MSXMapperIO.cc

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#include "MSXMapperIO.hh"
#include "MSXMotherBoard.hh"
#include "HardwareConfig.hh"
#include "XMLElement.hh"
#include "MSXException.hh"
#include "StringOp.hh"
#include "enumerate.hh"
#include "outer.hh"
#include "serialize.hh"
#include "stl.hh"
#include <algorithm>
 
namespace openmsx {
 
[[nodiscard]] static byte calcReadBackMask(MSXMotherBoard& motherBoard)
{
        std::string_view type = motherBoard.getMachineConfig()->getConfig().getChildData(
                                       "MapperReadBackBits", "largest");
        if (type == "largest") {
                return 0xff; // all bits can be read
        }
        auto bits = StringOp::stringTo<int>(type);
        if (!bits) {
                throw FatalError("Unknown mapper type: \"", type, "\".");
        }
        if (*bits < 0 || *bits > 8) {
                throw FatalError("MapperReadBackBits out of range: \"", type, "\".");
        }
        return byte(~(unsigned(-1) << *bits));
}
 
MSXMapperIO::MSXMapperIO(const DeviceConfig& config)
        : MSXDevice(config)
        , debuggable(getMotherBoard(), getName())
        , mask(calcReadBackMask(getMotherBoard()))
{
        reset(EmuTime::dummy());
}
 
void MSXMapperIO::setMode(Mode mode_, byte mask_, byte baseValue_)
{
        mode = mode_;
        mask = mask_;
        baseValue = baseValue_;
}
 
void MSXMapperIO::registerMapper(MSXMemoryMapperInterface* mapper)
{
        mappers.push_back(mapper);
}
 
void MSXMapperIO::unregisterMapper(MSXMemoryMapperInterface* mapper)
{
        mappers.erase(rfind_unguarded(mappers, mapper));
}
 
byte MSXMapperIO::readIO(word port, EmuTime::param time)
{
        byte value = [&] {
                if (mode == Mode::EXTERNAL) {
                        byte result = 0xFF;
                        for (auto* mapper : mappers) {
                                result &= mapper->readIO(port, time);
                        }
                        return result;
                } else {
                        return registers[port & 3];
                }
        }();
        return (value & mask) | (baseValue & ~mask);
}
 
byte MSXMapperIO::peekIO(word port, EmuTime::param time) const
{
        byte value = [&] {
                if (mode == Mode::EXTERNAL) {
                        byte result = 0xFF;
                        for (auto* mapper : mappers) {
                                result &= mapper->peekIO(port, time);
                        }
                        return result;
                } else {
                        return registers[port & 3];
                }
        }();
        return (value & mask) | (baseValue & ~mask);
}
 
void MSXMapperIO::writeIO(word port, byte value, EmuTime::param time)
{
        registers[port & 3] = value;
 
        // Note: the mappers are responsible for invalidating/filling the CPU
        // cache-lines.
        for (auto* mapper : mappers) {
                mapper->writeIO(port, value, time);
        }
}
 
 
// SimpleDebuggable
// This debuggable is here for backwards compatibility. For more accurate
// results, use the debuggable belonging to a specific mapper.
 
MSXMapperIO::Debuggable::Debuggable(MSXMotherBoard& motherBoard_,
                                    const std::string& name_)
        : SimpleDebuggable(motherBoard_, name_, "Memory mapper registers", 4)
{
}
 
byte MSXMapperIO::Debuggable::read(unsigned address)
{
        // return the last written value, with full 8-bit precision.
        auto& mapperIO = OUTER(MSXMapperIO, debuggable);
        return mapperIO.registers[address & 3];
}
 
void MSXMapperIO::Debuggable::write(unsigned address, byte value,
                                    EmuTime::param time)
{
        auto& mapperIO = OUTER(MSXMapperIO, debuggable);
        mapperIO.writeIO(narrow_cast<word>(address), value, time);
}
 
 
template<typename Archive>
void MSXMapperIO::serialize(Archive& ar, unsigned version)
{
        if (ar.versionBelow(version, 2)) {
                // In version 1 we stored the mapper state in MSXMapperIO instead of
                // in the individual mappers, so distribute the state to them.
                assert(Archive::IS_LOADER);
                ar.serialize("registers", registers);
                for (auto [page, reg] : enumerate(registers)) {
                        writeIO(word(page), reg, EmuTime::dummy());
                }
        }
        if (ar.versionAtLeast(version, 3)) {
                // In version 3 we store the mapper state BOTH here and in the
                // individual mappers. The reason for this is:
                // - There are MSX machines with a S1985 but without a memory
                //   mapper. To support those we need to store the state here.
                // - In rare cases (e.g. musical memory mapper) the mapper state
                //   can be different for specific mappers.
                ar.serialize("registers", registers);
        }
}
INSTANTIATE_SERIALIZE_METHODS(MSXMapperIO);
 
} // namespace openmsx