protected override bool readIsVanilla(EndianBinaryReader stream, AddressMapper addressMapper)
{
stream.Seek(addressMapper.toFileAddress((BSVAddr)0x8021214c), SeekOrigin.Begin);
var opcode = stream.ReadUInt32();
// subi r3,r3,0x15
return(opcode == PowerPcAsm.subi(3, 3, 0x15));
}
/// <summary>
/// Write the subroutine which takes a compressed venture card table as input and writes it into ventureCardDecompressedTableAddr
/// </summary>
/// <param name="ventureCardDecompressedTableAddr">The address for the reserved memory space to store the decompressed venture card table in</param>
private List <UInt32> writeSubroutine(VAVAddr ventureCardDecompressedTableAddr)
{
var asm = new List <UInt32>();
PowerPcAsm.Pair16Bit ventureCardTableAddrPair = PowerPcAsm.make16bitValuePair((UInt32)ventureCardDecompressedTableAddr);
///
/// assume:
/// r6 = ventureCardCompressedTableAddr
///
/// variables:
/// r4 = ventureCardId
/// r5 = ventureCardCompressedTableAddr
/// r6 = ventureCardDecompressedTableAddr
/// r7 = ventureCardCompressedWord
/// r8 = bitIndex
/// r0 = tmp / currentByte
///
/// return:
/// r6 = ventureCardDecompressedTableAddr
///
asm.Add(PowerPcAsm.li(4, 0)); // ventureCardId = 0
asm.Add(PowerPcAsm.mr(5, 6)); // r6 is ventureCardCompressedTableAddr at this point. Copy it to r5 with which we will be working
asm.Add(PowerPcAsm.lis(6, ventureCardTableAddrPair.upper16Bit)); // \ load the ventureCardDecompressedTableAddr into r6. This address is
asm.Add(PowerPcAsm.addi(6, 6, ventureCardTableAddrPair.lower16Bit)); // / where we will store the decompressed venture card table.
int whileVentureCardIdSmaller128 = asm.Count; // do {
{ //
asm.Add(PowerPcAsm.li(0, 0)); // \ load the next compressed word from ventureCardCompressedTableAddr
asm.Add(PowerPcAsm.lwzx(7, 5, 0)); // / into r7. We will decompress the venture card table word by word.
asm.Add(PowerPcAsm.li(8, 31)); // bitIndex = 31
int whileBitIndexGreaterEqual32 = asm.Count; // do
{ // {
asm.Add(PowerPcAsm.mr(0, 7)); // get the current compressed word
asm.Add(PowerPcAsm.srw(0, 0, 8)); // shift it bitIndex times to the right
asm.Add(PowerPcAsm.andi(0, 0, 1)); // retrieve the lowest bit of it -> r0 contains the decompressed venture card byte now.
asm.Add(PowerPcAsm.stbx(0, 4, 6)); // store it into ventureCardDecompressedTableAddr[ventureCardId]
asm.Add(PowerPcAsm.subi(8, 8, 1)); // bitIndex--
asm.Add(PowerPcAsm.addi(4, 4, 1)); // ventureCardId++
asm.Add(PowerPcAsm.cmpwi(8, 0)); //
asm.Add(PowerPcAsm.bge(asm.Count, whileBitIndexGreaterEqual32)); // } while(bitIndex >= 0)
} //
asm.Add(PowerPcAsm.addi(5, 5, 4)); // ventureCardCompressedTableAddr += 4
asm.Add(PowerPcAsm.cmpwi(4, 128)); //
asm.Add(PowerPcAsm.blt(asm.Count, whileVentureCardIdSmaller128)); // } while(ventureCardId < 128)
} //
asm.Add(PowerPcAsm.li(4, 0)); // \ reset r4 = 0
asm.Add(PowerPcAsm.li(5, 0)); // / reset r5 = 0
asm.Add(PowerPcAsm.blr()); // return
return(asm);
}
