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334 lines
11 KiB
C++
334 lines
11 KiB
C++
//
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// TIA.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 28/01/2017.
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// Copyright © 2017 Thomas Harte. All rights reserved.
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//
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#ifndef TIA_hpp
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#define TIA_hpp
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#include <cstdint>
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#include "../CRTMachine.hpp"
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namespace Atari2600 {
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class TIA {
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public:
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TIA();
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// The supplied hook is for unit testing only; if instantiated with a line_end_function then it will
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// be called with the latest collision buffer upon the conclusion of each line. What's a collision
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// buffer? It's an implementation detail. If you're not writing a unit test, leave it alone.
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TIA(std::function<void(uint8_t *output_buffer)> line_end_function);
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enum class OutputMode {
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NTSC, PAL
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};
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/*!
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Advances the TIA by @c number_of_cycles cycles. Any queued setters take effect in the
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first cycle performed.
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*/
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void run_for_cycles(int number_of_cycles);
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void set_output_mode(OutputMode output_mode);
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void set_sync(bool sync);
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void set_blank(bool blank);
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void reset_horizontal_counter(); // Reset is delayed by four cycles.
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/*!
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@returns the number of cycles between (current TIA time) + from_offset to the current or
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next horizontal blanking period. Returns numbers in the range [0, 227].
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*/
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int get_cycles_until_horizontal_blank(unsigned int from_offset);
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void set_background_colour(uint8_t colour);
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void set_playfield(uint16_t offset, uint8_t value);
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void set_playfield_control_and_ball_size(uint8_t value);
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void set_playfield_ball_colour(uint8_t colour);
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void set_player_number_and_size(int player, uint8_t value);
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void set_player_graphic(int player, uint8_t value);
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void set_player_reflected(int player, bool reflected);
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void set_player_delay(int player, bool delay);
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void set_player_position(int player);
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void set_player_motion(int player, uint8_t motion);
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void set_player_missile_colour(int player, uint8_t colour);
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void set_missile_enable(int missile, bool enabled);
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void set_missile_position(int missile);
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void set_missile_position_to_player(int missile, bool lock);
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void set_missile_motion(int missile, uint8_t motion);
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void set_ball_enable(bool enabled);
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void set_ball_delay(bool delay);
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void set_ball_position();
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void set_ball_motion(uint8_t motion);
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void move();
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void clear_motion();
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uint8_t get_collision_flags(int offset);
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void clear_collision_flags();
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virtual std::shared_ptr<Outputs::CRT::CRT> get_crt() { return crt_; }
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private:
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TIA(bool create_crt);
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std::shared_ptr<Outputs::CRT::CRT> crt_;
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std::function<void(uint8_t *output_buffer)> line_end_function_;
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// the master counter; counts from 0 to 228 with all visible pixels being in the final 160
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int horizontal_counter_;
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// contains flags to indicate whether sync or blank are currently active
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int output_mode_;
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// keeps track of the target pixel buffer for this line and when it was acquired, and a corresponding collision buffer
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alignas(alignof(uint32_t)) uint8_t collision_buffer_[160];
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enum class CollisionType : uint8_t {
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Playfield = (1 << 0),
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Ball = (1 << 1),
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Player0 = (1 << 2),
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Player1 = (1 << 3),
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Missile0 = (1 << 4),
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Missile1 = (1 << 5)
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};
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int collision_flags_;
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int collision_flags_by_buffer_vaules_[64];
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// colour mapping tables
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enum class ColourMode {
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Standard = 0,
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ScoreLeft,
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ScoreRight,
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OnTop
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};
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uint8_t colour_mask_by_mode_collision_flags_[4][64]; // maps from [ColourMode][CollisionMark] to colour_pallete_ entry
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enum class ColourIndex {
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Background = 0,
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PlayfieldBall,
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PlayerMissile0,
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PlayerMissile1
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};
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uint8_t colour_palette_[4];
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// playfield state
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int background_half_mask_;
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enum class PlayfieldPriority {
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Standard,
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Score,
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OnTop
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} playfield_priority_;
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uint32_t background_[2]; // contains two 20-bit bitfields representing the background state;
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// at index 0 is the left-hand side of the playfield with bit 0 being
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// the first bit to display, bit 1 the second, etc. Index 1 contains
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// a mirror image of index 0. If the playfield is being displayed in
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// mirroring mode, background_[0] will be output on the left and
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// background_[1] on the right; otherwise background_[0] will be
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// output twice.
