81A] != 0x00 || channel[0x81B] != 0x00) return false;
byte[] address = new byte[4];
byte[] data = new byte[2060];
byte[] data2 = new byte[2232];
byte[] eccP = new byte[172];
byte[] eccQ = new byte[104];
Array.Copy(channel, 0x0C, address, 0, 4);
Array.Copy(channel, 0x10, data, 0, 2060);
Array.Copy(channel, 0x10, data2, 0, 2232);
Array.Copy(channel, 0x81C, eccP, 0, 172);
Array.Copy(channel, 0x8C8, eccQ, 0, 104);
bool correctEccP = CheckEcc(ref address, ref data, 86, 24, 2, 86, ref eccP);
if(!correctEccP) return false;
bool correctEccQ = CheckEcc(ref address, ref data2, 52, 43, 86, 88, ref eccQ);
if(!correctEccQ) return false;
uint storedEdc = BitConverter.ToUInt32(channel, 0x810);
uint edc = 0;
int size = 0x810;
int pos = 0;
for(; size > 0; size--) edc = (edc >> 8) ^ edcTable[(edc ^ channel[pos++]) & 0xFF];
uint calculatedEdc = edc;
return calculatedEdc == storedEdc;
}
bool CheckEcc(ref byte[] address, ref byte[] data, uint majorCount, uint minorCount, uint majorMult,
uint minorInc, ref byte[] ecc)
{
uint size = majorCount * minorCount;
uint major;
for(major = 0; major < majorCount; major++)
{
uint idx = (major >> 1) * majorMult + (major & 1);
byte eccA = 0;
byte eccB = 0;
uint minor;
for(minor = 0; minor < minorCount; minor++)
{
byte temp = idx < 4 ? address[idx] : data[idx - 4];
idx += minorInc;
if(idx >= size) idx -= size;
eccA ^= temp;
eccB ^= temp;
eccA = eccFTable[eccA];
}
eccA = eccBTable[eccFTable[eccA] ^ eccB];
if(ecc[major] != eccA || ecc[major + majorCount] != (eccA ^ eccB)) return false;
}
return true;
}
}
}