413 lines
13 KiB
C#
413 lines
13 KiB
C#
//Copyright (c) 2012 BizHawk team
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//Permission is hereby granted, free of charge, to any person obtaining a copy of
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//this software and associated documentation files (the "Software"), to deal in
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//the Software without restriction, including without limitation the rights to
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//use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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//of the Software, and to permit persons to whom the Software is furnished to do
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//so, subject to the following conditions:
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//The above copyright notice and this permission notice shall be included in all
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//copies or substantial portions of the Software.
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//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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//IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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//FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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//AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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//LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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//OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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//SOFTWARE.
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//ECM File Format reading support
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//TODO - make a background thread to validate the EDC. be sure to terminate thread when the Blob disposes
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//remember: may need another stream for that. the IBlob architecture doesnt demand multithreading support
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using System;
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using System.IO;
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using System.Collections.Generic;
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using BizHawk.Common;
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namespace BizHawk.Emulation.DiscSystem
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{
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sealed partial class Disc
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{
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private class Blob_ECM : IBlob
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{
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FileStream stream;
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public void Dispose()
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{
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if(stream != null)
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stream.Dispose();
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stream = null;
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}
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private class IndexEntry
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{
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public int Type;
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public uint Number;
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public long ECMOffset;
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public long LogicalOffset;
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}
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/// <summary>
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/// an index of blocks within the ECM file, for random-access.
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/// itll be sorted by logical ordering, so you can binary search for the address you want
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/// </summary>
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private readonly List<IndexEntry> Index = new List<IndexEntry>();
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/// <summary>
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/// the ECMfile-provided EDC integrity checksum. not being used right now
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/// </summary>
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int EDC;
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public long Length;
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public void Parse(string path)
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{
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stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
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//skip header
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stream.Seek(4, SeekOrigin.Current);
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long logOffset = 0;
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for (; ; )
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{
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//read block count. this format is really stupid. maybe its good for detecting non-ecm files or something.
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int b = stream.ReadByte();
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if (b == -1) MisformedException();
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int bytes = 1;
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int T = b & 3;
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long N = (b >> 2) & 0x1F;
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int nbits = 5;
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while (b.Bit(7))
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{
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if (bytes == 5) MisformedException(); //if we're gonna need a 6th byte, this file is broken
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b = stream.ReadByte();
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bytes++;
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if (b == -1) MisformedException();
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N |= (long)(b & 0x7F) << nbits;
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nbits += 7;
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}
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//end of blocks section
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if (N == 0xFFFFFFFF)
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break;
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//the 0x80000000 business is confusing, but this is almost positively an error
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if (N >= 0x100000000)
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MisformedException();
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uint todo = (uint)N + 1;
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IndexEntry ie = new IndexEntry
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{
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Number = todo,
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ECMOffset = stream.Position,
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LogicalOffset = logOffset,
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Type = T
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};
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Index.Add(ie);
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if (T == 0)
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{
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stream.Seek(todo, SeekOrigin.Current);
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logOffset += todo;
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}
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else if (T == 1)
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{
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stream.Seek(todo * (2048 + 3), SeekOrigin.Current);
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logOffset += todo * 2352;
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}
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else if (T == 2)
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{
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stream.Seek(todo * 2052, SeekOrigin.Current);
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logOffset += todo * 2336;
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}
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else if (T == 3)
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{
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stream.Seek(todo * 2328, SeekOrigin.Current);
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logOffset += todo * 2336;
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}
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else MisformedException();
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}
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//TODO - endian bug. need endian-independent binary reader with good license
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var br = new BinaryReader(stream);
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EDC = br.ReadInt32();
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Length = logOffset;
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}
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void MisformedException()
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{
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throw new InvalidOperationException("Mis-formed ECM file");
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}
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public static bool IsECM(string path)
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{
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using (var fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read))
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{
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int e = fs.ReadByte();
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int c = fs.ReadByte();
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int m = fs.ReadByte();
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int o = fs.ReadByte();
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if (e != 'E' || c != 'C' || m != 'M' || o != 0)
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return false;
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}
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return true;
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}
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/// <summary>
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/// finds the IndexEntry for the specified logical offset
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/// </summary>
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int FindInIndex(long offset, int LastReadIndex)
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{
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//try to avoid searching the index. check the last index we we used.
