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489 lines
14 KiB
C++
489 lines
14 KiB
C++
//
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//
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// Storage.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 12/02/2023.
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// Copyright © 2023 Thomas Harte. All rights reserved.
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//
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#ifndef Storage_h
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#define Storage_h
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#include "LineBuffer.hpp"
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#include "YamahaCommands.hpp"
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#include <optional>
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namespace TI {
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namespace TMS {
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/// A container for personality-specific storage; see specific instances below.
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template <Personality personality, typename Enable = void> struct Storage {
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};
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template <> struct Storage<Personality::TMS9918A> {
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using AddressT = uint16_t;
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void begin_line(ScreenMode, bool) {}
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};
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// Yamaha-specific storage.
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template <Personality personality> struct Storage<personality, std::enable_if_t<is_yamaha_vdp(personality)>> {
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using AddressT = uint32_t;
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int selected_status_ = 0;
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int indirect_register_ = 0;
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bool increment_indirect_register_ = false;
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std::array<uint32_t, 16> palette_{};
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uint8_t new_colour_ = 0;
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uint8_t palette_entry_ = 0;
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bool palette_write_phase_ = false;
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uint8_t mode_ = 0;
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uint8_t vertical_offset_ = 0;
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/// Describes an _observable_ memory access event. i.e. anything that it is safe
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/// (and convenient) to treat as atomic in between external slots.
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struct Event {
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/// Offset of the _beginning_ of the event. Not completely arbitrarily: this is when
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/// external data must be ready by in order to take part in those slots.
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uint16_t offset = 1368;
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enum class Type: uint8_t {
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/// A slot for reading or writing data on behalf of the CPU or the command engine.
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External,
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//
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// Bitmap modes.
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//
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DataBlock,
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//
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// Sprites.
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//
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SpriteY,
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SpriteLocation,
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SpritePattern,
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//
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// Text and character modes.
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//
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Name,
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Colour,
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Pattern,
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} type = Type::External;
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uint8_t id = 0;
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constexpr Event(Type type, uint8_t id = 0) noexcept :
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type(type),
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id(id) {}
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constexpr Event() noexcept {}
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};
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// State that tracks fetching position within a line.
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const Event *next_event_ = nullptr;
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int data_block_ = 0;
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int sprite_block_ = 0;
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// Text blink colours.
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uint8_t blink_text_colour_ = 0;
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uint8_t blink_background_colour_ = 0;
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// Blink state (which is also affects even/odd page display in applicable modes).
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int in_blink_ = 1;
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uint8_t blink_periods_ = 0;
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uint8_t blink_counter_ = 0;
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// Sprite collection state.
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bool sprites_enabled_ = true;
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/// Resets line-ephemeral state for a new line.
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void begin_line(ScreenMode mode, bool is_refresh) {
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// TODO: reinstate upon completion of the Yamaha pipeline.
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// assert(mode < ScreenMode::YamahaText80 || next_event_ == nullptr || next_event_->offset == 1368);
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data_block_ = 0;
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sprite_block_ = 0;
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if(is_refresh) {
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next_event_ = refresh_events.data();
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return;
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}
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switch(mode) {
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case ScreenMode::YamahaText80:
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case ScreenMode::Text:
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next_event_ = text_events.data();
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break;
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case ScreenMode::MultiColour:
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case ScreenMode::YamahaGraphics1:
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case ScreenMode::YamahaGraphics2:
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next_event_ = character_events.data();
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break;
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default:
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next_event_ = sprites_enabled_ ? sprites_events.data() : no_sprites_events.data();
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break;
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}
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}
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// Command engine state.
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CommandContext command_context_;
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std::unique_ptr<Command> command_ = nullptr;
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enum class CommandStep {
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None,
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ReadSourcePixel,
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ReadDestinationPixel,
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WritePixel,
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ReadSourceByte,
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WriteByte,
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};
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CommandStep next_command_step_ = CommandStep::None;
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int minimum_command_column_ = 0;
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uint8_t command_latch_ = 0;
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void update_command_step(int current_column) {
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if(!command_) {
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next_command_step_ = CommandStep::None;
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return;
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}
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if(command_->done()) {
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command_ = nullptr;
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next_command_step_ = CommandStep::None;
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return;
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}
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minimum_command_column_ = current_column + command_->cycles;
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switch(command_->access) {
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case Command::AccessType::CopyPoint:
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next_command_step_ = CommandStep::ReadSourcePixel;
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break;
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case Command::AccessType::PlotPoint:
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next_command_step_ = CommandStep::ReadDestinationPixel;
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break;
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case Command::AccessType::WaitForColourReceipt:
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// i.e. nothing to do until a colour is received.
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next_command_step_ = CommandStep::None;
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break;
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case Command::AccessType::CopyByte:
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next_command_step_ = CommandStep::ReadSourceByte;
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break;
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case Command::AccessType::WriteByte:
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next_command_step_ = CommandStep::WriteByte;
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break;
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}
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}
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Storage() noexcept {
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// Perform sanity checks on the event lists.
