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383 lines
9.8 KiB
C++
383 lines
9.8 KiB
C++
//
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// YamahaCommands.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 26/01/2023.
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// Copyright © 2023 Thomas Harte. All rights reserved.
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//
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#ifndef YamahaCommands_hpp
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#define YamahaCommands_hpp
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#include "AccessEnums.hpp"
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namespace TI::TMS {
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// MARK: - Generics.
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struct Vector {
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int v[2]{};
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template <int offset, bool high> void set(uint8_t value) {
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constexpr uint8_t mask = high ? (offset ? 0x3 : 0x1) : 0xff;
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constexpr int shift = high ? 8 : 0;
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v[offset] = (v[offset] & ~(mask << shift)) | ((value & mask) << shift);
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}
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template <int offset> void add(int amount) {
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v[offset] += amount;
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if constexpr (offset == 1) {
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v[offset] &= 0x3ff;
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} else {
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v[offset] &= 0x1ff;
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}
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}
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Vector & operator += (const Vector &rhs) {
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add<0>(rhs.v[0]);
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add<1>(rhs.v[1]);
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return *this;
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}
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};
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struct Colour {
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void set(uint8_t value) {
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colour = value;
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colour4bpp = uint8_t((value & 0xf) | (value << 4));
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colour2bpp = uint8_t((colour4bpp & 0x33) | ((colour4bpp & 0x33) << 2));
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}
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void reset() {
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colour = 0x00;
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colour4bpp = 0xff;
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}
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bool has_value() const {
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return (colour & 0xf) == (colour4bpp & 0xf);
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}
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/// Colour as written by the CPU.
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uint8_t colour = 0x00;
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/// The low four bits of the CPU-written colour, repeated twice.
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uint8_t colour4bpp = 0xff;
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/// The low two bits of the CPU-written colour, repeated four times.
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uint8_t colour2bpp = 0xff;
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};
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struct CommandContext {
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Vector source;
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Vector destination;
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Vector size;
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uint8_t arguments = 0;
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Colour colour;
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Colour latched_colour;
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enum class LogicalOperation {
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Copy = 0b0000,
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And = 0b0001,
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Or = 0b0010,
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Xor = 0b0011,
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Not = 0b0100,
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};
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LogicalOperation pixel_operation;
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bool test_source;
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};
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struct ModeDescription {
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int width = 256;
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int pixels_per_byte = 4;
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bool rotate_address = false;
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};
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struct Command {
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// In net:
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//
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// This command is blocked until @c access has been performed, reading
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// from or writing to @c value. It should not be performed until at least
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// @c cycles have passed.
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enum class AccessType {
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/// Plots a single pixel of the current contextual colour at @c destination,
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/// which occurs as a read, then a 24-cycle gap, then a write.
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PlotPoint,
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/// Blocks until the next CPU write to the colour register.
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WaitForColourReceipt,
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/// Writes an entire byte to the address containing the current @c destination.
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WriteByte,
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/// Copies a single pixel from @c source location to @c destination,
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/// being a read, a 32-cycle gap, then a PlotPoint.
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CopyPoint,
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/// Copies a complete byte from @c source location to @c destination,
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/// being a read, a 24-cycle gap, then a write.
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CopyByte,
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/// Copies a single pixel from @c source to the colour status register.
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ReadPoint,
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// ReadByte,
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// WaitForColourSend,
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};
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AccessType access = AccessType::PlotPoint;
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int cycles = 0;
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bool is_cpu_transfer = false;
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bool y_only = false;
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/// Current command parameters.
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CommandContext &context;
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ModeDescription &mode_description;
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Command(CommandContext &context, ModeDescription &mode_description) : context(context), mode_description(mode_description) {}
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virtual ~Command() {}
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/// @returns @c true if all output from this command is done; @c false otherwise.
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virtual bool done() = 0;
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/// Repopulates the fields above with the next action to take, being provided with the
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/// number of pixels per byte in the current screen mode.
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virtual void advance() = 0;
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protected:
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template <int axis, bool include_source> void advance_axis(int offset = 1) {
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context.destination.add<axis>(context.arguments & (0x4 << axis) ? -offset : offset);
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if constexpr (include_source) {
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context.source.add<axis>(context.arguments & (0x4 << axis) ? -offset : offset);
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}
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}
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};
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namespace Commands {
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// MARK: - Line drawing.
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/// Implements the LINE command, which is plain-old Bresenham.
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///
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/// Per Grauw timing is:
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///
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/// * 88 cycles between every pixel plot;
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/// * plus an additional 32 cycles if a step along the minor axis is taken.
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struct Line: public Command {
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public:
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Line(CommandContext &context, ModeDescription &mode_description) : Command(context, mode_description) {
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// context.destination = start position;
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// context.size.v[0] = long side dots;
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// context.size.v[1] = short side dots;
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// context.arguments => direction
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position_ = context.size.v[1];
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numerator_ = position_ << 1;
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denominator_ = context.size.v[0] << 1;
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cycles = 32;
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access = AccessType::PlotPoint;
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}
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bool done() final {
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return !context.size.v[0];
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}
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void advance() final {
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--context.size.v[0];
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cycles = 88;
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// b0: 1 => long direction is y;
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// 0 => long direction is x.
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//
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// b2: 1 => x direction is left;
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// 0 => x direction is right.
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//
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// b3: 1 => y direction is up;
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// 0 => y direction is down.