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for(int i=0;i<2;i++) //try 2 times
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{
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IndexEntry last = Index[LastReadIndex];
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if (LastReadIndex == Index.Count - 1)
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{
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//byte_pos would have to be after the last entry
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if (offset >= last.LogicalOffset)
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{
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return LastReadIndex;
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}
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}
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else
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{
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IndexEntry next = Index[LastReadIndex + 1];
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if (offset >= last.LogicalOffset && offset < next.LogicalOffset)
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{
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return LastReadIndex;
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}
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//well, maybe we just advanced one sector. just try again one sector ahead
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LastReadIndex++;
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}
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}
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//Console.WriteLine("binary searched"); //use this to check for mistaken LastReadIndex logic resulting in binary searches during sequential access
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int listIndex = Index.LowerBoundBinarySearch(idx => idx.LogicalOffset, offset);
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System.Diagnostics.Debug.Assert(listIndex < Index.Count);
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//Console.WriteLine("byte_pos {0:X8} using index #{1} at offset {2:X8}", offset, listIndex, Index[listIndex].LogicalOffset);
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return listIndex;
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}
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void Reconstruct(byte[] secbuf, int type)
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{
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//sync
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secbuf[0] = 0;
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for (int i = 1; i <= 10; i++)
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secbuf[i] = 0xFF;
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secbuf[11] = 0x00;
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//misc stuff
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switch (type)
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{
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case 1:
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//mode 1
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secbuf[15] = 0x01;
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//reserved
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for (int i = 0x814; i <= 0x81B; i++)
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secbuf[i] = 0x00;
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break;
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case 2:
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case 3:
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//mode 2
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secbuf[15] = 0x02;
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//flags - apparently CD XA specifies two copies of these 4bytes of flags. ECM didnt store the first copy; so we clone the second copy which was stored down to the spot for the first copy.
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secbuf[0x10] = secbuf[0x14];
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secbuf[0x11] = secbuf[0x15];
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secbuf[0x12] = secbuf[0x16];
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secbuf[0x13] = secbuf[0x17];
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break;
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}
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//edc
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switch (type)
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{
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case 1: ECM.PokeUint(secbuf, 0x810, ECM.EDC_Calc(secbuf, 0, 0x810)); break;
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case 2: ECM.PokeUint(secbuf, 0x818, ECM.EDC_Calc(secbuf, 16, 0x808)); break;
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case 3: ECM.PokeUint(secbuf, 0x92C, ECM.EDC_Calc(secbuf, 16, 0x91C)); break;
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}
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//ecc
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switch (type)
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{
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case 1: ECM.ECC_Populate(secbuf, 0, secbuf, 0, false); break;
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case 2: ECM.ECC_Populate(secbuf, 0, secbuf, 0, true); break;
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}
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}
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//we dont want to keep churning through this many big byte arrays while reading stuff, so we save a sector cache.
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readonly byte[] Read_SectorBuf = new byte[2352];
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int Read_LastIndex = 0;
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public int Read(long byte_pos, byte[] buffer, int offset, int _count)
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{
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long remain = _count;
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int completed = 0;
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//we take advantage of the fact that we pretty much always read one sector at a time.
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//this would be really inefficient if we only read one byte at a time.
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//on the other hand, just in case, we could keep a cache of the most recently decoded sector. that would be easy and would solve that problem (if we had it)
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while (remain > 0)
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{
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int listIndex = FindInIndex(byte_pos, Read_LastIndex);
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IndexEntry ie = Index[listIndex];
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Read_LastIndex = listIndex;
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if (ie.Type == 0)
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{
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//type 0 is special: its just a raw blob. so all we need to do is read straight out of the stream
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long blockOffset = byte_pos - ie.LogicalOffset;
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long bytesRemainInBlock = ie.Number - blockOffset;
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long todo = remain;
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if (bytesRemainInBlock < todo)
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todo = bytesRemainInBlock;
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stream.Position = ie.ECMOffset + blockOffset;
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while (todo > 0)
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{
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int toRead;
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if (todo > int.MaxValue)
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toRead = int.MaxValue;
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else toRead = (int)todo;
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int done = stream.Read(buffer, offset, toRead);
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if (done != toRead)
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return completed;
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completed += done;
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remain -= done;
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todo -= done;
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offset += done;
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byte_pos += done;
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}
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//done reading the raw block; go back to check for another block
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continue;
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} //if(type 0)
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else
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{
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//these are sector-based types. they have similar handling.