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#ifndef NDEBUG
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const Event *lists[] = { no_sprites_events.data(), sprites_events.data(), text_events.data(), character_events.data(), refresh_events.data(), nullptr };
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const Event **list = lists;
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while(*list) {
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const Event *cursor = *list;
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++list;
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while(cursor[1].offset != 1368) {
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assert(cursor[1].offset > cursor[0].offset);
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++cursor;
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}
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}
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#endif
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// Seed to _something_ meaningful.
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//
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// TODO: this is a workaround [/hack], in effect, for the main TMS' habit of starting
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// in a randomised position, which means that start-of-line isn't announced.
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//
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// Do I really want that behaviour?
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next_event_ = refresh_events.data();
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}
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private:
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// This emulator treats position 0 as being immediately after the standard pixel area.
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// i.e. offset 1282 on Grauw's http://map.grauw.nl/articles/vdp-vram-timing/vdp-timing.png
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static constexpr int ZeroAsGrauwIndex = 1282;
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constexpr static int grauw_to_internal(int offset) {
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return (offset + 1368 - ZeroAsGrauwIndex) % 1368;
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}
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constexpr static int internal_to_grauw(int offset) {
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return (offset + ZeroAsGrauwIndex) % 1368;
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}
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template <typename GeneratorT> static constexpr size_t events_size() {
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size_t size = 0;
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for(int c = 0; c < 1368; c++) {
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const auto event_type = GeneratorT::event(internal_to_grauw(c));
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size += event_type.has_value();
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}
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return size + 1;
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}
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template <typename GeneratorT, size_t size = events_size<GeneratorT>()>
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static constexpr std::array<Event, size> events() {
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std::array<Event, size> result{};
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size_t index = 0;
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for(int c = 0; c < 1368; c++) {
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const auto event = GeneratorT::event(internal_to_grauw(c));
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if(!event) {
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continue;
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}
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result[index] = *event;
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result[index].offset = uint16_t(c);
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++index;
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}
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result[index] = Event();
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return result;
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}
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struct StandardGenerators {
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static constexpr std::optional<Event> external_every_eight(int index) {
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if(index & 7) return std::nullopt;
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return Event::Type::External;
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}
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};
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struct RefreshGenerator {
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static constexpr std::optional<Event> event(int grauw_index) {
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// From 0 to 126: CPU/CMD slots at every cycle divisible by 8.
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if(grauw_index < 126) {
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return StandardGenerators::external_every_eight(grauw_index - 0);
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}
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// From 164 to 1234: eight-cycle windows, the first 15 of each 16 being
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// CPU/CMD and the final being refresh.
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if(grauw_index >= 164 && grauw_index < 1234) {
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const int offset = grauw_index - 164;
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if(offset & 7) return std::nullopt;
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if(((offset >> 3) & 15) == 15) return std::nullopt;
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return Event::Type::External;
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}
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// From 1268 to 1330: CPU/CMD slots at every cycle divisible by 8.
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if(grauw_index >= 1268 && grauw_index < 1330) {
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return StandardGenerators::external_every_eight(grauw_index - 1268);
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}
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// A CPU/CMD at 1334.
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if(grauw_index == 1334) {
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return Event::Type::External;
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}
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// From 1344 to 1366: CPU/CMD slots every cycle divisible by 8.
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if(grauw_index >= 1344 && grauw_index < 1366) {
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return StandardGenerators::external_every_eight(grauw_index - 1344);
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}
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// Otherwise: nothing.
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return std::nullopt;
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}
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};
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static constexpr auto refresh_events = events<RefreshGenerator>();
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template <bool include_sprites> struct BitmapEventsGenerator {
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static constexpr std::optional<Event> event(int grauw_index) {
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if(!include_sprites) {
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// Various standard zones of one-every-eight external slots.
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if(grauw_index < 124) {
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return StandardGenerators::external_every_eight(grauw_index + 2);
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}
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if(grauw_index > 1266) {
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return StandardGenerators::external_every_eight(grauw_index - 1266);
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}
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} else {
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// This records collection points for all data for selected sprites.
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// There's only four of them (each site covering two sprites),
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// so it's clearer just to be explicit.
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//
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// There's also a corresponding number of extra external slots to spell out.
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switch(grauw_index) {
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default: break;
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case 1238: case 1302: case 2: case 66:
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return Event::Type::SpriteLocation;
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case 1270: case 1338: case 34: case 98:
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return Event::Type::SpritePattern;
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case 1264: case 1330: case 28: case 92:
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return Event::Type::External;
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}
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}
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if(grauw_index >= 162 && grauw_index < 176) {
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return StandardGenerators::external_every_eight(grauw_index - 162);
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}
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// Everywhere else the pattern is:
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//
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// external or sprite y, external, data block
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//
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// Subject to caveats:
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//
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// 1) the first data block is just a dummy fetch with no side effects,
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// so this emulator declines to record it; and
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// 2) every fourth block, the second external is actually a refresh.
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//
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if(grauw_index >= 182 && grauw_index < 1238) {
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const int offset = grauw_index - 182;
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const int block = offset / 32;
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const int sub_block = offset & 31;
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switch(sub_block) {
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default: return std::nullopt;
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case 0:
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if(include_sprites) {
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// Don't include the sprite post-amble (i.e. a spurious read with no side effects).
