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Sever the MemoryMap into a concrete portion.

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Thomas Harte committed 2026-04-26 10:13:26 -04:00
1 parent 82e66e7a1b
commit a31aa720c0
1 file changed
+94 -81
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Machines/Thomson/MO/MemoryMap.hpp
+94 -81
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@@ -30,19 +30,92 @@ enum class GraphicsModeAccess {
Inhibited = 1,
};
//
// Notes on the layout of the standard MO ROM images:
//
// The MO5 images are 16kb in total, representing what should go into the
// final 16kb of the memory map.
//
// The MO6 images are 64kb in total:
//
// * the first 32kb is the BASIC 1 portion: two 16kb pages that might appear from 0xc000, including the monitor;
// * the next 32kb is the BASIC 128 portion: two 16kb pages that might appear from 0xb000 or might not appear at all.
struct MemoryAccess {
template <typename AddressT>
uint8_t read(const AddressT address) const {
if(read_[address >> 12]) [[likely]] {
return read_[address >> 12][address];
} else {
return 0xff;
}
}
template <typename AddressT>
void write(const AddressT address, const uint8_t value) {
if(write_[address >> 12]) {
write_[address >> 12][address] = value;
} else {
Log::Logger<Log::Source::MO5>::info().append("Unmapped write of %02x to %04x", value, +address);
}
}
// Defined to work correctly only for in-RAM addresses.
uint8_t &operator[] (const size_t index) {
return write_[index >> 12][index];
}
// Works correctly across the board, but is read-only.
struct ConstIterator {
using self_type = ConstIterator;
using iterator_category = std::forward_iterator_tag;
using difference_type = std::ptrdiff_t;
using value_type = uint8_t;
using pointer = uint8_t *;
using reference = uint8_t &;
uint8_t operator *() {
return underlying_.read(uint16_t(address_));
}
ConstIterator operator++(int) {
ConstIterator prior = *this;
++address_;
return prior;
}
ConstIterator &operator++() {
++address_;
return *this;
}
auto operator <=>(const ConstIterator &rhs) const {
return address_ <=> rhs.address_;
}
private:
ConstIterator(const MemoryAccess &underlying, int address) : underlying_(underlying), address_(address) {}
const MemoryAccess &underlying_;
int address_;
friend MemoryAccess;
};
ConstIterator begin() const {
return ConstIterator(*this, 0);
}
ConstIterator end() const {
return ConstIterator(*this, 0x1'0000);
}
ConstIterator iterator(const uint16_t address) const {
return ConstIterator(*this, address);
}
protected:
void set_read(const size_t slot, const uint8_t *const pointer) {
read_[slot] = pointer ? pointer - (slot << 12) : nullptr;
write_[slot] = nullptr;
}
void set_readwrite(const size_t slot, uint8_t *const pointer) {
read_[slot] = write_[slot] = pointer ? pointer - (slot << 12) : nullptr;
}
uint8_t *write_[0x10]{};
const uint8_t *read_[0x10]{};
};
template <bool is_mo6>
struct MemoryMap {
struct MemoryMap: public MemoryAccess {
public:
MemoryMap() {
// Install RAM.
@@ -62,6 +135,14 @@ public:
// MARK: - ROM installation and connection for video.
void set_rom(const std::vector<uint8_t> &rom) {
//
// MO5 ROM images are 16kb in total, representing what should go into the final 16kb of the memory map.
//
// MO6 ROM images are 64kb in total:
//
// * the first 32kb is BASIC 1: two 16kb pages that might appear from 0xc000, including the monitor;
// * the next 32kb is BASIC 128: two 16kb pages that might appear from 0xb000 or might not appear at all.
//
rom_ = rom;
update_commutable_rom();
}
@@ -107,7 +188,7 @@ public:
return rom_page_;
}
// MARK: - Memory Access.
// MARK: - Read override.
template <typename AddressT>
uint8_t read(const AddressT address) {
@@ -129,64 +210,7 @@ public:
}
}
template <typename AddressT>
void write(const AddressT address, const uint8_t value) {
if(write_[address >> 12]) {
write_[address >> 12][address] = value;
} else {
Log::Logger<Log::Source::MO5>::info().append("Unmapped write of %02x to %04x", value, +address);
}
}
// Defined to work correctly only for in-RAM addresses.
uint8_t &operator[] (const size_t index) {
return write_[index >> 12][index];
}
// Works correctly across the board, but is read-only.
struct ConstIterator {
using self_type = ConstIterator;
using iterator_category = std::forward_iterator_tag;
using difference_type = std::ptrdiff_t;
using value_type = uint8_t;
using pointer = uint8_t *;
using reference = uint8_t &;
uint8_t operator *() {
return map_.passive_read(uint16_t(address_));
}
ConstIterator &operator++(int) {
ConstIterator prior = *this;
++address_;
return prior;
}
ConstIterator &operator++() {
++address_;
return *this;
}
auto operator <=>(const ConstIterator &) const = default;
private:
ConstIterator(const MemoryMap &map, int address) : map_(map), address_(address) {}
const MemoryMap &map_;
int address_;
friend MemoryMap;
};
ConstIterator begin() const {
return ConstIterator(*this, 0);
}
ConstIterator end() const {
return ConstIterator(*this, 0x1'0000);
}
ConstIterator iterator(const uint16_t address) const {
return ConstIterator(*this, address);
}
using MemoryAccess::write;
// MARK: - Register Access.
@@ -301,9 +325,6 @@ public:
}
private:
uint8_t *write_[0x10]{};
const uint8_t *read_[0x10]{};
void update_commutable_ram() {
const auto offset = ram_page_ * 16384;
if(offset < ram_.size()) {
@@ -348,14 +369,6 @@ private:
}
}
void set_read(const size_t slot, const uint8_t *const pointer) {
read_[slot] = pointer ? pointer - (slot << 12) : nullptr;
write_[slot] = nullptr;
}
void set_readwrite(const size_t slot, uint8_t *const pointer) {
read_[slot] = write_[slot] = pointer ? pointer - (slot << 12) : nullptr;
}
std::array<uint8_t, 0x4000> video_;
std::array<uint8_t, (is_mo6 ? (128 * 1024) : (32 * 1024))> ram_;
std::array<uint8_t, 0x7c0> floppy_rom_;