117 lines
4.0 KiB
C#
117 lines
4.0 KiB
C#
//-------------------
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//WARNING GPL CODE
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//-------------------
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//
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//this is stolen somewhat from neill corlett's code. almost certainly some kind of GPL. originally it came from mednafen, and then I think mednafen may have changed to use another. sorry for the confusion!
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//
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//it's kept in this project so that we can readily a/b test it against new algorithms
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#if false
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using System.Diagnostics;
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namespace BizHawk.DiscSystem
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{
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public static class GPL_ECM
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{
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static byte[] ecc_f_lut = new byte[256];
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static byte[] ecc_b_lut = new byte[256];
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static uint[] edc_lut = new uint[256];
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static GPL_ECM()
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{
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uint i, j, edc;
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for (i = 0; i < 256; i++)
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{
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j = (uint)((i << 1) ^ (((i & 0x80) != 0) ? 0x11D : 0));
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ecc_f_lut[i] = (byte)j;
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ecc_b_lut[i ^ j] = (byte)i;
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edc = i;
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for (j = 0; j < 8; j++)
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edc = (edc >> 1) ^ (((edc & 1) != 0) ? 0xD8018001 : 0);
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edc_lut[i] = edc;
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}
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}
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public static uint edc_partial_computeblock(uint edc, byte[] src, int count)
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{
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int i = 0;
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while (count-- != 0) edc = (edc >> 8) ^ edc_lut[(edc ^ (src[i++])) & 0xFF];
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return edc;
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}
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public static void edc_computeblock(byte[] src, int count, byte[] dest, int dest_offset)
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{
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uint edc = edc_partial_computeblock(0, src, count);
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dest[dest_offset + 0] = (byte)((edc >> 0) & 0xFF);
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dest[dest_offset + 1] = (byte)((edc >> 8) & 0xFF);
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dest[dest_offset + 2] = (byte)((edc >> 16) & 0xFF);
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dest[dest_offset + 3] = (byte)((edc >> 24) & 0xFF);
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}
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public static void edc_validateblock(byte[] src, int count, byte[] dest, int dest_offset)
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{
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uint edc = edc_partial_computeblock(0, src, count);
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Debug.Assert(dest[dest_offset + 0] == (byte)((edc >> 0) & 0xFF));
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Debug.Assert(dest[dest_offset + 1] == (byte)((edc >> 8) & 0xFF));
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Debug.Assert(dest[dest_offset + 2] == (byte)((edc >> 16) & 0xFF));
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Debug.Assert(dest[dest_offset + 3] == (byte)((edc >> 24) & 0xFF));
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}
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public static void ecc_validateblock(byte[] src, int src_offset, uint major_count, uint minor_count, uint major_mult, uint minor_inc, byte[] dest, int dest_offset)
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{
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uint size = major_count * minor_count;
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uint major, minor;
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for (major = 0; major < major_count; major++)
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{
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uint index = (major >> 1) * major_mult + (major & 1);
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byte ecc_a = 0;
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byte ecc_b = 0;
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for (minor = 0; minor < minor_count; minor++)
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{
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byte temp = src[src_offset + index];
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if ((major >> 1) * major_mult + (major & 1) == 12 && minor_inc == 86)
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System.Console.WriteLine(temp);
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index += minor_inc;
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if (index >= size) index -= size;
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ecc_a ^= temp;
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ecc_b ^= temp;
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ecc_a = ecc_f_lut[ecc_a];
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}
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ecc_a = ecc_b_lut[ecc_f_lut[ecc_a] ^ ecc_b];
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Debug.Assert(dest[dest_offset + major] == ecc_a);
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Debug.Assert(dest[dest_offset + major + major_count] == (byte)(ecc_a ^ ecc_b));
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}
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}
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public unsafe static void ecc_validate(byte[] sector, int sector_offset, bool zeroaddress)
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{
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byte[] dest = sector;
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int dest_offset = sector_offset+2076;
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byte address0 = 0, address1 = 0, address2 = 0, address3 = 0;
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//byte i;
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/* Save the address and zero it out */
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if (zeroaddress)
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{
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address0 = sector[sector_offset + 12 + 0]; sector[sector_offset + 12 + 0] = 0;
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address1 = sector[sector_offset + 12 + 1]; sector[sector_offset + 12 + 1] = 0;
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address2 = sector[sector_offset + 12 + 2]; sector[sector_offset + 12 + 2] = 0;
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address3 = sector[sector_offset + 12 + 3]; sector[sector_offset + 12 + 3] = 0;
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}
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/* Compute ECC P code */
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ecc_validateblock(sector, sector_offset + 0xC, 86, 24, 2, 86, dest, dest_offset);
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/* Compute ECC Q code */
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ecc_validateblock(sector, sector_offset + 0xC, 52, 43, 86, 88, dest, dest_offset + 172);
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/* Restore the address */
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if (zeroaddress)
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{
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sector[sector_offset + 12 + 0] = address0;
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sector[sector_offset + 12 + 3] = address1;
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sector[sector_offset + 12 + 2] = address2;
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sector[sector_offset + 12 + 1] = address3;
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}
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}
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}
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}
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#endif
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