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add special crc combiner for redump stuff

This commit is contained in:
zeromus 2015-07-11 09:43:38 -05:00
parent 91eecdca52
commit 95deb6f3f9
1 changed files with 147 additions and 50 deletions
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197
BizHawk.Emulation.DiscSystem/DiscHasher.cs
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@ -13,55 +13,6 @@ namespace BizHawk.Emulation.DiscSystem
Disc disc;
class SpecialCRC32
{
private static readonly uint[] CRC32Table;
static SpecialCRC32()
{
CRC32Table = new uint[256];
for (uint i = 0; i < 256; ++i)
{
uint crc = i;
for (int j = 8; j > 0; --j)
{
if ((crc & 1) == 1)
crc = ((crc >> 1) ^ 0xEDB88320);
else
crc >>= 1;
}
CRC32Table[i] = crc;
}
}
uint current = 0xFFFFFFFF;
public unsafe void Add(byte[] data, int offset, int size)
{
if (offset + size > data.Length)
throw new ArgumentOutOfRangeException();
if(offset<0)
throw new ArgumentOutOfRangeException();
fixed(byte* pData = data)
for (int i = 0; i < size; i++)
{
byte b = pData[offset + i];
current = CRC32Table[(current ^ b) & 0xFF] ^ (current>>8);
}
}
byte[] smallbuf = new byte[8];
public void Add(int data)
{
smallbuf[0] = (byte)((data) & 0xFF);
smallbuf[1] = (byte)((data >> 8) & 0xFF);
smallbuf[2] = (byte)((data >> 16) & 0xFF);
smallbuf[3] = (byte)((data >> 24) & 0xFF);
Add(smallbuf, 0, 4);
}
public uint Result { get { return current ^ 0xFFFFFFFF; } }
}
/// <summary>
/// calculates the hash for quick PSX Disc identification
/// </summary>
@ -73,7 +24,7 @@ namespace BizHawk.Emulation.DiscSystem
//the TOC isn't needed!
//but it will help detect dumps with mangled TOCs which are all too common
//
//a special CRC32 is used to help us match redump's DB elsewhere
//a possibly special CRC32 is used to help us match redump's DB elsewhere
SpecialCRC32 crc = new SpecialCRC32();
byte[] buffer2352 = new byte[2352];
@ -144,5 +95,151 @@ namespace BizHawk.Emulation.DiscSystem
}
return "no data track found";
}
/// <summary>
/// A stateful special CRC32 calculator
/// This may be absolutely standard and not special at all. I don't know, there were some differences between it and other CRC code I found in bizhawk
/// </summary>
public class SpecialCRC32
{
private static readonly uint[] CRC32Table;
static SpecialCRC32()
{
CRC32Table = new uint[256];
for (uint i = 0; i < 256; ++i)
{
uint crc = i;
for (int j = 8; j > 0; --j)
{
if ((crc & 1) == 1)
crc = ((crc >> 1) ^ 0xEDB88320);
else
crc >>= 1;
}
CRC32Table[i] = crc;
}
}
uint current = 0xFFFFFFFF;
public unsafe void Add(byte[] data, int offset, int size)
{
if (offset + size > data.Length)
throw new ArgumentOutOfRangeException();
if (offset < 0)
throw new ArgumentOutOfRangeException();
fixed (byte* pData = data)
for (int i = 0; i < size; i++)
{
byte b = pData[offset + i];
current = CRC32Table[(current ^ b) & 0xFF] ^ (current >> 8);
}
}
byte[] smallbuf = new byte[8];
public void Add(int data)
{
smallbuf[0] = (byte)((data) & 0xFF);
smallbuf[1] = (byte)((data >> 8) & 0xFF);
smallbuf[2] = (byte)((data >> 16) & 0xFF);
smallbuf[3] = (byte)((data >> 24) & 0xFF);
Add(smallbuf, 0, 4);
}
/// <summary>
/// The negated output (the typical result of the CRC calculation)
/// </summary>
public uint Result { get { return current ^ 0xFFFFFFFF; } }
/// <summary>
/// The raw non-negated output
/// </summary>
public uint Current { get { return current; } set { current = value; } }
uint gf2_matrix_times(uint[] mat, uint vec)
{
int matIdx = 0;
uint sum = 0;
while (vec != 0)
{
if ((vec & 1) != 0)
sum ^= mat[matIdx];
vec >>= 1;
matIdx++;
}
return sum;
}
void gf2_matrix_square(uint[] square, uint[] mat)
{
int n;
for (n = 0; n < 32; n++)
square[n] = gf2_matrix_times(mat, mat[n]);
}
/// <summary>
/// Incorporates a pre-calculated CRC with the given length by combining crcs
/// It's a bit flaky, so be careful, but it works
/// </summary>
public void Incorporate(uint crc, int len)
{
current = crc32_combine(current, crc, len);
}
//tables used by crc32_combine
uint[] even, odd;
//algorithm from zlib's crc32_combine. read http://www.leapsecond.com/tools/crcomb.c for more
uint crc32_combine(uint crc1, uint crc2, int len2)
{
if (even == null) even = new uint[32]; // even-power-of-two zeros operator
if (odd == null) odd = new uint[32]; // odd-power-of-two zeros operator
// degenerate case
if (len2 == 0)
return crc1;
// put operator for one zero bit in odd
odd[0] = 0xedb88320; //CRC-32 polynomial
uint row = 1;
for (int n = 1; n < 32; n++)
{
odd[n] = row;
row <<= 1;
}
//put operator for two zero bits in even
gf2_matrix_square(even, odd);
//put operator for four zero bits in odd
gf2_matrix_square(odd, even);
//apply len2 zeros to crc1 (first square will put the operator for one zero byte, eight zero bits, in even)
do
{
//apply zeros operator for this bit of len2
gf2_matrix_square(even, odd);
if ((len2 & 1) != 0)
crc1 = gf2_matrix_times(even, crc1);
len2 >>= 1;
//if no more bits set, then done
if (len2 == 0)
break;
//another iteration of the loop with odd and even swapped
gf2_matrix_square(odd, even);
if ((len2 & 1) != 0)
crc1 = gf2_matrix_times(odd, crc1);
len2 >>= 1;
//if no more bits set, then done
} while (len2 != 0);
//return combined crc
crc1 ^= crc2;
return crc1;
}
}
}
}