mirror of
https://github.com/claunia/romrepomgr.git
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235 lines
9.5 KiB
C#
235 lines
9.5 KiB
C#
// /***************************************************************************
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// Aaru Data Preservation Suite
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// ----------------------------------------------------------------------------
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//
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// Filename : Info.cs
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// Author(s) : Natalia Portillo <claunia@claunia.com>
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//
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// Component : Microsoft FAT filesystem plugin.
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//
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// --[ Description ] ----------------------------------------------------------
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//
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// Identifies the Microsoft FAT filesystem and shows information.
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//
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// --[ License ] --------------------------------------------------------------
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//
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// This library is free software; you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 2.1 of the
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// License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, see <http://www.gnu.org/licenses/>.
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//
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// ----------------------------------------------------------------------------
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// Copyright © 2011-2021 Natalia Portillo
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// ****************************************************************************/
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using System;
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using System.Diagnostics.CodeAnalysis;
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using System.IO;
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using System.Text;
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namespace RomRepoMgr.Core.Aaru
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{
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// TODO: This should be taken from Aaru as a nuget package in the future
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public static class FAT
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{
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static int CountBits(uint number)
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{
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number -= (number >> 1) & 0x55555555;
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number = (number & 0x33333333) + ((number >> 2) & 0x33333333);
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return (int)((((number + (number >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24);
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}
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public static bool Identify(string path)
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{
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try
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{
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return Identify(new FileStream(path, FileMode.Open, FileAccess.Read));
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}
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catch(Exception e)
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{
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return false;
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}
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}
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[SuppressMessage("ReSharper", "JoinDeclarationAndInitializer")]
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static bool Identify(Stream imageStream)
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{
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ushort bps;
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byte spc;
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byte numberOfFats;
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ushort reservedSecs;
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ushort rootEntries;
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ushort sectors;
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ushort fatSectors;
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uint bigSectors;
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byte bpbSignature;
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byte fat32Signature;
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ulong hugeSectors;
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byte[] fat32Id = new byte[8];
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byte[] msxId = new byte[6];
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byte[] dosOem = new byte[8];
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byte[] atariOem = new byte[6];
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ushort bootable = 0;
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byte[] bpbSector = new byte[512];
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byte[] fatSector = new byte[512];
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imageStream.Position = 0;
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imageStream.Read(bpbSector, 0, 512);
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imageStream.Read(fatSector, 0, 512);
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Array.Copy(bpbSector, 0x02, atariOem, 0, 6);
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Array.Copy(bpbSector, 0x03, dosOem, 0, 8);
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bps = BitConverter.ToUInt16(bpbSector, 0x00B);
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spc = bpbSector[0x00D];
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reservedSecs = BitConverter.ToUInt16(bpbSector, 0x00E);
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numberOfFats = bpbSector[0x010];
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rootEntries = BitConverter.ToUInt16(bpbSector, 0x011);
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sectors = BitConverter.ToUInt16(bpbSector, 0x013);
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fatSectors = BitConverter.ToUInt16(bpbSector, 0x016);
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Array.Copy(bpbSector, 0x052, msxId, 0, 6);
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bigSectors = BitConverter.ToUInt32(bpbSector, 0x020);
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bpbSignature = bpbSector[0x026];
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fat32Signature = bpbSector[0x042];
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Array.Copy(bpbSector, 0x052, fat32Id, 0, 8);
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hugeSectors = BitConverter.ToUInt64(bpbSector, 0x052);
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int bitsInBps = CountBits(bps);
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bootable = BitConverter.ToUInt16(bpbSector, 0x1FE);
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bool correctSpc = spc == 1 || spc == 2 || spc == 4 || spc == 8 || spc == 16 || spc == 32 || spc == 64;
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string msxString = Encoding.ASCII.GetString(msxId);
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string fat32String = Encoding.ASCII.GetString(fat32Id);
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string oemString = Encoding.ASCII.GetString(dosOem);
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ushort apricotBps = BitConverter.ToUInt16(bpbSector, 0x50);
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byte apricotSpc = bpbSector[0x52];