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// objects
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template<class T> struct Object {
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// the two programmer-set values
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int position;
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int motion;
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// motion_step_ is the current motion counter value; motion_time_ is the next time it will fire
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int motion_step;
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int motion_time;
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// indicates whether this object is currently undergoing motion
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bool is_moving;
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Object() : position(0), motion(0), motion_step(0), motion_time(0), is_moving(false) {};
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};
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// player state
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struct Player: public Object<Player> {
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Player() :
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adder(4),
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copy_flags(0),
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graphic{0, 0},
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reverse_mask(false),
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graphic_index(0),
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pixel_position(32),
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pixel_counter(0),
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latched_pixel4_time(-1),
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copy_index_(0),
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queue_read_pointer_(0),
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queue_write_pointer_(0) {}
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int adder;
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int copy_flags; // a bit field, corresponding to the first few values of NUSIZ
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uint8_t graphic[2]; // the player graphic; 1 = new, 0 = current
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int reverse_mask; // 7 for a reflected player, 0 for normal
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int graphic_index;
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int pixel_position, pixel_counter;
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int latched_pixel4_time;
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const bool enqueues = true;
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inline void skip_pixels(const int count, int from_horizontal_counter) {
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int old_pixel_counter = pixel_counter;
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pixel_position = std::min(32, pixel_position + count * adder);
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pixel_counter += count;
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if(!copy_index_ && old_pixel_counter < 4 && pixel_counter >= 4) {
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latched_pixel4_time = from_horizontal_counter + 4 - old_pixel_counter;
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}
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}
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inline void reset_pixels(int copy) {
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pixel_position = pixel_counter = 0;
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copy_index_ = copy;
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}
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inline void output_pixels(uint8_t *const target, const int count, const uint8_t collision_identity, int from_horizontal_counter) {
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output_pixels(target, count, collision_identity, pixel_position, adder, reverse_mask);
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skip_pixels(count, from_horizontal_counter);
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}
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void dequeue_pixels(uint8_t *const target, const uint8_t collision_identity, const int time_now) {
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while(queue_read_pointer_ != queue_write_pointer_) {
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uint8_t *const start_ptr = &target[queue_[queue_read_pointer_].start];
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if(queue_[queue_read_pointer_].end > time_now) {
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const int length = time_now - queue_[queue_read_pointer_].start;
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output_pixels(start_ptr, length, collision_identity, queue_[queue_read_pointer_].pixel_position, queue_[queue_read_pointer_].adder, queue_[queue_read_pointer_].reverse_mask);
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queue_[queue_read_pointer_].pixel_position += length * queue_[queue_read_pointer_].adder;
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queue_[queue_read_pointer_].start = time_now;
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return;
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} else {
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output_pixels(start_ptr, queue_[queue_read_pointer_].end - queue_[queue_read_pointer_].start, collision_identity, queue_[queue_read_pointer_].pixel_position, queue_[queue_read_pointer_].adder, queue_[queue_read_pointer_].reverse_mask);
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}
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queue_read_pointer_ = (queue_read_pointer_ + 1)&3;
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}
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}
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void enqueue_pixels(const int start, const int end, int from_horizontal_counter) {
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queue_[queue_write_pointer_].start = start;
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queue_[queue_write_pointer_].end = end;
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queue_[queue_write_pointer_].pixel_position = pixel_position;
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queue_[queue_write_pointer_].adder = adder;
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queue_[queue_write_pointer_].reverse_mask = reverse_mask;
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queue_write_pointer_ = (queue_write_pointer_ + 1)&3;
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skip_pixels(end - start, from_horizontal_counter);
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}
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private:
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int copy_index_;
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struct QueuedPixels {
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int start, end;
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int pixel_position;
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int adder;
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int reverse_mask;
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QueuedPixels() : start(0), end(0), pixel_position(0), adder(0), reverse_mask(false) {}
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} queue_[4];