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long blockOffset = byte_pos - ie.LogicalOffset;
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//figure out which sector within the block we're in
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int outSecSize;
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int inSecSize;
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int outSecOffset;
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if (ie.Type == 1) { outSecSize = 2352; inSecSize = 2048; outSecOffset = 0; }
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else if (ie.Type == 2) { outSecSize = 2336; inSecSize = 2052; outSecOffset = 16; }
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else if (ie.Type == 3) { outSecSize = 2336; inSecSize = 2328; outSecOffset = 16; }
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else throw new InvalidOperationException();
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long secNumberInBlock = blockOffset / outSecSize;
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long secOffsetInEcm = secNumberInBlock * outSecSize;
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long bytesAskedIntoSector = blockOffset % outSecSize;
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long bytesRemainInSector = outSecSize - bytesAskedIntoSector;
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long todo = remain;
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if (bytesRemainInSector < todo)
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todo = bytesRemainInSector;
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//move stream to beginning of this sector in ecm
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stream.Position = ie.ECMOffset + inSecSize * secNumberInBlock;
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//read and decode the sector
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switch (ie.Type)
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{
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case 1:
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//TODO - read first 3 bytes
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if (stream.Read(Read_SectorBuf, 16, 2048) != 2048)
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return completed;
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Reconstruct(Read_SectorBuf, 1);
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break;
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case 2:
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if (stream.Read(Read_SectorBuf, 20, 2052) != 2052)
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return completed;
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Reconstruct(Read_SectorBuf, 2);
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break;
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case 3:
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if (stream.Read(Read_SectorBuf, 20, 2328) != 2328)
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return completed;
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Reconstruct(Read_SectorBuf, 3);
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break;
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}
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//sector is decoded to 2352 bytes. Handling doesnt depend much on type from here
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Array.Copy(Read_SectorBuf, (int)bytesAskedIntoSector + outSecOffset, buffer, offset, todo);
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int done = (int)todo;
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offset += done;
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completed += done;
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remain -= done;
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byte_pos += done;
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} //not type 0
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} // while(Remain)
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return completed;
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}
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}
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}
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}
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//-------------------------------------------------------------------------------------------
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//The ecm file begins with 4 bytes: ECM\0
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//then, repeat forever processing these blocks:
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// Read the block header bytes. The block header is terminated after processing a byte without 0x80 set.
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// The block header contains these bits packed in the bottom 7 LSB of successive bytes:
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// xNNNNNNN NNNNNNNN NNNNNNNN NNNNNNNN TTT
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// N: a Number
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// T: the type of the sector
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// If you encounter a Number of 0xFFFFFFFF then the blocks section is finished.
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// If you need a 6th byte for the block header, then the block header is erroneous
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// Increment Number, since storing 0 wouldve been useless.
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// Now, process the block.
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// Type 0:
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// Read Number bytes from the ECM file and write to the output stream.
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// This block isn't necessarily a multiple of any particular sector size.
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// accumulate all those bytes through the EDC
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// Type 1: For Number of sectors:
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// Read sector bytes 12,13,14
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// Read 2048 sector bytes @16
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// Reconstruct sector as type 1
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// accumulate 2352 sector bytes @0 through the EDC
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// write 2352 sector byte @0 to the output stream
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// Type 2: For Number of sectors:
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// Read 2052 sector bytes @20
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// Reconstruct sector as type 2
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// accumulate 2336 sector bytes @16 through the EDC
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// write 2336 sector bytes @16 to the output stream
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// Type 3: For Number of sectors:
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// Read 2328 sector bytes @20
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// Reconstruct sector as type 3
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// accumulate 2336 sector bytes @16 through the EDC
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// write 2336 sector bytes @16 to the output stream
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//After encountering our end marker and exiting the block processing section:
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//read a 32bit little endian value, which should be the output of the EDC (just a little check to make sure the file is valid)
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//That's the end of the file
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