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ushort apricotReservedSecs = BitConverter.ToUInt16(bpbSector, 0x53);
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byte apricotFatsNo = bpbSector[0x55];
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ushort apricotRootEntries = BitConverter.ToUInt16(bpbSector, 0x56);
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ushort apricotSectors = BitConverter.ToUInt16(bpbSector, 0x58);
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ushort apricotFatSectors = BitConverter.ToUInt16(bpbSector, 0x5B);
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bool apricotCorrectSpc = apricotSpc == 1 || apricotSpc == 2 || apricotSpc == 4 || apricotSpc == 8 ||
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apricotSpc == 16 || apricotSpc == 32 || apricotSpc == 64;
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int bitsInApricotBps = CountBits(apricotBps);
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byte apricotPartitions = bpbSector[0x0C];
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switch(oemString)
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{
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// exFAT
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case "EXFAT ": return false;
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// NTFS
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case "NTFS " when bootable == 0xAA55 && numberOfFats == 0 && fatSectors == 0: return false;
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// QNX4
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case "FQNX4FS ": return false;
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}
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ulong imageSectors = (ulong)imageStream.Length / 512;
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switch(bitsInBps)
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{
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// FAT32 for sure
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case 1 when correctSpc && numberOfFats <= 2 && sectors == 0 && fatSectors == 0 &&
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fat32Signature == 0x29 && fat32String == "FAT32 ": return true;
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// short FAT32
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case 1
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when correctSpc && numberOfFats <= 2 && sectors == 0 && fatSectors == 0 && fat32Signature == 0x28:
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return bigSectors == 0 ? hugeSectors <= imageSectors : bigSectors <= imageSectors;
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// MSX-DOS FAT12
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case 1 when correctSpc && numberOfFats <= 2 && rootEntries > 0 && sectors <= imageSectors &&
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fatSectors > 0 && msxString == "VOL_ID": return true;
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// EBPB
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case 1 when correctSpc && numberOfFats <= 2 && rootEntries > 0 && fatSectors > 0 &&
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(bpbSignature == 0x28 || bpbSignature == 0x29):
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return sectors == 0 ? bigSectors <= imageSectors : sectors <= imageSectors;
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// BPB
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case 1 when correctSpc && reservedSecs < imageSectors - 1 && numberOfFats <= 2 && rootEntries > 0 &&
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fatSectors > 0: return sectors == 0 ? bigSectors <= imageSectors : sectors <= imageSectors;
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}
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// Apricot BPB
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if(bitsInApricotBps == 1 &&
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apricotCorrectSpc &&
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apricotReservedSecs < imageSectors - 1 &&
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apricotFatsNo <= 2 &&
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apricotRootEntries > 0 &&
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apricotFatSectors > 0 &&
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apricotSectors <= imageSectors &&
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apricotPartitions == 0)
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return true;
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// DEC Rainbow, lacks a BPB but has a very concrete structure...
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if(imageSectors != 800)
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return false;
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// DEC Rainbow boots up with a Z80, first byte should be DI (disable interrupts)
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byte z80Di = bpbSector[0];
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// First FAT1 sector resides at LBA 0x14
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byte[] fat1Sector0 = new byte[512];
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imageStream.Position = 0x14 * 512;
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imageStream.Read(fat1Sector0, 0, 512);
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// First FAT2 sector resides at LBA 0x1A
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byte[] fat2Sector0 = new byte[512];
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imageStream.Position = 0x1A * 512;
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imageStream.Read(fat2Sector0, 0, 512);
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bool equalFatIds = fat1Sector0[0] == fat2Sector0[0] && fat1Sector0[1] == fat2Sector0[1];
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// Volume is software interleaved 2:1
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var rootMs = new MemoryStream();
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byte[] tmp = new byte[512];
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foreach(long position in new long[]
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{
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0x17, 0x19, 0x1B, 0x1D, 0x1E, 0x20
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})
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{
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imageStream.Position = position * 512;
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imageStream.Read(tmp, 0, 512);
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rootMs.Write(tmp, 0, tmp.Length);
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}
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byte[] rootDir = rootMs.ToArray();
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bool validRootDir = true;
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// Iterate all root directory
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for(int e = 0; e < 96 * 32; e += 32)
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{
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for(int c = 0; c < 11; c++)
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if((rootDir[c + e] < 0x20 && rootDir[c + e] != 0x00 && rootDir[c + e] != 0x05) ||
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rootDir[c + e] == 0xFF ||
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rootDir[c + e] == 0x2E)
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{
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validRootDir = false;
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break;
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}
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if(!validRootDir)
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break;
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}
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return z80Di == 0xF3 && equalFatIds && (fat1Sector0[0] & 0xF0) == 0xF0 && fat1Sector0[1] == 0xFF &&
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validRootDir;
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}
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}
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} |