* Major rewrite

src/Athena/MCFileWriter.cpp

@@ -0,0 +1,99 @@
+// This file is part of libAthena.
+//
+// libAthena is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// libAthena is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with libAthena.  If not, see <http://www.gnu.org/licenses/>
+
+#include "Athena/MCFileWriter.hpp"
+
+namespace Athena
+{
+namespace io
+{
+
+MCFileWriter::MCFileWriter(Uint8* data, Uint64 length)
+    : base(data, length)
+{
+}
+
+MCFileWriter::MCFileWriter(const std::string& filename)
+    : base(filename)
+{
+}
+
+// TODO: Check the implementation, it seems to work fine, however it's not exactly correct,
+// looking at the disassembly, MC seems to do some weird checking that isn't being done with this solution
+// need to figure out what it's doing and whether it's relevant to the checksum.
+Uint16 MCFileWriter::calculateSlotChecksum(Uint32 game)
+{
+    Uint16 first = calculateChecksum((m_data + 0x34 + (0x10 * game)), 4);
+    Uint16 second = calculateChecksum((m_data + 0x80 + (0x500 * game)), 0x500);
+
+    first = (first + second) & 0xFFFF;
+    Uint16 result = first << 16;
+    second = ~first&0xFFFF;
+    second += 1;
+    result += second;
+
+    return result;
+}
+
+Uint16 MCFileWriter::calculateChecksum(Uint8 *data, Uint32 length)
+{
+    Uint16 sum = 0;
+    int i = length;
+
+    for (Uint32 j = 0; j < length; j += 2)
+    {
+        sum += *(Uint16*)(data + j) ^ i;
+        i -= 2;
+    }
+
+    sum &= 0xFFFF;
+
+    return sum;
+}
+
+// TODO: Rewrite this to be more optimized, the current solution takes quite a few cycles
+Uint8* MCFileWriter::reverse(Uint8* data, Uint32 length)
+{
+    Uint32 a = 0;
+    Uint32 swap;
+
+    for (;a<--length; a++)
+    {
+        swap = data[a];
+        data[a] = data[length];
+        data[length] = swap;
+    }
+
+    return data;
+}
+
+
+// TODO: Rewrite this to be more optimized, unroll more??
+void MCFileWriter::unscramble()
+{
+    if (!m_data)
+        return;
+
+    for (Uint32 i = 0; i < m_length; i += 4)
+    {
+        Uint32 block1 = *(Uint32*)reverse((m_data + i), 4);
+        Uint32 block2 = *(Uint32*)reverse((m_data + i + 4), 4);
+        *(Uint32*)(m_data + i) = block2;
+        *(Uint32*)(m_data + i + 4) = block1;
+    }
+}
+
+} // io
+} // zelda