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if(block < 32) {
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return Event::Type::SpriteY;
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}
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} else {
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return Event::Type::External;
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}
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case 6:
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if((block & 3) != 3) {
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return Event::Type::External;
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}
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break;
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case 12:
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if(block) {
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return Event::Type::DataBlock;
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}
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break;
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}
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}
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return std::nullopt;
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}
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};
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static constexpr auto no_sprites_events = events<BitmapEventsGenerator<false>>();
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static constexpr auto sprites_events = events<BitmapEventsGenerator<true>>();
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struct TextGenerator {
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static constexpr std::optional<Event> event(int grauw_index) {
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// Capture various one-in-eight zones.
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if(grauw_index < 72) {
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return StandardGenerators::external_every_eight(grauw_index - 2);
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}
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if(grauw_index >= 166 && grauw_index < 228) {
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return StandardGenerators::external_every_eight(grauw_index - 166);
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}
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if(grauw_index >= 1206 && grauw_index < 1332) {
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return StandardGenerators::external_every_eight(grauw_index - 1206);
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}
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if(grauw_index == 1336) {
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return Event::Type::External;
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}
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if(grauw_index >= 1346) {
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return StandardGenerators::external_every_eight(grauw_index - 1346);
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}
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// Elsewhere...
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if(grauw_index >= 246) {
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const int offset = grauw_index - 246;
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const int block = offset / 48;
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const int sub_block = offset % 48;
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switch(sub_block) {
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default: break;
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case 0: return Event::Type::Name;
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case 18: return (block & 1) ? Event::Type::External : Event::Type::Colour;
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case 24: return Event::Type::Pattern;
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}
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}
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return std::nullopt;
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}
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};
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static constexpr auto text_events = events<TextGenerator>();
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struct CharacterGenerator {
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static constexpr std::optional<Event> event(int grauw_index) {
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// Grab sprite events.
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switch(grauw_index) {
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default: break;
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case 1242: return Event(Event::Type::SpriteLocation, 0);
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case 1306: return Event(Event::Type::SpriteLocation, 1);
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case 6: return Event(Event::Type::SpriteLocation, 2);
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case 70: return Event(Event::Type::SpriteLocation, 3);
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case 1274: return Event(Event::Type::SpritePattern, 0);
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case 1342: return Event(Event::Type::SpritePattern, 1);
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case 38: return Event(Event::Type::SpritePattern, 2);
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case 102: return Event(Event::Type::SpritePattern, 3);
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case 1268: case 1334: case 32: case 96: return Event::Type::External;
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}
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if(grauw_index >= 166 && grauw_index < 180) {
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return StandardGenerators::external_every_eight(grauw_index - 166);
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}
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if(grauw_index >= 182 && grauw_index < 1238) {
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const int offset = grauw_index - 182;
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const int block = offset / 32;
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const int sub_block = offset & 31;
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switch(sub_block) {
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case 0: if(block > 0) return Event(Event::Type::Name, uint8_t(block - 1));
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case 6: if((sub_block & 3) != 3) return Event::Type::External;
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case 12: if(block < 32) return Event(Event::Type::SpriteY, uint8_t(block));
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case 18: if(block > 0) return Event(Event::Type::Pattern, uint8_t(block - 1));
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case 24: if(block > 0) return Event(Event::Type::Colour, uint8_t(block - 1));
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}
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}
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return std::nullopt;
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}
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};
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static constexpr auto character_events = events<CharacterGenerator>();
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};
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// Master System-specific storage.
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template <Personality personality> struct Storage<personality, std::enable_if_t<is_sega_vdp(personality)>> {
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using AddressT = uint16_t;
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// The SMS VDP has a programmer-set colour palette, with a dedicated patch of RAM. But the RAM is only exactly
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// fast enough for the pixel clock. So when the programmer writes to it, that causes a one-pixel glitch; there
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// isn't the bandwidth for the read both write to occur simultaneously. The following buffer therefore keeps
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// track of pending collisions, for visual reproduction.
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struct CRAMDot {
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LineBufferPointer location;
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uint32_t value;
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};
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std::vector<CRAMDot> upcoming_cram_dots_;
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// The Master System's additional colour RAM.
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uint32_t colour_ram_[32];
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bool cram_is_selected_ = false;
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// Programmer-set flags.
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bool vertical_scroll_lock_ = false;
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bool horizontal_scroll_lock_ = false;
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bool hide_left_column_ = false;
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bool shift_sprites_8px_left_ = false;
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bool mode4_enable_ = false;
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uint8_t horizontal_scroll_ = 0;
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uint8_t vertical_scroll_ = 0;
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// Holds the vertical scroll position for this frame; this is latched
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// once and cannot dynamically be changed until the next frame.
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uint8_t latched_vertical_scroll_ = 0;
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// Various resource addresses with VDP-version-specific modifications
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// built in.
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AddressT pattern_name_address_;
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AddressT sprite_attribute_table_address_;
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AddressT sprite_generator_table_address_;
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void begin_line(ScreenMode, bool) {}
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};
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}
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}
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#endif /* Storage_h */
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