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if(context.arguments & 0x1) {
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advance_axis<1, false>();
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} else {
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advance_axis<0, false>();
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}
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position_ -= numerator_;
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if(position_ < 0) {
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position_ += denominator_;
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cycles += 32;
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if(context.arguments & 0x1) {
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advance_axis<0, false>();
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} else {
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advance_axis<1, false>();
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}
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}
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}
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private:
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int position_, numerator_, denominator_, duration_;
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};
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// MARK: - Single pixel manipulation.
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/// Implements the PSET command, which plots a single pixel and POINT, which reads one.
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///
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/// No timings are documented, so this'll output or input as quickly as possible.
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template <bool is_read> struct Point: public Command {
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public:
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Point(CommandContext &context, ModeDescription &mode_description) : Command(context, mode_description) {
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cycles = 0; // TODO.
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access = is_read ? AccessType::ReadPoint : AccessType::PlotPoint;
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}
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bool done() final {
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return done_;
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}
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void advance() final {
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done_ = true;
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}
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private:
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bool done_ = false;
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};
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// MARK: - Rectangular base.
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/// Useful base class for anything that does logical work in a rectangle.
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template <bool logical, bool include_source> struct Rectangle: public Command {
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public:
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Rectangle(CommandContext &context, ModeDescription &mode_description) : Command(context, mode_description) {
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if constexpr (include_source) {
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start_x_[0] = context.source.v[0];
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}
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start_x_[1] = context.destination.v[0];
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width_ = context.size.v[0];
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if(!width_) {
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// Width = 0 => maximal width for this mode.
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// (aside: it's still unclear to me whether commands are
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// automatically clipped to the display; I think so but
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// don't want to spend any time on it until I'm certain)
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// context.size.v[0] = width_ = mode_description.width;
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}
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}
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/// Advances the current destination and, if @c include_source is @c true also the source;
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/// @returns @c true if a new row was started; @c false otherwise.
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bool advance_pixel() {
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if constexpr (logical) {
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advance_axis<0, include_source>();
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--context.size.v[0];
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if(context.size.v[0]) {
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return false;
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}
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} else {
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advance_axis<0, include_source>(mode_description.pixels_per_byte);
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context.size.v[0] -= mode_description.pixels_per_byte;
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if(context.size.v[0] & ~(mode_description.pixels_per_byte - 1)) {
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return false;
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}
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}
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context.size.v[0] = width_;
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if constexpr (include_source) {
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context.source.v[0] = start_x_[0];
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}
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context.destination.v[0] = start_x_[1];
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advance_axis<1, include_source>();
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--context.size.v[1];
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return true;
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}
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bool done() final {
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return !context.size.v[1] || !width_;
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}
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private:
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int start_x_[2]{}, width_ = 0;
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};
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// MARK: - Rectangular moves to/from CPU.
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template <bool logical> struct MoveFromCPU: public Rectangle<logical, false> {
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MoveFromCPU(CommandContext &context, ModeDescription &mode_description) : Rectangle<logical, false>(context, mode_description) {
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Command::is_cpu_transfer = true;
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// This command is started with the first colour ready to transfer.
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Command::cycles = 32;
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Command::access = logical ? Command::AccessType::PlotPoint : Command::AccessType::WriteByte;
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}
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void advance() final {
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switch(Command::access) {
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default: break;
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case Command::AccessType::WaitForColourReceipt:
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Command::cycles = 32;
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Command::access = logical ? Command::AccessType::PlotPoint : Command::AccessType::WriteByte;
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break;
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case Command::AccessType::WriteByte:
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case Command::AccessType::PlotPoint:
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Command::cycles = 0;
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Command::access = Command::AccessType::WaitForColourReceipt;
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if(Rectangle<logical, false>::advance_pixel()) {
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Command::cycles = 64;
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// TODO: I'm not sure this will be honoured per the outer wrapping.
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}
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break;
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}
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}
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};
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// MARK: - Rectangular moves within VRAM.
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enum class MoveType {
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Logical,
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HighSpeed,
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YOnly,
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};
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template <MoveType type> struct Move: public Rectangle<type == MoveType::Logical, true> {
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static constexpr bool is_logical = type == MoveType::Logical;
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static constexpr bool is_y_only = type == MoveType::YOnly;
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using RectangleBase = Rectangle<is_logical, true>;
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Move(CommandContext &context, ModeDescription &mode_description) : RectangleBase(context, mode_description) {
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Command::access = is_logical ? Command::AccessType::CopyPoint : Command::AccessType::CopyByte;
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Command::cycles = is_y_only ? 0 : 64;
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Command::y_only = is_y_only;
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}
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void advance() final {
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Command::cycles = is_y_only ? 40 : 64;
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if(RectangleBase::advance_pixel()) {
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Command::cycles += is_y_only ? 0 : 64;
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}
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}
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};
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// MARK: - Rectangular fills.
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template <bool logical> struct Fill: public Rectangle<logical, false> {
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using RectangleBase = Rectangle<logical, false>;
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Fill(CommandContext &context, ModeDescription &mode_description) : RectangleBase(context, mode_description) {
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Command::cycles = logical ? 64 : 56;
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Command::access = logical ? Command::AccessType::PlotPoint : Command::AccessType::WriteByte;
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}
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void advance() final {
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Command::cycles = logical ? 72 : 48;
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if(RectangleBase::advance_pixel()) {
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Command::cycles += logical ? 64 : 56;
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}
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}
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};
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}
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}
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#endif /* YamahaCommands_hpp */
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