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