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int queue_read_pointer_, queue_write_pointer_;
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inline void output_pixels(uint8_t *const target, const int count, const uint8_t collision_identity, int pixel_position, int adder, int reverse_mask) {
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if(pixel_position == 32 || !graphic[graphic_index]) return;
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int output_cursor = 0;
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while(pixel_position < 32 && output_cursor < count) {
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int shift = (pixel_position >> 2) ^ reverse_mask;
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target[output_cursor] |= ((graphic[graphic_index] >> shift)&1) * collision_identity;
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output_cursor++;
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pixel_position += adder;
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}
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}
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} player_[2];
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// common actor for things that appear as a horizontal run of pixels
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struct HorizontalRun: public Object<HorizontalRun> {
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int pixel_position;
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int size;
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const bool enqueues = false;
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inline void skip_pixels(const int count, int from_horizontal_counter) {
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pixel_position = std::max(0, pixel_position - count);
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}
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inline void reset_pixels(int copy) {
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pixel_position = size;
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}
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inline void output_pixels(uint8_t *const target, const int count, const uint8_t collision_identity, int from_horizontal_counter) {
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int output_cursor = 0;
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while(pixel_position && output_cursor < count)
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{
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target[output_cursor] |= collision_identity;
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output_cursor++;
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pixel_position--;
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}
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}
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void dequeue_pixels(uint8_t *const target, const uint8_t collision_identity, const int time_now) {}
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void enqueue_pixels(const int start, const int end, int from_horizontal_counter) {}
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HorizontalRun() : pixel_position(0), size(1) {}
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};
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// missile state
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struct Missile: public HorizontalRun {
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bool enabled;
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bool locked_to_player;
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int copy_flags;
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inline void output_pixels(uint8_t *const target, const int count, const uint8_t collision_identity, int from_horizontal_counter) {
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if(!pixel_position) return;
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if(enabled && !locked_to_player) {
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HorizontalRun::output_pixels(target, count, collision_identity, from_horizontal_counter);
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} else {
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skip_pixels(count, from_horizontal_counter);
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}
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}
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Missile() : enabled(false), copy_flags(0) {}
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} missile_[2];
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// ball state
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struct Ball: public HorizontalRun {
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bool enabled[2];
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int enabled_index;
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const int copy_flags = 0;
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inline void output_pixels(uint8_t *const target, const int count, const uint8_t collision_identity, int from_horizontal_counter) {
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if(!pixel_position) return;
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if(enabled[enabled_index]) {
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HorizontalRun::output_pixels(target, count, collision_identity, from_horizontal_counter);
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} else {
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skip_pixels(count, from_horizontal_counter);
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}
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}
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Ball() : enabled{false, false}, enabled_index(0) {}
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} ball_;
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// motion
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bool horizontal_blank_extend_;
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template<class T> void perform_border_motion(T &object, int start, int end);
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template<class T> void perform_motion_step(T &object);
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// drawing methods and state
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void draw_missile(Missile &, Player &, const uint8_t collision_identity, int start, int end);
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template<class T> void draw_object(T &, const uint8_t collision_identity, int start, int end);
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template<class T> void draw_object_visible(T &, const uint8_t collision_identity, int start, int end, int time_now);
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inline void draw_playfield(int start, int end);
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inline void output_for_cycles(int number_of_cycles);
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inline void output_line();
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int pixels_start_location_;
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uint8_t *pixel_target_;
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inline void output_pixels(int start, int end);
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};
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}
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#endif /* TIA_hpp */
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